Having an issue with inspector

T

Treg the electrician

Member
Location
lynnwood washington
Occupation
electrician
Inspector failed electrical on heat pump job stating that the disconnect needed to be fused. There was no issue with ampacity or wire size. On the name plate it gives an MCA and a max fuse size. It says nothing about MOCP it just lists those two categories. I have a correctly sized breaker. All NEC requirements are met. Does anyone have any advice on dealing with this? The installation instructions say that either a fused disconnect or a breaker can be used.
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Treg the electrician said:
Inspector failed electrical on heat pump job stating that the disconnect needed to be fused. There was no issue with ampacity or wire size. On the name plate it gives an MCA and a max fuse size. It says nothing about MOCP it just lists those two categories. I have a correctly sized breaker. All NEC requirements are met. Does anyone have any advice on dealing with this? The installation instructions say that either a fused disconnect or a breaker can be used.
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Does the data plate on the unit specifically say "Max fuse size"? If that's what it says, then you have to abide by it in a circuit breaker would not be allowed. However then the installation instructions say breaker or fuse is acceptable? That is odd. Did you show the inspector that statement in the instruction manual?
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
LarryFine said:
Because it's also about protecting the compressor unit.
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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.
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
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?
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Kind of speculating here, I admit I don't know the specifics about the testing/evaluating/listing process, but perhaps some of the components were evaluated with a certain type of ocpd but not others. Kind of like how equipment might be evaluated for A SCCR rating and a certain type of ocpd was required to get a certain rating.
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
electrofelon said:
Kind of speculating here, I admit I don't know the specifics about the testing/evaluating/listing process, but perhaps some of the components were evaluated with a certain type of ocpd but not others. Kind of like how equipment might be evaluated for A SCCR rating and a certain type of ocpd was required to get a certain rating.
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I was hoping that LarryFine would have something to offer.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
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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I would think that, generally speaking, fuses open more quickly for motor protection.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
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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