Home Inspector question

[Dennis Alwon]

yeah I thought of that as I was finishing the sentence but I think that's a little nitpicky. Perhaps you could oversize the few inches of shared neutral .

Nitpicky, So if nipple 3 wires to a 4 "sq. box right next to a panel and then continue on with 2 - 2 wire cables, I should not consider this a MWBC???

At what distance does it change? According to the definition distance has nothing to do with it.

 

[Jim W in Tampa]

yeah I thought of that as I was finishing the sentence but I think that's a little nitpicky. Perhaps you could oversize the few inches of shared neutral .

oversizing changes nothing.Now that we have a mwbc we would need to change the breakers.
best solution is add or change the neutral bar but even that can be shot down if we nit pick

 

[nakulak]

actually you don't even have to add a neutral bar. more than likely, you can add some double or triple lugs that are rated to fit under one lug space in the neutral bar and get your added lug space.

 

[iwire]

actually you don't even have to add a neutral bar. more than likely, you can add some double or triple lugs that are rated to fit under one lug space in the neutral bar and get your added lug space.

Huh?

For branch circuit conductors?

Got a link?

 

[LarryFine]

Nitpicky, So if nipple 3 wires to a 4 "sq. box right next to a panel and then continue on with 2 - 2 wire cables, I should not consider this a MWBC???

It would be up to that box, and it should have a handle-tied breaker pair.

 

[steelersman]

actually you don't even have to add a neutral bar. more than likely, you can add some double or triple lugs that are rated to fit under one lug space in the neutral bar and get your added lug space.

good idea. I've seen and used those a couple of times. Forgot about them.

 

[firelient]

I would make sure all connections wre tight then tell and show the home owner this was per code when built. We have problems like this all the time with home insp. and I just make a note on the bill as to the code when built. I'm sure there are a lot of other things that are wrong if you go by the 2005 code in that house. Right, so why pick one thing.

 

[Jim W in Tampa]

actually you don't even have to add a neutral bar. more than likely, you can add some double or triple lugs that are rated to fit under one lug space in the neutral bar and get your added lug space.

Carefull here your on thin ice.Not to sure this in itself does not create a mwmc.

 

[Dennis Alwon]

Carefull here your on thin ice.Not to sure this in itself does not create a mwmc.

Interesting...I think I agree with you there but then you would almost have to say that 2 neutrals under the same screw could be a MWBC if it were opposite phases. :wink:

 

[steelersman]

Interesting...I think I agree with you there but then you would almost have to say that 2 neutrals under the same screw could be a MWBC if it were opposite phases. :wink:

Man you guys and these MWBC's. Seems like you're trying to find every possible way to call it that. I don't see how you could consider it MWBC if you install an other bar tapped off of the original bar which installs using only 2 of the screws in the original bar but creating a few more. Too technical for my thinking.

 

[Dennis Alwon]

Man you guys and these MWBC's. Seems like you're trying to find every possible way to call it that. I don't see how you could consider it MWBC if you install an other bar tapped off of the original bar which installs using only 2 of the screws in the original bar but creating a few more. Too technical for my thinking.

It is just intreesting to think about. At what point does it become or not become a MWBC. It appears if the neutrals are connected together and the possiblity of one being disconnected without the other one would lead it to be a MWBC. I don't really think that adding another neutral bar would be considered a MWBC-- it was interesting to think about. Heck most panels do have two neutral bars connected together.

 

[wwhitney]

If you're going to pigtail, I would make no assumptions about phase on the circuits. Those could get rearranged and there is no x-3 cable to warn you of a multiwire branch circuit. I'd combine two #14's with a #10 and put the #10 on the neutral bar. Same with two #12's and a #8.

This comment made me think about whether this could be done outside the panelboard enclosure. Say you need to run 3 circuits to a particular location, each with a rating of 20 amps, and you're using conduit. Could you pull (3) 20 amp hots and (1) 60 amp grounded conductor? Does anything in the NEC prohibit this arrangement? Of course, this may never be useful or practical.

Thanks, Wayne

 

[iwire]

This comment made me think about whether this could be done outside the panelboard enclosure. Say you need to run 3 circuits to a particular location, each with a rating of 20 amps, and you're using conduit. Could you pull (3) 20 amp hots and (1) 60 amp grounded conductor? Does anything in the NEC prohibit this arrangement? Of course, this may never be useful or practical.

Thanks, Wayne

There is no doubt whatsoever that can be done with outside branch circuits (see 225.7(B) and in my opinion it is not prohibited anywhere.

 

[steelersman]

This comment made me think about whether this could be done outside the panelboard enclosure. Say you need to run 3 circuits to a particular location, each with a rating of 20 amps, and you're using conduit. Could you pull (3) 20 amp hots and (1) 60 amp grounded conductor? Does anything in the NEC prohibit this arrangement? Of course, this may never be useful or practical.

Thanks, Wayne

if you did that in a single phase panel (residential) then you would only need the grounded conductor to be rated @ 40 amps since 2 of the circuits would be on same leg and just carry the difference of current between the 2 which could possibly be 0 but not more than 20 and then of course 20 for the 3rd circuit. If in a 3 phase panel then the grounded conductor would only need to be 20 amps and you would make them all on a seperate phase.

 

[wwhitney]

There is no doubt whatsoever that can be done with outside branch circuits (see 225.7(B) and in my opinion it is not prohibited anywhere.

Good to know, thanks. Is it ever useful to combine grounded conductors in this manner? I'm hard pressed to think of an example where this would be a good idea (other than a 120V only panel), since it seems a MWBC would be probably be better.

Yours, Wayne

 

[wwhitney]

if you did that in a single phase panel (residential) then you would only need the grounded conductor to be rated @ 40 amps since 2 of the circuits would be on same leg and just carry the difference of current between the 2 which could possibly be 0 but not more than 20 and then of course 20 for the 3rd circuit.

Oh, I understand how MWBCs work, but I was just wondering about the proposed arrangement, which doesn't place any restriction on the which phases you use for the hots. But you are right, it seems like a MWBC would usually be a superior solution.

Cheers, Wayne

 

[Twoskinsoneman]

There is no doubt whatsoever that can be done with outside branch circuits (see 225.7(B) and in my opinion it is not prohibited anywhere.

Agreed. The NECH has a nice illustration but I can't seem to extract it/save it/copy it.
It must be protected....

(B) Common Neutral. The ampacity of the neutral conductor shall not be less than the maximum net computed load current between the neutral conductor and all ungrounded conductors connected to any one phase of the circuit.
Multiwire branch circuits consisting of a neutral and two or more ungrounded conductors are permitted, provided the neutral capacity is not less than the total load of all ungrounded conductors connected to any one phase of the circuit.

 

[iwire]

Agreed. The NECH has a nice illustration but I can't seem to extract it/save it/copy it.

It can be done, I grabed this one out of the 2002 NECH back a few yers ago.

 

[Jim W in Tampa]

Dont overlook that you created a mwbc and now needs handle ties.

 

[wwhitney]

Dont overlook that you created a mwbc and now needs handle ties.

Only if the hots come from different phases. In the NECH diagram, it appears they have 8 hots, 4 on each phase, and presumably the neutral is sized to 4 times the ampacity of the hots. So that is an MWBC. But you could use only hots from one phase, and size the neutral appropriately.

Cheers, Wayne