Max Overcurrent Protection (MOP) size of manufacturer

Status
Not open for further replies.
V

victor.cherkashi

Senior Member
Location
NYC, NY
I would like to know your opinion, what protection you will provide for attached equipment.
Most date sheet of mechanical equipment has "Max Overcurrent Protection (MOP)" - see attached file as example.
I was told by senior Electrical engineer always to go one o two size up from MOP shown in data sheet (fuse and feeder/branch circuit). His answer to my question why - just do it, don't ask too much questions.
In attached PDF as example, I required to provide 40A protection and 40A wiring (MOP = 30A).
In my opinion of something will go wrong in equipment and it burn inside, manufacturer can void warranty by saying the protection was too high according to data sheet of equipment.
Thanks in advance
 

Attachments

  • Max Overcurrent Protection (MOP) (A).pdf
    71.8 KB · Views: 15
It is a violation of the rules in the NEC to exceed the maximum overcurrent protection device sizing.
 
Electrically the only two numbers that matter on that data sheet are the MCA of 27 amps and the MOCPD of 30 amps. As Don stated you need to use a maximum 30 amp OCPD. I would question why you would want to go higher than the manufacturer's requirement?
 
iwire said:
I agree with the others and would expect a competent electrical inspector to fail the installation.
Click to expand...

I work in current New York city office for 3 years, always it is done this way. NEVER heard that electrical inspection failed, and NEVER received questions from contractor regarding fuses and feeder sizes.
 
victor.cherkashi said:
I work in current New York city office for 3 years, always it is done this way. NEVER heard that electrical inspection failed, and NEVER received questions from contractor regarding fuses and feeder sizes.
Click to expand...

Interesting. My experience is different.

One of the first red tags I ever got was using a 30A breaker on a HVAC gas pack/AC unit that had a MOCP of 25A.

I was new and asked the HVAC contractor what he needed instead of reading the nameplate. Never did that again.
 
Status
Not open for further replies.
Top