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10TA Service Manual

SERVICE OPERATIONS

4/28/14

9-8

Electronic Motor Protector Field Trouble Shooting

(4D & 6D compressors before March 2011).

In the event the motor compressor is inoperable or is not operating properly, the solid state control
circuit may be checked as follows:

If the compressor has been operating and tripped on the protector, allow the compressor to cool
for at least one hour before checking. This allows time for the motor to cool and the control
circuit to reset.

! WARNING !

Before checking the TI31AA model for its attached wiring sensor, be aware

that the sensor terminal “C” has the same voltage as terminal L1.

! WARNING !

Disconnect control circuit power to deenergize the module. Connect a jumper wire across the
"control circuit" ("M1-M2") terminals on the module control circuit terminal board. This will
bypass the "control contact" of the module.

Reconnect  control  circuit  power.    If  the  compressor  will  not  operate  with  the  jumper  wire
installed,  then  the  problem  is  external  to  the  solid  state  protection  system.    If  the  compressor
operates with the module bypassed, but will not operate when the jumper wire is removed, then
the control circuit relay or triac in the module is open.

If after allowing time for motor cooling, the protector still remains open, the motor sensors may
be checked as follows.

Disconnect control circuit power to deenergize the module. Remove the jumper of Step 2.
Remove wiring connections from the sensor and common terminals on the module control
circuit terminal board.

CAUTION: Use Ohmmeter with a maximum of 9 VAC for checking. The sensors are
sensitive, easily damaged, and no attempt should be made to check continuity through them
with other than an ohmmeter. Any external voltage or current applied to the sensors may
cause damage requiring compressor replacement.

Measure the resistance from each sensor terminal to the common terminal. The resistance
should be in the following range:

500

ohms (cold) to 20,000+ ohms (hot. compressor tripped)

Resistance readings in this range indicate the sensors are good.  A resistance approaching
zero indicates a short; a resistance approaching infinity indicates an open connection. Proper
operation of the control system is dependent on a continuous parallel circuit through all three
sensors with no individual resistance reading higher than 10,000 ohms.  On initial start-up,
and after any module trip due to high temperatures, the resistance of the sensors must be
below the module reset point before the module circuit will close.  Reset values are 2700-
4500 ohms.

If the sensors have the proper resistance, and are below 2700 ohms resistance, the compressor
will run with the control circuit bypassed, but will not run when connected properly, the solid
state module is defective, and must be replaced. The replacement module must be the same
voltage and be compatible with the original module on the compressor.