ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Breaker size allowances
In the motor.
Breaker size allowances
- Thread starter noj
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: Breaker size allowances
Thanks Mark, I left out the part regarding ground fault protection.
Thanks Mark, I left out the part regarding ground fault protection.
john m. caloggero
Senior Member
Re: Breaker size allowances
Gentlemen: First of all, if the unit is Listed by a testing laboratory, Section 110.3(B) comes onto the scene and requires that the manufacturers instruction must be followed, it is part of the listing.
If the nameplate specifies 25A as the maximum ground-fault short-circuit protection and specifies 25A fuses, then fuses must be used. The other problem is that if the unit breaks down, the manufacturer can say you have voided the warranty by not using the proper electrical protection.
Gentlemen: First of all, if the unit is Listed by a testing laboratory, Section 110.3(B) comes onto the scene and requires that the manufacturers instruction must be followed, it is part of the listing.
If the nameplate specifies 25A as the maximum ground-fault short-circuit protection and specifies 25A fuses, then fuses must be used. The other problem is that if the unit breaks down, the manufacturer can say you have voided the warranty by not using the proper electrical protection.
stud696981
Senior Member
Re: Breaker size allowances
Here is a thought, I have seen this done on many jobs and did this on my own system.
The name plate says 25amp max. Place a 30amp breaker in the panel, feed it to the a fused disconnect at the AC unit with 25amp fuses in the disconnect using all #10 wire.
The unit now has it's 25amp max protection, the wiring is adequate for the job and no inspector challenges the job and no warranty is voided.
Here is a thought, I have seen this done on many jobs and did this on my own system.
The name plate says 25amp max. Place a 30amp breaker in the panel, feed it to the a fused disconnect at the AC unit with 25amp fuses in the disconnect using all #10 wire.
The unit now has it's 25amp max protection, the wiring is adequate for the job and no inspector challenges the job and no warranty is voided.
- Location
- Massachusetts
Re: Breaker size allowances
Heres where it gets interesting, a unit marked with a Maximum fuse size of 25 will probably also have a Minimum circuit ampacity rating of 20 amps or less.
Which would mean you could use the 30 amp breaker at the panel, 25 amp fuses at the disconnect and use 14 AWG for the entire circuit.
Ryan summed it up nicely but I will add you may fuse at the maximum and provide wire for the minimum.
[ May 08, 2005, 05:48 AM: Message edited by: iwire ]
Stud many times that is exactly what has to be done, many large units specify that fuses must be used even if you can get a breaker of the correct rating.
Heres where it gets interesting, a unit marked with a Maximum fuse size of 25 will probably also have a Minimum circuit ampacity rating of 20 amps or less.
Which would mean you could use the 30 amp breaker at the panel, 25 amp fuses at the disconnect and use 14 AWG for the entire circuit.
Ryan summed it up nicely but I will add you may fuse at the maximum and provide wire for the minimum.
[ May 08, 2005, 05:48 AM: Message edited by: iwire ]
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: Breaker size allowances
Stud,
I would agree that this is a fine way to do this installation but some would feel that it's simply a waste of money since it's not required.
[ May 08, 2005, 01:02 PM: Message edited by: infinity ]
Stud,
I would agree that this is a fine way to do this installation but some would feel that it's simply a waste of money since it's not required.
[ May 08, 2005, 01:02 PM: Message edited by: infinity ]
allenwayne
Senior Member
Re: Breaker size allowances
Probably going to get jumped on but here goes
If there is a dadta plate that states a min ampacity and a max breaker then it is allowed to wire for min.19 amps IMO I would use #12 not #14,#14 is to me so cheezy
Probably going to get jumped on but here goes
If there is a dadta plate that states a min ampacity and a max breaker then it is allowed to wire for min.19 amps IMO I would use #12 not #14,#14 is to me so cheezy
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: Breaker size allowances
You're right you could use #12 or #10 for that matter but since the nameplate states that the minimum circuit ampacity is 19 amps than you could also use #14. A larger conductor can be used but is not required.
charlie
Senior Member
- Location
- Indianapolis
Re: Breaker size allowances
Don't lose sight of the fact that the NEC is a set of minimums and you are permitted to go beyond those requirements. Additionally, voltage drop may enter into the picture if the AC is not close to the service or the serving electric utility doesn't have the transformer close to the building.
Remember "91.1(B) Adequacy. This Code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, . . ." The #14 is going to be safe but it may not work properly.
Don't lose sight of the fact that the NEC is a set of minimums and you are permitted to go beyond those requirements. Additionally, voltage drop may enter into the picture if the AC is not close to the service or the serving electric utility doesn't have the transformer close to the building.
Remember "91.1(B) Adequacy. This Code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, . . ." The #14 is going to be safe but it may not work properly.
allenwayne
Senior Member
Re: Breaker size allowances
I for one don`t like using #14 nm in a home never mind an A/C condensor,IMHO I would use 10 solid for the whip sure overkill the cost is minimal.easy to terminate and IMHO a better install.I am sure others will argue that #14 is ok to use but when I shut my eyes at night I don`t see $ signs.But when I wake up I do have to look in the mirror and I like to look at what I see.
Not a NEC violation but makes me feel; better none the less
I for one don`t like using #14 nm in a home never mind an A/C condensor,IMHO I would use 10 solid for the whip sure overkill the cost is minimal.easy to terminate and IMHO a better install.I am sure others will argue that #14 is ok to use but when I shut my eyes at night I don`t see $ signs.But when I wake up I do have to look in the mirror and I like to look at what I see.
Not a NEC violation but makes me feel; better none the less
- Location
- Massachusetts
Re: Breaker size allowances
Alan if voltage drop is not an issue can you explain why 10 solid is better than 14 stranded or solid for a 20 amp load?
Lets say you run a 100 amp feeder in PVC.
Do you run a 8 AWG EGC or do you run a 3 AWG EGC so you sleep better?
Alan if voltage drop is not an issue can you explain why 10 solid is better than 14 stranded or solid for a 20 amp load?
Lets say you run a 100 amp feeder in PVC.
Do you run a 8 AWG EGC or do you run a 3 AWG EGC so you sleep better?
Re: Breaker size allowances
Allen,
The NEC has been put together by some pretty knowledgeable people, I would think using it is a pretty safe bet.
Roger
[ May 09, 2005, 06:16 PM: Message edited by: roger ]
Allen,
so are you saying those who may follow the minimum should hate themselves? :roll:
The NEC has been put together by some pretty knowledgeable people, I would think using it is a pretty safe bet.
Roger
[ May 09, 2005, 06:16 PM: Message edited by: roger ]
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: Breaker size allowances
I agree, although it is considered to be a minimum it is still a very safe bet.
electricmanscott
Senior Member
- Location
- Boston, MA
- Occupation
- Massachusetts Master Electrician, one man show.
Re: Breaker size allowances
:roll: Not this foolishness again.
John K.
John K.
I have been reading this thread. I do not see this issue addressed. The Condensor data plate calls for a Max. of 60 fuses and a min. of 37.5 amps. The max. breaker sizes is also 60 amps. The service company that installed the condessor installed 60 amp fuses. The result is the SQ. D. QO 60/60 breaker and the adjoining buss tab melted. I understand that this is in violation of art. 440.12 & 440.22. Am I correct in believing that the fuses should have blown before the breakers saw the over load? I understand the code to say the fuse must be sized at an ampicity less thatn the breaker. Is this correct? Also the older QO breaker is not listed for HACR. Isn't this a code violation?
John K.
I have been reading this thread. I do not see this issue addressed. The Condensor data plate calls for a Max. of 60 fuses and a min. of 37.5 amps. The max. breaker sizes is also 60 amps. The service company that installed the condessor installed 60 amp fuses. The result is the SQ. D. QO 60/60 breaker and the adjoining buss tab melted. I understand that this is in violation of art. 440.12 & 440.22. Am I correct in believing that the fuses should have blown before the breakers saw the over load? I understand the code to say the fuse must be sized at an ampicity less thatn the breaker. Is this correct? Also the older QO breaker is not listed for HACR. Isn't this a code violation?
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
rosebud said:
This is a duplicate post
See here: http://www.mikeholt.com/code_forum/showthread.php?t=78091
Rosebud, not to split hairs here but who says for sure that the circuit was overloaded. OP says that the breaker and bus tabs were melted and burned. It is entirely possiblr that this was caused by a loose connection on the breaker screws, loose bussing in the panel, a loose lug on the panel feeds, etc, etc. I would strongly suggest having a qualified electrician look the situation over and give his opinion as to what caused the meltdown. the installation, as described, should have been just fine, there must be a reason it failed.
John K.
John K.
I am a lic. Electrician here in CA. Because of the damge I am looking at all avenues. I do know about the loose breaker & wire issue's. Because the damage is extensive now we are tring to understand how and why it happened. If I did not mention it earlier this condensor unit was changed out aprox. 1 year ago. It is possible that the A/C tech did not have an electcian look at the panel then and the breaker & buss could have been damaged then. They may have just installed a new Condensor and sized the fuses accordingly. I am trying to understand all of the possiblities for failure here and am looking for input not an argument.
John K.
I am a lic. Electrician here in CA. Because of the damge I am looking at all avenues. I do know about the loose breaker & wire issue's. Because the damage is extensive now we are tring to understand how and why it happened. If I did not mention it earlier this condensor unit was changed out aprox. 1 year ago. It is possible that the A/C tech did not have an electcian look at the panel then and the breaker & buss could have been damaged then. They may have just installed a new Condensor and sized the fuses accordingly. I am trying to understand all of the possiblities for failure here and am looking for input not an argument.
A breaker does not melt from overload unless it malfunctions and does not open. The most likely cause of a breaker melting is that there was a loose connection somewhere causing excessive heat. It sounds like the installation was code compliant. Don't forget the baics of good workmanship and "thoroughly good" connections. I love that wording - when is a connection not just good, but thoroughly good? See 110.14(A).
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