Associated Environmental Systems SD-302, Инструкция по эксплуатации

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DESCRIPTION
2-3
A de-superheating expansion valve has been added to maintain acceptable suction gas
temperatures returning to the compressor when bypassing or when chamber pulls down from
high temperatures to low temperatures.
A pressure relief valve opens when the high side pressure goes above approximately 280 psig
and diverts the gas to the expansion tank. The gas is returned to the low side of the system via a
restrictive tube.
Charging is by static pressure or weight if system is empty. To check a static charge the unit
must not have been operated for at least 6 hours and have an ambient temperature of
approximately 70ºF. Leaving system off, connect gauges and equalize pressure between high
and low side. Optimum pressure should be between 100 psig and 125 psig.
R-404A-SYSTEM
When the mechanical refrigeration is switched on the R-404A compressor will start about 60
seconds before the SUVA-95 compressor to pre-cool the cascade and to minimize starting
current required for the chamber. The R-404A system incorporates a hot gas bypass system to
“unload” the compressor during low or no load conditions. Charging is done until the sight glass
is full.
Service Technician Please Note: When the refrigeration system is bypassing hot gas, bubbles or
a low liquid level will appear in the sight glass. This is normal and does not indicate an under
charged system. Likewise, when charging system make sure hot gas is not bypassing, or the
system will be overcharged. Bypass valve should be set to maintain 5-10 psig during no load
conditions. Charging is done to full or near to full sight glass.