EXAMPLE:
Start to Common -4.0 Ohms
Start to Run -3.0 Ohms
Start to Run -3.0 Ohms
Start to
Common
-
∞
Ohms
OPEN COMPRESSOR START WINDING--
-REPLACE THE COMPRESSOR .
7.The resistance from one winding terminal to any other terminal should be the same with three phase
compressors.
NOTE:
on larger 208/230 volt compressors the ohm values could be as low as 0.10 ohms,
THIS IS NOT A SHORTED WINDING .A winding is open if resistance measured is infinite(
∞
).
Compressors fail mechanically due to bearing failure ,valve failure ,or damage to the internal suspension
SYSTEM PUMP DOWN
refrigerant as intended or if it leaks out.
Procedure
1.
on the compressor shell, or in the line between accumulator and compressor. Connect the high
2.
rises above 400 psi,
Shut off about outdoor unit.
B. The ohm reading from the Start TERMINAL TO COMMON TERMINAL will be the middle ohm value
measured between the terminals and be approximately 2.0 to 3.0 ohms
C. The ohm reading from the Start TERMINAL TO Run terminal will be the highest ohm value of the
three measurements and will be approximately the sum of the first two measurements.
A . Run to Common -1.0 Ohms
Conclusion compressor motor does not have open or shorted wincings:
Start to Common -
∞
Ohms
B . Run to Common -
∞
Ohms
CONSLUSION COMPRESSOR COULD HAVE AN OPEN INTERNAL OVERLOAD-
ALLOW THE
COMPRESSOR MOTOR TO COOL AND THE INTERNAL OVERLOAD TO RESET, THEN RETEST.
C. Run to Common -1.0 ohms
Start to
Run
-
∞
Ohms
COMPRESSOR MECHANICAL CHECKS
system. Bearing and valve failure is almost always caused by liquid refrigerant.
COMPRESSORS ARE
or breaking them. Liquid refrigerant also damages bearings by diluting or foaming the lubricating oil.
the liquid line service valve. The procedure uses the compressor to trap all the refrigerant inside the
DESIGNED TO ONLY PUMP REFRIGERANT VAPOR
. Liquid refrigerant damages the valves by deforming
This procedure tests the compressor valves. It can indicate internal refrigerant leaks such as through
condensing coil (outdoor cooling). The technician’s gauges indicate if the condensing coil holds the
Connect the compound refrigerant gauge to a service port that reads suction pressure such as
pressure gauge to a service port that reads high pressure .
POSITIVE PRESSURE. DO NOT OPERATE THE COMPRESSOR WITH A NEGATIVE SUCTION
suction pressure should fall. The high pressure should also fall slightly. If the discharge pressure
3. SHUT OFF THE COMPRESSOR WHEN THE SUCTION PRESSURE DROPS TO 3-5 PSI.
With the unit operating, front seat (close) the liquid line service valve. Observe the gauges .The
PRESSURE OR IN A VACUUM.
29
Central Air Conditi
oning
Model: Heat Pump,
HR13-D
2
