Whether to replace the breaker?
Whether to replace the breaker?
(OP)
My mechanical people is going to downsize a condenser, which is fed from a 70A breaker in a panel, and with a local disconnect switch. the motor protection is integrated inside the unit. The new condenser only needs a 40A breaker. Now my question is do I really need to replace the 70A in panel or I can just leave as is and provide a new location 40A fused disconnect?
thank you in advance.
thank you in advance.






RE: Whether to replace the breaker?
The NEC states something along the lines of "neat and orderly". Extra breakers doing nothing might not fit this criteria in some cases.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Whether to replace the breaker?
Am I correct?
anyway, thanks a lot Itsmoked.
RE: Whether to replace the breaker?
You are correct. The main thing is to provide the 40 amp
protection to the condenser. I assume that is the mfg specs.
You say a fused disconnect. The mgf will provide a recommended over current rating. If a fuse is recommended
then it is ok to use it. However a breaker may be required
if the mfg says to use a 40 amp breaker.
RE: Whether to replace the breaker?
Fuses for a compressor... very bad juju! You will blow one fuse someday and lose the compressor. I've seen it a million times. Like clockwork. Use a breaker.
It is so bad a lot of compressor makers will void any and all warranties. Also make sure it is a breaker rated for HVAC.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Whether to replace the breaker?
Itsmoked, can you please tell me more detail about why i can not use fuse for compressor? I thought of fuse because i thought disconnect wouldn't do any protection and the upstream breaker is 70A. So I thought maybe I could use a fuse to provide some protection.
also 'a breaker rated for KVAC', is there anything special for that breaker?
thanks again for your helps.
RE: Whether to replace the breaker?
itsmoked's answer has to do with the fact that fuses allow for single phasing of 3 phase motors, because if only one fuse blows, the motor will get 1 phase power and may burn up before another fuse opens. Phase Loss Relays and many IEC style overload relays will protect against this however, so it depends on what else you have in the circuit. Your idea about adding fuses is sound from the standpoint of having closer protection for the motor windings against a short circuit, just make sure that you have supplementary phase loss protection.
Assuming you made a typo and the breaker is rated HVAC (not KVAC), that simply means that the breaker was designed to be used on motor loads in HVAC systems. But really that's just a marketing thing now, all breakers are rated the same and have been for years. That label is just a holdover from a bygone day.
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RE: Whether to replace the breaker?
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