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Having an issue with inspector

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LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
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ggunn said:
Oh, poor you. :D

When I asked what difference it would make (CB or fuses), LarryFine replied "Because it's also about protecting the compressor unit."
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The equipment manufacturer is in the unique position to decide what is best for their equipment.
 
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jim dungar

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ggunn said:
OK, but what's the difference between fuses and a CB for this purpose? Is it that a CB might respond more quickly and trip during startup where fuses would not blow? I am not an HVAC expert.
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It has to do with the UL testing procedures. Probably the manufacturer cheaped out and only paid for the fuse testing.

Neither branch circuit fuses nor breakers will protect the compressor, they simply protect the power system from a failed compressor. Motor running protection is what would protect a compressor.
 
T

Tulsa Electrician

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Tulsa
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Did find this, for what it's worth.
 

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don_resqcapt19

don_resqcapt19

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augie47 said:
With that nameplate I would make the same call as the inspector (fuse required).
My understanding is that units so marked have only been evaluated (listed) using the fuse as protection.
The unit has not been tested to assure a C/B will provide adequate protection.
(It may boil don to the manufacturer not wanting to pay for testing/listing with a C/B)
In addition, failure to use a fuse might well void any warranty
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Or they just don't understand how the rules work.
 
don_resqcapt19

don_resqcapt19

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david luchini said:
Seems odd to me to reject a perfectly legal installation.
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UL does not agree that it would be a legal installation. The product standard covers the require markings on the nameplate. The UL Marking and Application Guide for Electrical Heating and Cooling Equipment makes it clear that where the manufacture chooses only to say "fuse" on the nameplate, that is the only type of OCPD that permitted to be used. If they want to permit the use of a circuit breaker, they must put that marking on the nameplate. Putting it only in the instructions does not comply with the requirements of the product standard.
 
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wwhitney

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dkidd said:
UL says that you can only use fuses.
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Caveat to the following: I've only browsed maybe a dozen UL standards, and generally just skim them as they are so long. So I'm not as familiar with them as I am with the NEC.

Having said that, I took a look at UL 1995 "Heating and Cooling Equipment," and my conclusion is that the standard does not ascribe any meaning or enforceable requirements to whether the nameplate says "Max fuse" or "Max CKT BKR" or "Max OCPD". The basis for that:

Clause 44 covers Markings and 44.3 is a list of different markings that should or may appear.

44.3(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."

44.3(x) Where required by Clause 76.1, the following marking or equivalent, "CAUTION: USE TIME DELAY FUSES."
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Note that 44.3(i) gives you 3 options, but provides no guidance as when to use each option. Generally when a marking means that different tests were done, the line item in the Marking section would say something like (made up) "Where the cable has passed the UV exposure tests in Clause 53, the marking "SUNLIGHT RESISTANT" or equivalent." You can see the contrast between 44.3(i) and 44.3(x), where it references Clause 76.1 (more on that to follow)

44.3(i) does reference Figure 44.2 and Clause 44.15. But Clause 44.15 just tells you how to calculate the MOCP (same as the NEC), and Figure 44.2 illustrates that. Neither refers to fuses vs circuit breakers, just overcurrent devices.

The equipment setup sections starting at 44.16 do not specify what type of OCP to use.

Clause 76 is for cord connected units (intended for a general use branch circuit, I gather), and requires that they undergo a starting test with fuses and not blow them. So any cord connected unit will work with fuses, even if it happens to be labeled "MAX CKT BKR". 76.1 basically says that if it blows normal fuses at startup, repeat the test with time delay fuses, and if it passes, apply the marking mentioned in 44.3(x).

Cheers, Wayne
 
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wwhitney

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don_resqcapt19 said:
The UL Marking and Application Guide for Electrical Heating and Cooling Equipment makes it clear that where the manufacture chooses only to say "fuse" on the nameplate, that is the only type of OCPD that permitted to be used.
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It does say that ( https://code-authorities.ul.com/wp-content/uploads/2014/04/EHCMG_AG.pdf ), in particular (Section 17 in part):

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.
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However, I find no corresponding language in UL 1995, and the options listed above don't even correspond with those listed in UL 1995 44.3(i). As the guide does not provide references or footnotes, I don't see the basis for the above statement.

Now the guide may just be saying "of course 44.3(i) gives you different labeling options, as an opportunity for the manufacturer to provide instructions to the user." Which obviously makes some sense, although the guide language implies fuses are always OK, which is not what the plain meaning of "MAX CKT BKR" would be.

But if none of the testing is any different based on what OCPD labeling was chosen, and if the manufacturer's installation instructions contradict the nameplate, I see no reason to elevate the choice on the nameplate over the choice in the instructions.

If anyone can point to something in UL 1995 I've overlooked, that would be very welcome.

Cheers, Wayne
 
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