Adding GFCI/AFCI combo breaker/Outlet question

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Old 03-18-19, 06:20 AM
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Adding GFCI/AFCI combo breaker/Outlet question

Hi, I have a house that was built in 1956. Most of the outlets have been grounded to the metal box via BX. I've read all of different opinions on this form of grounding. Anyway I've decided to add some safety via breakers. GFCI/AFCI combo breakers. My question is what happens if I leave the ground on the outlets via metal box? Is it better to keep them in place or remove the grounds? So much confusion on this. Experience electricians even seem to have a divide on this.

Many Thanks!
 
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Old 03-18-19, 06:40 AM
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The receptacles should remain grounded to the metal boxes, and the BX cable spiral jacket should also remain bonded to the metal boxes. The GFCI and AFCI protection work independently of equipment grounding, and will provide a sufficient safety level to prevent electrical shock.

With this type of wiring it was grounded when it was new, but the problem is that the quality of the ground deteriorates over time due to rusting of the BX metal spiral. So what you have today is that some of your receptacles are probably grounded just fine, and some might be effectively ungrounded, just depending on which cables have corroded to which extent. To recognize this uncertainty, the code now just makes the assumption that all old BX circuits should be considered to be ungrounded; however in practice they do have some level of grounding and you should maintain that to the extent you can.
 
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Old 03-18-19, 06:42 AM
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Hi, I can not think of any reason to remove the grounds, not sure why any experienced electrician would be confused.
Geo
 
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Old 03-18-19, 06:55 AM
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It is confusing as you treat the circuits as ungrounded. Then NEC then states with any extension of an ungrounded system you are not to connect the grounding conductor. But since existing you can (should) leave the grounds connected.
 
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Old 03-18-19, 07:05 AM
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I bought the house in 2008. I'm pretty sure the 3 prong outlets were updated after initial construction. Probably 80's by looking at them. Question is I want to replace them all with newer outlets with the child protective sockets. Plus the prongs are very loose on some of them. Not very safe when my kids are plugging their devices into them all the time. I'm planning on replacing all of them as is just with updated outlets and keeping the wiring the same. The confusion s current code vs what functionally can work. 99% of everything we use is 2 prong anyway. Just want to make sure I'm doing things as safe as possible while keeping within my financial means.
 
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Old 03-18-19, 08:01 AM
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As long as the circuit has GFCI protection, you can install 3 prong receptacles on the ungrounded circuits. The code requirement in this case is that you put "GFCI PROTECTED OUTLET" and "NO EQUIPMENT GROUND" stickers on each receptacle faceplate. A sheet of stickers comes in the box with GFCI devices.
 
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Old 03-18-19, 08:15 AM
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I'm slowly upgrading all my outlets, too. My house was built in 1961 and is grounded via the "Boston Backwrap" method where all the boxes are metal (no BX), and the ground wire is wrapped around the romex (pretty old green/silver kind) and in contact with the box at the cable clamp where it enters the box. There are no ground wires connecting any of the switches or receptacles to the box - the old way just relies on the mounting screws to complete the ground, I guess.

Every switch or receptacle I've replaced, I make sure the clamp is tightened securely to maintain that ground connection, and I also add a ground wire to connect the switch/receptacle's ground screw directly to the metal box.
 
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Old 03-18-19, 09:55 AM
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Interesting points. My question is if the outlets are grounded to the box already and verified by testing, do I have to lable them ungrounded when I add the GFCI combo breaker in the panel?
 
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Old 03-18-19, 11:24 AM
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Regular electrical testers are not capable of doing the type of testing necessary to verify the ground is good. It will test as good, but when any sort of significant load is applied to the corroded connections in the spiral the impedance will increase sharply. The failure mode is that a hot wire shorts to the spiral somewhere far out in the branch circuit, and the impedance is too high to trip the breaker. The spiral then becomes a big toaster element running through the wall and starts a fire.

Even if it did test good this year, it might not be good next year because we know the spiral deteriorates even in dry areas, so we must assume it is not grounded.
 
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Old 03-18-19, 12:36 PM
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Would the cfgi/afci breaker trip before?
 
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Old 03-18-19, 12:55 PM
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Yes either a GFCI or AFCI device will trip off in that case.
 
 

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