UFC 3-410-01FA
15 May 2003
CHAPTER 5 EQUIPMENT
5-1
LOCATION OF EQUIPMENT. Specify air-conditioning equipment, including
air handlers, compressors, pumps and associated equipment that is suitable for outdoor
installation where life cycle cost effective. When comparing interior and exterior
equipment installations in life cycle cost analysis, include all associated building costs to
house interior equipment in the analysis, but also include in the consideration the longer
expected life of indoor equipment. Provide details on the drawings necessary to ensure
drainage for "winterizing" equipment where appropriate. When evaluating costs,
provide an allowance for costs due to failure to winterize outdoor equipment properly,
similar to the cost of insurance to offset the unexpected costs associated with a sudden
cold snap or electric heat-tracing cable failure.
5-2.
CHILLERS. Individual reciprocating machines will not exceed 200 tons
(700kW) capacity, and the total capacity of all reciprocating machines or packaged air-
conditioning units equipped with reciprocating compressor used for air conditioning a
single facility will not exceed 400 tons (1400kW). A single packaged unit will not contain
more than eight compressors. Where multiple chillers are specified, provide a chilled
water pump and a condenser pump for each chiller. With the exception of the criteria
listed herein, the number of chillers specified will be optimized in the life cycle cost
analysis. Where there is a combination of normal summer air-conditioning loads and
year-round air-conditioning loads optimize system zones and size system components
to support the entire facility load during warm weather and a portion of the equipment
may be essentially fully loaded during winter operations. In facilities when, because of
the small size of the off-hours or the small winter load, it is impractical to operate the
primary equipment in the central plant, an auxiliary refrigeration system may be
provided. Use heat recovery where it is life cycle cost effective.
5-2.1
Reciprocating Compressors.
5-2.1.1 For chillers over 10 tons (35 kW), use capacity control that reduces the power
requirement as the load varies.
5-2.1.2 Compressors operating in parallel will have the normal oil level at the same
elevation for all machines and the crankcases of these compressors will be provided
with gas and oil equalizing lines. When compressors are connected in parallel, arrange
the hot-gas discharge lines so that the oil from the common discharge line will not
collect in an idle unit while the other units are running, and size the lines to provide an
equal pressure drop between each machine and its respective condenser. The suction
lines will return refrigerant gas and oil from the evaporator to the compressor during
operation of the system, and will not allow oil or liquid refrigerant to be returned as slugs
at any time. Provide means for trapping oil in the common suction header to prevent oil
slugs from collecting in the idle compressor.
5-2.2
Centrifugal Compressors. When a two-stage centrifugal compressor is
selected, a refrigerant intercooler will also be required. For low-temperature
applications, where compressors with four or more stages may be needed, two-stage
20
Previous Page
