How to ground my home electrical in accordance with code?

December 6, 2011 4:57 PM

Help me understand the national electric code with regard to rewiring and updating several rooms in my 1940s-era house.

I am planning for some electrical work that I will be performing in my 1940s-era house. I have several rooms that have no grounded outlets or wiring and I plan to rewire them and add these. I grok the 'electricity' part, but I need to know more about the electrical code.

1. Does the national electric code (NEC) require me to add enough new outlets such that they can be spaced according to current standards?

2. Does the NEC permit me to tie an existing, ungrounded lighting circuit into a grounded branch circuit? (I'd do so because I won't be able to staple a new run of grounded wire to the studs in the enclosed wall cavity.)

3. In general, does the NEC require that anything I modify be done such that it would be consistent with the current standards? That is, if I modify one connection in an existing junction box, am I bound to update everything in that box?

These sorts of things might be totally under the purview of my local building codes; that's a totally reasonable response. I plan on asking my local inspector these (and many other) questions when I apply for a permit. I just want to know as much as possible about national statutes before having that conversation. Many thanks!

posted by JohnFredra to home & garden (8 answers total)

These answers will depend more on your local building inspector than the code.

The code does allow existing wiring to remain in place, however most local building codes require that at certain point, you must totally update it all. For example, in my county, if 50% of the electric in the house is modified, than all of it must brought up to code.

One thing that might help you, if you have un-grounded wire, you can install a GFCI receptacle, and thus have a three prong outlet on un-grounded wire. Installing GFCIs receptacles might be easier than re-wiring the room.
posted by Flood at 5:10 PM on December 6, 2011 [1 favorite]

You want Code Check Electrical.
posted by dhartung at 5:47 PM on December 6, 2011

Thanks Flood -- I'll ask if there's a tipping point.

And thanks, dhartung -- I've seen that before and it looks really handy. Just to clarify, my question is not as much about how to wire things according to current code, but to what extent I'm required to do so.
posted by JohnFredra at 5:57 PM on December 6, 2011

Seconding Flood: My local building department talked through my plans, and then said "put it down as 'repair outlets', that way as long as it's better than what was there we have to approve it." I haven't gotten to the electrical in my home yet (although I am in the process of doing the electrical in my workshop, but that's new construction), but my impression was that the building department in my Northern California city of 60k people was going to be more flexible on this than I thought because they'd rather have the chance to get a set of eyes on the results than to just have me do it without permits.
posted by straw at 6:02 PM on December 6, 2011

"Does the national electric code (NEC) require me to add enough new outlets such that they can be spaced according to current standards? "

Generally no, though you'd be restricted from reducing the current number of outlets.

"Does the NEC permit me to tie an existing, ungrounded lighting circuit into a grounded branch circuit? (I'd do so because I won't be able to staple a new run of grounded wire to the studs in the enclosed wall cavity.)"

This is complicated but generally you'd be allowed to do this. It's really going to depend on your Authority Having Jurisdiction (AHJ) IE: Electrical inspector.

"In general, does the NEC require that anything I modify be done such that it would be consistent with the current standards? That is, if I modify one connection in an existing junction box, am I bound to update everything in that box? "

Pretty well up to the AHJ. Sometimes it's a percentage. Other times it is some kind of personal preference of the AHJ. For example here when we do a service upgrade (Typical 60-100A fused panel to 200A breaker panel) we have to add:

1. Dedicated outdoor outlet
2. Dedicated outlet for the fridge
3. Bond the metal water supply and gas pipes.
4. GFCI receptacle in the bathroom

We don't however need to add:

1. GFCI kitchen outlets that would require GFCI in new construction
2. Bond cast iron sewer pipes
3. Install Arc Fault protection in bedrooms

Somewhat nonsensical but that's the way it is in my area.

Flood writes "One thing that might help you, if you have un-grounded wire, you can install a GFCI receptacle, and thus have a three prong outlet on un-grounded wire. Installing GFCIs receptacles might be easier than re-wiring the room."

Note that this increases safety but does not provide a ground.

"(I'd do so because I won't be able to staple a new run of grounded wire to the studs in the enclosed wall cavity.)"

FYI: A wire fished inside a cavity with no access that would permit stapling generally doesn't require stapling. The only gotcha is the wall cavity can't contain wiring that could be damaged by fishing (generally Knob and Tube) or anything that could damage the wire being pulled. So for example you can't fish loomex (NM-90) in a cavity under a asphalt shingled roof because the nails penetrating the roof deck stand a good chance of damaging the wire.
posted by Mitheral at 9:38 PM on December 6, 2011

Note that this increases safety but does not provide a ground.
A GFCI receptacle provides ground fault interruption. Having a GFCI is safer - which is why they are required to be installed within 6ft of a water source.

Installing a GFCI receptacle on ungrounded wire is a safe acceptable solution according to the NEC
posted by Flood at 2:59 AM on December 7, 2011

Thanks all! The local electrical inspector (who thankfully seems like a good guy) was in agreement with what has been said here.

>> FYI: A wire fished inside a cavity with no access that would permit stapling generally doesn't require stapling.

Mitheral, thanks for mentioning this. I wouldn't have even thought to ask about it otherwise.
posted by JohnFredra at 7:41 AM on December 7, 2011

Flood writes "Installing a GFCI receptacle on ungrounded wire is a safe acceptable solution according to the NEC"

I agree, it's a safe and cheap solution to upgrading ungrounded outlets. However because a GFCI doesn't create a ground some equipment that requires a ground to operate aren't going to operate on a no ground GFCI circuit. Most commonly this is an issue with surge protectors which depend on a ground to dump voltage spikes into. No ground means no protection. Some electronic equipment can also act flaky without a good reference ground.
posted by Mitheral at 6:45 PM on December 7, 2011