Arc Fault Breakers in a panel 3 wire feeder

[kwired]

Methinks there's some confusion, the OP panel is an older 3 wire w/bond to it's shell

Most are.

I'm willing to bet the meter , if similar vintage , is also , the GEC could exist at either, depending on the poco

~RJ~

I also initially understood it to be that way - even though not up to code (even at time of installation), that is typical when you do run into those situations.


Biggest issue with it is potential voltage rise on EGC's and obejects bonded to EGC's, and/or neutral current being carried on those paths. If it were a subpanel feeding an entire second floor and there were no conductive paths to anywhere else - it sort of really doesn't matter if you ran three wires to said panel and then ran separate EGC's beyond that point. We do similar with services even when there is ground/grounded objects around.

 

[Little Bill]

Methinks there's some confusion, the OP panel is an older 3 wire w/bond to it's shell

Most are.

I'm willing to bet the meter , if similar vintage , is also , the GEC could exist at either, depending on the poco

~RJ~

I also initially understood it to be that way - even though not up to code (even at time of installation), that is typical when you do run into those situations.


Biggest issue with it is potential voltage rise on EGC's and obejects bonded to EGC's, and/or neutral current being carried on those paths. If it were a subpanel feeding an entire second floor and there were no conductive paths to anywhere else - it sort of really doesn't matter if you ran three wires to said panel and then ran separate EGC's beyond that point. We do similar with services even when there is ground/grounded objects around.

If you all are talking about the subpanel being bonded, the OP says its not.

At the service the ground and neutral are bonded as per code it is only the feeder from there to the sub panel that does not have a dedicated ground only 2 hots and a neutral. At the sub panel the neutral/ground bar is not bonded to the can however all branch circuits are 12/2 with a ground so all grounds and neutrals are together. this is very typical for all the house in the area of this age built in the early to mid 80s or earlier.

 

[david]

Absolutely.

The AFCI does not need a ground reference to function. A ground reference may help with quicker development of conditions for it to respond to though.

This is no different then connecting that same breaker to an older wiring method that has no EGC, it will still do it's thing if the right conditions do develop.

I don't understand tell m e how the breaker is going to trip when the hot shorts to an unbonded panel enclosure

 

[kwired]

If you all are talking about the subpanel being bonded, the OP says its not.

Seen that a lot on old installs also, even at service equipment, from what he said the EGC's are still connected to the neutral bus, so just the panel cabinet is a problem. Though there is an improper feeder situation I'd still want to at least bond the cabinet in this situation.

I don't understand tell m e how the breaker is going to trip when the hot shorts to an unbonded panel enclosure

It is not, it won't trip any the other existing circuits should they do the same thing.

That won't prevent the breaker from protecting the rest of the circuit should there be a fault with low impedance return path.

This doesn't make the breaker useless, it just doesn't lead to high fault currents when there is a fault to something not bonded.

 

[david]

Seen that a lot on old installs also, even at service equipment, from what he said the EGC's are still connected to the neutral bus, so just the panel cabinet is a problem. Though there is an improper feeder situation I'd still want to at least bond the cabinet in this situation.


It is not, it won't trip any the other existing circuits should they do the same thing.

That won't prevent the breaker from protecting the rest of the circuit should there be a fault with low impedance return path.

This doesn't make the breaker useless, it just doesn't lead to high fault currents when there is a fault to something not bonded.

A lot of sub feed panels I see are within 10 ft of the service panel in damp basements mounted on a piece of ¾ board of some type.

A lot of panels next to a washer or dryer or some old furnace. I also see them from time to time in dry finished areas of a home not surrounded by any other grounded equipment or concrete walls and floors.

If I seen an unbounded panel enclosure I would say to them in a fault condition the breaker is never going to trip and leave that panel energized and someone is going to get hurt.

 

[kwired]

A lot of sub feed panels I see are within 10 ft of the service panel in damp basements mounted on a piece of ¾ board of some type.

A lot of panels next to a washer or dryer or some old furnace. I also see them from time to time in dry finished areas of a home not surrounded by any other grounded equipment or concrete walls and floors.

If I seen an unbounded panel enclosure I would say to them in a fault condition the breaker is never going to trip and leave that panel energized and someone is going to get hurt.

If it is within 10 feet of the service panel and everything is exposed, why not just replace with a feeder that has an EGC and make it right? Worst case bond what is existing. How often do you see the cabinet get energized, vs a fault in the furnace, washer, dryer, etc? Still good idea to bond it, but I think it is lower risk than a fault in an appliance.

If it is a panel in a remote part of the house, you may need to convince the owner it needs a change before just doing something like that. Especially if the only reason you were there is to add one circuit.

 

[ddservices]

afci

afci

The sub panel is approx. 90 ft from the service. The issue with repalcing the feeder is it is a 2 story house and the only way to re-run feeder will require substantial sheetrock damage. Also i am more than willing to do all the upgrades however if the customer cant or wont pay for labor and material I wont I am not a non-profit EC. Also just for some additional info the neutral is bonded at the service with the slab and ground rod. Correct me if I am wrong but We only bond the neutral at the point of service and if we bonded the neutral bar in this case that would be a code violation as well.

 

[al hildenbrand]

Also just for some additional info the neutral is bonded at the service with the slab and ground rod. Correct me if I am wrong but We only bond the neutral at the point of service and if we bonded the neutral bar in this case that would be a code violation as well.

Yes, installing a bonding jumper in the OP supanel is a Code violation, however, as is clearly being discussed in the posts above this one, leaving the subpanel enclosure floating leaves a real world hazard. . . Real world trumps paper.

 

[growler]

Yes, installing a bonding jumper in the OP supanel is a Code violation, however, as is clearly being discussed in the posts above this one, leaving the subpanel enclosure floating leaves a real world hazard. . . Real world trumps paper.

I do agree with you but I wouldn't leave any written evidence or even tell the customer that I bonded that panel. It could just sort of happen with no one the wiser.

 

[al hildenbrand]

I do agree with you but I wouldn't leave any written evidence or even tell the customer that I bonded that panel. It could just sort of happen with no one the wiser.

No one would be the wiser, but for the inspector involved with the OP situation. The inspector has already called out "something".

 

[al hildenbrand]

Without specifics of the present Premises Wiring, including the historical, AHJ approved practices from forty years ago, I think it's hard to say much more.

 

[kwired]

I do agree with you but I wouldn't leave any written evidence or even tell the customer that I bonded that panel. It could just sort of happen with no one the wiser.

I do that quite often when I run into that situation. Just put in a bond screw, and mention nothing to anybody.

No one would be the wiser, but for the inspector involved with the OP situation. The inspector has already called out "something".

If inspector is involved you either fail or get his blessing to do whatever he allowed. Won't necessarily eliminate any liability on you but does help lower it some.