Filter
Top Products
tion shown for the Tecumseh compressor is shown with the
triangle formed by the terminals pointing toward the top. The
configuration around the fusite terminals is the outline of the
terminal covers used on the specific compressors. The slot through
which the wires of the plug are routed is oriented on the bottom or
slightly to the left or right. The correct plug can be connected
easily to the compressor terminals and plug wires routed easily
through the slot in the terminal cover. Therefore, if a Carlyle or
Bristol compressor is substituted for a Tecumseh compressor, a
new plug must be installed. If the plug is not changed, proper
connection and routing of the plug wires through the terminal
cover will be impossible.
XIV. LOW-VOLTAGE TERMINALS
The low-voltage terminal designations, along with descriptions
and/or functions, are used on all split-system condensers and heat
pumps:
G—Energizes blower circuit from indoor thermostat.
E—Energizes emergency-heat relay.
W2—Energizes first-stage supplemental heat through defrost relay
(wht).
L—Energizes light on thermostat with service alarm.
W3—Energizes second- or third-stage supplemental heat.
R—Energizes 24v power from transformer (red).
Y—Energizes contactor for first-stage cooling or first-stage heat-
ing for heat pumps (yel).
O—Energizes reversing valve on heat pumps (orn).
C—Common side of transformer (blk).
RECIPROCATING COMPRESSOR
The compressor is the heart of the refrigeration system. It pumps
refrigerant through the system. If it malfunctions, system capacity
and efficiency could be negatively affected.
CAUTION: The compressor is an electrical (as well as
mechanical) device. Exercise extreme caution when
working near compressors. Power should be shut off, if
possible, for most troubleshooting techniques. Refriger-
ants in system present other safety hazards. Always wear
safety glasses and gloves when handling refrigerants.
Compressor failures are classified in 2 broad failure categories:
mechanical and electrical. Both types are discussed below.
I. MECHANICAL FAILURES
A compressor is a mechanical pump driven by an electric motor
contained in a welded or hermetic shell. In a mechanical failure,
motor or electrical circuit appears normal, but compressor does not
function normally.
CAUTION: Exercise extreme caution when reading
compressor currents when high-voltage power is on.
Correct any of the problems described below before
installing and running a replacement compressor. Wear
safety glasses and gloves when handling refrigerants.
LOCKED ROTOR
In this type of failure, compressor motor and all starting compo-
nents are normal. When compressor attempts to start, it draws
locked-rotor current and cycles off on the internal protection.
Locked-rotor current is measured by applying a clamp-on ammeter
around common (blk) lead of the compressor on a single-phase
compressor, or any 1 of the leads on a 3-phase compressor. Current
drawn when it attempts to start is then measured. LRA (locked-
rotor amp) value is stamped on compressor nameplate.
If compressor draws locked-rotor amps and all other external
sources of problems have been eliminated, compressor must be
replaced. Because compressor is a sealed unit, it is impossible to
determine exact mechanical failure. However, complete system
should be checked for abnormalities such as incorrect refrigerant
charge, restrictions, insufficient airflow across indoor or outdoor
coil, and so forth, which could be contributing to the failure.
RUNS, DOES NOT PUMP
In this type of failure, compressor motor runs and turns compres-
sor, but compressor does not pump the refrigerant. A clamp-on
ammeter on common leg of a single-phase compressor, or any 1
lead of a 3-phase compressor, shows a very low current draw,
much lower than RLA (rated load amps) value stamped on
compressor nameplate. Because no refrigerant is being pumped,
there is no return gas to cool compressor motor. It eventually
overheats and shuts off on its internal protection.
RUNS, DOES NOT PUMP, HIGH-TO-LOW SIDE LEAK
Fig. 27—Compressor Plug
A94002
LEAD 1
BLK.
LEAD 2
YEL.
CS
R
C
R
BRISTOL
COPELAND
CARLYLE
SC
R
S
LEAD 3
BLUE
LEAD 2
YEL.
LEAD 3
BLUE
C
R
S
TECUMSEH
C
S
R
LEAD 1
BLK.
LEAD 3
BLUE
C
SR
TECUMSEH
C
SR
LEAD 1
BLK.
LEAD 2
YEL.
LEAD 1
BLK.
LEAD 2
YEL.
LEAD 3
BLUE
C
SR
MILLENNIUM
C
S
R
—25—