Technical Requirements -
Mechanical/Plumbing/Electrical
HVAC
The following represents the highlights of the mechanical system design. Refer to
the VA HVAC Design Manual for Regional Office Projects for more detailed
information.
1. Public Law 95-619 requires a 20-year life cycle cost analysis to be performed to
determine the most cost effective HVAC system for the building.
2. Use of roof mounted penthouse-type air handling units for mild weather
conditions, or indoor factory fabricated air handling units are acceptable. In
computer room provide two (2) Computer Room Air Conditioning Units (CRAC
units) which are 2 stage, _______ ton (dependent on actual or design heat load)
including a primary and staged secondary compressor system. One stage on
each CRAC unit with both units running should carry the full computer room heat
load with about 30% excess capacity per stage. Heat exchange in the CRAC
units shall be to either a closed loop cooling system with cooling towers or a
chilled water system to remove heat from the CRAC units. These units must
have integral humidification either by low pressure steam or a water system
depending on utilities present or planned and CRAC unit manufacturer (A/E
coordinate in planning stage).
3. No reheat is permitted in the interior zones, except a warm up cycle may be
employed where required.
4. Winter humidification is not permitted except in areas where outdoor design
temperature is 0 or below. In general office areas of the regional office where
design outside air temperature is below 0 degrees Fahrenheit, humidification
through fresh air handlers is necessary.
5. Fully ducted return air system is not permitted. Use of ceiling return air plenum is
acceptable.
6. Ceiling mounted fan coil units are not permitted. Location of fan coil units under
the windows in the perimeter zone is preferred.
7. A separate chilled water system may be employed to meet the building block
load when either chilled water is not available from the medical center or when
not economical to tie into the medical center system.
Page 4-10
VBA Design Guide
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