Pigtailed neutrals on MWBC

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LarryFine said:
Do the same experiment, but remove the incoming white wire from the receptacle instead of the outgoing white wire.

Now what happened?
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Feed a split (black & red side split) receptacle directly from the breaker. What you are proposing is that the white wire would need a pigtail. No way.
 
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LarryFine said:
Agreed, and no, that's not the same thing.
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Now take the split receptacle and feed a normal receptacle from one side of it. No MWBC concern since the MWBC is not extended.

That is different from the MH graphic that shows the MWBC extends beyond the first receptacle rather than stopping there.
 
mivey said:
Now take the split receptacle and feed a normal receptacle from one side of it. No MWBC concern since the MWBC is not extended.
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And how is that different than what the OP has?

We can use our imagination with the graphic.

If you take the neutral of the red circuit in the graphic out from under the wire nut of the pigtail and land it on the neutral screw of the receptacle instead, you have what the OP has.


JAP>
 
mivey said:
Now take the split receptacle and feed a normal receptacle from one side of it. No MWBC concern since the MWBC is not extended.

That is different from the MH graphic that shows the MWBC extends beyond the first receptacle rather than stopping there.
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Even though the MWBC is not extended beyond the split receptacle, the grounded conductor is. The splice of the "non-MWBC grounded conductor" to the MWBC grounded conductor, as Larry Fine's excellent example above demonstrates, when there is a hot-to-neutral load running on each hot supplied through the MWBC, will experience voltage swings in a non-pigtail splice situation.

In your example, in red italics above, run a 120 V load from the normal receptacle, and plug a second 120 V load into the other hot of the split receptacle and run it as well. Now, some in this thread are saying that the MWBC grounded conductor can be directly connected to the terminals of the split receptacle, and the extension non-MWBC can also be connected directly to the split receptacle. In this scenario, with the loads running, removing the MWBC from the split receptacle terminal FLOATS the neutral between the running loads.

So, even though the MWBC is not extended in your red italics scenario, there is a MWBC concern.

This is the core of the words of 300.13(B). The disconnection of the grounded conductor from the device or fixture or etc. cannot interrupt the continuity of the grounded conductor where there is a MWBC.
 
al hildenbrand said:
Even though the MWBC is not extended beyond the split receptacle, the grounded conductor is. The splice of the "non-MWBC grounded conductor" to the MWBC grounded conductor, as Larry Fine's excellent example above demonstrates, when there is a hot-to-neutral load running on each hot supplied through the MWBC, will experience voltage swings in a non-pigtail splice situation.

In your example, in red italics above, run a 120 V load from the normal receptacle, and plug a second 120 V load into the other hot of the split receptacle and run it as well. Now, some in this thread are saying that the MWBC grounded conductor can be directly connected to the terminals of the split receptacle, and the extension non-MWBC can also be connected directly to the split receptacle. In this scenario, with the loads running, removing the MWBC from the split receptacle terminal FLOATS the neutral between the running loads.

So, even though the MWBC is not extended in your red italics scenario, there is a MWBC concern.

This is the core of the words of 300.13(B). The disconnection of the grounded conductor from the device or fixture or etc. cannot interrupt the continuity of the grounded conductor where there is a MWBC.
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Not really.
Not for myself anyway.
The rule is not about randomly disconnecting a neutral.
The rule is about continuity not being broken by removal of a device.

If you remove the device (which is the receptacle itself) in the OP's scenario you have nothing more than 2blacks, 2whites,2 reds and their EGC's hanging out of the box doing nothing at all.

Jap>
 
jap said:
Not really.
Not for myself anyway.
The rule is not about randomly disconnecting a neutral.
The rule is about continuity not being broken by removal of a device.

If you remove the device (which is the receptacle itself) in the OP's scenario you have nothing more than 2blacks, 2whites,2 reds and their EGC's hanging out of the box doing nothing at all.

Jap>
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I have every expectation that you always lock out and tag out your work and you have all the PPE required for every single task . . . but LOTO and PPE are not in the rule. . . ONLY breaking continuity. As a human in the real world, I am not capable of doing the disconnection of the device in a single motion of the hand. I have to start with a single conductor. If I am not a knowledgeable person, I may well work it hot and disconnect the MWBC grounded conductor from the device first. The 300.13(B) rule addresses that by having the only condition being breaking continuity of the grounded conductor

No matter how much you protest, you cannot guarantee that my scenario will never happen.
 
al hildenbrand said:
I have every expectation that you always lock out and tag out your work and you have all the PPE required for every single task . . . but LOTO and PPE are not in the rule. . . ONLY breaking continuity. As a human in the real world, I am not capable of doing the disconnection of the device in a single motion of the hand. I have to start with a single conductor. If I am not a knowledgeable person, I may well work it hot and disconnect the MWBC grounded conductor from the device first. The 300.13(B) rule addresses that by having the only condition being breaking continuity of the grounded conductor

No matter how much you protest, you cannot guarantee that my scenario will never happen.
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Some may well work it hot and take that chance, but, I thought this forum was for professionals not DIY's.
You're correct, I cant guarantee your scenario will never happen.
Only mine because I'm an electrician and I know better than to do so.

Jap>
 
Tell you what.

I'll give up my protest,if you'll agree that in the OP's scenario,to get the receptacle out you'd have to remove the cover plate.

To remove the cover plate you'd need to unplug the 2 appliances.

If someone unplugs the 2 appliances takes the cover plate off,takes the receptacle out,remove the grounded conductor from the receptacle,plugs the appliances back into the receptacle, and turn the appliances back on, they probably deserve their appliances to be burnt up. :p

Jap>
 
al hildenbrand said:
In your example, in red italics above, run a 120 V load from the normal receptacle, and plug a second 120 V load into the other hot of the split receptacle and run it as well. Now, some in this thread are saying that the MWBC grounded conductor can be directly connected to the terminals of the split receptacle, and the extension non-MWBC can also be connected directly to the split receptacle. In this scenario, with the loads running, removing the MWBC from the split receptacle terminal FLOATS the neutral between the running loads.
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You can also plug two loads into a endpoint split receptacle but not need a pigtail.

For my example with only one side extended, how are you proposing to lift the grounded conductor when a running appliance is plugged into one side of the split receptacle? You tell me that is a valid concern and I will tell you it is also just as valid a concern for the endpoint split receptacle.
 
Mivey, look at the rule again:
jumper said:
300.13(B) Device Removal. In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity.
Click to expand...

mivey said:
You can also plug two loads into a endpoint split receptacle but not need a pigtail.
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Not germane to the example because there is only one grounded conductor. This one grounded conductor is spliced to the device, yes, which can be removed, yes, and, if that one grounded conductor is lifted while two loads are running from the split duplex receptacle outlets, the neutral side of the receptacles floats and voltages on the loads will be a function of an impedance based voltage divider, i.e., a concern.

mivey said:
For my example with only one side extended, how are you proposing to lift the grounded conductor when a running appliance is plugged into one side of the split receptacle?
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Why, with a screwdriver. Are you missing the fact that the neutral terminals of the MWBC split receptacle are NOT split? The equivalent representation of the split receptacle neutral terminal screws and neutral back-stabs, and including the extending grounded conductor and the neutral side of the "normal receptacle", is a single node.

mivey said:
You tell me that is a valid concern and I will tell you it is also just as valid a concern for the endpoint split receptacle.
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Yes, both situations result in the neutral between the two receptacle outlets floating.

However, the conductive path of the device, between the device neutral terminals and the device female contacts (for connection to a male cord plug) is ONLY in the receptacle device and is not what 300.13(B) means with "grounded conductor".

The difference between these two situations is the presence of a SECOND grounded conductor, normally in the form of a white insulated copper wire, in the extension towards the "normal receptacle". The connection of this SECOND grounded conductor to the MWBC grounded conductor, inside the box of the "split receptacle", IS regulated by 300.13(B) simply because there are two grounded conductors that are spliced together.
 
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al hildenbrand said:
if that one grounded conductor is lifted while two loads are running from the split duplex receptacle outlets, the neutral side of the receptacles floats and voltages on the loads will be a function of an impedance based voltage divider, i.e., a concern.
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And I think that's where you are confused.
The rule does not say "where the grounded conductor is lifted"

Yes, you are correct, if you "lift" the neutral that's what will happen no doubt and probably would in any other scenario other than the Original Post.

But, the rule mentions nothing about working things hot, nor should it.

Read what the rule says.

Where the "Removal of such device" would interrupt the continuity.

The grounded conductor is not a device. It is a conductor.

If the receptacle (or device) was removed in the OP's scenario, hopefully with the power shut off, and the wires that were terminated to the receptacle were left in the box and capped off , As Dave put it, "Nothing bad would happen downstream on that red circuit that used to come from that receptacle when the circuit was turned back on.

If there were something downstream of it on the red circuit , it simply wouldn't work, but, it wouldn't burn up.

You'd have to go back to the box where the receptacle was removed and wire nut the grounded conductor back to the incoming grounded conductor to get your stuff back on.

Now, with that said there are many wiring scenarios where you would burn things up if you simply removed the device by itself. but, not in this one.
Removal of this device (which is the receptacle itself) would take away any chance of a 240v series load ever happening.

JAP>
 
jap said:
And I think that's where you are confused.
The rule does not say "where the grounded conductor is lifted"

Yes, you are correct, if you "lift" the neutral that's what will happen no doubt and probably would in any other scenario other than the Original Post.

But, the rule mentions nothing about working things hot, nor should it.

Read what the rule says.

Where the "Removal of such device" would interrupt the continuity.

The grounded conductor is not a device. It is a conductor.

If the receptacle (or device) was removed in the OP's scenario, hopefully with the power shut off, and the wires that were terminated to the receptacle were left in the box and capped off , As Dave put it, "Nothing bad would happen downstream on that red circuit that used to come from that receptacle when the circuit was turned back on.

If there were something downstream of it on the red circuit , it simply wouldn't work, but, it wouldn't burn up.

You'd have to go back to the box where the receptacle was removed and wire nut the grounded conductor back to the incoming grounded conductor to get your stuff back on.

Now, with that said there are many wiring scenarios where you would burn things up if you simply removed the device by itself. but, not in this one.
Removal of this device (which is the receptacle itself) would take away any chance of a 240v series load ever happening.

JAP>
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The rule is ONLY about grounded conductor continuity being interrupted. . . what happens with the hot(S) is NOT in the rule. Whether there is a receptacle (or other load or outlet) at the far end of the OP scenario extension from the disposal / dishwasher receptacle doesn't matter. . . it is simply that the act of completely removing the disposal / dishwasher receptacle interrupts the continuity of the grounded conductor in that box where the MWBC is present.

300.13(B) doesn't care what happens to the hots.

I use the term "lift" by way of referring to Larry Fine's example of how the real world "removal" might let the smoke out.
 
And again, to be redundantly clear: I am saying a pigtail IS required in the OP scenario by 300.13(B) because there are two grounded conductors present with the MWBC in the disposal / dishwasher box.
 
al hildenbrand said:
The rule is ONLY about grounded conductor continuity being interrupted..

300.13(B) doesn't care what happens to the hots.

I use the term "lift" by way of referring to Larry Fine's example of how the real world "removal" might let the smoke out.
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I completely agree, but, your not stating the whole rule.

Your stopping at interrupted.

The rule says " where removal of the device".

If we remove the device in this scenario and that neutral up to the switch doesn't go any further, we're simply left with a spare MWBC under the sink.

JAP>
 
jap said:
I completely agree, but, your not stating the whole rule.

Your stopping at interrupted.

The rule says " where removal of the device".

If we remove the device in this scenario and that neutral up to the switch doesn't go any further, we're simply left with a spare MWBC under the sink.

JAP>
Click to expand...

What? "a spare MWBC"? ? Where's the second MWBC?
 
jap said:
If the receptacle (or device) was removed in the OP's scenario, hopefully with the power shut off, and the wires that were terminated to the receptacle were left in the box and capped off , As Dave put it, "Nothing bad would happen downstream on that red circuit that used to come from that receptacle when the circuit was turned back on.
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I totally agree with the above. And if 300.13(B) said "removal of the device must not allow anything bad to happen downstream" then pigtailing would not be required in the OP.

But the wording of 300.13(B) is about continuity of the grounded conductor. Removal of the device must not interrupt continuity of the grounded conductor, so pigtailing is required. There is no additional limiting text that says "only when the grounded conductor is used downstream for loads from more than one ungrounded conductor."

Basically, pigtailing in the OP's case is not required for electrical reasons, but it is required for code compliance reasons, because 300.13(B) is not written so precisely. The OP's situation is a corner case.

Cheers, Wayne
 
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