Code compliant sub from a 3-wire sub.
- Thread starter Srv52761
- Start date
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
IMO, No... Fuses can be okay as a means of disconnect depending if it is in a fusible disconnect switch or something similar
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
I agree with Dennis. Fuse disconnects are perfectly suitable as disconnecting means. I don't see any legal way that you can extend The wiring from a panel that is no longer code compliant.
It does seem to me that's been quite some time since you've been able to wire a panel this way. Probably about time to replace the panel and the wiring anyway.
It does seem to me that's been quite some time since you've been able to wire a panel this way. Probably about time to replace the panel and the wiring anyway.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
If the "3-wire sub panel" is located in an outbuilding, so that the existing ungrounded feeder is allowed for continued use, then the EGC system gets reestablished at the sub panel with a N-G bond, and it would be fine to run a 4-wire feeder from there, right?
Cheers, Wayne
Cheers, Wayne
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Why would this matter? It is not currently compliant.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
We don't actually know that. If the subpanel referred to in the OP is in an outbuilding, then being supplied by an ungrounded feeder would be compliant for an existing install.
Cheers, Wayne
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
It was (maybe) compliant when installed. It was legal until the 08 code I believe. May have been a cycle either way, but somewhere in that time frame it was compliant. If the neutral & EGC are bonded in the subpanel, and a GEC and electrode is installed, I don't see a problem with running a 4-wire from there to a new subpanel. Of course the new subpanel would have to comply with current code with neutral & ground separated.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
I don't know how much you are allowed to add to an existing piece of hardware that is no longer compliant.
The Op seemed to indicate maybe it was a fused panel. I am not sure there is a compliant way to tack on to an existing fuse style panel.
he may also find he has a load problem once he does his load calculations.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I tend to agree. "Grandfathered" implies compliant. It's functionally an extension of the service. As long as it includes proper electrode(s), I see no reason a compliant feeder can not be supplied from it.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Grandfathered means it is NOT compliant but allowed to remain in service.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Right. By "compliant" I mean compliant when installed under past rules, and allowed to remain in the present rules.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It is compliant for the existing panel in the other building, we don't know if that is the case here, but adding another panel, IMO is not compliant
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
What code would prohibit supplying a 4-wire feeder from a legal-when-installed 3-wire-fed sub-panel?
The 3-wire sub-panel, with a neutral/ground bond, looks exactly like a service panel to the new feeder.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
IMO, the 3 wire is not compliant now but was at one time so when you add to the panel then you are adding something that is not compliant since the panel would now need a 4 wire feeder. I know there are 2 ways to look at this. Some inspectors here will let it go while others will not.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I've pulled feeders off of several fused panels. Usually I use one of the pull-out fuse blocks to feed the subpanel. Then take the load that was on the fuse block and add it to the subpanel. No problem in sending 4 wires from that to the sub.
Greentagger
Senior Member
- Location
- Texas
- Occupation
- Master Electrician, Electrical Inspector
What code would prohibit supplying a 4-wire feeder from a legal-when-installed 3-wire-fed sub-panel?
The 3-wire sub-panel, with a neutral/ground bond, looks exactly like a service panel to the new feeder.
250.24(A)(5), 250.142(B).
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
The hypothetical that I posited, that the subpanel is in a detached building (which is what grandfathered 3 wire subpanel brings to my mind) is allowed under 250.32(B)(1) Exception 1, and hence is compliant with both of the sections you referenced.
Cheers, Wayne
Greentagger
Senior Member
- Location
- Texas
- Occupation
- Master Electrician, Electrical Inspector
Agreed.
I did not fully understand the OP.
I was referencing to the usual bootleg 3 wire interior sub panels we see quite frequently in this area.
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