s BLC.A Boiler Load Compensator Introduction BLC.A The prime function of the BLC.A is to adjust boiler output temperature to ensure the boiler operates at or near its peak efficiency whilst maintaining comfort conditions. Typical boiler efficiency curve The BLC.A cannot increase the efficiency of the boiler - but it WILL ensure it runs at or near its peak efficiency. The BLC.A is a heating controller which can be used as either a weather dependent compensator or as a system load compensator. Technical Description The BLC.A must be set on site to suit one of the following types of systems. Gravity or fully pumped systems. Combi boiler systems. A full description of the various types is given in the setting up section. The following optional functions must also be set or switched on or off depending on the system type and your preferences. Pump overrun, in addition to boiler pump overrun which will be preserved Pump kick - runs for minute every 4 hours 3 Frost protection - opens heating valve in frost condition to provide full frost protection to heating circuit 4 Max number of boiler burns per hour BLC.A PAGE
5 Min boiler return temp 6 Max outside temperature cut off 7 Manual override duration 8 Start up boost 9 Boiler output reduction as building warms up Choice of Operation Weather Compensation Load Compensation Recommendation System Selection and Sensor Locations Mounting Setting Parameters and Commissioning NB 6, 8 & 9 are only available in weather compensation mode. Full details are given later. The BLC.A can be installed to operate in one of two ways As a weather compensated controller or As a load compensator The BLC.A will adjust the circulation temperature of the boiler depending on the outside temperature. As it gets warmer outside the boiler temperature will be reduced and vice versa. To operate in this way the outside temperature sensor must be fitted on a north (or north east) facing wall. If this cannot be achieved the BLC.A must be set up as a load compensator. In this mode, the BLC.A adjusts the boiler temperature according to the load on the system, which it does by monitoring flow and return temperatures. As the load reduces (i.e. as the building warms up) the boiler temperature will be reduced. In both the above cases, the BLC.A controls the boiler output by adjusting the circulation temperature. Whilst both methods of operation will improve the overall system efficiency, the load compensation method will be easier to install in most properties because an outside temperature sensor is not required. The weather compensation method will usually give higher overall system efficiency. Having decided on the mode of operation required, the two sensors should be installed. Outside sensors must be mounted on a north or north-east facing wall at high level and away from sunlight and any sources of heat such as windows, ventilators, flues etc. The cable can often be run through the loft to get across the building. The locations of the pipe temperature sensors are dependent on the system type - refer to the circuit diagrams and notes to the setting tables. Sensor cables must be mains rated. The outside sensor should be fitted inside the white plastic protective cover with the opening facing downwards. The detachable terminal block provided can be used to connect inside the cover or to extend the cable within the building. Pipes should be cleaned before fitting the sensors. The sensors should be fixed in position with at least two layers of the aluminium adhesive tape provided. The tape should overhang the end of the sensor assembly by about 0mm. the tape down well around pipe and sensor to ensure good adhesion. Replace pipe insulation if fitted. The BLC.A should be mounted as near as possible to the existing wiring centre or junction box. All wiring (except for the sensor cables) should be run to a junction box. The BLC.A should not be used as a wiring centre. Once the wiring has been completed according to the appropriate diagram it will now be necessary to set up and commission the BLC.A. Select the appropriate chart for Weather or Load compensation and fill in the desired value entries to suit the system. Most entries are factory pre-set with valves to suit standard systems. These may be altered to suit different systems or improve performance. It is recommended to start off with the factory settings. BLC.A PAGE
Normal Function Display User Keys Programming for LOAD compensation mode The following values are displayed on the screen during normal operation. Fn: O Normal operation Fn: SO Normal operation - saving mode. The flashing S prefix means that the boiler is being held off by the BLC.A. Fn: Frost protection is operating (plant is on because a frost condition has been detected). Fn: Outside temperature cut-off is in operation (outside temperature is higher than the set cut-off temperature). Fn: S Heating programmed but held off by BLC.A due to high outside temperature. Fn: 3 Boiler is on full output because manual override has been pressed (will self cancel after the set time). Four keys are provided for setting and override factors,,, and. The manual override, is for end user operation, the, and keys are only needed for setting up and commissioning. Setting the parameters on the BLC.A. Set boiler thermostat to maximum. USE THE KEYS:,, and, as indicated in the chart below. Where a desired value is shown it indicates our recommended value. Empty boxes require entries to be made to suit the application. To revert to factory settings: Switch off hold down, switch on release. Normal display on BLC.A will be FN : O (or other value as listed on page : normal function display). To start parameter setting routine press. Read out A Factory set Function Compensation mode Range = Weather = Load Desired value Comments Compensation mode required A System type = pump/gravity = combi Sets system type. See note. A3 L L L3 9 6 Auxiliary controls Return temp low limit Load/temp slope Boiler response to load = room stat = TRV 0 to 50 C to 6 0 to 40 9 6 Set control type. See note. For oil-fired boilers. Check data sheet. See note 3. Set system warm-up rate. See note 4. Increases boiler output. See note 5. UNDER HEATING PROBLEM?. Check that room thermostat is on.. Increase L3 by 4 points, e.g. from 6 to 0. WARM UP TOO LONG? Increase L by points, e.g. from 9 to. U U U3 P F C h 0s hr 5m hr Pump run-on after DHW Pump run-on CH pump run-on Pump kick Frost protection Min. burner cycle time Override duration 0 to 30s 30 to 50 C 0. to 8 hours 0 = off = on 0 = off = on 5 to 60 mins to 4 hours 0s hr 5m hr Operates after DHW. Thermal pump run-on. See note 6. Timed run-on. See note 7. Runs pump min every 4 hours. See note 8. See note 9. See note 0. Sets manual override duration. BLC.A PAGE 3
Programming for WEATHER compensation mode Setting the parameters on the BLC.A. Set boiler thermostat to maximum. USE THE KEYS:, and, as indicated in the chart below. Where a desired value is shown it indicates our recommended value. Empty boxes require entries to be made to suit the application. To revert to factory settings: Switch off hold down, switch on release. Normal display on BLC.A will be FN :O (or other value as listed on page : normal function display). To start parameter setting routine press. Read out Factory set Function Range Desired value Comments A Compensation mode = Weather = Load Compensation mode required A System type = pump/gravity = combi Sets system type. See note and 9. A3 L Auxiliary controls Return temp low limit = room stat = TRV 0 to 50 C Set control type. See note. For oil-fired boilers. Check data sheet. See note 3. L L3 L4 b 9 +3 C 8 C 50% Outside/inside temp slope Offset value Outside cut-off Start-Up boost to 6 5 to +5 C 0 to 5 C 0 to 50% 9 +3 C 8 C 50% Slope angle. See note. Allowance for internal heating. See note. Mild weather cut-off. Slope increase at start-up. See note 3. Underheating problem? Check that room thermostat, if fitted, is on. b b3 d hrs 0.5hr 0% Qualifying time Start-Up boost duration Return temp tail-off to 9.0 hours 0 to 5.0 hours 0 to 50% hrs 0.5hr 0% Off time required. See note 3. See note 3. See note 3. Takes too long to heat up? Increase Start up boost time (b3) by / hour or press. Underheating in mild weather? Reduce offset (L3) by 3. Underheating in cold weather? Increase slope (L) by. Underheating towards end of heating period? Reduce tail off percentage (d). d d3 U U U3 P F C h.5hrs hrs 0 secs hr 5 mins hr Standard slope time Period of d spread Pump run-on after DHW CH pump run-on temperature CH pump run-on time Pump kick Frost protection Min burner cycle time Override duration 0 to 5 hours 0 5 hrs 0 30 secs 30 to 50 C 0. to 8 hours 0 = off = on 0 = off = on 5 to 60 mins to 4 hours.5hrs hrs 0 secs hr 5 See note 3. Time over which d is spread. Operates only after DHW use. Thermal pump run-on. See note 6. Timed run-on. See note 7. Runs pump min every 4 hrs. See note 8. See note 0. See note. Sets manual override duration BLC.A PAGE 4
Notes Combi boilers are expected to have internal circulation pumps which are not controllable externally. Combis may or may not have a built in time-switch. Combi boilers intended for use with an external pump should be set up as pump/gravity type (A: ). Systems with full TRV control and a room thermostat should have A3 set to and the room thermostat set to operate as high limit only (e.g. ). Hybrid systems having some rooms controlled by TRVs, but which rely on a room thermostat for overall control should have A3 set to, just as they would for a room thermostat controlled system. 3 Compensating controllers need to operate over a wide range of boiler temperatures to achieve high efficiency. Unless there is an overriding reason to do so, e.g. oil boiler, do not increase the return low limit setting. 4 This factor matches the boiler heat-up rate to that of the building and thus prevents temperature overshoots. If set too low it could prolong the heat up time. 5 This factor controls the rate of temperature increases in response to load. Too high a setting will cause temperature overshoots and too low will cause underheating. 6 The pump run-on temperature setting ensures that the pump is kept running to signal temperature information to the BLC.A. This parameter cannot be set higher than L. Not offered for combis. 7 The pump run-on time prevents the pump running for too long if no further demand is encountered. Whichever of U and U3 is reached first will stop the pump. This time setting is also used to determine when a room thermostat system is to be considered as off. Not available for combi systems. 8 Pump kick should be set OFF for combination boilers. 9 When installing the BLC on a gravity system there must be a cylinder thermostat or a pipe thermostat fitted. 0 With frost protection selected, if a pipe sensor is below 4 C or the outside sensor below C the CH valve will open and the pump will run. If the pipe sensor does not see a temperature of 5 C within 6 minutes, then the boiler will be fired until a pipe temperature of 6 C is achieved. In the case of combi boilers, the boiler will be run for 3 minutes or more in order to achieve the same result. The process will repeat once per hour. Frost protection is not provided for combi boilers with internal time-switches. The minimum cycle time is the time from boiler firing to next firing. With a setting of 5 minutes the boiler once fired cannot be re-fired until 5 minutes has elapsed thus producing a maximum of burns per hour. Five minutes is the most effective setting, but if the boiler is noisy, the setting can be increased to reduce annoyance to the householder. The slope setting controls the relationship between outside temperature and the circulation temperature as shown in the diagram overleaf. The factory setting of 9 for conventional boilers should be changed to 7 for condensing boilers and for underfloor heating. 3 There is a certain amount of heat generated by electrical appliances such as lighting, cookers, PC s, HiFi s, etc. This is taken into account by the Offset value. It has the effect of moving the slope line sideways making the outside temperature appear slightly higher than it is. See the diagram overleaf. 4 Start Up Boost and Return Temperature Tail Off are used to speed up building pre-heat and then gradually reduce heat input as the building fabric warms up. This ensures the best comfort and efficient use of fuel. Not available to combi systems having internal time-switches, in such cases b and d must be set to 0%. BLC.A PAGE 5
Weather Compensation Graph Offset = 3 C i.e. the internal heat gains are assumed to be equivalent to an outside temperature 3 C higher than the temperature actually measured. Default Slope = 9 NB Slope 9 gives 70 C return at - C (outside temperature) Weather Compensation Operation Required system temperature (based on outside temperature) example at constant outside temperature BLC.A PAGE 6
When starting from cold the boiler must produce max. heat to raise the temperature of the building as quickly as possible. Once the system is up to temperature we can allow the boiler output to tail off until we reach the final required temperature. The above graph shows how this is achieved and cross references the adjustable parameters included in the BLC.A program. The values given in the explanation are the factory set values. Starting from a system off position b hrs System off time after which warm up boost is available i.e. if the system (clock) has been off for hrs it will automatically start in warm up boost mode. bi 50% During warm up the return temp will be raised to 50% of its normally required value to ensure fast warm up. b3 /hr Having raised the return temp to its Boost level the BLC.A will maintain this new temp for /hr ensuring that the building has reached temperature. d hrs The return temp is now allowed to fall to the calculated normal temp over a period of hrs. di 0% Having now run for hrs at normal temp we can allow the return temp to tail off by approx. 0% (without drop in room temp). d3 hrs This drop in temp is spread over a period of hrs until the final working temperature is reached. The following parameters are available to interrogate the BLC.A. Access, when in the FN: display, by holding down, and pressing, then scroll with and. Exit display by pressing. y Flow/outside temperature. This will also give sensor check. If <-9 then sensor is shorted, if >99 then sensor is open circuit. y Return temperature (actual). This will also give sensor check. If <-9 then sensor is shorted, if >99 then sensor is open circuit. y3 y4 y5 y6 Target return temperature (desired return temperature as calculated by BLC.A). Demand status c = CH demand, d = DHW demand, indicates whether CH or HW has been selected on time control (and stats if fitted are calling for heat). Pump and burner status, p = pump, b = burner, indicates whether pump and boiler are on ( pump on - boiler off indicates saving mode). Valve status, c = ch valve open, d = dhw valve open (if known) indicates required valve positions. 999 Siemens Building Technologies Ltd. BLC.A PAGE 7
Siemens Building Technologies Ltd. Landis & Staefa Division Hortonwood 30, Telford TF 4ET Tel: (095) 677690 Fax: (095) 60059 Help Desk Tel: (095) 60048 Orders Fax: (095) 60063 BLC.A PAGE 8