PROJECT DESCRIPTION
Mowat Construction Company is an existing 2-story office building with an existing variable air volume system and general exhaust system. Also, space includes server room and loading/receiving dock space. Below is a detailed description of the existing/new HVAC system.
An existing Variable Air Volume (VAV) Packaged Rooftop unit provides Air Conditioning for this building. AC-1 serves the first and second floor office areas. In conjunction with the AC unit, Fan Terminal Units (FTU) serves the interior and perimeter office areas. A VAV pinch-of box unit is serving the computer room. Return air path is coming from the space through a common plenum duct and up to the AC unit on the roof.
In addition to the large VAV unit, there is AC-2 ductless split system unit that serves the Telephone/Data/Server Room for after hour’s usage. The large VAV Packaged Rooftop units supply conditioned air to the FTU’s and VAV terminal units. The FTU and VAV terminal units respond to a space or zone temperature sensor and vary the amount of supply air being delivered to the space to maintain space comfort. The small Constant Volume Split System unit AC-2 responds directly to a space temperature sensor and modulates the supply air temperature as needed to maintain space temperature desired.
In addition to the Packaged Rooftop Air Conditioning unit, the HVAC system has other components necessary for the operation of the system. (27) Fan Terminal Units (FTU). The series fan powered units deliver a constant quantity of supply air to the space(s) they serve. To maintain space comfort, the FTU units modulate the amount of conditioned air from the large AC unit and mixed with return air, and then deliver variable air temperature to the space in response to a space temperature sensor. Electric heaters are used when the mixture of conditioned air and return air cannot satisfy space heating. (1) Variable Air Volume Terminal (VAV) Units. The VAV units modulate the amount of supply air delivered to the space served in response to a space temperature sensor.
The FTU boxes include 30% efficient throwaway filters, UL Listed, and hinged access doors. Low-pressure ductwork and diffusers distribute the conditioned air. The supply ducts are located in the ceiling space. The return air path is ducted back to the main unit. Ductwork runs location and sizes were coordinated with all trades for clearance requirements in the building. Also, all design for this project complied with the 2000 Washington State Building/Mechanical Code, and the 2000 WA State Energy Code. Fire/Smoke dampers and Fire Dampers were provided at all areas where ducts and transfer openings penetrated though rated assemblies/exit enclosures, per building code.
BUILDING MANAGEMENT CONTROL SYSTEM
This building is equipped with an existing Honeywell Energy Management Control System (EMCS), where the new equipment was tied into. The EMCS controls the operation of most of the HVAC equipment, including all of the FTU units.
BASIS OF DESIGN CRITERIA
- Summer Indoor = 74°F
- Winter Indoor = 70°F
- Summer Outdoor = 83°F DB/65° WB
- Winter Outdoor =24°F D
- Lights = 1.2 watts/sq. ft.
- Misc. load allowance = 2.5 watts/sq. ft.
- Ventilation = 20 CFM/person
- Occupancy = 1 person per 150 square feet