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cabalen (Mechanical) (OP)
22 Dec 06 8:39
We are trying to troubleshoot a refrigeration system running on freon 12. The reciprocating compressor trips off during 30 mins of run. The comressor motor and mechanical system is newlyh reconditioned and tested before installation. What could be the possible causes and your recommendations. Thanks
zekeman (Mechanical)
22 Dec 06 10:47
Check the rated current. Measure the current during the 30 minute run and if it exceeds the rated, you have a compressor problem which can range from bad bearings to excessive pressures. If the rated current is less than rated and the circuit breaker is the one specified by the unit, then it is possible that the breaker is faulty.
MintJulep (Mechanical)
22 Dec 06 12:42
Single phase?  Three phase?

Trips on what?  External breaker, external thermal?  Internal thermal?
HVAC68 (Mechanical)
24 Dec 06 20:30
Check the system as a whole.  High condenser pressures ?  Is the condenser coil (if it's an air-cooled unit) choked ?  


cabalen (Mechanical) (OP)
26 Dec 06 4:34
Its 3-phase, trips on external breaker. Thanks
ScottyUK (Electrical)
26 Dec 06 14:34
We're talking breaker not thermal overload here? If the breaker is tripping as soon as the machine attempts to start then it is probably tripping on the 'magnetic' or instantaneous element. Usually this is adjustable to accomodate the starting current drawn by the motor, typically 6 - 8 times full load current but not always. It might be indirectly quoted on the nameplate as a NEMA code, e.g. Design B, Design C, etc. This letters equate to multiples of running current.

Sometimes breakers get tired and the mag trip gets trigger-happy. Other times they are just set wrongly. Can you post some details of the breaker type, rating and settings, and also any data from the motor nameplate? At present there are too many unknowns to provide any sensible direction.

  Sometimes I only open my mouth to swap feet...

imok2 (Mechanical)
26 Dec 06 17:53
Similer situation with a heat pumpin cooling mode amp reading kept going up tillthe breaker tripped. The system was grossly overcharged.
berkshire (Aeronautics)
27 Dec 06 2:30
cabalen (Mechanical)
Have you put a set of gauges on this system and checked the head pressure?
 Until this crew knows  the head pressures are normal, they cannot give you a definitive answer, any thing else is speculation.

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