required, with resilient seat and with flanged body in sizes 13 mm 1/2 inch
and larger. Valve shall provide positive shutoff at [10.3] [13.8] [20.7]
kPa [1-1/2] [2] [3] psi differential pressure.
2.21.3
Liquid Solenoid Valves
Valves shall comply with ARI 760 and shall be suitable for continuous duty
with applied voltages 15 percent under and 5 percent over nominal rated
voltage at maximum and minimum encountered pressure and temperature service
conditions. Valves shall be direct-acting or pilot-operating type,
packless, except that packed stem, seal capped, manual lifting provisions
shall be furnished. Solenoid coils shall be moistureproof, UL approved,
totally encapsulated or encapsulated and metal jacketed as required.
Valves shall have safe working pressure of 2758 kPa 400 psi and a maximum
operating pressure differential of at least 1380 kPa 200 psi at 85 percent
rated voltage. Valves shall have an operating pressure differential
suitable for the refrigerant used.
2.21.4
Expansion Valves
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NOTE: Choose ARI 750 for fluorocarbon service and
ASHRAE 17 for ammonia service.
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Expansion valves shall conform to the requirements of [ARI 750] [ASHRAE 17
]. Valve shall be of the diaphragm and spring type with internal or
external equalizers, and bulb and capillary tubing. Valve shall be
provided with an external superheat adjustment along with a seal cap.
Internal equalizers may be utilized where flowing refrigerant pressure drop
between outlet of the valve and inlet to the evaporator coil is negligible
and pressure drop across the evaporator is less than the pressure
difference corresponding to 1 degree C 2 degrees F of saturated suction
temperature at evaporator conditions. Bulb charge shall be determined by
the manufacturer for the application and liquid shall remain in the bulb at
all operating conditions. Gas limited liquid charged valves and other
valve devices for limiting evaporator pressure shall not be used without a
distributor or discharge tube or effective means to prevent loss of control
when bulb becomes warmer than valve body. Pilot-operated valves shall have
a characterized plug to provide required modulating control. A
de-energized solenoid valve may be used in the pilot line to close the main
valve in lieu of a solenoid valve in the main liquid line. An isolatable
pressure gauge shall be provided in the pilot line, at the main valve.
Automatic pressure reducing or constant pressure regulating expansion
valves may be used only where indicated or for constant evaporator loads.
In direct-expansion unit cooler applications, thermostatic expansion valve
discharge shall be through distributor and distributing tubes or through a
single tube outlet leading to an orificed header provided by the unit
cooler manufacturer, supplying an evaporator coil with not more than four
circuits. Distributor orifices shall be sized for application conditions
and distributor shall be provided by the thermostatic expansion valve
manufacturer as a matched combination to suit evaporator coil circuitry.
Where indicated, distributor tube shall be fitted with side inlet for hot
gas bypass or defrosting. In single compressor/evaporator combinations,
where compressor capacity control is only by on-off cycling, and if
recommended by the compressor manufacturer, thermostatic expansion valve
shall be furnished with a small bleed passage between inlet and outlet to
facilitate equalization of high and low side during off cycle.
SECTION 15652A
Page 34
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