Halton Vario Design Guide Enabling Wellbeing
Table of contents 1. Halton Vario - ventilation and air conditioning system overview 3 1.1 Room level, Zonal level and central level 4 1.2 Flexible design and adaptable HVAC systems reduce churn costs 6 2. Room level 8 2.1 Requirements for design of indoor environment and cooling demand 9 2.2 Air water system 12 2.2.1 Operation (demand based ventilation and VAV beam principle) 12 2.2.2 Layout and control zone considerations 15 2.2.3 System & component overview 16 Halton Rex chilled beams 16 - Integration of controls into chilled beams 16 Controls 16 2.3 All air system 18 2.3.1 Operation (demand based ventilation and VAV beam principle) 18 2.3.2 Layout and control zone considerations 21 2.3.3 System & component overview?? Active diffusers and controls?? - Integration of controls into room units?? Controls?? 3. Zonal level 24 3.1 Operation based on constant pressure ductwork 24 3.1.1 Principle Design of constant pressure ductwork 28 3.1.2 System & component overview 32 Ductwork components 32 Controls 32 3.1.3 design examples 33 4. Central level 4.1 Operation?? 4.2 System and component overview?? 4.3 Design examples?? 5. Communication 5.1 Lon, Backnet, Modbus?? 5.2 Network structure?? 5.3 Communication with slave units?? 2
1. Halton Vario - ventilation and air conditioning system overview In Halton Vario system, energy and environmental efficiency is implemented together with good indoor environment quality and wellbeing of users. Indoors conditions are maintained by demandbased and only when the spaces are occupied the indoor conditions are actively controlled. Halton Vario system's adaptable indoor conditions impact on: Users health Users comfort Energy efficient of the real estate Carbon footprint of the energy use Adaptability for future users needs Reliability and safety for operation Asset value Those items give benefits for developers, tenants and owners to run their operation more effective way and improve their profitable. The benefits for different stake-holders are summarized in the table 1. Developer Tenants Owners Higher return of investment (ROI) Health and comfort of employees Lower risk Lower risk of investment Productivity of workers Lower life-cycle costs Easier to get financing Better brand Easier to rent Easier to sell Can employ better people Lower churn costs of continuous changes Easier to adapt changes during construction phase Fast and easy layout changes for alteration use of space Less IEQ complains Table 1. Halton Vario system's benefits for developer, tenants and owners. Halton Vario overview 3
Fig. 1. Halton Vario system air-water concept. 1.1 Halton Vario system offers solutions for both air-water and all-air water ventilation and air-conditioning systems Halton Vario air-water system The system is based on smart controls and Halton Vario system s chilled beams. Halton Vario is a total system for ventilation, cooling and heating in rooms together with the required controls at room, zonal and system level. Halton Vario air- water system provides solution for room, zonal and central levels: Zones Halton Vario system divides the system into ventilation zones to ensure flexibility and controllability of airflow rate changes in different spaces, that enables linear operation of control damper of chilled beam and makes possible to integrate constant airflow (CAV) and variable airflow rate (VAV) room units into same duct branch. Constant static pressure zones enable layout flexibility and minimize the churn cost while making the adjustment simple. Rooms Halton Vario system's chilled beams are used in office rooms, open plan office and meeting rooms. In offices, unoccupied or occupied space, the airflow is adjusted accordingly. In meeting rooms, airflow is adjusted from minimum to maximum. Control of conditions is based on CO 2, temperature and occupancy. The room controller ensures perfect conditions in occupied work places and saves energy when spaces are unoccupied. In the room control system, there should be integrated e.g. window switch and condensation sencor to prevent condensation. System level Halton Vario system's Optimizer monitors the performance of the ventilation system. It minimises energy consumption by keeping the lowest possible pressure in the ductwork that is required for operation. The positions of zone dampers are monitored and the system optimizes the pressure loss so that unnecessary high pressure drop does not happen in zone dampers. Halton Vario air-water system is one the most energy efficient solution resulting in up to 50% energy savings compared to typical non-demand based controlled airwater system. The scheme of the whole Halton Vario air-water system is presented in Fig.1 Halton Vario overview 4
Halton Vario system is low temperature heating and high temperature cooling system. Thus, cooling energy could be provider e.g. from chiller, free cooling or ground coupled systems. Low temperature heating can be provided from e.g. district heating, boiler or heat pump systems. In the air-handling unit, the supply air temperature and airflow rates are controlled. At air-handling unit, the supply air is dehumidified to prevent condensation during summer conditions. Halton Vario all-air system The Halton Vario system is based on smart controls and active diffusers. Halton Vario all-air system is for ventilation and cooling in rooms with controls at room, zonal and system levels. Halton Vario system s all-air system provides solution for room, zonal and central levels: Rooms: Halton Vario active diffusers for office rooms, open plan offices and meeting rooms. In offices and meeting rooms, unoccupied or occupied space, the airflow is adjusted accordingly. Control of conditions is based on CO2, temperature and occupancy sensor. The room controller ensures perfect conditions and saves energy when spaces are unoccupied. Zones Halton Vario divides the system into ventilation zones to ensure flexibility and controllability of airflow rate changes in different spaces. Constant static pressure is maintained in zonal ductworks. Zones allow regulating the ventilation system the most efficient way by reducing unnecessary pressure in the system. Constant static pressure zones enable layout flexibility and minimize the churn cost while making the adjustment simple. System level: Halton Vario system's Optimizer monitors the performance of the ventilation system. It minimises energy consumption by keeping the lowest possible pressure in the ductwork that is required for operation. The positions of zone dampers are monitored and the system optimizes the pressure loss so that unnecessary high pressure drop does not happen in zone dampers. The scheme of the whole Halton Vario all-air system is presented in Fig.2. In the air-handling unit, the supply air temperature is controlled. Supply airflow rate is the master that exhaust (slave) follows. The fan power is controlled to provide required operation conditions of the branch control dampers. Fig. 2. A schematic of the whole Halton Vario all-air system. Halton Vario overview 5
1.2 Flexible design and adaptable HVAC systems reduce churn costs The adaptability of office space is one of the main issue in designing a system for sustainable buildings. In a modern office environment, balance is sought between work performed by individuals and in interaction between employees. The systems must adapt to changed loads and partition wall locations. For a room system, adaptability means taking changes in the supply air flow, cooling effect and throw pattern of the supply air device into consideration. All this makes possible to change office to meeting room quicly and cost-effectively. The functionality of the workspace significantly affects the productivity of employees. Often a compromise must be made among the needs of the employee, team and organisation when arranging workspaces. Addressing the interaction and privacy needs of employees, both of which are important considerations in organisations, is particularly challenging. In general, it can be stated that, from the perspective of dispersing silent information (views, experiences, intuitions), fully autonomous workspaces do not support the business models of most companies. On the other hand, reducing the autonomy afforded by individual workspaces reduces acoustic privacy, which disturbs concentration. Organisational changes in most companies are continuous and require flexible changes in work methods and workspaces. The traditional oneperson office areas, or cells, and open offices, or hives, seen in traditional offices are today changing into spaces that are more suited to team work, referred to as dens or clubs (Table 2). Space Interaction Autonomy Operation Example Hive low low customer service Cell low high support tasks call centre Den high low team work media Club high high expert work financial administration consultancy Table 2. Adapting space types and business processes in office buildings. Halton Vario overview 6
Moving people is expensive. The cost of a move depends on the extent to which the facility must be modified to accommodate the changes. Often new walls, new or additional wiring, new telecommunications systems, or other construction are needed to complete the move. When the number of occupants or the use of the space changes, the indoor environment quality and the system performance should always be checked. In Table 3, presents typical costs when the office space is modified to meeting room with traditional system. But change can be easy- churn costs and the required time for the change can be minimized if the system is adaptable. Halton s Vario system provides minimized churn costs and time for the change. The change of office to meeting room happens within 15 minutes. Depending on the selected systems, the cost of modifying a space and varies a lot. With traditional system, the costs are easily over 100 /floor-m 2 and the total required time including design and retrofitting is 1 3 months. Costs of traditional system Cost Design work 30-40 /m 2 Changes in automation systems 10-20 /m 2 Changes in mechanical systems 40-100 /m 2 Changes in electrical systems 30-40 /m 2 TOTAL 110-200 /m 2 Table 3. Churn costs of traditional system. Halton Vario overview 7
2. Room level Room level 8
2.1 Requirements for design of indoor environment and cooling demand For the selection of room units, the required ventilation rate must be specified based on national requirements or using the recommended methods in the standard. As a minimum, space must be ventilated to dilute the bio effluents from the occupants. In addition, the air flow rate is increased to take into account the emissions from the building materials. Recommended airflow rates for diluting emissions are categorized. Typically good and excellent level of air quality requires 1.5 2.0 l/s per floor-m 2 in offices and 4-6 l/s per floor-m 2 in meeting rooms in standards. For achieving healthy, comfortable and energy efficient buildings, it is important to consider the required airflow rates taken into account the material emissions. Indoor climate classifications and ventilation rates are specified in European Standard EN 15251. When material emissions are low, the airflow rates in office rooms are 1.5 2.0 l/s per floor-m 2 and in meeting room 4-6 l/s per floor-m 2. Using non-low polluting material in offices increases significantly the required airflow rates. Table 4 presents air flow rates according to EN 15251. In Europe EN15251 is now used by many countries but several countries do have their own standards and building codes. Also, building classification schemes requires higher airflow rates than standard specify to reach maximum scores in the evaluation. EN15251 and ISO EN 7730 gives target values for thermal comfort for both the whole body thermal sensation and local thermal discomfort e.g. draught. Table 5 on page 10 shows three categories of thermal environment. In heating mode, the temperature gradient between floor and ceiling can t be too high. Table 6 shows (see page 10), there is shown the categories of local thermal discomfort parameters (vertical temperature gradient, floor temperature and radiant temperature asymmetry). Due to individual variation of the physiological and psychological conditions, it is difficult to ensure an environment satisfying all occupants exposed to the same thermal environment. Experimental data show that a certain amount of persons is always dissatisfied with the thermal conditions. Building type Ventilation rate of Occupancy Floor area m 2 /p Occupancy l/s/m 2 Ventilation rate of Building Materials Very low polluting Low polluting Non-low polluting Material Total Material Total Material l/s/m 2 l/s/m 2 l/s/m 2 Cellular office I 10 1.0 0.5 1.5 1.0 2.0 2.0 3.0 II 10 0.7 0.3 1.0 0.7 1.4 1.4 2.1 III 10 0.4 0.2 0.6 0.4 0.8 0.8 1.2 Landscape office I 15 0.7 0.5 1.2 1.0 1.7 2.0 2.7 Total II 15 0.5 0.3 0.8 0.7 1.2 1.4 1.9 III 15 0.3 0.2 0.5 0.4 0.7 0.8 1.1 Conference room I 2 5 0.5 5.5 1.0 6.0 2.0 7.0 II 2 3.5 0.3 3.8 0.7 4.2 1.4 4.9 III 2 2 0.2 2.2 0.4 2.4 0.8 2.8 Table 4. Ventilation rates in offices according European Standard EN 15251. Room level 9
During design phase, it is important to analyze air velocities in the occupied zones and thus make sure that the selected solution does not cause draught. With Halton HIT, it is easy to carry out the required air velocity calculations. In demanding cases, it is recommended to use CFDanalysis and mock-ups to guarantee the performance. Halton provides CFD and mock-up services to analyze the performance. Cooling demand The actual cooling demands should be computed with dynamic energy simulation program. When the room units are selected, it is important to make a difference beintween sensible cooling and total cooling loads. Chilled beams are sized by sensible cooling demand. Windows are playing a significant role in cooling demand. It is profitable to use solar shading or window with low g-values. Nowadays with good solar shading and energy efficient lights, it is possible to reach 60-80 W/floor-m 2 also on perimeter spaces. The energy consumption of a building depends on the qualities of building envelope and the energy efficiency of the selected HVAC- system. The properties of the windows are the most significant factor on cooling demand in modern offices, where energy efficient light fittings and laptop computers are enabled. With good solar shading, the cooling requirement can be significantly reduced. The reduction of cooling loads also expands the variety of HVAC-systems, which can be used in buildings. Low temperature heating and high temperature cooling air-water systems can be more easily introduced in such buildings where efficient solar shading is introduced. During the design phase, it is important to make a difference between sensible cooling and total cooling loads, when air-water systems are considered. In airwater room air conditioning systems, only sensible cooling load is covered with room units. The latent load is compensated in air-handling unit by dehumidifying the supply air flow to required level to avoid condensation in the room space. Thus, the cooling capacity is much lower compared to e.g. condensing fan-coil units, where the major part of dehumidification occurs in the fan-coil unit in the room spaces. Category Thermal state of the body as a whole PPD % PMV Operative temperature C Summer (0,5 clo) Cooling Winter (1 clo) Heating Max. mean air velocity m/s Summer (0,5 clo) Cooling A < 6-0.2 < PMV < + 0.2 23,5 25,5 21,0 23,0 0,18 0,15 B < 10-0.5 < PMV < + 0.5 23,0 26,0 20,0 24,0 0,22 0,18 C < 15 0.7 < PMV < + 0.7 22,0 27,0 19,0 25,0 0,25 0,21 Table 5. Three categories of thermal environment. Winter (1 clo) Heating Category Vertical air temperature difference K Floor surface temperature C Radiant temperature asymmetry K Warm ceiling Cool ceiling Cool wall Warm wall A < 2 19-29 < 5 < 14 < 10 < 23 B < 3 19-29 < 5 < 14 < 10 < 23 C < 4 17-31 < 7 < 18 < 13 < 35 Table 6. Recommended categories for local thermal discomfort parameters. Room level 10
When an air conditioning system is sized, it is important to calculate the actual cooling demand by using dynamic energy simulation program. If the effect of the thermal mass is not taken into account, the whole system is over-sized. In the cooling demand, window properties are playing a significant role. If there is no solar shading or window with bad solar heat gain coefficient (g value), the required cooling capacity can easily be 1.4-1.6 times higher than with low solar transfer windows. The cooling analysis of the effect of window structure was carried out in different climate zones in Europe. Case-study: envelope and window The simulated office room area was 10.8 m 2 (4.0 x 2.7 x 3 m, L x W x H). U-value of the window was 1.1 W/m 2 K and g value was 0.4. Four different heights of window. U-value of the external wall was 0.3 W/m 2 K. The exterior wall was a concrete wall (heavy) and interior walls were plaster board structures (light). Fig 3. Office building module with four different window heights. Case-study: heat gains and schedules Two occupants, lighting 10 W/floor-m 2 and appliance load 10 W/floor-m 2 were from 9.00 a.m. to 6.00 p.m Fans operate from 7.00 a.m. to 8.00 p.m. providing a constant outdoor airflow rate of 2 l/s,floor-m 2 Room air temperature set point was 24 C and supply air temperature was 14 C. In the case-study, the coil capacity was the most significant portion in the cooling capacities of the office rooms. The sensible cooling of the chilled beam coil was 60-75 % of the office room. The maximum sensible cooling power in south rooms varied between 80 to 120 W/floor-m 2. By reducing the window height to 1.6 m, it is possible maintain the set room air temperature using the cooling power of 80 W/floor-m 2. In to the east and west facing office rooms, the maximum cooling capacity was 120 W/floor-m 2. When the window height was 1.6 m and 1.2 m, the required cooling capacity reduced to 90 W/ floor-m 2 and 80 W/ floor-m 2 South Office Cooling load from air flows Cooling load from beams West Office Cooling load from air flows Cooling load from beams 180,0 200,0 160,0 180,0 Cooling power (W/m2) 140,0 120,0 100,0 80,0 60,0 40,0 Cooling power (W/m2) 160,0 140,0 120,0 100,0 80,0 60,0 40,0 20,0 20,0 0,0 1,2m 1,6m 2m 2,8m 1,2m 1,6m 2m 2,8m 1,2m 1,6m 2m 2,8m Helsinki Paris Rome 0,0 1,2m 1,6m 2m 2,8m 1,2m 1,6m 2m 2,8m 1,2m 1,6m 2m 2,8m Helsinki Paris Rome Fig.4. A case study of the required sensible cooling capacity of south and west offices in some European cities with different window heights. Room level 11
2.2 Air-water system 2.2.1 Operation In Halton Vario, air temperature for a beam system is normally room air by varying the water flow rate. The control of air quality is based on variable airflow rate. The delivered outdoor air flow rate is adjusted to maintain the required zone CO 2 concentration. Air flow rate adjustment could happen in three modes: unoccupied, occupied and boost. Thanks to the constant pressure ductwork and linearized performance of Halton Vario control damper, airflow rate is easy to adjust and measure. Halton Vario makes possible to control outdoor airflow rate within wide range and also guarantee ideal throw pattern and draught-free operation. Room air temperature The control of space air temperature for a beam system is normally accomplished by varying the water flow rate while maintaining a constant outdoor air flow rate temperature or set according to the season. Traditionally, outdoor airflow rate has been constant, but now with Halton Vario system, airflow rate is also possible to control demand-based. In tradional systems when the constant supply air temperature is used e.g. in meeting rooms and offices, unoccupied spaces could be over cooled with outdoor air even when water valve is closed. With Halton Varion, over cooling is not happening because airflow rate is demand-based controlled. In Fig. 5, there is illustrated room air temperature control based on 4-pipe connection chilled beams. Control of the water side is a closed loop control system in which the room temperature is the controlled variable, and the chilled or warm water flow is adjusted by the control valve installed as part of the water piping to the beams in the space. Between heating and cooling modes, the controller operates on zero-energy band and both heating and cooling valves are closed. The control valve can operate either as two-position (on-off) or modulating. On-off control may cause significant fluctuations in the delivered air temperature of active beams, leading to swings in room conditions. When applying conventional modulating control valves care must be taken to adequately select the valves so that they have enough authority in the hydraulic circuit. When modulating pressure independent control valves are applied the valves always have full authority, the selection of the control valve becomes more simple, not Room level 12
requiring authority verification and an excellent quality of the room temperature control can more easily be achieved. Space mode Heating mode Cooling mode Occupied 20 C 25 C Stand-by 19 C 26 C Unoccupied 18 C 28 C Table 7. Examples of room air temperature set points. Fig.5. Room air temperature control sequences with Halton 4-pipe Vario system's chilled beam. Room air temperature set point can be different for heating and cooling modes and can be varied also based on the room occupancy mode. This adapts room air temperature according to outdoor conditions and saves energy on stand-by and unoccupied modes. In Table 7, there is presented typical room air temperature set points. All presented values are parameters that user can change. User can change the room air temperature set point with wall mounted or remote user panel. The set point shift range is defined as parameter. The default value of the shift is ± 3 C. Several different room air temperature control sequences can be chosen by controller configuration (Fig. 6): 2-pipe application for cooling only 2 pipe application using change-over control for cooling or heating 4-pipe application for cooling and heating 2 pipe application for cooling and electric heating 2 pipe application using change-over for cooling and heating and additional electric heating element for reheat 2-pipe, heating sequence only 2-pipe, heating or cooling change over 2-pipe with electric heating, water cooling 2-pipe with electric heating, water heating or cooling change over 4-pipe, heating and cooling 2-pipe, cooling only Fig.6. Control sequences of heating and cooling. Room level 13
The air quality control sequence can be used also as extra cooling by providing extra outdoor air into the space. The increased outdoor air flow rate can be used as a primary of secondary cooling sequence (Fig. 7). Air quality Air quality is controlled based on room occupancy mode and room conditions. The control of air quality is based on variable airflow rate. In offices, airflow rate is typically adjusted according to occupancy of the space. In meeting rooms, additional airflow rate is provided based on occupancy and air quality. Control of air quality is based on CO 2 sensor. Demand control ventilation involves varying the outdoor air flow rate in response to the quantity of occupants in the space. Typically, sensors monitor the CO 2 levels and a room space controller measures the delivered outdoor air flow rate to maintain the required zone CO 2 concentration. In the room control system, there could be integrated e.g. window switch and condensation sensor to prevent condensation. Those switches and sensors stop stop water flow rate when there is a risk of condensation. In meeting rooms, airflow is adjusted from minimum to maximum (e.g. from 10 to 100%). In meeting room, there are three modes: unoccupied, occupied and boost. In offices the airflow is adjusted according to occupancy of the space. In offices, there are two Air flow rate configured as second cooling sequence. Air flow rate configured as first cooling sequence. Fig 7. Air flow rate configured as second or first control sequence. Fig.8. Airflow rate is controlled based on occupancy and air quality sensors. Room level 14
modes: unoccupied and occupied. Fig. 8 illustrates demand control ventilation with Halton Vario system's beams. nozzle size), level of static pressure in ductwork and controller parameter settings. The normal and maximum airflow can be selected from Halton HIT. BMS system adjusts to the system either night or day operation mode. In unoccupied spaces, there could be different airflow rate setting for night and day times. In Table 8, there are shown operation modes and airflow control functions in unoccupied and occupied spaces during day and night times. The actual Halton Vario system's chilled beam airflow rate depends on the selected beam type (length and In the unoccupied and stand-by modes, the Halton Rex beam airflow is reduced and therefore heating or cooling capacity of the room unit is decreased. To prevent space temperature exceeding temperature setting, the controller will reset the unit airflow rate to normal airflow value until room conditions are again on the desired level. When the room air temperature has reached the set point, the airflow rate is then readjusted to the unoccupied and stand-by settings. BMS Room CO2 Operation modes and airflow rate control > 400 ppm Boost Increased airflow Increased airflow based on room conditions Occupied Normal airflow Normal Halton Rex beam airflow Stand-by Reduced airflow Adjustable by parameter Unoccupied Eco settings Adjustable by parameter, or off Occupied Normal settings Normal Halton Rex beam airflow Table 8. Operation modes and the control of airflow rate. Room level 15
Throw pattern In Halton Vario system, airflow rate is controlled in 3 steps. In unoccupied mode (step 1), airflow rate is minimal e.g. 0.3 l/s per m 2. When the occupancy sensor realizes that the space is occupied, airflow rate set to value based on the standard e.g. 1.5 2 l/s per m 2 (step 2). Airflow rate is boosted and modulated when air quality sensor demands more outdoor air (step 3). In Fig. 9, there is presented the thrown pattern in three different operation modes. It should be noted that when the outdoor airflow rate is increased, the amount of the induced air through the water coil also increased. Thus with high outdoor airflow rates, there is possible, if needed, to increase cooling capacity from water side. In Halton Rex chilled beam dual-chamber structure, airflow rate is released to room space from two nozzle rows (Fig. 10). This concept makes possible to control outdoor airflow rate within wide range and also guarantee ideal throw pattern and draught-free operation. Thanks to the constant pressure ductwork and linearized performance of Halton Vario system's control damper, airflow rate is easy to adjust and measure using product data. A principle of the control strategy is shown in Fig.11: in unoccupied mode, the minimum airflow 5 l/s rate is adjusted with the control signal of 0.7 V. With the control signal of 5 V, the airflow rate is set to be 20 l/s that is required in the occupied mode. By the changing the control signal from 5 V to 10 V, airflow rate is modulated from 20 l/s to 75 l/s. Fig.10. Air is released from two nozzle rows in Halton Vario concept. l/s 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 V (DC) Control signal V (DC) Fig.11. A principle of the correlation between control signal and the outdoor airflow rate in Halton Vario system. Fig.9. Thrown pattern in unoccupied, occupied and boosts modes. Room level 16
2.2.2 Layout and control zone considerations Chilled beam layout selection takes into account room module dimensions, intended use of the space and flexibility requirements. Beams installation could be in parallel or perpendicular to the façade. Zone control covers room air temperature, outdoor airflow rate and exhaust airflow rate control schemes. The floor area of the single control zone should not be more than 50 m 2. This means that the space controller is the master for 1-4 room units. The layout has some influence on the horizontal air discharge in the space and should thus be taken into account at the design stage. As thrown pattern depends on the room or module dimensions, intended use, and flexibility required. One of the first considerations is architectural requirements and owner s wishes for flexibility, Whether active beams can be arranged in parallel or perpendicular to the façade primarily depends on the application. It is recommended to use perpendicular installation (Fig.12). In perpendicular installation, thermal plume of window has lower influence on air distribution than with parallel installation (Fig.13). When active beams are installed parallel to the façade their air discharges towards the exterior wall and the internal zone. During winter time, the discharge towards the cold façade leads higher draught risk. With good quality windows and solar protection difference between two types of installations becomes neglectable. Fig.12. Installation of active beams perpendicular to the façade. Fig.13. Installation of active beams parallel to the façade. Room level 17
In perpendicular installation typically, the length of the beam is from 2.7 m to 4 m. To suit architectural requirements, the length of the beam casing can be selected longer than the actual capacity requires (e.g. as long as the room). In this case the coil is sized according to the required cooling load. The distance between the beam rows are selected based on the selected module size and to guarantee draught-free air distribution. Typical distance between the rows is from 2.5 m to 4 m. In parallel installation, the beam length is selected to fit with the room modules and flexible demands. Typically, the length of the beam is between 1.2 m- 4.0 m. Depending on the module size, there could be one or two beam rows in the module. Selection of control zone, it is always balancing of flexibility (future churn costs) and first cost. Naturally, small control zone enables high flexibility and on the contrary increases first costs. Some cases it makes sense to utilize different beam lengths and to build demand-based size of the control zones. In Fig.15, there is shown an example of different sizes of the control zones in an open layout office. In 7.5 m x 16 m module, 5 different zones are designed (red lines). The marked red lines are predesigned locations of walls. That is accomplished with 2 beam lengths (1.2 m and 2.4 m) installed in 5 rows. Zone control covers room air temperature, outdoor airflow rate and exhaust airflow rate control schemes. Control zone could be a room or several room units could be controlled parallel. In practice, the area of the control zone should not be more than 50 m 2 to maintain good controllability of internal conditions in open layout office. In Fig.16, there is shown of an example of the control zone selections where one (~10 m 2 ) and five (~50 m 2 ) room units consists a control zone. In the control zone of five room units and a common room controller, the room air temperature happens with a common valve or all beams are equipped with valves and those valves are parallel controlled. In five room units zone, indoor air quality is controlled with the room unit specific control dampers. Those dampers are controlled individually or parallel using one or several occupancy sensor. needs a modified image* now too unclear 2.2.3 System & component overview The Halton Vario system controller is a room controller dedicated to complete room applications providing the control of cooling, heating, demand controlled ventilation. The Halton Vario system's room controller manages chilled beam operation by controlling chilled water and hot water control valves in 2- or 4-pipe applications. Also electric heating can be used. The system can operate as standalone or connected to a bus system. In Halton Vario system, the room control package covers all required sensor, actuators, valves and dampers that makes possible to control room air temperature and indoor air quality. In Fig. 17, there is described the possible options to integrate for room control scheme. Room controller and sensor could be factory installed into Halton Rex chilled beam unit. Fig.15. Utilization of two beam lengths makes it possible to build different sizes of the control zones. All read lines are the boundaries of the control zones. Control zones are equipped with enough number of occupancy sensors. Typically one occupancy sensor cover ~15 m 2. Room level 18
new clearer image needed here' Fig.16. An example of the selection of control zones where the dotted lines indicate the boundaries of the selected zones. Wall control panel Halton Rex integrated room controller Halton Rex Vario 600 with airflow control damper Multi-sensor Room air temperature measurement to control space temperature Occupancy sensor for demand based CO2 sensor operation with airflow rate control damper Room controller Air quality control with carbon dioxide sensor, CO 2 Condense sensor Remote control panel Cooling with chilled water control valve Heating with hot water control valve or electrical heating as an option Window switch Several user interface options, either wall mounted or hand-held remote controller Condense prevention Unit integrated temperature sensor Heating valve Cooling valve Energy saving window switch operation Fig.17. Components for the room controller. Room level 19
System components 1) Halton Rex chilled beams with ventilation, cooling and heating (water or electric), Valves and actuator Damper and actuator 2) Room controller, user interface and sensors User interface panel Room air temperature sensor Occupancy sensor Carbon dioxide sensor Window switch Condensation sensor Light and sun blinds control Occupancy sensor is a fundamental element of demand based room condition control. It detects presence of people and therefore adjusts the space either to unoccupied or occupied mode. The remote controller is communicating with Halton multi-sensor. The multi-sensor includes occupancy sensor, light sensor and remote controller interface (Fig. 18). When a person enters the room, the occupancy sensor sends a signal to the Halton Vario system's controller to inform that the space is occupied ( ). The controller set automatically airflow rate and room air temperature setpoint to a comfort level. When leaving the space the occupancy sensor sends an off signal to the Halton Vario system's controller that the space is empty. After a chosen time delay the controller will use the setpoints for unoccupied space ( ) sensor covers of the space area of 38 m 2 (7x 5.5 m). Thus, an occupancy sensor can serve 1 or 2 chilled beams in open layout office. The building management system (BMS) may participate in operating mode definition by sending day and night information. In this document the day ( ) represents normal office hours and night ( ) refer to time when most people are out of office. The combination of occupancy sensor and BMS information defines the actual room mode (Table 9) where all modes have individual room air temperature and airflow rate settings. BMS Room Operation modes and airflow rate control Occupied Stand-by Unoccupied Occupied Table 9. Occupancy based space operation modes. Comfort settings Be ready for comfort, while saving energy Eco settings Comfort settings Room air temperature can be measured either by wall mounted user panel or Halton Rex chilled beam unit integrated temperature sensor (Fig. 19). Wall mounted user panel is the most beneficial, when feasible ceiling structure is available. The control unit integrated temperature sensor ensures most flexible layout structure of floor space. The Halton Rex chilled beam can be located either in open floor space or at dedicated room. The temperature sensor is measuring the temperature of the space, and controls the heating and cooling valves according to room air temperature set point. Fig. 19. Room temperature control panel and integrated temperature sensor. Fig. 18. Occupancy sensor and remote controller interface. Room level 20
Condense sensor prevents water coil condensation. In case of condensation the cooling valve will be closed and airflow control damper is set to predefined position (configurable: remain in normal control, closed or fully open). Normal cooling operation will be re-activated after a delay, when condensation has vanished. the heating valve or electrical heating is activated to prevent water coil icing. Normal control operation starts after predefined delay when the window is re-closed. Fig. 20. Condense sensor. Window switch is used to detect open window. If window is opened, both heating and cooling will be closed down (water valves and optional electrical heating). The airflow control damper of Halton Rex chilled beam is set to predefined airflow rate position (configurable: previous value, min, med or normal). In all cases the freeze protection mode stays active. The freeze protection mode is activated, if room air temperature falls below +8 C. At freeze protection Fig. 21. Window switch to detect open window. For demand based ventilation, CO 2 - concentration is used as an indicator of indoor air quality. Supply airflow rate is controlled to maintain the set target value of CO 2 when the occupancy ratio of person is changed. The set value of CO 2 - sensor is typically 600-900 ppm (Fig.22). Fig. 22. Control principle of indoor air quality with CO 2 - sensor. Room level 21
2.3 All-air system 2.3.1 Operation The Halton Vario system is based on active diffusers and constant static pressure. Room air conditions are controlled by modulating supply air flow rate. The controlling sensor can be a temperature sensor, a CO 2 sensor, a presence sensor or a combination of these. The throw pattern is constant in all operation conditions and thus draught risk is minimized. The flow is determined based on the device's opening (between 0 to 100%) and the underlying constant static pressure. Therefore, in order to assure proper work of the variable VAV diffusers, the level of a pressure in the inlet side should be strictly controlled. This is assured with installing active control dampers on the ducts serving different zones for maintaining constant pressure. Depending on how the change in the pressure of the zone duct is managed, the all-air terminal units are classified as pressure independent or pressure dependent units. A pressure independent VAV- unit can be defined as a device where the airflow control is not disturbed by the fluctuations of the static pressure at the inlet of the device. Keeping the required static pressure in the main ducts after the fan system can control terminal units. In Fig. 23, there is shown a concept of pressure independent VAV- system. A pressure dependent VAV-unit is a device where the airflow control is depending on the static pressure at the inlet side of the device. The airflow will vary with the fluctuations in static pressure before the device if the static pressure in the zone duct is not maintained constant. Halton Vario system's all-air system is based on the constant pressure ductwork and pressure depending active diffusers. In Fig. 24, there is shown a concept of pressure dependent VAV- system. Room level 22
Fig.23. A traditional VAV system with pressure independent space supply air terminal units. Fig.24. Halton Vario all-sir system based on the constant static ductwork. Room level 23
In traditional VAV system with pressure independent supply air terminal units, the pressure sensor SP set point value is kept on a level that can assure a proper work of a pressure independent VAV terminal unit at the design airflow rate. In pressure independent air terminal unit, the pressure drops over the device is typically 30-50 Pa. Room air temperature Room air conditions are controlled by modulating supply air flow rate. In cooling mode, during unoccupied mode the supply airflow rate at minimum value. In the sequence, the system is standby mode. When loads/pollutions increase, the airflow rate is increased to reach the set target value. Exhaust follows as a slave supply side. In heating mode, the operation is as in cooling except separate set of parameters The parameters that control the amount of air supplied to the room can be temperature, CO 2 or presence in the room. User could boost by hand switch the airflow and if window is open ventilation is stopped. In Fig. 25, there is shown a principle of the sequences for air temperature control. User can change the room air temperature set point with wall mounted or remote user panel. The set point shift range is defined as parameter. The default value of the shift is ± 3 C. Air quality Air quality is controlled based on room occupancy mod, temperature and indoor air quality. In offices, airflow rate is typically adjusted according to room air temperature and occupancy of the space. In meeting rooms together with room air temperature and occupancy, indoor air quality is controlled. Control of air quality is based on CO 2 sensor. Demand control ventilation involves varying the outdoor airflow rate in response to the quantity of occupants in the space. Halton diffuser Jaz increased automatically supply airflow rate and maintain the set CO 2 - level, When both room air temperature and CO 2 - sensors are used, the higher demand controls the supply airflow rate. Fig. 26 illustrates demand control ventilation with Halton Jaz active diffuser concept. BMS system adjusts to the system either night or day operation mode. In unoccupied spaces, there could be different airflow rate setting for night and day times. In Table 11, there are shown operation modes and airflow control functions in unoccupied and occupied spaces during day and night times. Fig.25. Halton Vario Room air temperature control sequences with Halton Vario air terminal unit. In Table 10, there is presented typical room air temperature set points. All presented values are parameters that user can change. Space mode Occupied 25 C Stand-by 26 C Unoccupied 28 C Cooling mode The actual Halton diffuser Jaz airflow rates depend on selected active diffuser size, level of static pressure in ductwork and controller parameter settings. The airflow range for the specific condition can be found from Halton HIT. In the unoccupied and stand-by modes, the Halton diffuser Jaz airflow is reduced and therefore heating or cooling capacity of the room unit is decreased. To prevent space temperature exceeding temperature setting, the controller will reset the unit airflow rate to normal airflow value until room conditions are again on the desired level. When the room air temperature has reached the set point, the airflow rate is then readjusted to the unoccupied and stand-by settings. Table 10. Examples of room air temperature set points. Room level 24
Office room, typical airflow operation Meeting room, typical airflow operation Fig. 26 Airflow rate is controlled based on occupancy, room air temperature and air quality. BMS Room CO2 Operation modes and airflow rate control 600-900 ppm Boost Increased airflow Increased airflow based on room conditions Occupied Normal airflow Adjusted by parameter Stand-by Reduced airflow Adjustable by parameter Unoccupied Eco settings Adjustable by parameter, or off Occupied Normal settings Normal diffuser airflow Table 11. Operation modes and the control of airflow rate. Throw pattern The draught risk may occur when using VAV terminal units together with supply air diffusers with constant discharge area, such as CAV supply air devices. The airflow pattern issuing from the diffuser, which discharges the air horizontally across the ceiling, has a natural tendency to attach to the surface. If the discharge area of the diffuser remains constant, the velocity of the supply air stream falls in direct proportion to the reduced airflow rate, resulting a risk of the supply air jet falling away from the ceiling. Max. flow 100% Min. flow 10% Fig.27. A scheme of the thrown patter of Halton Vario active diffuser. Halton Jaz all-air active diffuser controls throw pattern and thus prevent draught risk. Draught risk has been avoided with active diffuser work, which controls the diffuser openings in a way that relatively constant air velocity range is maintained and dumping will be avoided. The throw pattern of Halton Jaz active diffuser with maximum and minimum airflow rate is illustrated in Fig. 27. Halton Jaz Vario maintains thermal conditions With low airflow rates, the throw pattern is detached from ceiling: Coanda- effect is utilized even when airflow rates are at the minimum level Demand-based airflow rate saves energy. In Halton active diffuser, the airflow control and room air distribution components are integrated into the same terminal unit. The number of required system components is reduced compared standard VAVsystem. Room level 25
Active diffuser changes its outlet configuration automatically when controlling the supplied airflow rate. The air is supplied between a controlling plate with a distance that varies according to the airflow rate needed (Fig.28). The position of the plate is controlled by a traversing motor, which gets impulses from the controlling sensor locating in the room. The controlling sensor can be a temperature sensor, a CO 2 sensor, a presence sensor or a combination of these. The flow is determined based on the diffuser's opening, which is between 0 to 100% and the underlying constant static pressure. The basic idea behind the variable supply air diffuser is to maintain a constant velocity of the supply air stream discharged from the diffuser with a decreasing supply airflow rate. In zones where is several supply units, the airflow rate of the each units are controlled parallel. The number of the parallel control unit should not be higher than 4 and the maximum size of the control zone should not be larger than 50 m 2. Exhaust airflow rate could be ducted in each zone. Exhaust ductwork is possible simplified by only providing supply airflow rate in the spaces. Because of over-pressure to surroundings, exhaust is leaded to corridor and further towards centralized exhaust system. In rooms, there are installed transfer grilles. The transfer grilles should have required attenuation property to maintain acoustics privacy In the spaces. In Fig. 29, there is shown a n example of Halton Jaz all-air concept where the supply and exhaust airflow rates are balanced at zone level. In Fig. 30, there is an example of one floor of open layout office where the exhaust is centralized. It should be noted that in the centralized exhaust concept airflow rate balance is not really fulfilled in each rooms. The balance between supply and exhaust airflow rates is valid only at zone level. Fig. 28. A principle of the operation of Halton Jaz active diffuser. 2.3.2 Layout and control zone considerations Zone control covers room air temperature, outdoor airflow rate and exhaust airflow rate control schemes. The floor area of the control zone should not be more than 50 m 2. The number of parallel controlled units should not be more than five. To maintain exact space level airflow rate balance between supply and exhaust airflow rates, exhaust side should be provided control damper. Supply air flow rate is the master and exhaust airflow rate is the slave that follows supply airflow rate and maintain the set pressurization. To provide in both supply and exhaust demand-based control, the investment costs is higher than with centralized exhaust system. A balance between the supply and exhaust air should be assured in all operation conditions. The balance between supply and exhaust side is controlled at zone level. Based on the supply air flow rate measurement, the exhaust airflow rate is set to maintain the required pressurization or equal flows in supply and exhaust sides. Balanced control zone could be a room or several room units could form a control zone. Room level 26
'need a new clearer image without the red text* Fig.29 An example of the selection of control zones with Halton Jaz system. Fig.30. An example of installation in open layout office with Halton Jaz diffuser. Room level 27
System & component overview The Halton Vario system's Jaz controller is a room controller dedicated to complete room applications providing the control of cooling and demand controlled ventilation. In Fig. 31, there is described the possible options to integrate for room control scheme. Room controller and sensor could be factory installed into Halton Jaz active diffuser. The system can operate as standalone or connected to a bus system. In Halton Vario system Jaz diffuser, the room control package covers all required sensor, actuators and dampers that makes possible to control room air temperature in cooling mode and indoor air quality. System components 1) Halton Vario system Jaz active diffuser for cooling and ventilation, embedded travelsing actuar and control plate Occupancy sensor Carbon dioxide sensor Window switch Light and sun blinds control Occupancy sensor is a fundamental element of demand based room condition control. It detects presence of people and therefore adjusts the space either to comfort or energy saving mode. The remote controller is communicating with Halton multi-sensor. The multi-sensor includes occupancy sensor, light sensor and remote controller interface (Fig. 32). One sensor could cover of 15 m 2 floor area. When a person enters the room, the occupancy sensor sends a signal to the Halton Vario system's 2) Room controller, user interface and sensors User interface panel Room air temperature sensor Fig. 32. Occupancy sensor and remote controller interface. Wall control panel Halton Jaz diffuser integrated room controller alton Jaz Vario active diffuser ith airflow control damper Multi-sensor Room air temperature measurement to control space temperature Room controller CO2 sensor Occupancy sensor for demand based operation with Jaz airflow control, installed on suspended ceiling Air quality control with carbon dioxide sensor, CO 2 Remote control panel Cooling with Jaz airflow control Window switch Unit integrated temperature sensor Several user interface options, either wall mounted or hand-held remote controller Energy saving window switch operation Fig. 31. Components for the room controller. Room level 28
controller to inform that the space is occupied ( ). The controller set automatically airflow rate and room air temperature set point to a comfort level. When leaving the space the occupancy sensor sends an off signal to the Halton Vario system's controller that the space is empty. After a chosen time delay the controller will use the set points for unoccupied space ( ) and adjust the space into eco mode. The occupancy sensor covers of the space area of 38 m 2 (7x 5.5 m). Thus, an occupancy sensor can serve 1 or 2 Jaz active diffusers in open layout office. The building management system (BMS) may participate in operating mode definition by sending day and night information. In this document the day ( ) represents normal office hours and night ( ) refer to time when most people are out of office. The combination of occupancy sensor and BMS information defines the actual room mode (Table 12) where all modes have individual room air temperature and airflow rate settings. Window switch is used to detect open window (Fig.35). If window is opened, cooling with supply air will be stopped. The traversing motor of Halton Vario system's Jaz diffuser is set to predefined airflow rate position). For demand based ventilation, CO 2 - concentration is used as an indicator of indoor air quality. Supply airflow rate is controlled to maintain the set target value of CO 2 when the occupancy ratio of person is changed. The set value of CO 2 - sensor is typically 400-500 ppm (Fig.36). Fig. 33. Room temperature control panel and integrated temperature sensor. BMS Room Operation modes and airflow rate control Occupied Stand-by Unoccupied Occupied Comfort settings Be ready for comfort, while saving energy Eco settings Comfort settings Fig. 34. Perforated and solid bottom plate option for Halton Jaz Halton Vario system's units. Table 12. Occupancy based space operation modes. Room air temperature can be measured either by wall mounted user panel or Halton Jaz diffuser unit integrated temperature sensor (Fig. 33). Wall mounted user panel is the most beneficial, when feasible ceiling structure is available. The control unit integrated temperature sensor ensures most flexible layout structure of floor space. The Halton Jaz diffuser can be located either in open floor space or at dedicated room. The temperature sensor is measuring the temperature of the space, and controls the heating and cooling valves according to room air temperature set point. Fig. 35. Window switch to detect open window. Temperature and CO 2 - sensors can be integrated into perforated supply of Halton Jaz diffuser units. Sensor integration is available for solid and perforate bottom plate exhaust units. Alternatively wall mounted user panel where room temperature sensor is installed could be used. In Fig. 34, there is presented two available bottom plates option. Fig. 36. Control principle of indoor air quality with CO 2 - sensor. Room level 29
3. Zonal level 3.1 Operation based on constant pressure ductwork The constant static pressure ductwork guarantees the performance of the demand- based room terminals. Balancing and monitoring of space airflow rate is simple thanks the linear function of the space damper. In the same zone, it is possible to integrate constant and variable airflow rate terminal units. The purpose of supply ductwork is to deliver air from the fan to the room terminals which distribute air to the room. The required pressure differential required by the fan is a function of duct design. The objective of duct design is to size the duct such that: Enable easy change of airflow rates of spaces Minimize pressure drop Minimize noise Minimized cost Simplify Balancing Proper duct design required knowledge of the factors that affect pressure drop and velocity in the duct. Pressure in a duct system is the sum of two components, static pressure and velocity pressure. Static pressure is equal in all directions. Velocity pressure (dynamic pressure) is due to the momentum of the air. Velocity pressure is directional. Dynamic pressure can be calculated using Equation 1 where v is air velocity and ρ = density of air (1.2 kg/m 3 ). P dyn = ½*ρ*v2 (1)D Dynamic pressure plus static pressure (Ps) is equal to total pressure as shown in Equation 2. P t =P dyn +P s (2) If the outlet area is larger than the inlet area, the velocity pressure at the outlet must decrease. With a frictionless system where total pressure remains constant (P t ), static pressure (P s ) must increase at the same rate that velocity pressure (P dyn ) decreases. This phenomenon is known as static regain. In constant pressure ductwork concept this static regain is utilized. Zonal level 30
However, both ductwork and fittings introduce friction. In straight duct, friction losses are due to fluid viscosity. Friction losses of fittings are caused by turbulence between the main and branch ducts when the airflow path direction change. Friction losses are irreversible and are the conversion of mechanical energy into heat. Generally speaking, friction losses per unit length of straight duct are less severe than friction losses in fittings. Frictional losses occur at the expense of static pressure. Frictional losses do not impact velocity pressure. In Fig. 37, there is shown development of the total, dynamic and static pressure in a ductwork from the air intake to the terminal unit. The sum of the static pressure plus dynamic pressure at any point equals the total pressure in the duct system. The loss in total pressure is a direct result of the loss in static pressure due to frictional and turbulence losses. Most engineers use the equal friction loss method in ductwork design. Typical design value of the friction loss is 0.5-1 Pa per linear meter. With the equal friction loss method, this leads to air velocity of 4...6 m/s. This method is forcing the designer to constantly decrease the free area of the duct. In Fig. 38, there is described the total, dynamic and static pressures when the constant pressure loss method is used. With the constant static pressure method, the pressure loss of duct branch is regained by decreasing the air velocity after the branch. This happens when the duct is not reduced. The same size of ductwork and relatively low velocity (< max 3..5 m/s) guarantees in practice that the static pressure over the zone is constant. Fig. 37. Development of the static, dynamic and total pressure in a ductwork. Zonal level 31
The benefits of the static pressure ductwork are: Give flexibility to control space airflow rates with linear control dampers To ensure optimal pressure level in all duct branches Possible to integrate constant airflow rate (CAV) and variable airflow rate (VAV) units in the same ductwork Easy balancing: only static pressure should be checked Reduced noise generation in ductwork because of low velocities Lower fan power compared equal friction design because of low velocities Enables fan optimization by optimization damper positions for the required zonal static pressure Fig. 38. The change of the total, dynamic and static pressures with constant friction loss method. In a simplified case-ductwork (Fig. 40), there is demonstrated the difference of the pressure levels between the equal friction loss and constant static pressure methods. By maintaining the constant friction loss (constant air velocity), the static pressure reduces a lot over the duct zone. In this case-duct, the static pressure is at the first terminal unit 110 Pa and reduced to 30 Pa at the end even the set value of the zone is 150 Pa. The total pressure level of the main duct is 300 Pa and high velocity requires sound attenuator in all branches. Using low velocities and constant duct size in zone ducts, the static pressure maintain constant. There is no need of zonal sound attenuators. The total pressure level of the system is low (110 Pa) and thus the performance is energy efficient. Constant static pressure makes possible to introduce linear control of zone dampers and integrate CAV and VAV terminals in the same zone duct. Linearization gives also advantage for commissioning and airflow rate monitoring. By knowing the static pressure and the position of the damper, it makes easily to check the actual airflow rate of the space. Fig. 39. The change of the total, dynamic and static pressures with constant static pressure method. Zonal level 32
Fig. 40. The difference of pressure levels between the equal friction loss (panel above) and constant static pressure methods (panel below) (by courtesy of Skanska). Zonal level 33
In the zonal level, the supply and exhaust airflow rates should be balanced. In the supply side, the constant pressure damper is equipped with the measurement unit that gives the set value for exhaust side. Exhaust airflow rates follows as a slave the supply side. In Fig. 41, there is presented in Halton Vario chilled beam system a centralized exhaust concept where exhaust airflows are transferred through wall or ceiling installed transfer grilles towards to centralized exhaust point. The supply zonal duct static pressure is kept constant to ensure the optimum operation of the Halton Rex chilled beam and the Halton Jaz active diffuser. The MSS pressure sensor unit measures the duct static pressure and sends the value to the HFS pressure controller (0-10 Vdc). The HFS controls the duct static pressure level according to the set point by changing damper blade position. The HFS measures the actual airflow rate on supply duct and sends it (network variable and/or 0-10 Vdc) to the exhaust airflow control damper, HFB. The measured supply airflow rate is the setpoint to the exhaust airflow damper to ensure balanced ventilation in each zone. The exhaust HFB setpoint can be shifted related to the supply airflow to maintain the designed over-pressure or under-pressure balance of space. (Fig.42). The exhaust unit can be either a common exhaust grille or Jaz diffusers installed the spaces. Larger floor space can be divided to several duct zones and supply duct pressure level is controlled individually on each zone. This makes it possible to have different duct pressure levels on different zones and enables use of different products like Halton Rex beam and Halton Jaz diffuser at same floor space (Fig.43). In the main supply and exhaust ducts, there are installed static pressure measurement units. Those units give the set static pressure that the fan at airhandling unit control (Fig. 44). Fig. 41. Constant static pressure supply zone with centralized zone exhaust in Halton Rex chilled beam. Fig. 44. In large ductworks, the airflow rates should also balancing in the main air conduit. Zonal level 34
Room units Supply: Halton Rex chilled beam with integrated room controller Room units Supply: Halton Jaz active diffuser with integrated room controller Supply: Halton Jaz active diffuser with integrated room controller Exhaust: Common exhaust grille. Exhaust: Halton Jaz exhaust unit with equal outlook with supply unit Fig. 42. Constant static pressure supply zone with the combination of space and centralized exhaust. Fig. 43. Office floor plan with combination of Halton Jaz diffuser and Halton Rex units and with Halton Jaz units. Zonal level 35
3.1.1. Design of constant pressure ductwork The maximum variation of the static pressure could be 10-20 Pa to achieve inaccuracy of airflow rate less than 10 % at terminal units. By using low air velocity of 3.. 5 m/s and the constant duct size, it is possible to maintain constant static pressure in zone duct. Depending on the design airflow rates and duct topology, 10-20 terminal units could be installed in a zone. Constant pressure duct design is based on the static regain after duct section. The same size of zone duct and relatively low velocity guarantees that the pressure conversation from dynamic pressure to static pressure happens after the junction and the static pressure is almost constant over the whole zone duct. It should be noted in exhaust duct is not possible to utllize static regain principle. Ducts are sized based on constant velocity. The air velocity could be higher in exhaust duct than in supply air duct. The air velocity of 5 m/s could be used in exhaust ducts. Design starts with determination of the zones. The zone could be the whole floor area or part of the floor. The total required airflow rate is determined for the specified zone. The airflow rate is computed taken into account of the future needs to change space program. In this phase, it is important to consider what is the reserved ratio of the meeting (4 l/s per m 2 ) and office room (2 l/s per m 2 ). Also, the possible location (beginning or end of duct) of meetings room should be considered. By using in the starting point air velocity of 3..5 m/s, the duct size is determined. In practice, the space constrain gives the limit for possible duct size. For the round ducts, the maximum size is typically 400 or 500 mm. With wide rectangular ducts, it is possible to increase to the supply airflow rate with the same height of the space constrain. Ventilation rate Duct size 400 Duct size 500 Offices Meeting rooms Percentage of meeting rooms Percentage of meeting rooms l/s/m 3 l/s/m 3 10% 30% 10% 30% 1 4 590 400 905 620 1.5 4 430 335 675 525 2 4 340 290 535 455 Table 13. Zone estimation according to ventilation rates. In the Table 13, there is shown estimated floor areas of the zone that are possible to cover with 10 % and 30 % ratio of the meeting rooms ( 4 l/s per m 2 ) and office rooms ( 1-2 l/s per m 2 ). This depicts that with the following assumption the zone area is from 300.. 900 m 2. It should be noted that actual zones should be specified with the ductwork calculations where the static pressure levels over the ductwork are analyzed in different operation conditions. With the used ductwork topology and duct size, the changes in the static pressure over the zone should be analyzed. Larger variation in the static pressure leads higher inaccuracy with the airflow rate of the terminal units. Chilled beams operate typically at level of 80.. 100 Pa. In order to achieve airflow rate inaccuracy of less than 10% at room terminal level, the deviation of the static pressure level can t be higher than 10... 20 Pa. Design of the static pressure ductwork happens in the following steps: Airflow rate Calculate maximum zone airflow rate including the need of meeting rooms and boosted offices. Size of zone ducts Air velocity max 3..5 m/s in supply duct Air velocity of 5 m/s in exhaust duct Whole zone supply duct as equal size Exhaust duct sized by constant air velocity Connection ducts of terminal units The length of connection duct is recommended to be short < 3 m. Number of units Typically 10-20 units in duct branch (with ring duct number of units much higher) Static pressure sensor Locate the pressure sensor at 1/2-- 2/3 of the branch length in supply duct Exhaust duct sensor at 1/2 1/1 of the branch length Static pressure set point Design room units with Halton HIT and increase 5-10 Pa to the set point. Selection of the zone control damper 5-7 m/s with maximum airflow rate 1-2 m/s with minimum airflow rate Zonal level 36
Examples of ductwork topology The final ductwork topology and duct size determination is a project specific issue. Many cases trade-offs are required e.g. because of the space constrains and possible locations of air conduit. It is recommended to use symmetric ductwork. In large ductworks, ring ducts assist to maintain the constant static pressure. In Fig. 45, there is an example of the variation of the static pressure in a ductwork where the maximum air velocity and the total airflow rate are 5 m/s and 258 l/s. The constant size of round duct is 315 mm and the length of the duct is 50 m. The static pressure sensor is installed in the middle of the zone. The pressure drop of the room units is set to 80 Pa. In the duct zone, there are 9 offices with the airflow rate of 20 l/s. At the end of the ductwork, there is meeting area with two 40 l/s room units. In this case, the static pressure varied only 10 Pa in the main duct from the set value leading inaccuracy of 5 % in the room unit. The final ductwork topology and duct size determination is a project specific issue. Many cases trade-offs are required. Halton HIT Balance assists the design of the ductworks. It makes possible to analyze different ductwork topologies, the location of the static pressure sensor and duct sizes. Hit Balance makes possible to optimize solution for the set design demands and to guarantee the performance. In Fig. 46, there is an example of floor ductwork design where the static pressure levels are analyzed in a complicate ductwork. It is recommended to use symmetric ductwork. Also in large ductworks, it is recommended to introduce ring ducts to maintain the constant static pressure. In Fig. 47, there is an example of the floor level where the ring duct concept is introduced. Fig. 47. An example of ring duct design (by courtesy of Skanska). needs a new figure so that can see the figures' Fig. 45. The static pressure and air flow rates in a case-study constant pressure duct. Zonal level 37
Fig. 46. An example of complicate ductwork where the performance is optimized with Hit Balance. Zonal level 38
3.1.2 System & component overview The constant static pressure level is maintained in the ductwork with HFS- control damper (Fig. 48) and the static measurement unit MSS (Fig. 49). For HFScontrol damper, there is integrated with flow measurement unit ( 0-10 V output signal) as an accessory. The operation range of the measurement device is from 1-7 m/s. Sound attenuator with different lengths (600 and 100 mm) is also available as an accessory. The MSS unit includes static type pressure measurement sensor with digital display. Adjustable pressure measurement ranges corresponding to 0-10 VDC output signal. The measurement inaccuracy of MSS less than ± 10 % in typical applications. Fig. 48. Zone damper HFS. In the exhaust side as a slave for supply, HFB control damper is used (Fig. 50). The variable airflow damper HFB contains an averaging airflow measurement probe, airflow controller and actuator. Airflow is controlled based on actual flow measurement by changing the damper blade position. The operation range of the measurement device is from 1-7 m/s. Sound attenuator with different lengths (600 and 100 mm) is also available as an accessory. Fig. 49. Measurement unit MSS. In the rectangular ducts, control damper UKV is used to maintain constant static pressure or the set airflow rate (Fig. 51). UKV is suitable for large air flow rates from face velocity of 1 m/s up-to 11 m/s in some applications. UKV width is from 200 mm to 1600 and height from 200 mm to 1000 with the increments of 50 mm. Fig. 50. Zone damper HFB. Fig. 51. Zone damper UKV for rectangular ducts. Zonal level 39
3.1.3 Example of the specification of zone airflow rates Application of Halton Rex Chilled Beam with Centralized Exhaust In Halton Rex chilled beam solution, airflow rate is varied in response to space and zone occupancy. In unoccupied spaces, outdoor airflow rates are set to minimum level e.g. at 0.3 l/s per m 2. When the room is occupied, airflow rates are increased (e.g. 1.2-2 l/s per m 2 ) to meet air quality targets. In meeting rooms when occupancy rate increased or there is a need to boost airflow rate, the airflow rates are modulating e.g. up to 4 l/s per m 2. Thus in the zone duct level, the airflow rate varied a lot. In Fig. 52, there is shown a Halton Rex chilled beam concept for zone level airflow balancing. In supply duct, constant static pressure is maintained in supply duct and the measured supply airflow rate gives the set value for exhaust damper. Selection of control dampers is based on the duct size and the minimum and maximum airflow rate of zone damper. When the maximum airflow rate is determined, there is need to specify what is the ration between meeting and office rooms. Typically 15-50 % of space area is reserved for meeting rooms. As an example of the zone design, there is the area of 240 m 2 where are 24 pieces of 10 m 2 room modules. As a breakdown of the room units, there are 18 offices (15 l/s per module) and 6 pieces of meeting rooms (40 l/s per module). Thus, the total airflow rate is 510 l/s. With the selection of 400 mm round duct, this leads to the maximum velocity of ~ 4 m/s. The minimum airflow rate is 0.5 l/s per m 2 means 120 l/s and 1 m/s velocity in the ductwork. Fig. 52. Airflow rate control at zonal level with a Halton Rex chilled beam concept. Zonal level 40
Halton Vario Optimizer (HVO) By optimizing fan power, it is possible to reach a significant energy savings. Proportionality laws set a correlation where the power consumption of the fan changes to third power with volumetric flow ratio. Halton Vario system's Optimizer maintains duct pressure as low as possible and communicates with zonal pressure control dampers. System solution By optimizing fan power, it is possible to reach a significant energy savings. Proportionality laws set a correlation where the power consumption of the fan changes to third power with volumetric flow ratio. In demand-based system, room airflow rate is controlled in room units. Constant pressure ductwork is maintained with zone control dampers. If the static duck pressure is not optimized, the pressure is unnecessary high. Halton Vario Optimizer (HVO) master module: Communication to AHU Network analog (0-10V) (4-20mA) Monitors all slave modules AHU minimum and maximum air flow The HVO slave Communication to HVO master Network Up to 6 constant pressure damper Damper position Individual airflow measurement 4 inputs for fire dampers Zone damper Communication with HVO slave Network Damper position Airflow Halton Vario system's Optimizer consists three hierarchic levels operations: master level, zonal level HVO- slave units and zonal dampers whose functions are described below: In Fig. 53, there is presented the system architecture of HVO- concept. Fig. 53. The system architecture of Halton Vario fan optimizator (HVO). Zonal level 41
Operation The target is to maintain a duct pressure level that is as low as possible in order to save on fan power consumption. The Halton Vario system's Optimizer HVO monitors the opening of each zone damper and detects the most open damper. If this most demanding and open damper has unnecessary high pressure drop loss level, the HVO adjusts the Air Handling Unit s pressure at the optimal level. This is conducted with the Trim and Response Logic leading to a lower pressure level in the entire whole system. The HVO-slave monitors all the dampers position of each damper in the zone. In each zone, a pressure sensor is installed (MSS) to the zone damper that registers the pressure in each zone. In the zone damper, the air flow rate is also measured with the measurement device. Information of the opening of the damper and air flow rate is sent to the HVO slave. HVO slave- units maintain the adjusted static pressure and airflow rate in the zone and thus guarantee excellent thermal comfort in each work place. If the damper position is according to the actual need for flow and static pressure, there is no need for this is a Belimo image*. Can we use it? should we put below Belimos name? Fig. 54. Optimization of the static pressure level with Halton Vario system's Optimizator. Zonal level 42
adjustment. But if the damper opening is above the specified position, the HVO-slave will send a message the HVO master that more airflow is required. The HVO-master sends also a message to the AHU to increase the static pressure to get more airflow to the spaces. If the damper opening is below a certain point e.g. 60%, the HVO-master sends a signal to the AHU to decrease the pressure. This ensures that the most open damper position will be increased. The values are sent every 2 minutes (adjustable) to adjust the static pressure. The HVO master maintains the set minimum static at the air-handling. Also, the HVO computers the sum of the zone airflow rates and guarantees that the zonal airflow rate is over the set minimum airflow rate. HVO fan optimization happen with following three steps (Fig. 54): 1. Zone control dampers maintain the set static pressure 2. Airflow rate reduces and zone dampers are closing to maintain the set static pressure 3. HVO reduces the total static pressure level at airhandling unit and zone dampers opens to optimal position that maintain the set static pressure in zone levels. Communication Halton Vario system offers a total solution from management to room conditions, zone static pressure and the pressure optimization of air-handling unit. Halton Vario system supports the most common communication protocols: LON, BACnet and Modbus. Halton Rex beam and Jaz diffuser control systems covers the operation at room, zone and central level (Fig. 55). Halton Vario system's Master- unit is integrated to building management system (BMS) where operation of the system is monitored and the collected information is utilized in facility management. Fig. 55. Halton Vario system control platform and integration with BMS. Zonal level 43