Mechanical Overview​

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The mechanical equipment of this building is made of variable volume ACFs, 100% outside air constant volume ACFs, constant volume ACFs, FCUs, split systems, exhaust fans, and a heat recovery unit. The VAV ACFs and one CAV ACF are new additions, primarily serving the newer portion of the building. The rest are re-used due to their good condition. All the ACFs (with one exception) are located in the mechanical penthouse. The building is served with chilled water from the campus chilled water system. A heat exchanger is provided to isolate the campus system from the building heat exchanger side distribution system. The campus chilled water supply is designed at 42°F in the summer and 48°F in the winter. The campus chilled water supply operates at a 12°F temperature difference between supply and return water.

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The VAV ACFs have humidifiers, economizers, and hot water reheating systems. The economizer dampers operate with a dependence on both dry bulb temperature and enthalpy of the outside air. A minimum of 20% outside air is always provided by the VAV systems, which is ensured by the outside air dampers. There are two fans for supply and return. Both fans are controlled by a variable frequency drive. The systems have a preheat coil, a cooling coil, and local reheat coils by hot water. The systems are each assigned a specific zone in the newer portion of the building, which include west offices, east offices, core offices, and atrium space.

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As for the 100% outside air CAV ACFs, they are coupled with exhaust fans that have a heat recovery unit. The two ACFs supply labs and animal labs. The heat from the air exhausted from both labs is recovered by a heat recovery coil, before the exhaust fans exhaust the air to the outside. Also, the two systems have economizers, humidifiers, and variable frequency drive that controls the supply fans. A preheat coil, heat recovery coil, a cooling coil, and local reheating coils are utilized by the two systems. The CAV ACF that does not supply 100% outside air is a relatively small ACF that only supplies one lecture hall.

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FCUs and split systems serve the renovated portion of the building, mainly laboratories and service/storage rooms. There are continuously FCUs running supported with split systems serving the service rooms of the building. Other FCUs serve laboratories and are either continuous or scheduled.

 

Mechanical Depth

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Adding Radiant Floor Heating to Atrium Area

The atrium area is a very important area in the HHD building. To get to most spaces in the building, people need to pass through the atrium. Also, the atrium has many seating areas which are generally used by students to meet, study, or socialize. The atrium offers a great view of College Avenue through the large curtain wall on HHD building’s south side. Due to the importance of the atrium, the mechanical system serving this area needs to provide good thermal comfort for the occupants.

The mechanical system serving the atrium may be fulfilling ventilation and load requirements, but is not providing the best thermal comfort needed for such an important area of the building. The atrium is served by ACF-07, which is a VAV air handler. The diffusers providing the atrium with conditioned air are located on side walls on the 1st, 2nd, 3rd, and 4th floors at ceiling height. During the winter season, the diffusers provide hot air that ends up rising towards the top of the atrium, leaving the bottom portion of the space colder than the rest of the space. Adding radiant floor heating to the atrium area would minimize the temperature difference between the bottom portion and the top portion of the atrium, while allowing for a better temperature distribution across the bottom portion.

Not only would the radiant floor heating create a more comfortable environment, but also it could reduce the energy consumption of ACF-07 that is supplying the atrium. The very large area of the atrium and the number of people it can accommodate increase the ventilation rate, which increases the load on ACF-07. The radiant floor heating would be able to meet a portion of the load on the ACF, reducing the ACF’s load and energy consumption. Radiant floor heating would require hot water flowing through the pipes in the floor which would generally cause an increase in operation cost of the building. HHD building is supplied with steam from the campus loop and the steam is used to create hot water for the building. Because the campus loop supplies the building with steam, providing hot water for the radiant floor heating would cost significantly less than if the building was creating its own hot water using a boiler. Also, accessibility to hot water is never going to be a problem because the steam supply from campus is reliable.

 

Replacing Radiant Walls with Radiant Floor Systems.

All of the new portion of HHD building is served by several VAV systems. During the winter, these systems heat the spaces they serve using preheat coils and reheat coils. In addition to the VAV systems, tube radiation under the windows for parameter heating also help with heating spaces. The tube radiators were designed to have 140°F water running through them, and according to occupants it is not enough. There are two ways in which this issue could be solved. The first way could be to simply increase the water temperature to around 180°F, but the radiators were designed only for 140°F. The second solution is to replace parameter heating systems with radiant floor systems. The radiant floor systems would cover more area in the offices, allowing for better thermal comfort and would be able to cover more of the load. Radiant floor systems would be more expensive initially due to the extra piping required, but as previously discussed, the operation cost should not be an issue and the heating load on the VAV systems should be reduced.

 

Replacing 2nd Floor Lab FCUs With DOAS VAV Systems

The 2nd floor labs in the renovated portion of the building are served with independent FCUs that condition the air inside. As for ventilation, the FCUs brings outside air and exhaust fans exhaust the lab air to the outside. Using the FCUs could be less energy efficient than using one larger DOAS VAV system with energy recovery.

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Increase Ventilation For ASHRAE 62.1 Non-Compliant System

The ventilation analysis done in Technical Report 1 showed that all the mechanical systems of the building complied with ASHRAE 62.1 ventilation requirements, with exception of one ACF. As discussed in Technical Report 1, this ACF, ACF-08 serves conference rooms and a lecture hall. When increasing the ventilation, the increase in load must be considered. Since there will be an increase in load, the schedule at which ACF-08 works needs to be carefully organized so that it operates only when needed. Conference rooms and lecture halls are not usually used as often as other spaces like offices or labs, therefore it should be possible to save energy when the operation schedule is optimized, even with increased ventilation. 

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Breadths

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Electrical

For the mechanical depth, I will be replacing FCU units with one larger DOAS VAV system. This replacement will definitely have an effect on the electrical system due to the different loads on the electrical system. Also, radiant heating systems will be placed in some portions of the building, reducing the load on the mechanical systems in these areas. If the systems need to be resized, the load on the electrical system could differ. In my breadth I will be examining the effect of the depth changes on the electrical system and find whether any modifications need to be made.

 

Structural

The new VAV equipment will be placed on the roof of the building. Before placing the system on the roof, a structural analysis must be made to ensure that the roof will be able to hold the system. Based on the analysis, a decision will be made to determine whether any changes are required for the roof’s structure.