Balanced neutral?

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ritelec

ritelec

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Jersey
Wondering how you guys handle balancing a neutral on an existing job (residential 3 wire). Either doing a panel change or working in a panel, you come across a multi wire branch circuit with both hots on the same phase.
Do you leave it that way? re install it that way after a panel change? Install the hot conductors on separate phases and hope all is correctly wired in those circuits? Splice the hots together and create one circuit? advise the costumer, trace out the circuits in the field and put them correctly on separate phases?

Thoughts?

Thank you
 
If it's 1 mwbc, I connect as it supposed to be Regardless of how it was connected before. If connecting it properly causes an issue, that becomes an unforeseen issue that needs to be addressed with a new set of charges
 
James L said:
If connecting it properly causes an issue, that becomes an unforeseen issue that needs to be addressed with a new set of charges
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Like a burnt computer or fridge ?

wondering how you would convince owner of new sets of charges? "Everything was OK before you touched it"
 
An electrical inspector should be able to check and find the MWBC wired incorrectly on the same phase so you risk failing the inspection if you put it back the way that it was.
 
Change order.

I have multiple possibilities for triggering change orders in my contracts, and discovering dangerous, non-compliant, decayed, damaged, or otherwise unserviceable conditions, require a change order.

On the remodeling end of my business, this comes up frequently.
 
I actually just came across this situation. Existing is existing.
The only time(s) intervention is merited is (1) if it is customer approved, or (2) poses a safety risk.

In this case, two hots on the same phase, sharing a neutral, will be constructive wave interference and possibly overload the neutral. That is a definitive safety risk and one that would, IMO, merit intervention.

Obviously this would require more work and the customer should be informed. If they refuse the additional work, put it back as is and walk away, just maybe be sure to document that your final installation equals what was existing.. and that you correctly warned the customer of the possible safety risks. Documentation is key.

Generally speaking, if I modify a portion of a circuit, IMO, that merits investigation of the entire circuit.
 
infinity said:
An electrical inspector should be able to check and find the MWBC wired incorrectly on the same phase so you risk failing the inspection if you put it back the way that it was.
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I find and cite at least one per week. Had one a couple of weeks ago in a Church where the neutral insulation had turned brown.
 
infinity said:
An electrical inspector should be able to check and find the MWBC wired incorrectly on the same phase so you risk failing the inspection if you put it back the way that it was.
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To be clear, I think this does qualify as a safety issue, and merits intervention, less a load calc for both branch circuits that quantitatively shows the neutral would NOT be overloaded.

However, say the customer refused the additional work, but already paid for the panel work, so you put it back as was.

Would you still fail? This gets into the popular issue of "how much is *required* for a panel upgrade."
If a service is upgraded, do the existing branch circuits have to be updated? If they do, panel upgrades just became A LOT more expensive.

I still argue no, unless it falls under something more explicit, such as 210.12 where modifying a circuit more than 6ft requires AFCI protection, but that particular section of code explicitly refers to the branch circuit, defined as starting AFTER the OCPD.

I'm sure inspectors would fail people for this, but the question is, is it justified per the NEC.
 
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I don't think there's anything in the code that *requires* MWBC's to be on opposite phases, unless you figure the constructive neutral current from both legs surpassing what the neutral wire is rated for...

But there's also 210.4(B) Disconnecting Means, which would be impossible to do if they are on the same phase. Most panel construction prohibits it.

I'm just thinking out loud and wondering, if you did fail for this, what, if any, would be the substantiation?
 
Jerramundi said:
I don't think there's anything in the code that *requires* MWBC's to be on opposite phases, unless you figure the constructive neutral current from both legs surpassing what the neutral wire is rated for...

But there's also 210.4(B) Disconnecting Means, which would be impossible to do if they are on the same phase. Most panel construction prohibits it.

I'm just thinking out loud and wondering, if you did fail for this, what, if any, would be the substantiation?
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The substantiation is in the intended design, and the fact that it's possible to overload the neutral which makes an unsafe condition.

Where I do about half my work, they have amended the code in a few areas. One is that if there is any electrical work done, they require everything in the panel to be correct - even if no work was done in the panel.
 
Jerramundi said:
I'm sure inspectors would fail people for this, but the question is, is it justified per the NEC.
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Of course it's justified, in fact how would an inspector who writes up the violation know that it wasn't wired correctly in the old panel and that the guy doing the upgrade made the mistake? A miswired MWBC gets a violation write up every time in my book. :)
 
infinity said:
Of course it's justified, in fact how would an inspector who writes up the violation know that it wasn't wired correctly in the old panel and that the guy doing the upgrade made the mistake? A miswired MWBC gets a violation write up every time in my book. :)
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Thank you and well said
 
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