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tkrussell Posts: 9,673, Reputation: 3698
Senior Electrical & Lighting Expert
 
#10

Jul 15, 2007, 05:14 AM


Missed your last response with questions.

You did exactly what should be done, follow the manufacturer's instructions.

A manufacturer will always err on the side of caution, to eliminate product liability issues. Be sure they know what they are doing. I am not sure your being fair to them, since it appears your not sure yourself, and apparently not familiar with HVAC codes.

HACR rating will be found in the manufacturers specifications and "HACR" will be stamped on the circuit breaker. This means that the overcurrent protection device has the characteristics that will allow a refrigeration unit to start. All motors have what is called Locked Rotor Amperage, which is the large amount of current a motor will draw upon starting under load.

All refrigeration compressors start under load, and more so that a fan or fluid pump, due to the immersion in refrigeration gas under pressure.

The LRA for a compressor can exceeding 6 to 10 times the running amps. Have you noted that a compressor can have an overcurrent protection device rated at a minimum of 175% of the nameplate current, up to a maximum of 225%?

Since the codes in Article 440 are and have been a bit confusing, several years ago the manufacturers had been mandated to state the minimum circuit size and the maximum OCPD on their nameplates.
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