Associated Environmental Systems SD-302, Инструкция по эксплуатации

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DESCRIPTION
2-2
CIRCULATION SYSTEM
The circulation system consists of electric motor(s) and fan blade(s). The electric motor is a split
phase, TEFC with automatic reset thermal overload. The motor has a stainless steel shaft, which
extends into the chamber and then into the fan blade. The bearings are the permanently
lubricated type, so no further lubrication is required. Since the motor is single phase there is no
need to check for proper rotation after new chamber installation. If motor is replaced or
serviced, rotation should be checked since the motor can be wired for standard or opposite
rotation.
HEATING SYSTEM
Heating is produced by nichrome wire on ceramic core type heaters, used for their quick
response. Consult electrical schematic for heating capacity.
When the controller senses heat is required, it energizes a series of relays and the pilot light.
Should the failsafe circuit be energized, a separate relay will de-energize the chamber heat and
illuminate the failsafe pilot.
There are also heat links located in the chamber. Their purpose is for chamber protection only.
Once they are opened, replacement is necessary. Never short or jump out heat links.
REFRIGERATION SYSTEM
Cooling is accomplished by a cascade stage mechanical system using two (2) semi hermetic
compressors. Compressor utilizes polyester oil (POE) for lubrication. The actual cascade is a
brazed heat exchanger. The low or SUVA-95 system removes the heat from the chamber and
delivers it to the cascade in the form of high pressure gas. The high or R-404A system removes
the heat from the cascade and delivers it to the surroundings using the fan (or water) cooled
condenser. In the cascade, the SUVA-95 goes from a high pressure gas to a high pressure liquid
or simply condenses. The R-404A transforms from a low pressure liquid to a low pressure gas or
simply evaporates. An air cooled condenser is utilized.
SUVA-95 SYSTEM
When the controller senses that cooling is required, it energizes the mechanical refrigeration
(cool) pilot light and a solenoid valve (located before the SUVA-95 evaporator expansion valve,)
letting liquid refrigerant into the chamber evaporator. When cooling is not required a solenoid
valve energizes bypassing hot gas (through a regulating valve or restricted tubing) from the high
side to the low side. The hot gas bypass has been incorporated to “unload” the compressor
during low or no load conditions since the compressor does not cycle on an off.