AFCI pigtailing...

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1793

1793

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Location
Louisville, Kentucky
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Inspector
I was on a job today and noticed that in a 120/240 3 phase panel the electrician stacked, A,B,C AFCI breakers and pigtailed the neutrals from each breaker to form a single with a #12 and landed the one neutral on the neutral buss. These are 15A circuits.

Would this kind of connection cause any problems with AFCIs'?
 
1793 said:
I was on a job today and noticed that in a 120/240 3 phase panel the electrician stacked, A,B,C AFCI breakers and pigtailed the neutrals from each breaker to form a single with a #12 and landed the one neutral on the neutral buss. These are 15A circuits.

Would this kind of connection cause any problems with AFCIs'?
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Overloaded neutral wire. The entire load of the circuit runs through that white wire. Also he may have a big problem on B phase if it is 120/240 and not 208.
 
acrwc10 said:
Overloaded neutral wire. The entire load of the circuit runs through that white wire. Also he may have a big problem on B phase if it is 120/240 and not 208.
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This a 4 wire system. I measured 240 between any two of the three phases and 120 each phase to neutral or ground.
 
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1793 said:
This a 4 wire system. I measured 240 between any two of the three phases and 120 each phase to neutral or ground.

I would see this as a MWBC sharing a neutral but I'm not sure about the AFCIs'.
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Wow a 240 without a high leg, haven't seen that yet, although it makes sense. Better heating with ovens and such.
 
They are common now and They would still be common if they were individual on the neutral buss. With the highest possible current inbalance I think it would be slightly over 20 amps about 26 amps if I figured right If I were to do this I would probably go to 10 wire but I am not going to do this anyway why tempt fate? The load sides cannot be combined like this .
 
1793 said:
This a 4 wire system. I measured 240 between any two of the three phases and 120 each phase to neutral or ground.
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Never seen that either. Are you sure of the voltages?
If all three phases are the same to neutral it would be a wye. I can't quite figure where the 240 would come from.
If it is a delta I don't think we can get the same reading to neutral or ground from each phase.
What do you think it is? Is neutral to ground reading 0 volts?
 
1793 said:
This a 4 wire system. I measured 240 between any two of the three phases and 120 each phase to neutral or ground.
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Not possible. It's either 208Y/120 or 240D/120 w/hi leg. Either three 208's or two 120's and one 208.

As long as it's really 3-ph, I see no issue, and that shared wire will never see more than 15a.
 
LarryFine said:
Not possible. It's either 208Y/120 or 240D/120 w/hi leg. Either three 208's or two 120's and one 208.

As long as it's really 3-ph, I see no issue, and that shared wire will never see more than 15a.
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I was using my wiggy to test the voltage I guess I may have not been able to feel the difference. I may be going back for more work so I'll check with a DMM.
 
1793 said:
I was using my wiggy to test the voltage I guess I may have not been able to feel the difference. I may be going back for more work so I'll check with a DMM.
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When you need the voltage reading is one of the few times a VM is needed. It's still best to check that voltage while a load is connected. I've seen POCO guys not realize that during open-neutral service calls.
 
I am going to assume that this is not a dwelling since it has 3 phase, although there are a few out there with that. Rare to find ark fault breakers getting used in anything but residential, so my first question is why are they there in the first place? Second thing is this, if it is a dwelling you most likely will never get a fully loaded on any single circuit unless its a space heater or air conditioner. Therefore the pigtailing of the three neuts if it is a dwelling is probably not such a hazard as it might seem, the single wire connecting to the neutral bus probably would not see any thing close to an overload.
 
LarryFine said:
Not possible. It's either 208Y/120 or 240D/120 w/hi leg. Either three 208's or two 120's and one 208.

As long as it's really 3-ph, I see no issue, and that shared wire will never see more than 15a.
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I agree. If in fact it's 208Y/120 the pigtail will never see more than the largest current imbalance which is 15 amps as Larry stated.

As Mac asked, where is this installation with that voltage system that they're using AFCI CB's?
 
infinity said:
I agree. If in fact it's 208Y/120 the pigtail will never see more than the largest current imbalance which is 15 amps as Larry stated.

As Mac asked, where is this installation with that voltage system that they're using AFCI CB's?
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These circuits are for bedrooms in one unit of a 4 unit Condo complex.

I was wrong about the voltage, it is 208Y/120. I had been outside for 5.5 hrs at a temp. of 10 with a wind chill below 0. Sorry
 
1793 said:
These circuits are for bedrooms in one unit of a 4 unit Condo complex.

I was wrong about the voltage, it is 208Y/120. I had been outside for 5.5 hrs at a temp. of 10 with a wind chill below 0. Sorry
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No need to apologize. ;)

It was -1 at 7 AM here this morning so I know what you mean.

Now it's all starting to make sense. The pigtail is fine in the installation that you've described.
 
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