A/C wire size.

L

letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
LarryFine said:
The inspector is saying that, because the conductors are larger than required, they therefore must have been "increased in size," which means the EGC must likewise be increased proportionately.
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That's because he's thinking the sizing is for voltage drop.

If he's not going to budge do a fused disconnect and a full size breaker
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
tortuga said:
The OP is proposing to use a 40A OCPD with a #10 equipment ground this is done and passes inspections every day.
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Given 250.122(B), that's not enough info to decide if #10 is sufficient. If you used #6 Cu conductors on your 40A circuit due to voltage drop, then you'd have to upsize the #10 EGC to #8.

Cheers, Wayne
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Another case where that technically applies is, when converting a 240v electric range circuit using #6NM w/a #10 EGC to a 120v gas range circuit, the #10 EGC is now not large enough for a 15a breaker.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
letgomywago said:
But there isn't anything to say that it's not.
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Sure there is: If "why" matters, ask the person who chose the wire size.

letgomywago said:
When over 10-2 romex I go straight to 6-3 SER. It is cheaper and AC disconnects arr dual rated and it has an oversized ground anyway.
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Absolutely! And it's easy to transition to copper for loads that require it.
 
L

letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
LarryFine said:
You mean the electrician or the inspector (both of whom really should know!)?


"That wire is larger than needed. Is that for voltage drop?"

"No."
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Remember half of people are bellow average.

After realizing half of electricians are below average was when I had to explain that a hardwired hot tub still needs gfi here in Oregon where they don't require gfi on normal dedicated circuits and that back in WA multiple competitors didn't know that you had to size overcurrent to the hvac max ampacity not just match the wire like 30a is good for everything even from inspectors that I'm gonna just do me when silly stuff comes up.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
infinity said:
This entire 250.122(B) code section needs to go away or at least be rewritten to the point where questions like this never come up again.
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As I have said before, it should be written to apply only to cases where the upsizing was done specifically for voltage drop, and the AHJ should decide if that is the real reason. I'll add I think that the exception should still be there.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
jaggedben said:
As I have said before, it should be written to apply only to cases where the upsizing was done specifically for voltage drop, and the AHJ should decide if that is the real reason. I'll add I think that the exception should still be there.
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That would work now someone needs to write it up. :)

Also if you have a metal raceway that is a listed EGC then 250.122(B) shouldn't even apply.
 
E

Eddie702

Licensed Electrician
Location
Western Massachusetts
Occupation
Electrician
Per the table above 250.122 the equipment grounding conductor is sized based on the overcurrent protection. Has nothing to do in this case with the size of the ungrounded conductors. As long as the overcurrent protection does not exceed 60 amps a #10 is adequate
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Eddie702 said:
Per the table above 250.122 the equipment grounding conductor is sized based on the overcurrent protection. Has nothing to do in this case with the size of the ungrounded conductors. As long as the overcurrent protection does not exceed 60 amps a #10 is adequate
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No, that's the whole point of 250.122(B), sometimes the table isn't adequate.

Cheers, Wayne
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
wwhitney said:
No, that's the whole point of 250.122(B), sometimes the table isn't adequate.

Cheers, Wayne
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Agreed. The times that it may not be adequate are most likely due to voltage drop and not much else as illustrated by several of the scenarios in this thread. Remove a VD drop situation from a normal installation and then you should be able to ignore 250.122(B)
 
kwired

kwired

Electron manager
Location
NE Nebraska
wwhitney said:
No, that's the whole point of 250.122(B), sometimes the table isn't adequate.

Cheers, Wayne
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I've seen many instances in irrigation applications where long distances inhibits rapid opening of overcurrent protection. Many times a component will fail and open a circuit instead of the overcurrent device opening the circuit on short circuits or ground faults. Same fault condition without long conductor runs would open same overcurrent device pretty rapidly.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
kwired said:
I've seen many instances in irrigation applications where long distances inhibits rapid opening of overcurrent protection. Many times a component will fail and open a circuit instead of the overcurrent device opening the circuit on short circuits or ground faults. Same fault condition without long conductor runs would open same overcurrent device pretty rapidly.
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So were the EGCs upsized on these installations per 250.122(B)?
 
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