(d) See Article 1.3 for ductwork.
(e) See VA Standard Detail 15000-29 for VAV terminal units sound ratings.
2.4.2 SPECIAL CONSIDERATIONS
(a) For all occupied patient spaces, exterior and interior, the minimum
setting of air terminal units shall be such that the minimum ventilation
needs of the occupants are met at all times. Provide reheat coils for the
terminal units serving the perimeter spaces.
(b) For the interior spaces serving the patient areas, such as examination
and treatment rooms etc., the air terminal units shall be equipped with
reheat coils to ensure minimum ventilation at all times. For the remaining
non-patient interior spaces, the air terminal units can assume fully closed
position when the internal heat gain is non-existent.
(c) During winter occupied mode, when the supply air volume is expected to be
less than the design summer air volume, evaluate the following parameters:
(1) Supply and return air volumes and the fan performances at part-load
conditions.
(2) Winter mixed air conditions and the need for a preheat coil.
(d) The volumetric control for the supply and return air fans shall be
accomplished by the airflow measuring devices and the variable frequency
drives. The sequence of operation shall be such that the constant difference
in air quantity shall be maintained between the supply and return airflows
from full load to part load conditions.
2.5 ROOM FAN-COIL UNITS
2.5.1 GENERAL
(a) Use of fan coil units for cooling in new construction areas, as well as
cooling of patient care and waiting areas in the high humidity areas of the
country is not permitted. However, in existing buildings with physical
limitations such as inadequate furred ceiling and shaft spaces and mechanical
rooms for equipment and ductwork use of fan coil units is permitted. Areas
having above mean annual dew point temperature of 40-45 degrees are
considered high humidity areas.
(b) Floor mounted, vertical, four-pipe fan coil units (located under the
windows) shall be used for perimeter patient rooms, offices, and other
exterior spaces requiring mechanical cooling, provided the system is proved
to be cost effective on the basis of a life cycle cost analysis when compared
with other HVAC systems. The minimum outdoor air for this system shall be
directly distributed to the spaces from central air handling unit (s) via
ductwork and air outlets. The outdoor air shall either be exhausted through
the patient toilets or directly from the spaces. The minimum outdoor air
shall meet requirements of Article 1.3.5, and meet exhaust needs and space
latent load.
2.5.2 EXCEPTION
Where approved by the VA for austere projects in mild climate areas, with
Winter Design Temperature 4 degree C (40 degrees F) or above, outdoor air may
HVAC DESIGN MANUAL
2-10
HVAC SYSTEMS AND EQUIPMENT
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