Low Ambient By-Pass Valve; Sealed Refrigeration System Repairs - Friedrich 2001 Hazardgard SH14J30A-1 Service Manual

LOW AMBIENT BY–PASS VALVE
The HazardGard unit is designed to operate at
low outside ambient temperatures. This is
accomplished by the use of a by–pass 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 by–pass 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 by–pass 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.

LOW AMBIENT BY-PASS VALVE

8
1. Voltmeter
2. Ammeter
3. Ohmmeter
4. E.P.A Approved Refrigerant Recovery
5. Vacuum Pump (capable of 200 microns or
6. Acetylene Welder
7. Electronic Halogen Leak Detector G.E.
8. Accurate refrigerant charge measuring
9. High Pressure Gauge - (0-400 lbs.)
10. Low Pressure Gauge - (30" - 150 lbs.)
11. Vacuum Gauge - (0-1000 microns)
1. Recovering CFC's as low as 5%.
2. Evacuation from both the high side and low
3. Introducing refrigerant charge into the high
4. Accurately weighing the refrigerant charge
FIGURE 8
5. Facilities for flowing nitrogen through the
SEALED REFRIGERATION SYSTEM
REPAIRS
EQUIPMENT REQUIRED
System
less vacuum).
Type H-6 or equivalent).
device such as:
a. Balance Scales - 1/2 oz. accuracy
b. Charging Board - 1/2 oz. accuracy
EQUIPMENT MUST BE CAPABLE OF:
side of the system simultaneously.
side of the system.
actually introduced into the system.
refrigeration tubing during all brazing
processes.