Data plate max breaker size

[elgato]

The data plate on outdoor units for AC and heat pumps indicates a maximum and minimum over-current protection device amperage ( among many other bits of pertinent info) Is this number absolute? That is if the max is 45 amp and the installer used a 50 amp breaker, is this not a problem? I thought I read that under certain circumstances that number is not absolute. However, I forget why????

[inspector57]

Yep, on HVAC units it is absolute.

[Jim Katen]

The data plate on outdoor units for AC and heat pumps indicates a maximum and minimum over-current protection device amperage ( among many other bits of pertinent info) Is this number absolute? That is if the max is 45 amp and the installer used a 50 amp breaker, is this not a problem? I thought I read that under certain circumstances that number is not absolute. However, I forget why????

Absolute according to whom?

If you're talking about complying with the NEC or the manufacturer's requirements then, yes, the number is absolute. If the data plate says 45 amp breaker maximum, that's what it means.

Now, if you're a trouble maker and you want to know what bad thing will happen if you install a 50-amp breaker, well, the only bad thing that will happen is that the manufacturer will no longer support the warranty.

- Jim Katen, Oregon

[elgato]

Thanks. That's the answer I was hoping to get.

[MPdesign]

I have been out of electrical for while - so I may not bee 100% right on this; but I seem to remember the exception has to do with computed load. The load is computed and the next larger "standard" breaker size can be used.

This is not your case.

[Jim Katen]

I have been out of electrical for while - so I may not bee 100% right on this; but I seem to remember the exception has to do with computed load. The load is computed and the next larger "standard" breaker size can be used.

This is not your case.

Yes. You're thinking of 240.4(B). It allows you to size the conductor for the load but protect it with the next highest standard overcurrent device.

This is an often abused code section. Some electricians seem to think that "standard" means "what I have in the truck" or "what's normally stocked at the supply house."

25-, 35-, & 45-amp breakers are, in fact, standard sizes.

As you said, it doesn't really relate to the original post. With an AC condenser unit, the data plate will require a standard size OCPD and it's not negotiable.

- Jim Katen, Oregon

[elgato]

Yes, the issue of "computed load" strikes a key. That is in the opinion that I had read, and caused me to question whether or not I should comment on the 50 amp breaker for a unit that specifies a max OCPD of 45 amps.