True Manufacturing Company GDIM-26, GDIM-49 If the Compressor will Not RUN, Starts but Trips

True Food Service Equipment, Inc.

MAINTENANCE, CARE & CLEANING

IF THE COMPRESSOR WILL

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