Shared neutrals used anymore?

kwired

Electron manager
Location
NE Nebraska
As much as I used MWBC in the past, there is no way I would remove required handle ties. They aren’t there for those of us that grew up with, them. Remove if you want while trouble shooting but put them back. That next kid may not have the slightest.
Some area ECs were installing AFCIs then taking them out after inspection. Grrr.
AFCI is a different animal, that needs to be exterminated. I don't typically remove handle ties either.
 

kwired

Electron manager
Location
NE Nebraska
When I hear something similar to what you are saying, others reply and say this is why a person must be 'trained and qualified' before they start playing with electricity. This is why some electricians get paid the big bucks . lol.
I was fine with handle ties being required when multiple ungrounded conductors were on the same device(s). Handle ties on all MWBC's isn't as big of a deal as some other code that has come out since that requirement and doesn't bother me all that much anymore.
 

kwired

Electron manager
Location
NE Nebraska
Doesn't that just needlessly create a "Trouble in one circuit shut down two" situation?

JAP>
In a dwelling, so what.

In some commercial or industrial applications - might cause more troubles. Should you need to disturb the neutral for some reason you are shutting off all the ungrounded conductors anyway most the time.
 

jap

Senior Member
In a dwelling, so what.

In some commercial or industrial applications - might cause more troubles. Should you need to disturb the neutral for some reason you are shutting off all the ungrounded conductors anyway most the time.
I would say dwelling units are where most of the complaints come from when the power goes out.
It's in those cases that the home owner is actually responsible for the thawing food in the refrigerators and freezers, or, where they cant heat up their hot pocket. :)

JAP>
 

kwired

Electron manager
Location
NE Nebraska
I would say dwelling units are where most of the complaints come from when the power goes out.
It's in those cases that the home owner is actually responsible for the thawing food in the refrigerators and freezers, or, where they cant heat up their hot pocket. :)

JAP>
I've had more complaints of GFCI or AFCI trips thawing out refrigerator/freezer than MWBC issues.

I also haven't nor have I seen an abundance of MWBC's in dwellings, even from installs before the handle tie rules set in. Suppose this does vary from region to region to some extent.

Most the MWBC's in dwellings I used to install was for panel move/changeout situations, or maybe DW and DISP on same MWBC or something of that nature. I do know there were some that liked to run the SABC's on MWBC's. I seldom did that. If the home run had much length maybe it got more consideration.
 

jap

Senior Member
I've had more complaints of GFCI or AFCI trips thawing out refrigerator/freezer than MWBC issues.
Exactly my point.

Go back and read post #10.

If most complaints come from a GFI or AFCI Tripping, putting a 2p arc fault on an existing MWBC or a new MWBC for that matter simply increases the number of items that will go down when the breaker trips.

JAP>
 

kwired

Electron manager
Location
NE Nebraska
Exactly my point.

Go back and read post #10.

If most complaints come from a GFI or AFCI Tripping, putting a 2p arc fault on an existing MWBC or a new MWBC for that matter simply increases the number of items that will go down when the breaker trips.

JAP>
YMMV but I am not running into very many multipole GFCI or AFCI (outside of when needed on a 240 volt circuit in recent code editions or a pool/hot tub application) My GFCI/AFCI nuisance trip calls are usually on single pole breaker or receptacle style devices. Yes the freezer still thaws, no it not because of a ground fault on so called unrelated circuit but has a common handle tie.
 

Jerramundi

Senior Member
Location
Chicago
Occupation
Licensed Residential Electrician
You can always use the first opening exception w/ AFCI requirements. You would still have to separate the neutral from that point going forward, but it can sometimes be easier. Then again, now you have to deal with protection devices all throughout the home as opposed to one singular location.

Personally, I avoid MWBC's and just pull dedicated neutrals. Until major changes to AFCI requirements are made or not made, that's the direction we're going in, like it or not. One could argue that you're following code in being mindful of future applications by avoiding MWBC's.

Personally, I don't think the cost of one wire length merits MWBC's in smaller branch circuits. With larger circuits a valid argument could be made in regards to cost of the conductor, but in 99% of residential branch circuit applications, the cost savings is negligible... especially when compared to the cost of the future work needed to separate the MWBC into two circuits for AFCI, GFCI protection.
 

jap

Senior Member
You can always use the first opening exception w/ AFCI requirements. You would still have to separate the neutral from that point going forward, but it can sometimes be easier.
Not sure what you mean here?

I'm not aware of a 2p Arc Fault device other than a breaker.

JAP>
 

kwired

Electron manager
Location
NE Nebraska
You can always use the first opening exception w/ AFCI requirements. You would still have to separate the neutral from that point going forward, but it can sometimes be easier. Then again, now you have to deal with protection devices all throughout the home as opposed to one singular location.

Personally, I avoid MWBC's and just pull dedicated neutrals. Until major changes to AFCI requirements are made or not made, that's the direction we're going in, like it or not. One could argue that you're following code in being mindful of future applications by avoiding MWBC's.

Personally, I don't think the cost of one wire length merits MWBC's in smaller branch circuits. With larger circuits a valid argument could be made in regards to cost of the conductor, but in 99% of residential branch circuit applications, the cost savings is negligible... especially when compared to the cost of the future work needed to separate the MWBC into two circuits for AFCI, GFCI protection.
In Chicago required metallic wiring methods it is no problem. With NM cable and an new circuit you need to AFCI protect the entire circuit or have listed device combinations at the beginning of the circuit and first device that may or may not exist.
 

jap

Senior Member
meaning only MWBC part of the circuit is the home run itself.
Also meaning, If you didn't separate the load side neutrals and land them on the neutral terminals of the arc fault device you'd have no arc fault protection at all.

JAP>
 

kwired

Electron manager
Location
NE Nebraska
Also meaning, If you didn't separate the load side neutrals and land them on the neutral terminals of the arc fault device you'd have no arc fault protection at all.

JAP>
As long as it doesn't trip on GFP function is that a bad thing? :)
 

Jerramundi

Senior Member
Location
Chicago
Occupation
Licensed Residential Electrician
In Chicago required metallic wiring methods it is no problem. With NM cable and an new circuit you need to AFCI protect the entire circuit or have listed device combinations at the beginning of the circuit and first device that may or may not exist.
I'm aware of the exception within Chicago Code that exempts AFCI protection for metallic wiring methods, but I'm not licensed in the city. It's an entirely different animal and is really, REALLY political. Getting licensed in Chicago itself requires a manila envelope full cash, lol.

I was merely suggesting to the OP that, as you pointed out, the MWBC could still exist in the homerun portion of the circuit as long as the AFCI protection follows 210.12 at the first opening.

I did it a few times when I first learned about it, but now it's more of a reserve option for certain situations. I really hate scattering protection devices throughout the home. It should all be in one central location IMO
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
I'm aware of the exception within Chicago Code that exempts AFCI protection for metallic wiring methods, but I'm not licensed in the city. It's an entirely different animal and is really, REALLY political. Getting licensed in Chicago itself requires a manila envelope full cash, lol.
I personally wish that the metallic wiring method exemption for AFCIs was universal.

In fact, I'd previously suggested the idea of having a menu of 'enhanced safety systems' where the installer would pick from a list of systems that increase price for increased safety, and picking one branch of the menu would mean that you didn't have to pick from the other.

For example:

1) Install AFCI devices on all circuits
or
2) Use metallic wiring methods with GFCI devices
or
3) Use metallic wiring methods with advanced hard wire smoke detectors
or
4) Install sprinklers.

So if you spent the money on sprinklers you wouldn't have to spend it on AFCIs. IMHO sprinklers give better life safety 'bang for the buck' than AFCIs, though 'nuisance tripping' with sprinklers is rather more of a mess.....

-Jon
 

kwired

Electron manager
Location
NE Nebraska
I'm aware of the exception within Chicago Code that exempts AFCI protection for metallic wiring methods, but I'm not licensed in the city. It's an entirely different animal and is really, REALLY political. Getting licensed in Chicago itself requires a manila envelope full cash, lol.

I was merely suggesting to the OP that, as you pointed out, the MWBC could still exist in the homerun portion of the circuit as long as the AFCI protection follows 210.12 at the first opening.

I did it a few times when I first learned about it, but now it's more of a reserve option for certain situations. I really hate scattering protection devices throughout the home. It should all be in one central location IMO
Unless I not reading correctly the typical NM cable home run can not have the AFCI protection at the first outlet for an entirely new circuit, NEC wants to protect the entire circuit as much as possible (whether that is good or bad is a different debate). If metallic wiring method to the first outlet then there becomes some options. My comment was those options are kind of already available in Chicago with their required metallic wiring method requirements - if they keep AFCI requirements as written in NEC.
 

tortuga

Senior Member
Location
(44.057116, -123.103394)
Occupation
field supervisor
I am also curious if people are still using 4 wire MWBC's specifically for LED and electronic ballasted lighting?
And if so do any of you have concerns about harmonics and upsize the neutrals?
Seems like most lights these days feed back a distorted waveform.
 
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