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

[jim dungar]

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?

There is nothing wrong with having a feeder protected by a breaker, but the final branch protection needs to be a fuse. This is why there is such a plethora of 30A visible disconnect switches available.
In Europe it is not uncommon to find the fuse in the plug of these devices.

IMHO the fuses don't prevent the device from being problematic, but they protect problems from escalating beyond the unit.

 

[wwhitney]

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

UL 1995 "Heating and Cooling Equipment" Clause 46.16 specifies that the requisite tests are performed with supply conductors to the unit that are sized based on the 75C ampacity, unless per Clause 45.11 the operational tests cause temperatures higher than 75C in the terminal compartment, in which case the unit is to labeled and tested with an appropriately higher minimum insulation temperature rating.

So if I understand correctly, all UL 1995 listed equipment will have 75C rated terminals.

Cheers, Wayne

 

[Jaybone812]

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

I 100% agree . I don’t feel like using a breaker to protect the unit instead of a fuse effects compromises the safety of the installation or effects has an effect on how the unit operates . And that’s been made pretty clear by the amount of times a breakers is used instead of the fuse . But the instructions don’t create create a conflict with any code rules so we can be cited if we don’t use the fuse .


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[electrofelon]

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.

Any idea why they would choose to have it tested with a fuse instead of a circuit breaker? Did someone wake up and forget it's 2024?

 

[don_resqcapt19]

Any idea why they would choose to have it tested with a fuse instead of a circuit breaker? Did someone wake up and forget it's 2024?

that is very likely the answer

 

[Jaybone812]

UL 1995 "Heating and Cooling Equipment" Clause 46.16 specifies that the requisite tests are performed with supply conductors to the unit that are sized based on the 75C ampacity, unless per Clause 45.11 the operational tests cause temperatures higher than 75C in the terminal compartment, in which case the unit is to labeled and tested with an appropriately higher minimum insulation temperature rating.

So if I understand correctly, all UL 1995 listed equipment will have 75C rated terminals.

Cheers, Wayne

I was aware the product standard for listed hvac equipment had been a 75c rating for a long time but wasn’t wasn’t aware it was almost 30 years though ! Thanks for the info


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[don_resqcapt19]

UL 1995 "Heating and Cooling Equipment" Clause 46.16 specifies that the requisite tests are performed with supply conductors to the unit that are sized based on the 75C ampacity, unless per Clause 45.11 the operational tests cause temperatures higher than 75C in the terminal compartment, in which case the unit is to labeled and tested with an appropriately higher minimum insulation temperature rating.

So if I understand correctly, all UL 1995 listed equipment will have 75C rated terminals.

Cheers, Wayne

That is 100% correct and that requirement has been in the standard for a long time.

 

[wwhitney]

I was aware the product standard for listed hvac equipment had been a 75c rating for a long time but wasn’t wasn’t aware it was almost 30 years though !

1995 is the number of the UL listing standard, not a year.

Cheers, Wayne

 

[infinity]

That is 100% correct and that requirement has been in the standard for a long time.

So it's fair to say the confusing information in the notes in post #8 is not relevant to conductor sizing because there is no listed equipment that uses 60° C terminals.

 

[Jaybone812]

1995 is the number of the UL listing standard, not a year.

Cheers, Wayne

Realized that after I made the post was waiting for someone to call me on that that’s what I get for for only reading the post in detail before replying to it .


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[wwhitney]

Hmm, I just scanned through UL 1995 looking for references to the type of OCPD. Clause 44.3(i) requires marking the unit:

(i) For each hazardous voltage circuit which powers more than one motor or a motor and other loads rated 1.0A or more as shown in Figure 44.2 (see Clause 44.15) "MAX FUSE ____," or "MAX. CKT. BKR. ____," or "Maximum overcurrent protective device."

Clause 44.15 just tells you how to calculate the maximum rating and doesn't differentiate between fuses and circuit breakers. And Clause 44.3(i) has no language indicating that any of the 3 choices of text is restricted or required based on testing results or chocies.

The only test I found that refers to the branch circuit OCPD is section 64 "Limited short-circuit test." Clause 64.1 refers to the "branch circuit protective device of the type and rating specified in Clause 23.18". That clause refers to conditions under which the section 64 test can be skipped.

The upshot is I haven't found any language in UL 1995 where the choice of terminology under Clause 44.3(i) actually matters with respect to testing conditions or results. But perhaps I simply missed it; the free online access at "shopulstandards.com" does not permit text searching.

Cheers, Wayne

 

[jim dungar]

Clause 44.3(i) requires marking the unit:

So there is a requirement to mark the unit in one of three specific ways.
Where is the language that says the installer can ignore the required nameplate?

 

[wwhitney]

So there is a requirement to mark the unit in one of three specific ways.
Where is the language that says the installer can ignore the required nameplate?

If the choice in Clause 44.3(i) is not referenced anywhere else in the standard in any way, then that choice has no significance. Manufacturers might choose "Max Fuse" just because it's shortest and takes up the least space on the placard. In which case obviously there's no need to comply with the choice make on the wording on the nameplate, that choice was arbitrary.

Conversely, if there's some language that says such and such a test or such and such a computation shall be done with the branch circuit OCPD type specified in Clause 44.3(i) (and done twice if the manufacturer choses the "Maximum Overcurrent Protective Device" language, once with fuses and once with a circuit breaker), then obviously the choice matters and needs to be complied with.

I was looking for that language, but if it's present, it escaped me. In the several UL standards I've perused, the clause that describes optional markings usually references a clause describing testing that is required or depends on the marking. But UL 1995 Clause 44.3(i) doesn't do that.

So I'm left uncertain whether the wording choice has a significance or not.

Cheers, Wayne

 

[TX+ MASTER#4544]

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.

2023 NEC

Buy a current NEC edition that has been adopted in your jurisdiction.
Use your Code book and not anything else on the 'net' including "chatter".

Article 440 Air Conditioning and Refrigerating Equipment

"lighter gauge than required" what does that mean?

Section 440.4 (A) Hermetic Refrigerant Motor......
Section 440.4(C)
Section 440.6 (A)
Use the nameplate on the equipment. Do not exceed the OCPD rating size or if it requires the use of a fuse for the OCPD in lieu of a CB.
There should be a MCA label on the nameplate (Minimum Circuit Ampacity) Obey MFG listing.
GFCI not required in 2023 NEC,210.8(F) Exception No.2 for HVAC Expires in September 2026.

Thanks for reading
Comments accepted
TX+MASTER#4544

 

[infinity]

"lighter gauge than required" what does that mean?

That means that you do not need to follow the normal rule limits for small conductors like in Article 240: #14=15 amps, #12= 20 amps, #10=30 amps, etc.

 

[mtnelect]

This might help to explain

 

[TX+ MASTER#4544]

That means that you do not need to follow the normal rule limits for small conductors like in Article 240: #14=15 amps, #12= 20 amps, #10=30 amps, etc.

2023 NEC
infinity poster
If it's in the Code book about small conductors, yes you do need to follow the rules.
This includes ambient temperature and number of conductors after any corrections.
Yes, I agree that a lot of Code rules are modified to fit other articles.

Section 240.4(D) Small Conductors (D) (1) through (D8) For OCPD
And the asterick foot note at bottom of T.310.16.

Thanks for reading
Comments accepted
TX+MASTER#4544

 

[infinity]

infinity poster
If it's in the Code book about small conductors, yes you do need to follow the rules

Actually you do not if the loads are equipment like motors or HVAC units. In those cases the small conductor rules I noted do not apply.

 

[Jaybone812]

Actually you do not if the loads are equipment like motors or HVAC units. In those cases the small conductor rules I noted do not apply.

The parent text 240.4(d) tells us 240.4(d)(1-8) doesn’t apply to applications listed in 240.4(g)

 

[don_resqcapt19]

The UL Marking Guide for Electrical Heating and Cooling Equipment says:
[quote
17. BRANCH-CIRCUIT, SHORT-CIRCUIT AND GROUND-FAULT PROTECTION
Units required to be marked with a minimum circuit ampacity (see “Minimum Circuit Ampacity”)
are also required to show the maximum ampere rating of the short-circuit and ground-fault
protective device for each applicable circuit. These markings also conform with NEC® Section
430.7(D). They are computed in accordance with Section 430.53 and take into account any
remote loads used in the ampacity calculations. The branch-circuit, short-circuit and ground-fault
protection marking is included on the same label as the ampacity marking and is typically
identified as “Maximum Fuse Amps,” “Maximum Fuse or HACR Type Circuit Breaker Amps,”
“Maximum Fuse or Circuit Breakers Amps,” “Maximum Overcurrent Protection Amps” or their
suitable abbreviations.
There are several other situations when the maximum ampere rating of the short-circuit and
ground-fault protective device must be marked on the unit, even though a marking for minimum
circuit ampacity may not be required. Typical examples are overcurrent protection devices for
separate high voltage control circuits or transformers in the unit. These markings are identified in
the same manner as described above, but can be located on an attached wiring diagram (see
“Wiring Diagram”) or adjacent to the terminals or leads to which the supply circuit wires are to be
connected, rather than on or adjacent to the unit nameplate.
The markings for short-circuit and ground-fault protection always include some indication of the
type of protection device as well as the maximum current rating. This is significant since the
various types of devices recognized by the NEC® to provide this protection do not necessarily
provide the same level of protection for all units. Briefly, if the marking indicates:
1) Only “Fuse,” then only fuses are to be used;
2) “Circuit Breaker” and “Fuse,” then either fuses or circuit breakers
3) “Fuse or Circuit Breaker” or “Overcurrent Protection,” then fuses or any type of circuit
breaker (including “HACR Type”) may be used[/quote]
I see this marking guide as well as the label as both being 110.3(B) listing and labeling instructions.