using old main panel as sub panel?

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kmc

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Where do I start? I think I may have found my first job as a EC and boy am I ready to run from this one. This customer has built an addition(framed) on the side of house where the existing service drop entered, and now wants to upgrade his service. He was told by an electrician friend that he can move the service drop, upgrade his panel to 225 amps and then just feed his existing panel (with breaker) through the new panel ( the idea is not to rewire existing panel). The distance between the new panel and existing panel is roughly 25 feet. Has anyone ever done anything like this? I would just like to run this by the forum before I go to the AHJ and possibly look foolish. run forest run?
 
Yeah, no sweat. I do several of those each year, for various reasons. Get a ground bar for that old panel, and seperate the grounds and neutrals. Take out the bonding means in that old panel. Refeed it with 4-wire from your new panel or disconnect. Nothing unusual or hard about it. Naturally, all your service grounding will need moved over to the new service equipment.
 
Thanks much, I ve done this on commerial sites just never a home before. It seemed possible, but I have never done or seen this before. Do you use SE cable to feed the existing panel?
 
kmc said:
Do you use SE cable to feed the existing panel?
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Yeah, normally. SER, specifically. I struggle to not refeed a Federal Pacific or Sylvania/Zinsco panel or any brand of split buss panel if I can help it. You might want to double check to make sure you're going to refeed something that's worth the effort. If not, I'll use that old panel as a J-box and refeed each individual circuit from the new panel.
 
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It is a Sqaure D and looked like it was in pretty good shape. thank you again
 
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Here's a head's up for you that might save you some grief... make sure that panel you propose to refeed as a sub is in a compliant location with regard to working space. Some inspectors will grandfather a non-compliantly located panel when you refeed it, some will not. Just double check for width, headroom, pipework, etc. If you determine that there are any working space contradictions, ask your inspector ahead of time to save the ambush at actual inspection time.
 
bradleyelectric said:
Is that a local amendment for you?
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I'd say no, it's not. Think about it: where would you connect the existing neutral that was, at the time, allowed to also be used for equipment grounding also, as long as it was either insulated or within an SE cable?

Plus, it had to originate at the main panel, where the neutral and ground were one and the same. Now that this panel is being rendered a sub-panel, and the neutrals and grounds separated, the appliance must be re-fed with a 3-conductor-plus-ground method.


To add: I installed an ATS and generator on one job, I was able to show the inspector that it was impossible to run a new cable to the existing cooking and dryer appliances, and I was allowed to white-tape up the bare in the SE cables, and attach them to the neutral bus.

The problem is that, now, the appliances are not 'officially' grounded with an EGC separate from the circuit neutral, but I wasn't going to complain, and neither was my customer. It wasn't the ideal solution, but it was acceptable to the AHJ. In theory, I admit it's still wrong.
 
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Larry,
Read it a little closer. It only has to originate at the service for uninsulated neutral (SE cable), not if it has an insulated neutral. Then it makes sense that the inspector would allow tape to be used (if I ever get in that situation I'll have to ask our inspector if that would be allowed).

When I first read that section I was trying to figure out why that case had to originate at the service. I realized it was because a bare neutral would be hard to keep separate from the ground in the subpanel, which isn't an issue with an insulated neutral.
 
Yet another glorious example of clarity in the NEC.

250.140 Exception Condition (3)...is it:

( The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service entrance cable ) and ( the branch circuit originates at the service equipment. )

or is it:

( The grounded conductor is insulated ) , or ( the grounded conductor is uninsulated and part of a Type SE service entrance cable and the branch circuit originates at the service equipment. )

Parenthesis added to demarcate clauses.

I tend to believe that the first parsing of this exception is the correct one, since otherwise unbalanced loads on the subpanel would tend to energize the frame of the oven, whereas unbalanced loads on the main panel would tend to energize the entire house, with the oven at the same potential as the water pipes, for example.

However the position of that comma seems to point to the second parsing of the exception.

Yuk.

-Jon
 
Well, i obviously read it the second way. And since it is in a list of requirements, if originating at the service was always a requirement it could have been listed as a separate bullet.

Edit: I agree it is bad English. The things joined by AND are not equal.
 
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ptonsparky said:
I have always figured it the first way. Never made sense to me to keep the grounded and grounding conductors separate through one, two or more subpanels, then allow the Dryer or Range frame to be grounded via the neutral conductor. Kind of wastes the whole effort.
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They only allow it (as an exception) to prevent having to tear open an existing house to improve the service. Doesn't mean that if you have the chance you shouldn't do it right. Thats why new ones have to have 4 wires.
 
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