A/C Breaker size

[David A. Nice]

Large carrier A/C unit calls for Max breaker size of 58 amps. Is a 60 amp breaker in the main panel a problem?

[Bruce A. King]

Are you sure it had 58 amps listed? Very weird.

60 amp breaker is above the limit and technically wrong but anyone who writes this up needs to spend more time looking for something that matters.

Lots of inspectors agree that going up to 5 amps over the limit is ok and necessary due to the available breaker sizes.

[David A. Nice]

Originally Posted by bking

Are you sure it had 58 amps listed? Very weird.

60 amp breaker is above the limit and technically wrong but anyone who writes this up needs to spend more time looking for something that matters.

Lots of inspectors agree that going up to 5 amps over the limit is ok and necessary due to the available breaker sizes.

Yes, it is a brand new Carrier A/C unit and it's prety large. It really says 58 amp max. I'm not "writing it up", I'm just including the data in the report.

It's new construction and everything else is near flawless.

[Michael R. Boyett]

That would have to be one honker of a system. Any idea as to the tonnage?

[Mathew Hawley]

Bruce,

This does matter, a breaker that is larger than the data plate has labled will void the manufacturers warranty and it will void a home warranty plan as well (Anything to get out of paying a claim)

All A/C manufacturers have a phone# for tech support, they are more than happy to answer any questions for home inspectors, A/C techs ect.

Call the manufacturer and give them the model #

[David A. Andersen]

There may be more or less than a 2 amp difference depending on the voltage supplied.

Is your meter true RMS? Or are you assuming it's 110, 120, 128 VAC. What effect does voltage drop have on the supply...

I agree, lets worry about the more important stuff.
A mechanical contractor is the one in contact with the Mfg. and I don't see too many 58 amp breakers out there. What standard size breaker would you recommend, other than 60?

[Speedy Petey]

I too find this weird. When stating "minimum circuit ampacity" they typically give the actual number.
When stating "Max fuse or breaker size" they usually do use a standard size.

If it did in fact say 58 amps max fuse or breaker then 60 IS appropriate.
Not to get all NEC on you but it is clearly explained that if no standard breaker exists for a given circuit size/wire ampacity then we round UP to the nearest "stock" size.

[Marc Benz]

May i step in for a min guys ;

for the Central Air conding units ,, for the outdoor units they will useally listed both max and min rating so you can used the running amp and go up to max rating. but it can be allow to round up to next standard size

like this unit if say 58 amp you can use the 60 breaker that is fine


merci , Marc

[Mathew Hawley]

Many times I see data plates that says max breaker 30-amps and the unit will be on a 35 or 40-amp breaker. Per manufacturer this is wrong and will void their warranty. I heard of home warranty companies voiding their warranty as well

I have not seen a 58-amp max yet. I know there are some brands you have to round up to get the tons as well.

[Frank P. Newman]

I agree about the warranty if the nameplate or instructions say 30 A max BREAKER. However, if it states that the max LOAD is 58 A that is another story, IMHO. Since the is no 58 A breaker, you must use 60, because any smaller would result in nusiance tripping at or near rated load.

[Marc D. Shunk]

I think someone mis-read the dataplate. Got a picture? The 58 number sounds more typical of the number that would be in the LRA blank of the dataplate. When I did HVAC work, Carrier was my line. I never saw an odd number like that in the 'max fuse or breaker size' blank. I'd rather think that's the LRA for the unit in question.

[David A. Andersen]

I have not seen a 58-amp max yet. I know there are some brands you have to round up to get the tons as well.

Carrier is notorious for "off numbers" but I think your on line Marc.

[William E. Siegel]

We see that situation all the time. There is no such thing as a 58 amp breaker, so they go to the next size up, which is a 60 amp breaker. Anything higher will cause a problem.

[rgallahorn]

What part of "maximum" do we not understand? I agree 58 is an odd spec, but if it is as such, then the breaker must be smaller.

[Paul W. Abernathy]

Originally Posted by rgallahorn

What part of "maximum" do we not understand? I agree 58 is an odd spec, but if it is as such, then the breaker must be smaller.

I would reconsider that statement....

(B) Devices Rated 800 Amperes or Less.

The next higher
standard overcurrent device rating (above the ampacity of
the conductors being protected) shall be permitted to be
used, provided all of the following conditions are met:
(1) The conductors being protected are not part of a multioutlet
branch circuit supplying receptacles for cordand-
plug-connected portable loads.
(2) The ampacity of the conductors does not correspond
with the standard ampere rating of a fuse or a circuit
breaker without overload trip adjustments above its rating
(but that shall be permitted to have other trip or
rating adjustments).
(3) The next higher standard rating selected does not exceed
800 amperes.