15A MOCP & 20A breakers

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Steve-R

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I assume that a device with a 15A MOCP connected to a 20A breaker or fuse is violating some code or rule, but I'm not sure what code or rule it would be. I don't know of any requirement in the NEC that requires the OCPD to match MOCP (maybe I'm missing it). Is this an NEC requirement, or something else? Is it only a violation of the UL listing?

FWIW, we do always have an OCPD sized to match the MOCP, but as I stated I'm not sure what requirement dictates this.
 
Good old 110.3(B) as a start. The OCPD can be smaller, but not larger.

(B) Installation and Use. Listed or labeled equipment
shall be installed and used in accordance with any instructions
included in the listing or labeling.
 
Steve-R said:
I assume that a device with a 15A MOCP connected to a 20A breaker or fuse is violating some code or rule, but I'm not sure what code or rule it would be. I don't know of any requirement in the NEC that requires the OCPD to match MOCP (maybe I'm missing it). Is this an NEC requirement, or something else? Is it only a violation of the UL listing?

FWIW, we do always have an OCPD sized to match the MOCP, but as I stated I'm not sure what requirement dictates this.
Click to expand...

What is the MOCP?:?
 
Assuming it is HVAC equipment


440.52 Application and Selection.
(A) Protection of Motor-Compressor. Each motorcompressor
shall be protected against overload and failure
to start by one of the following means:

(3) A fuse or inverse time circuit breaker responsive to
motor current, which shall also be permitted to serve as
the branch-circuit short-circuit and ground-fault protective
device. This device shall be rated at not more than
125 percent of the motor-compressor rated-load current.
It shall have sufficient time delay to permit the
motor-compressor to start and accelerate its load. The
equipment or the motor-compressor shall be marked
with this maximum branch-circuit fuse or inverse time
circuit breaker rating.
Click to expand...
 
Steve-R said:
I assume that a device with a 15A MOCP connected to a 20A breaker or fuse is violating some code or rule, but I'm not sure what code or rule it would be. I don't know of any requirement in the NEC that requires the OCPD to match MOCP (maybe I'm missing it). Is this an NEC requirement, or something else? Is it only a violation of the UL listing?

FWIW, we do always have an OCPD sized to match the MOCP, but as I stated I'm not sure what requirement dictates this.
Click to expand...

I get the feeling that since you are asking about a smaller amp values of 15 or 20 amp that maybe this is some type of A/C or refrigeration equipment fed from a 20 amp branch circuit because the specs on the job called for "minimum 20 amp branch circuits" as seen often in commercial construction. If so, that does not relieve you of using the max over current device as stated on the nameplate. In other words if the nameplate says "max overcurrent protective device 15 amp" that is what you have to use. Just guessing at your scenario, so correct me if I'm on the wrong path.
 
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