MBNA Career Services Center The Pennsylvania State University University Park Campus

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1 University Park Campus Variable Air Volume System and Dedicated Outdoor Air System with Fan Coil Units Comparison AE Senior Thesis Primary Consultant Spring 2003 Dr. Bahnfleth

2 Table of Contents Executive Summary.. 3 Background. 4 The Building s Name Interior Description Site and Architecture 6 Site Conditions Exterior Architecture Existing Building System Conditions.. 8 Electrical Structural System Design (Depth Study) Proposal Background on DOAS (Dedicated Outdoor Air System) Design Energy Comparison Cost Analysis Conclusion Electrical System Design (Breadth Study) 25 Proposal Design Conclusion Structural System Design (Breadth Study).. 27 Proposal Design Conclusion Overall Conclusion.. 30 Acknowledgements. 31 Appendix A HAP (Hourly Analysis Program) Design Information B Drawings of DOAS/FCU System C Energy Wheel and Air Handling Unit Information D Fan Coil Unit Information E Electrical Drawings and Panels Penn State University AE Senior Thesis Spring 2003 Page 2 of 32

3 Executive Summary The MBNA Career Services Center is a 44,140 sq. ft. office type building with three floors of occupied space and a basement located at University Park, Pennsylvania. The MBNA Center is one of Penn State s more recent building projects, with construction completion in July The overall project costs total approximately 9.5 million dollars. The mechanical system design analysis compares the existing variable air volume system with the proposed dedicated outdoor air system paralleled with fan coil units. The analysis involves comparing the energy usage and first cost of the two mechanical systems. The implications of replacing the current system with the DOAS/FCU system are investigated with regards to the electrical and structural systems. The existing mechanical system is comprised of three air handling units that distribute a total of 40,000 cubic feet per minute to variable air volume boxes that regulate the air flow to each space or groups of spaces. The chiller plant in the Computer Building, an adjacent building, provides the MBNA Center with 44 degree chilled water. The total cooling coil load is 1600 MBH. Hot water is used for heating which is provided to the building from Penn State s steam distribution system. A heat exchanger with in the building transfers heat from the steam loop to the building hot water loop. The proposed mechanical system has one air handling unit that conditions 100% outdoor air for the entire building and fan coil units throughout the building mix the 100% outdoor air with return air to be supplied to the spaces. The air handling unit has an enthalpy wheel to recover energy from the return air stream and the unit distributes approximately 11,500 cubic feet per minute of outdoor air to the fan coil units. Most of the fan coil units are between cfm. The chilled water is still provided from the Computer Building for the time being, but the MBNA Center will be connected to the University Chiller Plant system within the next few years. The total cooling load on the air handling unit cooling coil is 322 MBH. The cooling load on the coil for all the fan coil units combined is 828 MBH. The energy comparison between the two systems is based totally on electricity usage since the building does not have a chiller plant or a heating plant. The DOAS/FCU system uses less electricity than the VAV system primarily because of a reduction in fan usage. Over the course of a year, 22% of the electricity used by the VAV system is from the HVAC system whereas only 11% of the electricity used by the DOAS/FCU system is from HVAC equipment. From a first cost analysis of the two systems, the dedicated outdoor air system with fan coil units is more expensive due to the cost of the enthalpy wheel, fan coil units, additional chilled water piping to each fan coil unit and condensate piping. Considering just mechanical related costs, the DOAS/FCU system is $14,326 more expensive. The reduction in the size of ductwork for the proposed system saved $20,742 but this savings is not enough to out weigh the additional costs of equipment. By incorporating the costs alterations associated with electrical and structural changes, although minimal, results in a net difference of $10,800 over the cost of the variable air volume system. Penn State University AE Senior Thesis Spring 2003 Page 3 of 32

4 Background The Building s Name The MBNA Career Services Center has brought together all of Penn State s career related services into one building. Prior to the construction of the building, these services were scattered across campus at various locations. The MBNA Center opened in late July 2002, one year after construction began. One unique aspect about the building is evident in its name. The MBNA Career Services Center is the first building at Penn State s University Park campus to include the name of a corporation in its title. MBNA America provided funding for the design and construction of the building. Contributions were also made by companies who wished to have their own interview room when visiting campus to interview students. The companies that decided to make a donation received plaques which are mounted just outside the door to their interview room to display their company name. Each company also received wall space along the corridor to hang an abstract about their company. Interior Description The basement level of the MBNA Center does not span the full length of the building and only takes up the middle third portion of the buildings footprint. The basement is primarily used to house mechanical equipment including two air handling units which occupy a majority of the space. There is also a Janitors Room, Electrical Room and Telecommunications Room in the basement. The first floor is the entrance level. There are three side by side program spaces that are separated by accordion style folding partitions which can be opened to create a large meeting area. Several offices as well as a career information room are located on the first floor. A small café is located near the center of the first floor for refreshments and gatherings. Light wells on each side of the café are created from skylights located at the second floor roof level. Figure 1 This picture was taken while on the second floor looking towards one of the skylights. Behind the three interior windows are interview rooms which also benefit from the daylight. Penn State University AE Senior Thesis Spring 2003 Page 4 of 32

5 Figure 2 Interview room with an interior window located along a light well to capture natural daylight. An open staircase located in the center of the building leads from the first floor to the second floor only. A majority of the second floor is comprised of interview rooms; there are forty-four of them to be exact. One of these interviews is seen in Figure 2 above. There are two large meeting rooms, several conference rooms as well as a few offices located on the second floor. For students arriving for an interview either before or after a class, there are changing rooms available for the student s convenience. The third floor occupies the front half of the buildings footprint. Located on the third floor is the Morgan Center, which provides an area for student athletes to speak with advisors. There is also a mechanical room on the third floor that contains an air handling unit to condition the third floor. Penn State University AE Senior Thesis Spring 2003 Page 5 of 32

6 Site and Architecture Site Conditions As mentioned early, the MBNA Career Services Center is located along Bigler Road across from the outdoor pool and just south of the Computer Building. The location on the site where the MBNA Center sits today was originally a parking lot. Since the Eisenhower Parking Deck is located on the west side of the MBNA Center, parking is conveniently available for visitors. The site is ideal with regards to location since it is roughly a five minute walk to the Bryce Jordan Center which is where both the Fall and Spring Career Fairs are held each year. The admissions office, in Shields Building, is also only a few minute walk to the MBNA Center. The size of the site is approximately 75,000 square feet with the buildings footprint occupying 15,400 square feet and the south half of the site containing trees and a steeper slope. Because of the long and narrow shape of the building, there is minimum area on the east and west sides of the building. The south side of the building is landscaped beautifully. Doors located near the café on the first floor provide a way for people to sit on the patio located on the south side. Architecture The architectural components of the building are primarily functional since each space is created with a specific purpose in mind. However, the aesthetics of the MBNA Career Services Center are very pleasing and inviting to students, companies and visitors to Penn State. Figure 3 MBNA Career Services Center main entrance. Penn State University AE Senior Thesis Spring 2003 Page 6 of 32

7 Along the front exterior of the building there are six banners hanging on poles each one representing a different college within Penn State. The façade of the building is mostly brick with some vertical concrete elements which give the otherwise long and short building more height. The semi-circle protrusion at the front of the building makes the entrance more prominent and displays the name of the building (see figure 3 below). A band of windows wraps entirely around the building near the roof on the third floor. Large six foot overhangs accentuate the roof and provide shading for the high window area on the third floor. The overhangs above the windows on the south side of the building are purely decorative since they are not solid and allow large amounts of sunlight through. An image of these overhangs can be seen in the bottom right picture on the cover page of this report. Balconies on the second and third floors provide occupants an opportunity to get some fresh air without having to travel down to the first floor. Penn State University AE Senior Thesis Spring 2003 Page 7 of 32

8 Existing Building System Conditions Overview The mechanical system within the MBNA Career Services Center is a Variable Air Volume (VAV) System. Three air handling units (AHUs) within the building distribute conditioned air to VAV boxes located throughout the building. In some cases fan powered boxes (FPB) are used instead of VAV boxes because of a higher load within certain spaces. The MBNA Center does not have a chiller plant therefore chilled water for the building is piped over from the Computer Building located just to the north. Steam from the campus wide distribution system provides the building with hot water for heating. Air Side Description Air handling unit #1 is located in the basement and is the smallest of the three air handling units. The volume flow rate of air distributed by AHU-1 is 3500 cfm and the cooling coil load on AHU-1 is 238 MBH. The function of AHU-1 is to provide ventilation air to the three fan powered boxes located in the three adjacent program spaces on the first floor. The distribution of supply air to the remaining rooms on the first floor along with the second floor is provided by AHU-2, with a volume flow rate of 28,000 total cfm and a cooling coil load of 1088 MBH. Supply fan operation is based on a time of day schedule programmed into a DDC system. The typical schedule for operation is 8a.m. to 5p.m., Monday through Friday. Occupied supply air temperature control is based on 72 degrees F space temperature. Economizer dampers, a cooling coil and a heating coil maintain the temperature of the supply air. On the third floor of the MBNA Career Services Center is air handling unit #3, which provides 7900 cfm of air to spaces on the third floor. The cooling load on the coil in AHU-3 is 260 MBH. The outdoor air intake for this air handling unit is located on the west side of the building. The location mechanical room on the third floor is near the center-front of the building which requires additional outdoor air ductwork and more importantly the mechanical room occupies valuable floor area on the third floor. Once the supply air leaves the air-handling units, variable volume boxes with hot water reheat or in some cases fan powered boxes regulate the amount of air entering the occupied spaces throughout the building. Typically, there is more than one room on a single VAV box which can present some control issues. However, in most of the cases all of the rooms connected to a certain VAV box have the same exterior exposure and occupancy therefore each room will more than likely see the same load conditions. The telecommunications equipment room and the two server rooms located with in the MBNA Career Services Center are conditioned with their own split system air conditioning units. Since the equipment in these rooms are highly sensitive to climate change, the independent system for each of these rooms will maintain the required conditions without regards to the buildings central system. Packaged controls regulate the temperature and humidity within each of these Penn State University AE Senior Thesis Spring 2003 Page 8 of 32

9 rooms. The DDC system monitors these conditions and sounds an alarm if the temperature or humidity is beyond the limits. Additional heating is provided by cabinet heaters near the entrances since the heating loads in these spaces during the winter months can be too extreme to condition adequately with the building conditioning system. Water Side Description The MBNA Career Services Center receives chilled water from the Computer Building. Since the total cooling load for the building is around 133 tons, it was decided that the chiller plant at the Computer Building would be able to handle the additional load. This decision was not made until after careful consideration of the implications of designing a chiller plant for the MBNA Center, however. The building has a relatively low cooling load which would eliminate the option of using a water cooled chiller because of not being feasible. The next best option to piping chilled water from the Computer Building would have been to use an air cooled chiller. However, integrating the equipment with the site created problems for the designers. So, in order to reduce cost and save energy, chilled water is fed from an already existing chiller plant in the Computer Building to the MBNA Center. Two pumps, one duty and one stand-by, are located in the basement to circulate the 45 degree F chilled water to the air handling units in the basement and to AHU-3 on the third floor. The total volume flow rate is 265 gpm with a 7.5 hp motor. The hot water distributed to the heating coils at the air handling units and the reheat coils at the variable air volume boxes is available after steam from Penn State s campus wide system is sent through a shell and tube heat exchanger. The steam enters the building at 150 psig and is reduced down to 10 psig almost immediately. Later in the system the steam is reduced again to 2 psig before entering the heat exchanger. Hot water leavings the heat exchanger at 180 degrees F. Two pumps, one duty and one stand-by, are used to circulate the hot water throughout the building. The total volume flow rate is 130 gpm with a 5 hp motor. Electrical The electrical service entrance is located on the north side of the MBNA Career Services Center below the front entrance to the building and the transformer vault is located on the west side of the building. The main power feed is 208Y/120V 3P 4W, 1200A service. Emergency power is provided by Penn State through a separate service. A main distribution panel provides protection for three lighting panels, six power panels, mechanical panel and an outdoor lighting panel. One lighting panel for each floor and two power panels per floor with the west half of the building on A panels and the east half on B panels. Lighting panels are 100A, 42 breaker panels and contain plenty of space for additional load. The power panels for the first floor are 225A with 84 breaker slots. The power panels for the second and third floors are 225A panels with 42 breakers. The only panel that has a limited number of additional breaker slots is the third floor A power panel. Penn State University AE Senior Thesis Spring 2003 Page 9 of 32

10 The lighting on the exterior of the MBNA Career Services Center consists of metal halide lamps with an up/down fixture that illuminates the building façade. On the interior there is indirect and direct fluorescent lighting throughout, primarily 2x4 parabolic fluorescent fixtures. Decorative pendants of various shapes and colors hang over reception desks. See figure 3 for an example of these pendants. Adjustable downlights accent the abstracts provided by contributing companies along the second floor corridors making the space feel like a gallery. Figure 4 Decorative Pendants accent counter at the Café/Eatery on the first floor. Daylighting within the building reduces the need for artificial light and saves electrical energy. A majority of the windows in the building are located along the south and north sides of the building which is the ideal location for optimum daylighting. The windows along the south side have overhangs to reduce the amount of sunlight entering the building during the summer. The overhangs however are not solid so light still passes through the breaks and into the building. Skylights above corridors on the first floor create lightwells that provide additional daylight into the building, as seen earlier in Figure 1. Structural Structurally the MBNA Career Services Center is different from every other building on Penn State s University Park Campus. Most buildings at Penn State have concrete load bearing walls, where as the MBNA Center has a brick face with metal stud backup. There are two main reasons why this type of construction was chosen, first cost and construction scheduling. Because of the short construction schedule, the metal stud backup system is constructed much more quickly than the load bearing wall system. With the metal stud backup, the structural support for the building and the wall system are no longer integrated which allows for all the steel to be put in place first and then the wall system can be constructed. With a loading bearing concrete wall system, there is more time and coordination required between the steel erectors and the masons throughout the construction of the bearing wall system. Penn State University AE Senior Thesis Spring 2003 Page 10 of 32

11 System Design (Depth) Proposal With a variable air volume system, the outdoor air is mixed with return air at the air handling unit and distributed throughout the entire building. With this type of system, the amount of outdoor air let into a space does not meet the ventilation requirements. A variable air volume system is designed by determining a critical z-value, which is the ratio of outdoor air to supply air, out of all the spaces within the building. Therefore, if the critical space ventilation requirement is met then all other spaces within the building will receive adequate outdoor air, however this is not the case. The problem arises at the VAV box which has a damper that allows only a certain percentage of an already partial outdoor air mixture through. In order to insure that the MBNA Career Services Center has sufficient ventilation, the outdoor air stream and the additional conditioning air will have to be separated. The proposed solution will include a comparison of the existing VAV system with a DOAS/Fan Coil Unit system based on energy and first cost of mechanical equipment, rentable space obtained as well as the material costs of alterations to the electrical and structural systems. The reasoning behind designing a dedicated outdoor air system along with the Fan Coil Units as the parallel system is to provide each space with the required amount of ventilation air. A majority of the spaces within the MBNA Career Services Center are roughly 120 square foot offices and interview rooms. The second floor of the building in particular contains 44 interview rooms. During the course of the year, these rooms are vacant approximately 56% on the time. Because of this fact, energy can be saved during the daytime when the interview rooms are unoccupied by mixing 20% outdoor air, instead of 100%, with return air to maintain the temperature within the space. The 20% will prevent contaminants from building up over the several months that the spaces may remain unoccupied. The spaces on the first and thirds floors, which are occupied on a daily basis, will receive the required amount of outdoor air that they needed when occupied. During unoccupied periods, the DOAS unit will be shut off and the fan coil units will maintain a setback temperature during the winter time only. Another important consideration behind the DOAS/Fan Coil Unit System is that the size of the ductwork is greatly reduced because the only air flowing through the ducts is outdoor air. In addition to reducing the amount and cost of the ductwork, some of the vertical shaft space along with the 221 square foot mechanical room on the third floor will be eliminated. Background on DOAS (Dedicated Outdoor Air System) Indoor air quality in buildings has received a lot of attention over the past several years as more buildings are identified as the reason for occupants feeling uncomfortable at work or even becoming sick. Poor indoor air quality can be caused by many factors including moisture, inadequate ventilation air and indoor contaminants from materials such as paint and carpeting. Many mechanical/hvac engineers, designers and especially researchers are focusing on breaking the paradigm of designing conventional systems such as Variable Air Volume systems and developing new ways to condition and distribute air within buildings to improve indoor air quality. One such design is a Dedicated Outdoor Air System (DOAS) with a parallel system which could be a variety of systems, such as radiant cooling panels or fan coil units. Penn State University AE Senior Thesis Spring 2003 Page 11 of 32

12 The main idea behind the DOAS system is to supply 100% outdoor air directly to where it is needed without mixing it with return air. This method insures that the right amount of ventilation air enters the space since the distribution of the outdoor air is more controlled. Since conditioning outdoor to meet the needs of the entire cooling/heating load on the building requires an immense amount of energy, two additional key components are needed to make the DOAS system feasible and in many cases actually reduce energy consumption. These components are an enthalpy wheel and a parallel system. The enthalpy wheel is part of the air handling unit responsible for distributing the 100% outdoor air throughout the building. The purpose of the enthalpy wheel is to recover heat and moisture from the return air in the winter time and remove heat and moisture from the outdoor air during the summer. The enthalpy wheel spins slowly between the two separated air streams of return air and outdoor air. The efficiency of these enthalpy wheels are typically around 70%. Even with the enthalpy wheel the energy needed to condition the total volume flow rate required by the building is extremely high with only distributing purely outdoor air. Therefore, a parallel system is used to make up the difference in volume flow rate between the space requirement and the ventilation requirement, which is determined by how many people typically occupy the space. Radiant cooling panels have received a lot of scrutiny because of the issue of condensation that can form if the space dew point temperature is higher than the temperature of the panels. In a DOAS/Radiant Cooling Panel System, the entire latent load is taken care of by the cooling coil at the air handling unit greatly reduces, if not eliminates, the possibility for condensation problems to arise. The radiant panels are a separate system used to provide additional sensible cooling to the space. Sensors are typically installed as well to monitor the dew point within the space and prevent condensation. Another parallel system is the use of fan coil units (FCU), which are basically mini air handling units that are placed within the plenum space of a building similar to VAV boxes. Each fan coil unit has a fan, filter, mixing box, cooling coil and heating coil. The outdoor air is sent through ducts to each fan coil unit where it is mixed with return air from the plenum, conditioned to the desired temperature and distributed to the space. Although the return air and outdoor air are mixing, the mixing occurs immediately before going into the space ensuring that the supply air contains the correct amount of outdoor air. If there are multiple rooms on a single fan coil unit, then the multiple spaces equation still applies unless each room receives exactly the same amount of ventilation air. By using fan coil units as opposed to radiant cooling panels, there is less of a concern about condensation issues. Having the cooling coils at the FCUs run dry would be an ideal situation in order to prevent condensate from collecting in drain pans, which can be of some concern if the pans do not drain properly or are not maintained. However, in order to only have sensible cooling at the FCU, the supply chilled water temperature must be lower than usual at the air handling unit and a little higher than usual at the fan coil unit. So, in essence, the supply air in the summer time would in some cases be cooler than the temperature of the chilled water at the fan coil unit. Penn State University AE Senior Thesis Spring 2003 Page 12 of 32

13 Design The total outdoor air required by the MBNA Career Services Center is 11,210 cfm, which is based on 20 cfm/person. The loads on each of the fan coil units as well as the load on the Energy Recovery Unit (ERU), an air handling unit with an enthalpy wheel, is calculated through using Carrier s HAP (Hourly Analysis Program). The total load for all the fan coil units combined is 828 MBH and the total load on the ERU is 480 MBH. Further details on the system and zone requirements can be found in Appendix A. Energy recovery unit #1 contains design information regarding the basement, first and third floors and ERU #2 is for the spaces on the second floor. In order to model the scheduling as described below, the second floor had to be separated from the other three floors. Scheduling/Controls A typical schedule for the rooms located on the first and third floors of the building is occupancy from 8am-6pm, Monday through Friday. The interview rooms on the second floor were analyzed using a schedule of occupancy during peak times throughout the year such as Fall and Spring Career Fairs and FTCAP (freshman placement testing) during the summer. Figure 5 below shows in more detail the times when the interview rooms are used to full capacity Usage of 44 Interview Rooms at the MBNA Career Services Center January February March April May June July August September October November December Interviews - Near Full Interviews - Near Full Capacity Capacity FTCAP - Full Capacity Figure 5 Typical Yearly Interview Room Occupancy Schedule Penn State University AE Senior Thesis Spring 2003 Page 13 of 32

14 During daytime hours when the rooms are not typically occupied, the fan coil units are set to supply 20% of the outdoor air required. This scheduling method for the interview rooms is implemented for the purposes of analysis. Since companies visit Penn State throughout the entire year and not just during the campus wide Career Fairs, the interview rooms will be used at times outside of this specified schedule. As part of the controls of the DOAS/Fan Coil Unit system, a person at the MBNA Center will be able to program into a computer when certain rooms are scheduled for use. Since in most cases there are three rooms on a fan coil unit, the unoccupied one or two rooms will still be supplied with ventilation air, which is a better situation than the entire floor receiving 100% outdoor just because a couple of the rooms are occupied. Additional energy will be saved by selecting rooms for interviews to be held that are close to one another. The second floor is divided into roughly four sections of interview rooms. Energy Recovery Unit Based on the outdoor air ventilation requirements for the building, a TRANE, MCC Energy Wheel Module, size 25, is chosen. Cut sheets from TRANE on the Energy Wheel and the additional air handling unit components can be found in Appendix C. With a volume air flow of approximately 12,000 cfm, there is a pressure drop of 1.04 in w.g. through the wheel and the efficiency is 73%. The wheel also requires a ¼ hp motor. The wheel reduces 90 degree F, 196 gr/lb outdoor air to 84 degrees F and 70 gr/lb. The air is then reduced to 55 degrees F by a cooling coil before being distributed to the fan coil units. During the winter, the enthalpy wheel is used to recover moisture from the return air stream. Outdoor air at -10 degrees F is increased to 43 degrees F and 25 gr/lb. For more details about the conditions at various locations through the ERU, see Figure 6 on page 14. In order to maximize the energy recovered by the enthalpy wheel the supply air and return air volume flow rates are equal. Since the outdoor air supplied is greater than the exhaust air requirements of the restrooms, there is no cause for concern with regards to the exhaust air entering the building. With the improvement of building construction and providing adequate ventilation air to the building spaces, the issue of infiltration is no longer as much of a concern. The energy recovery unit is located in the basement with plenty of access room on either side of the unit. A plan view drawing of the basement can be found in Appendix B. The unit serves all three floors, so the mechanical room on the third floor is no longer needed. The additional floor area located in the front of the building is incorporated in the cost breakdown which will be discussed later in the report. Penn State University AE Senior Thesis Spring 2003 Page 14 of 32

15 o Cooling Coil Figure 6 Energy Recovery Unit State Points The cooling coil at the energy recovery unit is sized based on the total and sensible load on the coil as determined by HAP (see Appendix A) and a 10 degree delta T across the coil. The table below summarizes the values used to select a cooling coil for the ERU. Symbol ERU-1 Serves all spaces Total cfm Energy Recovery Unit Chilled Water Cooling Coil EAT (F) LAT (F) SP Total Sens gpm Water DB WB DB WB (IN) MBh MBh Vel EWT (F) LWT (F) 11, WPD FT The cooling coil is selected using the USA Coil & Air selection program. The coil is four rows of 5/8 diameter pipe with aluminum fins. Further details regarding the cooling coil selected can be found in Appendix C. Penn State University AE Senior Thesis Spring 2003 Page 15 of 32

16 o Chilled Water Pump The chilled water pump for the VAV system is inadequate for the demands of the DOAS/FCU system. The chilled water pump currently in the building sends chilled water at 265 gpm to the cooling coils in the air handling units in the basement as well as the air handling unit on the third floor. The critical loop head loss seen by the existing pump would include the water pressure drop through the horizontal pipe to AHU-3 and the pressure drop through the cooling coil in AHU-3. This total head pressure equals 25 ft H2O. Figure 7 Chilled Water Pumping Schematic For the DOAS/FCU system, there are two loops to consider when determining the maximum total head loss for the pump to overcome. As seen in Figure 7, the total pressure drop on the ERU loop is 18.4 ft H2O and on the FCU loop the total pressure drop is 15.6 ft H2O. Since the two loops are in parallel, the pump is sized with regards to the loop with the greatest pressure drop and the sum of the volume flow rates required for each loop. A pump curve in Appendix C is selected for a possible pump that will work for the proposed system. The table below is a breakdown of the pressure drop for each loop. The length of chilled water pipe is the horizontal distance only since it is a closed loop system. Penn State University AE Senior Thesis Spring 2003 Page 16 of 32

17 o Supply Fan Pump Sizing Chilled Water System Pressure Drop Location of Pressure Drop (ft H2O) FCU Loop Chilled Water Piping 12.3 using: 265 gpm 7 fps 3.5 ft H2O/100 ft 352 ft. pipe FCU Cooling Coil 3.3 Farthest on loop FCU Loop Total Pressure Drop 15.6 AHU Loop Chilled Water Piping 1.4 using: 80 gpm 4.5 fps 2.8 ft H2O/100ft 50 ft. pipe AHU Cooling Coil 17.0 AHU Loop Total Pressure Drop 18.4 Pump Head 18.4 ft H2O The size of the fan required to overcome a total static pressure drop of approximately 3.5 in w.g. is a 10 hp, forward curved 1273 rpm fan with a maximum total static pressure of 5 in w.g. The table below lists the pressure drop of each component that the fan needs to overcome. Fan Sizing Energy Recovery Unit Supply Air Pressure Drop (in w.g.) Damper 0.07 Air Blend Module 0.17 Filter 1.61 ER Wheel 1.04 Cooling Coil 0.24 Heating Coil 0.1 Ductwork 0.29 Total 3.52 Penn State University AE Senior Thesis Spring 2003 Page 17 of 32

18 Fan Coil Units The existing mechanical system required 75 VAV boxes and fan powered boxes (FPB). The DOAS/Fan Coil System replaced the VAV boxes at approximately the same location in the ceiling plenum. An additional five FCUs were added to allow for individual room temperature control in spaces that did not see the same load demands. Most fan coil units are located in corridors to reduce the noise generated above the occupied spaces. The corridor plenum is also a good location for the fan coil units to extract the amount of return air needed to maintain the space temperature. A return grille in the ceiling of each space takes air into the plenum above the room, then Z-ducts are used to transfer return air into the corridor spaces. In the existing design, the first and third floors had ducted return where as the second floor had a plenum return. In order to make the DOAS/FCU system work, all floors now have a return plenum which allows for the air to drawn towards the fan coil units as well as back down to the ERU in the basement. The fan coil units selected are manufactured by TRANE and are available in sizes up to 3000 cfm. The fan coil units contain a mixing box with filter, a 2,4 or 6 row main coil, a 1 or 2 row auxiliary coil, drain pan, fan and motor. The FCU selected for the proposed system will be 4- pipe units since both cooling and heating are need during the winter months depending on the location of the unit within the building. Piping to circulate the hot water to each FCU already exists in the building since the VAV boxes had hot water reheat. For the DOAS/FCU system, additional piping will be needed to circulate chilled water as well as piping to drain the condensate from the cooling coil. In order to insure that the condensate does not build up in the drain pans, maintenance are instructed to clean the pans when filters need replaced. Figure 7 shows a plan view of a typical fan coil unit. Figure 8 Typical Fan Coil Unit Penn State University AE Senior Thesis Spring 2003 Page 18 of 32

19 The following information broken down per fan coil unit can be found in Appendix D. Corresponding Zone as indicated on the HAP analysis sheets in Appendix A Fan Coil Unit Number Total Cfm Location of FCU Rooms served by the FCU Cooling and Heating Load and GPM Requirements take from HAP Actual Cooling and Heating Capacities of FCU Number of rows of coil needed Air Side Pressure Drop FCU Size Velocity at Coil Filter and Mixing Box Pressure Drops Total Static Pressure Drop BHP, RPM and HP of Fan The locations of the fan coil units throughout the building can be seen on the drawings located in Appendix B. The plans show the location of the supply, ventilation and return ductwork. Even though each room on the drawings is not shown as having a return grille and transfer duct, they do exist and additional transfer ducts needed are included in the cost analysis. The ductwork distributing the outdoor air throughout the building is labeled with duct sizes and the volume rate of air flowing through each section. The ductwork leaving the FCUs has not been sized since the flow rate of air through that portion of the duct has not changed enough to make a difference. Two vertical mechanical shafts along the south façade of the building have been eliminated because of the reduction in duct size. The return and supply ducts on located in separate shafts near the center of the building. Since a mechanical room is located on the third floor in the existing design, the supply and return ducts connected to the AHUs in the basement were stopped at the second floor. For the DOAS/FCU system, the supply and return shafts had to be extended to the third floor. The supply shaft is located near the elevator and it has been extended up through the third floor at the same location, which caused the hallway leading to the east side of the building to be blocked. The corridor wall of two offices had to be moved to create enough space in the corridor and thus reduced the office space by only a few feet. It is impossible to bring the return duct straight up through the floor so the duct travels horizontally under the floor for a short distance before penetrating through to the third floor. The area taken up by the new mechanical shafts is still less than the floor area gained by removing the existing unused mechanical space, as shown in the table below. Penn State University AE Senior Thesis Spring 2003 Page 19 of 32

20 Total Amount of Rentable Space Gained from New System Area not used in Additional Area Needed New System (ft^2) by New System (ft^2) 26 vertical shaft 19 vertical shaft on 3rd floor 36 vertical shaft 35 vertical shaft on 3rd floor 221 Mech. Room (3rd fl) 66 decrease in office space 283 Total 120 Total 163 Sq. Ft. of Gained Rentable Space Space Comparison Between Existing and Proposed Systems As mentioned early the amount of ductwork for the DOAS/FCU system would be greatly reduced because of the reduction in air volume flowing through the ductwork. In Figure 9 below, the weight of ductwork, both supply and return, required by the VAV system and the DOAS/FCU system is outlined. Total Amount of Supply and Return Ductwork Summary Density Volume 28 Gauge Galvanized Steel Thickness (in) Area (in^2) Steel (in^3) New System Ductwork Additional Transfer Grilles Volume (ft^3) lb. 1,235, , Total 5778 Existing System Ductwork ,458,416 36, Total Similar to the existing variable air volume system, several fan coil units serve more than one space. Multiple rooms on one FCU occur throughout the building, but can be primarily seen on the second floor. Providing a separate unit for each room is impractical and costs will add up quickly especially for the 44 interview rooms on the second floor. A majority of the zones with multiple spaces are located along the same side of the building which means they have similar envelope loads, the number of occupants within the rooms will typically be the same and the room areas are similar. The multiple spaces equation is used in cases of varying supply air and outdoor air requirements between rooms on the same zone. There are 16 such instances in the MBNA Career Services Center. The calculations using the multiple spaces equation can be found in Appendix D. Energy Comparison Using a simulation program distributed by Carrier Corporation called HAP (Hourly Analysis Program), the variable air volume system with three air handling units and the proposed dedicated outdoor air system with fan coil units were both entered into the program. Since the MBNA Career Services Center is connected to the campus steam distribution system and in the Penn State University AE Senior Thesis Spring 2003 Page 20 of 32

21 near future will receive chilled water from a campus chiller plant instead of the Computer Building, the basis for comparing the two systems is based on electricity usage. The University pays about $0.023 per kwh for electricity. The DOAS/Fan Coil Unit system uses approximately half as much electricity as the VAV system during the course of a year even when all the interview rooms are on the same schedule as the first and third floors, which is occupied on a daily basis from about 8am to 6pm. The two pie graphs below how the percentage of electricity usage for HVAC and non-hvac loads for both the VAV system and the DOAS/FCU system. HVAC Electric 23.3% 23.3% HVAC Electric HVAC Electric 11% 11.0% HVAC Electric Non-HVAC Electric89.0% Non-HVAC Electric76.7% Non-HVAC Electric 76.7% Non-HVAC Electric 89% Existing Variable Air Volume System Proposed Dedicated Outdoor Air System with Fan Coil Units Another contributing factor to the energy savings with the DOAS/FCU system is that during unoccupied times, the fan coil units are used to maintain the setback temperature in each zone by circulating the room air instead of signaling the central air handling unit to turn on. Therefore the ERU can remain off when the building is unoccupied. Cost Analysis When a new design idea is proposed, the first question an owner asks is how much will it cost?. In order to effectively compare the VAV system with the DOAS/FCU system, the first cost of the equipment, piping, electrical, structural and other items associated with the change in systems are collected and analyzed. The first cost of the proposed system is expected to be higher than that of the VAV system since fan coil units are roughly six to seven times more expensive. The costs for the air handling units, VAV boxes, fan powered boxes, fan coil units and the enthalpy wheel are actual TRANE equipment costs. All other costs are taken from RSMeans 2001 Cost Data. The costs are for equipment/materials only, they do not include the cost of labor. The mechanical equipment that is part of the VAV system that is no longer needed for the DOAS/FCU system is itemized in the table below. A majority of the cost of the VAV system is in the air handling units and the ductwork. The cost of items eliminated from the VAV system will be subtracted from the total first cost of the DOAS/FCU system. The positive difference is the Penn State University AE Senior Thesis Spring 2003 Page 21 of 32

22 added cost of installing the proposed system and a negative difference is the first cost savings of the proposed system. HVAC MBNA Career Services Center Breakdown of First Cost - Central AHUs/VAV boxes Item Size Unit Quantity Cost per Unit Total Cost Air Handling Units AHU-1 -- cfm 3500 $1.25 $4,375 AHU-2 -- cfm $1.25 $35,000 AHU-3 -- cfm 7900 $1.25 $9,875 VAV boxes ~300 cfm 3 each 37 $160 $5,920 ~500 cfm 6 each 29 $160 $4,640 ~1400 cfm 11 each 5 $160 $800 ~3000 cfm 17 each 0 $200 $0 Fan Powered boxes ~500 cfm -- each 2 $450 $900 ~1000 cfm -- each 9 $550 $4,950 Ductwork 28 gauge steel -- per lb $4.50 $46,742 Sub-Total $113,202 Structural Steel Joist 3rd Floor (old mech rm) 24LH11 LF 160 $11.45 $1,832 Sub-Total $1,832 Other Total Cost of Items Eliminated $115,034 The itemized first cost per design area is located in the table below for the DOAS/FCU system. Take notice to the cost savings for the ductwork in comparison to the VAV system ductwork cost. The proposed system requires 4600 pounds less ductwork than the VAV system, which saves a little over $20,000 dollars. The cost of the pump needed for the chilled water of the proposed system did not result in a significant cost increase therefore it is not included in the first cost estimate. The electrical equipment for the DOAS/FCU system also did not vary from the existing VAV system since no new panels needed to be added and breakers that are removed from some panels balance out the cost of breakers that needed to be added to other panels. Penn State University AE Senior Thesis Spring 2003 Page 22 of 32

23 HVAC Total Cost Energy Recovery Unit ERU-1 12,000 cfm 1 $1.30 $12,000 Enthalpy Wheel 25 each 1 $12,000 $12,000 Fan Coil Units 12 each 44 $900 $39, each 13 $1,000 $13, each 15 $1,100 $16, each 4 $1,200 $4, each 2 $1,400 $2,800 Ductwork 28 gauge steel -- per lb $4.50 $26,003 Piping CHW to FCUs varies L.F. 150 $3.00 $450 Condensate varies L.F. 150 $2.50 $375 Structural Sub-Total $127,528 Steel Joist 3rd Floor (old mech rm) 24LH09 LF 160 $9.45 $1,512 Sub-Total $1,512 Other MBNA Career Services Center Breakdown of First Cost - DOAS/Fan Coil Unit System Item Size Unit Quantity Cost per Unit Rentable Savings for 1 yr Additional Area -- sq.ft. 163 $ $3,260 Sub-Total -$3,260 Total Cost of Items Added $125,834 The difference in cost between the two systems is $10,800 dollars. With an overall project cost of $9.5 million dollars, an additional $10,800 has a minimal impact and the additional cost is definitely worth the energy savings and the improvement in indoor air quality. Conclusion The overall performance based on energy consumption of the dedicated outdoor air system surpasses the performance of the conventional variable air volume system. There are a number of benefits to the DOAS/FCU system in addition to the energy savings. equipment occupied floor space is reduced because of the need for only one central air handling unit instead of three. The size of the ductwork is reduced considerably due to the decrease in air volume that must be taken from the central AHU to the fan coil units. The incorporation of an enthalpy to recover energy from the exhaust air reduces the outdoor air load Penn State University AE Senior Thesis Spring 2003 Page 23 of 32

24 on the cooling coil. And the most important benefit is the improvement in indoor air quality throughout the building. Some of the downsides to the DOAS/Fan Coil Unit system compared to the VAV system include an increase in first cost of the equipment as shown in the above cost analysis section. The addition of chilled water piping through the building to serve the fan coil units also increases the first cost of the DOAS/FCU system as well as the need for condensate pipe to all fan coil units. The benefits of the proposed DOAS/FCU system will greatly affect the occupants of the building and the owner in the long run because of the healthy working environment and the annual energy savings. Penn State University AE Senior Thesis Spring 2003 Page 24 of 32

25 Electrical System Design (Breadth) Proposal Alterations to the electrical system reflect the change in mechanical equipment associated with the DOAS/FCU system compared to the VAV system. The electrical load for the proposed system will be increased for the terminal units since they have changed from VAV boxes to fan coil units, which contain a fan and motor. However, two fans have been eliminated due to the reduction in air handling units from three to one. Design For the VAV system, each fan powered box has its own circuit and all the variable air volume boxes on the west side of the building are on one circuit in panel A and those located on the east side are on a single circuit also in panel B. As described in the existing electrical design on page 8, there is an A and B panel on the first through third floors. Alterations were also made to panel M in the basement which serves the mechanical equipment. Energy Recovery Unit The enthalpy wheel requires a ¼ hp motor at 230V/3 phase and an amperage of 1.6. The enthalpy wheel will replace one of the relief fans on the M panel. The 10 hp supply fan and an estimated 5 hp for the return fan will replace the existing 30 hp supply fan and 15 hp return fan required by AHU-2 on the VAV system. Supply and return fans for the other two existing air handling units are no longer needed. Fan Coil Units Electrical circuits serving the fan coil units including the conductors, conduit and circuit protection are sized using the following procedure and requirements. o Full Load Amps (FLA) rating taken directly from the Electrical Data provided by TRANE, the manufacturer of the Fan Coil Units (see Appendix D for manufacturer cut sheet) o The load on the wire feeding the Fan Coil Units is determined by using the following formula. [(FLA of largest motor x 125%) + (FLA sum of all other motors)] o Conductor Size: NEC Table o Conduit Size: NEC Chapter 9, Tables 3A & 3B o Circuit Protection: Time delay circuit breaker = 250% from NEC (Table 13.3). Take [(FLA*250%)+(FLA sum of all other motors)] = minimum required circuit breaker rating A listing of all fan coil units with corresponding electrical information including panel locations, FLA, conductor size, conduit size and breaker protection can be found in Appendix E. No additional panels are required since the existing panels had enough slots for the breakers needed. Most of the fan coil units have ¼ hp or 1/3 hp motors and there are a couple ½ hp and ¾ hp motors also. There are at most three fan coil units on one circuit breaker. The full load amp Penn State University AE Senior Thesis Spring 2003 Page 25 of 32

26 (FLA) capacity for the fan coil units is based on a 120V, single phase service. The locations of the fan coil units within the building were in groups of roughly eight to nine FCUs, which allowed for the units to be on adjacent circuits and share a neutral wire. Electrical drawings showing junction boxes at the fan coil units and homeruns can be found in Appendix E. Conclusion With the DOAS/FCU system only needing one central air handling unit to distribute outdoor air, the electrical loads on the building have been greatly reduced. The central supply and return fan motor sizes combined equal that of one return fan of the existing VAV system. The electrical requirements for the fan coil units are fairly minimal. Because each fan coil unit is only responsible for maintaining the temperature in one, two or three spaces, the fan does not necessarily run continuously. With a VAV system, the fans need to run constantly in order to maintain the temperature in every space it serves. Penn State University AE Senior Thesis Spring 2003 Page 26 of 32