2 Existing Mechanical System

Transcription

1 2 Existing Mechanical System 2.1 Design Objectives and Requirements The Gossett Field House project consists of a 25,000 sqft addition and a 40,000 sqft renovation of the existing facility for the University of Maryland football team. There are several unique characteristics of this facility that lent themselves to specific design objectives and requirements. The main objective undertaken by the design team during the planning of this facility was to provide the University of Maryland football team with a state of the art building dedicated solely to the football team. This facility was to include classroom space, a dedicated dining hall, and a state of the art auditorium. The university was hoping to sustain the success of its football program by banking on a new facility helping to draw recruits to the university as opposed to going out of state to other programs, thus ensuring their success for years to come. As with most universities with more prominent football programs, the football team brings in a large amount of revenue for the university, through ticket sales, sales of apparel, etc. This revenue was something the university was hoping to have for years to come as well, and was influential in their decision to renovate and expand the football team s facilities. That being said, one of the more important requirements for the project was to ensure that the existing facility would remain open to the football team during the times necessary. While the team now uses the facility year round, the university deemed it acceptable that the facility could be occupied only during the football season, and the bulk of construction being done in the off season. While this opened up more time for construction, it still placed limitations on the general contractor. For instance, the college football season is from September through November, and continuing on into December and as late as the first week of January if a team makes a bowl game. In addition, there are summer practices for a month or more before the season starts. So while the general

2 contractor had over half the year to perform most of the major renovation work without affecting the football team s use of the facility, this portion of the year consisted of the late fall, winter, and early spring months, which are not necessarily the best parts of the year to undertake major construction. Once the renovation work was done on the existing facility, it was much easier to work year round, without having any impact upon the football team s use of the facility. Aside from these unique and somewhat unusual conditions and requirements that were specific to this project, more common requirements also existed. For instance, the conflict between ceiling heights and mechanical ceiling space was a requirement created by the architectural design. The architect on the job wanted to keep the ceilings as high as possible, thus creating some design challenges, particularly in the new kitchen and dining room. In this particular space there is a large amount of mechanical equipment required such as the make up air units, exhaust fans for the kitchen hoods, as well as the supply ductwork for the heating and air conditioning of the space. Containing all of this ductwork within the ceiling why designing for maximum ceiling height was a large design challenge that required a creative solution. In addition to the limited ceiling space, there was also limited floor space for mechanical equipment as well. In the area that was to be renovated, no additional space was to be used for mechanical equipment. In the addition section of the construction the mechanical space was kept to a minimum. Because of this, the major mechanical equipment such as the packaged air conditioners and kitchen make up are units were located on the roof, while low profile variable air volume boxes were used as the terminal devices. Using the VAV boxes in this configuration allows for the maximum ceiling height to be maintained. The final challenge faced by the design team was the large amount of glass in certain parts of the facility. For instance in the new dining room addition, the walls consisted entirely of glass. This posed a unique challenge of how condition the space, even with the high transmission properties of the glass. This problem was solved by

3 using linear slot diffusers around the perimeter to create a buffer between the perimeter windows and the outside. 2.2 Design Conditions The following sets of outdoor and indoor design conditions were obtained from the design engineer and were used for all necessary calculations for the Gossett Field House Project. These conditions are as follows: Outdoor Design Conditions Summer Conditions Outdoor summer dry bulb: 94 F Outdoor summer wet bulb: 75 F Winter Conditions Outdoor winter dry bulb: 10 F Indoor Design Conditions Indoor Cooling Indoor dry bulb: 75 F Indoor Relative Humidity: 50% Indoor Heating Indoor dry bulb: 70 F

4 2.3 Air System Summary Gossett Field House has two distinctly different air systems to provide heating and cooling to the building. The first type of system services the existing part of the building that was renovated and consists of two air handling units, AC-1 & AC-2. These air handling units are located in the mechanical penthouse on the roof. Both of these units are variable air volume units with chilled water coils and steam pre-heat coils. Reheat is provided by duct mounted hot water booster coils. Terminal devices for these systems are ceiling diffusers. AC-1 has a ducted return and serves the existing office space located on the second floor. AC-2 is a 100% outdoor air unit with no energy recovery. This unit serves the first floor, which consist primarily of a weight room, player locker rooms for both the home and away teams. A schedule of the unit capacities is provided below: Table 1 Existing Air Handling Unit Schedule COOLING HEATING FAN (MBH) (MBH) CFM OA CFM ESP (IN. WC) AC AC In addition to the system mentioned above that serves the renovated section of the building, there is a completely different type of system that is used to serve the additions to the building. Six packaged rooftop units provide the heating and cooling to the addition sections of the building. These units are equipped with DX cooling and gas fired heating. RAC-1 serves the multipurpose room, RAC-2 serves the kitchen area, RAC-3 serves the team film rooms that were added, RAC-4 serves the new auditorium, RAC-5 serves the new classrooms and computer room, and RAC_6 serves the hallway that connects the auditorium and kitchen. RAC-1, RAC-2, and RAC-4 are constant volume units while RAC-3, RAC-5, and RAC-6 are variable air volume units. RAC-3 and RAC- 5 also use VAV boxes with hot water reheat as terminal devices. A schedule of the unit capacities is provided below:

5 Table 2 Existing Packaged Unit Schedule FAN COOLING HEATING (MBH) (MBH) CFM OA CFM ESP (IN. WC) RAC RAC RAC RAC RAC RAC Hydronic System Summary There are several major pieces of mechanical equipment that provide the chilled water and hot water for the systems that serve the renovated section of the building. A single air cooled liquid chiller supplies the chilled water for AC-1 and AC-2. The chilled water is circulated by two base mounted pumps, one of which is on stand by. Hot water for the duct mounted booster coils and VAV reheat coils is provided via a steam to hot water shell and tube type heat exchanger. The hot water is then circulated to the coils via an inline circulation pump. Steam enters the building at 125 psi and passes through a pressure reducing valve resulting in 10 psi steam. Schedules for the existing mechanical equipment mentioned above are located in Appendix A.