HVAC OCPD is oversized by 5 amps from the manufacturer's plate.

[zimm]

Help out a home inspector. Split HVAC heat pump- 240VAC OCPD was 30 amps and the manufacturer's plate on the exterior unit said max is 25 amps. I know that the branch wiring can be lighter gauge than required for a circuit on HVAC, but can the breaker be oversized? I think not, but then again google shows a bunch electrician chatter about 5 amps over is okay and home inspectors overreact. I just want to report was is right and wrong here.

I can't seem to find an actual copy of NEC 440 without buying a subscription either.

 

[d0nut]

Maximum means maximum. If the unit's nameplate said max 25 amps, there needs to be a 25A or smaller circuit breaker or fuse in the branch circuit.

 

[zimm]

Maximum means maximum. If the unit's nameplate said max 25 amps, there needs to be a 25A or smaller circuit breaker or fuse in the branch circuit.

Thanks for clarifying.

 

[infinity]

I agree with d0nut 5 amps is not okay. "Caveat emptor" when you get info from the Internet.

 

[solarken]

I can't seem to find an actual copy of NEC 440 without buying a subscription either.

 

[augie47]

Also read the nameplate carefully. Some minisplits we see call for "Fuse protection" as opposed to fuse or breaker. If the name plate only mentions fuse the protection must be by a fuse at the panel or disconnect.

 

[Crash117]

Also read the nameplate carefully. Some minisplits we see call for "Fuse protection" as opposed to fuse or breaker. If the name plate only mentions fuse the protection must be by a fuse at the panel or disconnect.

To continue with Augie’s thread, if it’s fuses only, just leave the 30 amp breaker as long as you’re on 10 gauge wire and use a fused disconnect with 25 amp fuses and you’re covered just right.

 

[mtnelect]

Also, read the Installation Instructions from the manufacturer ... It might require 60 degree wiring only, usually located as a "foot note".

 

[curt swartz]

Also, read the Installation Instructions from the manufacturer ... It might require 60 degree wiring only, usually located as a "foot note".

The footnote in the image you posted does not require 60C wiring. It is stating their recomended wire size is based on 60C wire 50' long.

Also don't put too much into manufactures spec sheets. They don't always match the actual units nameplate that should be used for circuit sizing.

 

[jaggedben]

I see oversized OCPDs on HVAC units *all the time*.

 

[ramsy]

can't seem to find an actual copy of NEC 440 without buying a subscription either.

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2020 NFPA-70 422.62(B)(1) nameplate data requirements, with max fuse or breaker, are subject to temperature limits per 110.14(C).

Meaning wire size is restricted by the lowest temperature tolerance.

 

[Jaybone812]

Also, read the Installation Instructions from the manufacturer ... It might require 60 degree wiring only, usually located as a "foot note".

The cut sheet you posted does not restrict the branch circuit conductors to their 60c ampacity . It means that the whatever size wire they recommend in fhe intructions is based on that conductors 60c ampacity. The product standard for hvac equipment is and has been a rating of 75c for quite a while . Branch circuits for these units should only be restricted to 60c ampacity when using a 60c wiring method like nm cable


Sent from my iPhone using Tapatalk

 

[Jaybone812]

Also read the nameplate carefully. Some minisplits we see call for "Fuse protection" as opposed to fuse or breaker. If the name plate only mentions fuse the protection must be by a fuse at the panel or disconnect.

I’ve seen quite a few mini splits lately that restrict the ground fault short circuit protection to a fuse . There are so many’s guys who will argue til they are blue in the face that the nameplate isn’t saying only a fuse can be used they will argue that it’s only referring to a ocpd in general and a fuse and breaker are interchangeable. That’s a frequent debate in threads in the fb electrical groups .

 

[electrofelon]

I’ve seen quite a few mini splits lately that restrict the ground fault short circuit protection to a fuse . There are so many’s guys who will argue til they are blue in the face that the nameplate isn’t saying only a fuse can be used they will argue that it’s only referring to a ocpd in general and a fuse and breaker are interchangeable. That’s a frequent debate in threads in the fb electrical groups .

While true, I am highly skeptical that when they say fuse it is because any actual testing was done and found that a fuse was required to protect the unit. I admit I will ignore that most of the time

 

[Jaybone812]

While true, I am highly skeptical that when they say fuse it is because any actual testing was done and found that a fuse was required to protect the unit. I admit I will ignore that most of the time

I attached the enhanced content of 440.21 2023 NEC from NFPA link which addresses that issue and references 110.3(b) when referring to the product listing . Not calling anybody a hack for using a breaker at all because like you I’ve ignored the restriction as well, but on a service call when the fuses weren’t readily available . I try to stick to fuses if the nameplate calls for them . There’s also a difference in knowing what’s called for and disregarding the fuse because you know it’s safe with a breaker and won’t compromise the equipment , and just thinking calling fuse a fuse is just the max ocpd in general

 

[infinity]

While true, I am highly skeptical that when they say fuse it is because any actual testing was done and found that a fuse was required to protect the unit. I admit I will ignore that most of the time

I agree. It think that dumb manufacturers use the term fuse when the unit is just fine with a circuit breaker.

 

[don_resqcapt19]

While true, I am highly skeptical that when they say fuse it is because any actual testing was done and found that a fuse was required to protect the unit. I admit I will ignore that most of the time

If it says fuse, either they have not complied with the requirements of the listing standard, or they only had it tested with a fuse and did not pay the listing lab to do the second test with a circuit breaker.

 

[infinity]

If it says fuse, either they have not complied with the requirements of the listing standard, or they only had it tested with a fuse and did not pay the listing lab to do the second test with a circuit breaker.

I find it hard to believe that in 2024 any manufacturer is making regular ole AC equipment that cannot be protected by a circuit breaker. To echo electrofelon IMO in some instances it's more likely that some noob is not putting the correct info on the nameplate.

 

[jim dungar]

...it's more likely that some noob is not putting the correct info on the nameplate.

in which case the manufacturer is not following its UL Listing procedures, like FPE 2 pole breakers, and the product should be considered Non-listed. If they can't get a simple nameplate right what other things have they not done correctly?

 

[infinity]

in which case the manufacturer is not following its UL Listing procedures, like FPE 2 pole breakers, and the product should be considered Non-listed. If they can't get a simple nameplate right what other things have they not done correctly?

So what's your opinion of electrofelons statement that these units labeled fuses only will actually never be problematic if they're supplied by a circuit breaker?