MOCP nameplate NEC requirement

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fcguy

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Good Morning Everyone,

Long time reader of the forum, first post.

TLDR: What part of the code requires that manufacturer nameplate MOCP be adhered to?

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I'm trying to find out if/which section of code requires that the MOCP for an HVAC unit must be adhered to.

Here's why:

I'm working on a project and got the equipment schedule from the mechanical guys. MOCP of 15A on two units. No problem, they make 15A two pole 208 breakers commonly. So that's what I put on the panel schedule.

Markups from PE come back and one of his comments is "20 Amp minimum on commercial projects". I send back a new set but I mark this up as "15 Amp MOCP per mechanical". I get the next drawing set back and it says "20 Amps is the minimum we use on commercial projects. Never use 15 amps. Change it".

At this point I'm floored. Just "change it"? No mention of a fused disconnect or anything like that. So I change it and send it back. But everything I've been taught up to this point is that MOCP on a nameplate is because the conductors inside the device are sized such that you need to use a maximum size breaker. And we just busted that.

I've been looking through 100, 300, and 400 but I can't seem to find anything along the line of "thou shalt follow the nameplate" or "MOCP or die". Anyone know what part of the code might require the nameplate MOCP to be followed?
 
The maximum is 15 amps so that's what you use. Whoever is saying we don't use less than 20 amps doesn't understand the code when it comes to this equipment.

Welcome to the forum. :)
 
Time for some remedial training for the P.E. He is clearly wrong and this would be a violation of the code to do as he describes.
 
dkidd said:
110.3(B)

I've fought that battle before.
Click to expand...

I think this is the one I need. I can't imagine the HVAC unit wont be listed or labeled by NEC definition of the terms. Thus instructions must be followed.

Many thanks!
 
The PE didn't say the code said to use a 20 amp circuit, He said "We" use 20a minimum circuits on commercial projects.

Can't say I blame him.

If it's his design and he's responsible for it so be it.

On that same note, he must allow you to draw in a Fused disconnect that can be fused to the appropriate MOCP or the unit must come with an intergral disconnecting means with the appropriate MOCP device installed in it.

If he doesn't allow one or the other, then yes, ya'll actually "busted it" .

JAP>
 
This sounds like boiler plate nonsense. Sure use all 20 amp circuits for power and lighting but for specific equipment you might have to deviate. Yes you could use a 15 amp supplemental OCPD at the end of the 20 amp branch circuit but that sounds pretty dumb when you can just use a 15 amp OCPD instead.
 
I feel just the opposite.

For lighting and receptacle outlets sure, go ahead with your 15 amp circuits if you want to.

But, I would say the cost difference in installing a 15 amp circuit vs a 20 amp circuit to a HVAC unit in the commercial world would be minimal at best.

To choke things down to 15 amps from the panel all the way to an HVAC application sounds pretty dumb to me.

JAP>
 
LarryFine said:
There would be no issues with using #12 wire and a 15a breaker.
Click to expand...

No one said there would be an issue, but, for the price difference, you'd have a lot more options with a #12 conductor pulled out there in case you needed it in the future than if you had only pulled #14.

JAP>
 
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