2.5.3.5
Water Pump
The water pump shall be the bronze-fitted centrifugal or turbine type, and
may be mounted as an integral part of the unit or remotely on a separate
mounting pad. Pumps shall have cast-iron casings. Impellers shall be
bronze, and shafts shall be stainless steel with bronze casing wearing
rings. Shaft seals shall be the mechanical type. Pump casing shall be
factory coated with epoxy paint. Pump motors shall have [open] [dripproof]
[totally enclosed] [explosion proof] enclosures. A bleed line with a flow
valve or fixed orifice shall be provided in the pump discharge line and
shall be extended to the nearest drain for continuous discharge. Pump
suction shall be fully submerged and provided with a galvanized steel or
monel screened inlet.
2.5.3.6
Drift Eliminator
Eliminators shall be provided to limit drift loss to not over 0.005 percent
of the specified water flow. Eliminators shall be constructed of
zinc-coated steel or polyvinyl chloride (PVC). Eliminators shall prevent
carry over into the unit's fan section.
2.5.3.7
Evaporator Controls
Unit shall be provided with modulating capacity control dampers mounted in
the discharge of the fan housing. On a decrease in refrigerant discharge
pressure the dampers shall modulate to reduce the airflow across the
condensing coil. Controls shall include a proportional acting pressure
controller, a control transformer, motor actuator with linkages and end
switches to cycle fan motor on and off. Cycling of a fan motor on and off
shall be in accordance with the manufacturer.
2.5.4
Compressor
Compressor shall be direct drive, semi-hermetic or hermetic reciprocating,
or scroll type capable of operating at partial load conditions. Compressor
shall be capable of continuous operation down to the lowest step of
unloading as specified. Compressors of 35 kW 10 tons and larger shall be
provided with capacity reduction devices to produce automatic capacity
reduction of at least 50 percent. If standard with the manufacturer, two
or more compressors may be used in lieu of a single compressor with
unloading capabilities, in which case the compressors shall operate in
sequence, and each compressor shall have an independent refrigeration
circuit through the condenser and evaporator. Compressors shall start in
the unloaded position. Each compressor shall be provided with vibration
isolators, crankcase heater, thermal overloads, [lubrication pump,] [high]
[high and low] pressure safety cutoffs and protection against short cycling.
2.5.5
Refrigeration Circuit
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NOTE: Filter-driers are optional and may be deleted
on most precharged systems.
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Refrigerant containing components shall comply with ASHRAE 15 and be
factory tested, cleaned, dehydrated, charged, and sealed. Refrigerant
charging valves and connections, and pumpdown valves shall be provided for
each circuit. Filter-drier shall be provided in each liquid line and be
reversible-flow type. Refrigerant flow control devices shall be an
SECTION 15700A
Page 20
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