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COOLING CYCLE
INDOOR
INDOOR COIL
FAN
ACCUMULATOR
SUCTION SERVICE
PORT AT SERVICE
VALVE (CLG CYCLE)
STRAINER
(METERING)
HEAT PUMP
ACCESSORY
LIQUID LINE SERVICE PORT
FILTER DRIER
AT SERVICE VALVE (CLG CYCLE)
(DUAL FLOW)
Fig. 42—Heat Pump Refrigerant-Flow Diagrams
CAUTION: Due to the high pressure of nitrogen, it
should never be used without a pressure regulator on the
tank.
Leaks in a system pressurized with refrigerant can be spotted with
a leak detector that detects extremely small refrigerant leaks. This
discussion assumes that system is pressurized with either all
refrigerant or a mixture of nitrogen and refrigerant.
If system has been operating for some time, make first check for
a leak visually. Since refrigerant carries a small quantity of oil,
traces of oil at any joint or connection are an indication that
refrigerant is leaking at that point.
A simple and inexpensive method of testing for leaks is to use soap
bubbles. Any solution of water and soap may be used. Soap
solution is applied to all joints and connections in system. A small
pinhole leak is located by tracing bubbles in soap solution around
leak.
Use electronic leak detector to check for leaks. This unquestion-
ably is the most efficient and easiest method for checking leaks.
There are various types of electronic leak detectors. Generally
speaking, they are all portable, and most are lightweight, consist-
ing of a box with several switches and a probe or sniffer. Detector
is turned on and probe is passed around all fittings and connections
in system. Leak is detected by either a movement of a pointer on
detector dial, by a buzzing sound, or a light.
MODE OF OPERATION
18-PIN CONNECTOR
All
Low-speed Cooling
High-speed Cooling
Low-speed Heating
High-speed Heating
Defrost
Second Stage of
Auxiliary Heat
Cooling Second-
stage Latching
REVERSING VALVE
(ENERGIZED)
OUTDOOR FAN
COMP
STRAINER
OUTDOOR
COIL
SUCTION
LIQUID LINE
SERVICE
PRESSURE SWITCH
PORT
(BYPASSING)
A88400
TABLE 19—24V PIN CONNECTION TROUBLESHOOTING
TERMINAL
LOCATION ON
DESIGNATION
CONTROL BOARD
R-C
2-1
Y1,0-C
8,6-1
Y1, Y2, 0-C
8,7,6-1
Y1-C
8-1
Y1-C
8-1
Y2-C
7-1
Y1-C
8-1
Y2, W2, 0-C
7,5,6-1
Y1, W2-C
7,5-1
W3, Y2-C
9,8-1
Y1, Y2, 0-C
8,7,6-1
In all instances, when a leak is found, system charge must be bled
down and leak repaired before final charging and operation. After
leak testing or leak is repaired, evacuate system, and recharge with
correct refrigerant charge.
III. BRAZING
When brazing is required in the refrigeration system, certain basics
should be followed:
1. Clean joints make the best joints. To clean:
a. Remove all oxidation from surfaces to a shiny finish
before brazing.
VOLTAGE
VOLTAGE
PATH
REQUIRED
Input
24
Input
24
Input
24
Input
24
Input
24
Output
24
Input
24
Output
24
Input
24
Output
24
Input
24
—37—
Fig. 43—Leak Detector
POSSIBLE SOURCE
OF PROBLEM
Check transformer (secondary)
Check thermostat
Check thermostat
Check thermostat
Check thermostat
Outdoor temperature below
speed; change temperature
Check thermostat
Outdoor temperature below 50°F;
Coil temperature less than 30°F
Check thermostat
Check balance-point setting
Ambient thermistor failure;
Check second-stage POT
A88401
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Troubleshooting
