Friedrich Hazardgard SH15L30-A, Service & Parts Manual

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8
LOW AMBIENT BYPASS VALVE (Figure 9)
The HazardGard unit is designed to operate at low
outside ambient temperatures. This is accomplished by
the use of a bypass valve installed in the refrigeration
circuit. The valve is connected between the discharge
line at the compressor and the suction process tube.
The valve responds to suction pressure which, when
reduced in the system, causes the valve to open and
bypass hot gas from the high pressure side to the low
pressure side of the system. The hot gas entering the
compressor mixes with the cool gas returned through
the suction line, thus increasing the suction pressure.
The valve is preset to open when the suction pressure
reaches 50 psig. This pressure setting cannot be
altered. The system can be operated at outdoor
temperatures as low as 45°
F before the evaporator
coil will begin to accumulate frost.
To determine if the valve operates, block the return air
to the evaporator coil. Turn on the unit and touch the
tube at the bypass valve outlet which connects to the
suction process tube. When the low side pressure
reaches approximately 50 psig, the valve will begin
to open and the tube will get hot. This method will
determine if the valve is responding to the suction
pressure change.
FIGURE 9
LOW AMBIENT Bypass
VALVE
EQUIPMENT REQUIRED:
1. Voltmeter
2. Ammeter
3. Ohmmeter
4. E.P.A Approved Refrigerant Recovery System
5. Vacuum Pump (capable of 200 microns or less
vacuum).
6. Acetylene Welder
7. Electronic Halogen Leak Detector (G.E. Type
H-6 or equivalent).
8. Accurate refrigerant charge measuring device
such
as:
a. Balance Scales - 1/2 oz. accuracy
b. Charging Board - 1/2 oz. accuracy
9. High Pressure Gauge - (0-400 lbs.)
10. Low Pressure Gauge - (30" - 150 lbs.)
11. Vacuum Gauge - (0-1000 microns)
EQUIPMENT MUST BE CAPABLE OF:
1. Recovering CFC’s as low as 5%.
2. Evacuation from both the high side and low side
of the system simultaneously.
3. Introducing refrigerant charge into the high side of
the system.
4. Accurately weighing the refrigerant charge actually
introduced into the system.
5. Facilities for flowing nitrogen through the
refrigeration tubing during all brazing processes.
SEALED REFRIGERATION SYSTEM
REPAIRS