In a house with 2-wire receptacles throughout, I'm considering replacing the panel. The existing panel has a common neutral/ground bus. Would the new panel require neutral and ground to be on separate bus? What about GFCI circuits--any implications there?
Residential Panel Replacement
- Thread starter msteiner
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wbalsam1
Senior Member
- Location
- Upper Jay, NY
Hi: Are you putting a main service disconnect before the panelboard or is the MCB within the panelboard? What sort of problems do you anticipate with GFCI-protected 2-wire receptacles? :-? 
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Are you considering replacing the panel or are you just designing it.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Not if this panel contains the main (i.e., first) disconnect. Make sure it still will be able to after the upgrade.msteiner said:
GFCI devices do not depend on the presence of EGC's, only that the service neutral be grounded.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The reason I asked because you are an electrical engineer are you also a licensed electrician?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Okay if this is your main service panel it will need to have the grounds and neutrals bonded together. Once the wires leave the panel the grounds and neutrals must be isolated form each other. Thus if you added a sub panel you would be required to have a 4th wire as the EGC.
You will only need 3 wires from the meter to the panel.
There should be no problems with GFCI circuits on a 2 wire system (no ground).
You will only need 3 wires from the meter to the panel.
There should be no problems with GFCI circuits on a 2 wire system (no ground).
mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
Actual author of this post....
Actual author of this post....
Thanks guys for your responses to this thread.
I'm the one replacing the 2-wire 100A, MCB panel, and I had asked msteiner to post to this forum for a response.
And now I've finally registered - as I should have long ago!
To reiterate the question, and sum up the responses:
I was asked by a friend to fix his house panel, because the main breaker is broken. Upon inspection, I determined it to be a 1960s vintage Square D QO panel with a 100 amp type Q1 breaker. It is a 2-wire installation, in that all receptacles are 2-wire, and all grounds and neutrals are tied together at the panel.
I found a reconditioned Q1 100 A MCB for about $100 - but the panel is 40+ years-old, so a better approach is to replace it with a new MCB panel.
If I do that, all of the breakers would be replaced as well. That prompted me to think about the 2-wire receptacles - and the NEC GFCI replacement requirement in 406.3(D)(3)b. But since I'm leaving 2-wire receptacles alone and just replacing the breakers, I realize that I don't need to supply GFCI breakers for the receptacle circuits - unless there are existing 3-wire replacement receptacles.
Thanks for the assistance..... and I'll be baaaaaack!
mayanees
Actual author of this post....
Thanks guys for your responses to this thread.
I'm the one replacing the 2-wire 100A, MCB panel, and I had asked msteiner to post to this forum for a response.
And now I've finally registered - as I should have long ago!
To reiterate the question, and sum up the responses:
I was asked by a friend to fix his house panel, because the main breaker is broken. Upon inspection, I determined it to be a 1960s vintage Square D QO panel with a 100 amp type Q1 breaker. It is a 2-wire installation, in that all receptacles are 2-wire, and all grounds and neutrals are tied together at the panel.
I found a reconditioned Q1 100 A MCB for about $100 - but the panel is 40+ years-old, so a better approach is to replace it with a new MCB panel.
If I do that, all of the breakers would be replaced as well. That prompted me to think about the 2-wire receptacles - and the NEC GFCI replacement requirement in 406.3(D)(3)b. But since I'm leaving 2-wire receptacles alone and just replacing the breakers, I realize that I don't need to supply GFCI breakers for the receptacle circuits - unless there are existing 3-wire replacement receptacles.
Thanks for the assistance..... and I'll be baaaaaack!
mayanees
mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
I'm the one who's doing the 2-wire panel replacement, and I had asked msteiner to post the question for me as to the NEC requirements.
I should have registered before - but I'm here now!
Thanks for your responses.
To summarize the question and responses:
A friend asked me to fix a broken main breaker in his 2-wire house panel. Upon inspection I find that it's a 1960s vintage QO panel with a Q1 100 amp main breaker. I found a replacement breaker for $100 - but I think it's better money spent to replace the entire panel.
A responder wrote that in the new panel I should keep the N & G wires separated - Agreed.
My other question was rooted in NEC's 2-wire receptacle replacement requirements - being a GFCI 406.3(D)(3)(b), a 2-wire receptacle, or a GFCI breaker protected 3-wire.
I mistakenly brought this thinking back to the panel, where I thought I might need to feed those receptacle circuits with a GFCI. But after reading the section - I've concluded that I don't need to install GFCI breakers for the receptacle circuits unless there are existing replacement 3-wire receptacles.
Again Thanks for the responses.
mayanees
I should have registered before - but I'm here now!
Thanks for your responses.
To summarize the question and responses:
A friend asked me to fix a broken main breaker in his 2-wire house panel. Upon inspection I find that it's a 1960s vintage QO panel with a Q1 100 amp main breaker. I found a replacement breaker for $100 - but I think it's better money spent to replace the entire panel.
A responder wrote that in the new panel I should keep the N & G wires separated - Agreed.
My other question was rooted in NEC's 2-wire receptacle replacement requirements - being a GFCI 406.3(D)(3)(b), a 2-wire receptacle, or a GFCI breaker protected 3-wire.
I mistakenly brought this thinking back to the panel, where I thought I might need to feed those receptacle circuits with a GFCI. But after reading the section - I've concluded that I don't need to install GFCI breakers for the receptacle circuits unless there are existing replacement 3-wire receptacles.
Again Thanks for the responses.
mayanees
- Status