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 | ||||
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| between each capacitor terminal and the | the protector or protectors. All external | ||||
1. If there is no voltage at the |
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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. |
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compressor to the power supply to find | Substitute a “known to be good” start |
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where the circuit is interrupted. |
| IF THE MOTOR COMPRESSOR | |||||
2. If power is available at the |
| capacitor if available. If compressor | STARTS BUT TRIPS |
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| then starts and runs properly, replace | REPEATEDLY ON THE |
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compressor terminals, and the |
| the original start capacitor. | OVERLOAD PROTECTOR |
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compressor does not run, check the |
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If a capacitor tester is not available, an | 1. Check the compressor suction |
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voltage at the compressor terminals | and discharge pressures while the |
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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 | ||||
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| 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 |
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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. |
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determine if wire sizes are adequate, | then gradually increase to infinity. |
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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. |
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supply is inadequate. |
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| 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 |
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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 |
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closed during the initial starting cycle, | the terminals and check for continuity | operating. The voltage should be |
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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 |
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| continuity from terminals C to R, and C | voltage supply must be brought |
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Remove the wires from the starting | to S. On compressors with line break |
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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. |
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continuity throughout the relay |
| If the compressor is warm, wait one |
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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 |
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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. |
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| shell. If there is a ground, replace the |
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Any capacitor found to be bulging, | compressor. |
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leaking, or damaged should be |
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| Continued on next page |
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replaced. |
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14 | ............ www.truemfg.com | 14 |