John K.

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rosebud

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I had the opportunity yesterday to see a SQ D QO panel that had a burnt 60/60 breaker and melted tabs. This breaker is for the A/C condensor. The manufacture data plate on the condensor calls for a min. of 37.9 and a max. of 60 amp fuse. Also is calls for a max breaker of 60 amps HACR rated. The tech who installed the new condensor (I say new because of its condition) changed the fuses to 60's. The breaker remained a 60. It is my understanding that this is not in compliance to art. 440.12 & 440.22. I understand the fuses are there to protect not just the equipment and wiring but also the breaker in the panel from any potential damage. Am I wrong on this? Also becuase the breaker is not listed for HACR (this is an older SQ QO breaker) this is also a violation. Am I correct?
 

infinity

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Location
New Jersey
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Journeyman Electrician
The 60 amp CB is fine if it's HACR rated. Since the nameplate says an HACR CB or fuses either will be code compliant. Since the CB isn't HACR rated you'll need fuses. The fuses can be any size between the MCA and the maximum OCPD listed on the unit. With the 60 amp fuses, the installation is code compliant.
 

rosebud

Member
John K.

Because both the fuses, rate at 60 amps (not HACR rate) and the breaker SQ QO 60/60 amps. (also not HACR rated) how can there be any protection for the breaker from damage from the condensor unit. Shouldn't the fuses be say 40 amps and then the breaker at 60 amps?
 

infinity

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Location
New Jersey
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Journeyman Electrician
rosebud said:
Because both the fuses, rate at 60 amps (not HACR rate) and the breaker SQ QO 60/60 amps. (also not HACR rated) how can there be any protection for the breaker from damage from the condensor unit. Shouldn't the fuses be say 40 amps and then the breaker at 60 amps?


What is it that you're thinking might cause damage to the unit? The nameplate tells you what is required to protect the unit. Only the CB is required to be HACR rated. The fuses can be any size from the MCA to the maximum which in this case is 60 amps.
 

haskindm

Senior Member
Location
Maryland
The fuses are there because the circuit breaker was not HACR rated and the unit specified fuses or HACR rated breaker. If the breaker was HACR rated an unfused disconnect could have been used. The fuses are not there to protect the circuit breaker, but to meet the installation requirements of the unit. Circuit breakers are installed to protect conductors, we do not need to protect circuit breakers. The breaker was most likely damaged from heat caused by a loose connection, either at the conductors to the breaker or at the breaker to the buss. This damge probably had nothing to do with the fact that the breaker was not HACR rated. The same damage would have occured regardless of the rating of the fuses in the disconnect.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I agree and just to clairify - the non-HACR breaker is fine as long as there are also 60A fuses in the circuit.

Steve
 

hillbilly

Senior Member
steve66 said:
I agree and just to clairify - the non-HACR breaker is fine as long as there are also 60A fuses in the circuit.

Steve
Point me to the code section that requires fuses with a non-HACR breaker.
A HACR breaker has built in time delay (inverse time). This allows it to start inductive loads without tripping (if properly sized). The non-HACR breaker (if non-adjustable) is instantaneous trip. I know that some units are required to be fused by the manufacturer, but I don't think it requires fuses just because you use a non-HACR breaker. I may be wrong. It wouldn't be the first time.
steve
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
Steve,
A HACR breaker has built in time delay (inverse time). This allows it to start inductive loads without tripping (if properly sized). The non-HACR breaker (if non-adjustable) is instantaneous trip.
All standard breakers are inverse time, some have an additional instantaneous (magentic) trip. The only time you can use an instantaneous trip only type is as part of a listed comination starter.
The following is from a SquareD FAQ:
QuestionWhat distinguishes a HACR breaker from other breakers?
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AnswerOnly the label. All UL489 listed breakers are granted the HACR rating. However, manufacturers label only some of them as HACR.

Don
 

electricman2

Senior Member
Location
North Carolina
Occupation
Retired Electrical Contractor
hillbilly said:
Point me to the code section that requires fuses with a non-HACR breaker.
A HACR breaker has built in time delay (inverse time). This allows it to start inductive loads without tripping (if properly sized). The non-HACR breaker (if non-adjustable) is instantaneous trip. I know that some units are required to be fused by the manufacturer, but I don't think it requires fuses just because you use a non-HACR breaker. I may be wrong. It wouldn't be the first time.
steve
There is no code requirement that requires fuses with a non-HACR breaker, that is the manufacturer's requirement and must be complied with per 110.3(B)
 

haskindm

Senior Member
Location
Maryland
To repeat what others have said: there is no code section that requires that HACR breakers be used on A/C equipment. Many of the equipment labels say: "Maximum Fuse or HACR Rated Breaker". If it says that, then a HACR breaker is required or a non-HACR breaker may be installed if it is supplemented with fuses. If the label says "maximum fuse size" (which many older units do) then there must be fuse protection in the circuit regardless of the rating of the circuit breaker (if any). In this case we are complying with the labelling of the equipment, not the NEC.
 
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