True Manufacturing Company T-35 If the Compressor will, Not RUN, If the Motor Compressor

True Food Service Equipment, Inc.

INSTALLATION / OPERATION INSTRUCTIONS

IF THE COMPRESSOR WILL		Make sure capacitors are discharged	5. If the compressor has an external
NOT RUN		before checking. Check for continuity	protector, check for continuity through
		between each capacitor terminal and the	the protector or protectors. All external
1. If there is no voltage at the
compressor terminals, follow the		case. Continuity indicates a short, and	inherent protectors on compressors can
wiring diagram and check back from		the capacitor should be replaced.	be replaced in the field.
compressor to the power supply to find		Substitute a “known to be good” start
where the circuit is interrupted.			IF THE MOTOR COMPRESSOR
2. If power is available at the		capacitor if available. If compressor	STARTS BUT TRIPS
		then starts and runs properly, replace	REPEATEDLY ON THE
compressor terminals, and the		the original start capacitor.	OVERLOAD PROTECTOR
compressor does not run, check the
		If a capacitor tester is not available, an	1. Check the compressor suction
voltage at the compressor terminals			and discharge pressures while the
while attempting to start the		ohmmeter may be used to check run	compressor is operating. Be sure the
compressor.		and start capacitors for shorts or open	pressures are within the limitations
		circuits. Use an ohmmeter set to its	of the compressor. If pressures are
If voltage at the compressor terminals is		highest resistance scale, and connect
			excessive it may be necessary to clean
below 90% of the nameplate voltage, it		prods to capacitor terminals.	the condenser, purge air from the
is possible the motor may not develop		a) With a good capacitor, the	system, replace crankcase pressure
sufficient torque to start. Check to		indicator should first move zero, and	regulating valve.
determine if wire sizes are adequate,		then gradually increase to infinity.
electrical connections are loose, the		b) If there is no movement of the	An excessively low suction pressure
circuit is overloaded, or if the power		ohmmeter indicator, an open circuit is	may indicate a loss of charge.
supply is inadequate.		indicated.
		c) If the ohmmeter indicator	On units with no service gauge parts
3. On single phase compressors,		moves to zero, and remains there or on
			where pressures can be checked,	check
a defective capacitor or relay may		a low resistance reading, a short circuit	condenser to be sure it is clean and fan
prevent the compressor starting. If		is indicated. Defective capacitors	is running. Excessive temperatures on
the compressor attempts to start but		should be replaced.	suction and discharge line may also
is unable to do so, or if there is a		4. If the correct voltage is available	indicate abnormal operating conditions.
humming sound, check the relay to
see if the relay contacts are damaged		at the compressor terminals, and no	2. Check the line voltage at the motor
or fused. The relay points should be		current is drawn, remove all wires from	terminals while the compressor is
closed during the initial starting cycle,		the terminals and check for continuity	operating. The voltage should be
but should open as the compressor		through the motor windings. On single	within 10% of the nameplate voltage
comes up to speed.		phase motor compressors, check for	rating. If outside those limits, the
		continuity from terminals C to R, and C	voltage supply must be brought
Remove the wires from the starting		to S. On compressors with line break
			within the proper range, or a motor
relay and capacitors. Use a high		inherent protectors, an open overload	compressor with different electrical
voltage ohmmeter to check for		protector can cause a lack of continuity.	characteristics must be used.
continuity throughout the relay		If the compressor is warm, wait one
coil. Replace the relay if there is not		hour for the compressor to cool and	3. Check the amperage drawn while
continuity. Use an ohmmeter to check		recheck. If continuity cannot be	the compressor is operating. Under
across the relay contacts. Potential		established through all motor windings,	normal operating conditions, the
relay contacts are normally closed when		the compressor should be replaced.	amperage drawn will seldom exceed
the relay is not energized, current relay		Check the motor for ground by means	110% of the nameplate amperage.
contacts are normally open. If either			High amperage can be caused by low
gives an incorrect reading, replace the		of a continuity check between the	voltage, defective running capacitors,
relay.		common terminal and the compressor	or a defective starting relay.
		shell. If there is a ground, replace the
Any capacitor found to be bulging,		compressor.
leaking, or damaged should be			Continued on next page
replaced.
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