60 amp panel upgrade

[highendtron]

I am upgrading an old fuse panel to a newer service and ran across 4 runs of 12/3. It looks like the neutral for each 12/3 run were being shared on 110 v branch circuits. Was this a common practice with 60 amp services? Thanks.

 

[Dennis Alwon]

I am upgrading an old fuse panel to a newer service and ran across 4 runs of 12/3. It looks like the neutral for each 12/3 run were being shared on 110 v branch circuits. Was this a common practice with 60 amp services? Thanks.

If you are asking is it common practice to share a neutral when the hot conductors are connected to the same phase-- I would say no and it is not legal. If you are asking if it is common practice to share a neutral when the hot conductors are on different phases I would say yes. The latter is still common practice but it will change with the arc fault situation.

 

[iwire]

If you are asking is it common practice to share a neutral when the hot conductors are connected to the same phase-- I would say no and it is not legal.

That is not a MWBC but IMO is not a code violation as long as the neutral is large enough for the load.

 

[Dennis Alwon]

That is not a MWBC but IMO is not a code violation as long as the neutral is large enough for the load.

If it is the same size neutral as hot conductors, as it is in a 12/3 then how can one be certain of the load. You know it is a bad install and would be sited. Sure if the 12/3 served 2 motors that had a combined load of 20 amps or less it would not be a violation-- But if this load is serving receptacles and lighting or perhaps kitchen sabc how can you be certain that the load won't exceed 20 amps?

I understand your point but ...

 

[iwire]

Dennis my only point was your blanket statement was misleading.

share a neutral when the hot conductors are connected to the same phase-- I would say no and it is not legal.

That makes it sound like it will always be a violation.

 

[highendtron]

Because I don't want to burn the guys house down...I am going to install a junction box and splice the two ungrounded conductors toghether that are in the same 12/3 run. The nuetral has been carrying the load from both for a long time. I will just have to see how heavy the load is once we fire it back up.I was just amazed that it was done.

 

[infinity]

Because I don't want to burn the guys house down...I am going to install a junction box and splice the two ungrounded conductors toghether that are in the same 12/3 run. The nuetral has been carrying the load from both for a long time. I will just have to see how heavy the load is once we fire it back up.I was just amazed that it was done.

A MWBC is a common installation practice. Is this a 120/240 volt service or 120 volt service?

 

[EBFD6]

Because I don't want to burn the guys house down...I am going to install a junction box and splice the two ungrounded conductors toghether that are in the same 12/3 run. The nuetral has been carrying the load from both for a long time. I will just have to see how heavy the load is once we fire it back up.I was just amazed that it was done.

If this is a properly installed MWBC, the neutral has been carrying very little load for a long time and you will be doing more harm than good by combining the two circuits into one.

Again, assuming this is a properly installed MWBC!

 

[highendtron]

how would combining the ungrounded conductors hurt more than help? The house service is 110/220 but the nuetrals in each of the 12/3 runs does not look like it has been too hot meaning that the combined loads have not hurt the nuetral. Please explain the logic and the code violation if I put the ungrounded conductors together on one nuetral.

 

[Dennis Alwon]

how would combining the ungrounded conductors hurt more than help? The house service is 110/220 but the nuetrals in each of the 12/3 runs does not look like it has been too hot meaning that the combined loads have not hurt the nuetral. Please explain the logic and the code violation if I put the ungrounded conductors together on one nuetral.

Here is the problem. If, and you have not told us if this is true, the neutral is common to 2 conductors that are hooked to the same phase then there is a risk of overheating the neutral. If this is truly a mwbc then the neutral will only carry the unbalanced current of the 2 circuits. Thus if Phase A was connected to 10 amps and phase B was connected to a 12 amp load then the neutral would only carry 2 amps. If those hot conductors were both connected to say Phase A then the neutral would be carring the combined load of 22 amps. If this is a #12 you are overloading the neutral or grounded conductor in this case.

 

[Dennis Alwon]

If you are upgrading the panel then there should be no issue with insuring that both conductors are on opposite phases. If you are under the 2008 make sure you look at art 210.4(B).

This brings me to an interesting point. If someone upsizes a neutral to carry the load for 2 conductors on the same phase then does 210.4 come into play. It is not a MWBC... Oh it's fun to find loopholes

 

[SiddMartin]

edit .....................

 

[SiddMartin]

If you are upgrading the panel then there should be no issue with insuring that both conductors are on opposite phases. If you are under the 2008 make sure you look at art 210.4(B).

This brings me to an interesting point. If someone upsizes a neutral to carry the load for 2 conductors on the same phase then does 210.4 come into play. It is not a MWBC... Oh it's fun to find loopholes

what is the def of MWBC? I would say if you do upsize the neu, and stay on same phase, the hazard that 210.4 is preventing is still present. Not sure how you would do this and comply with 210.4

edit: since the hazard is still there, is it still considered a MWBC

 

[frizbeedog]

Please explain the logic and the code violation if I put the ungrounded conductors together on one nuetral.

OK, check this.

 

[Dennis Alwon]

what is the def of MWBC? I would say if you do upsize the neu, and stay on same phase, the hazard that 210.4 is preventing is still present. Not sure how you would do this and comply with 210.4

edit: since the hazard is still there, is it still considered a MWBC

Here......

Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.

 

[SiddMartin]

Here......

so if they are on the same phase, then no voltage between, no MWBC. 210.4 does not apply, right?

 

[220/221]

If you are asking is it common practice to share a neutral when the hot conductors are connected to the same phase-- I would say no and it is not legal. If you are asking if it is common practice to share a neutral when the hot conductors are on different phases I would say yes. The latter is still common practice but it will change with the arc fault situation.

Way to confuse the poor guy with TMI

The 3 wire circuits were and are common. Keep the hot circuits on opposite phases.

 

[Dennis Alwon]

so if they are on the same phase, then no voltage between, no MWBC. 210.4 does not apply, right?

That's my take but I would like to state that I would probably never do an install like that.

 

[Dennis Alwon]

Way to confuse the poor guy with TMI

The 3 wire circuits were and are common. Keep the hot circuits on opposite phases.

Sounds like TLI in your post. :smile:

 

[stickboy1375]

Nothing wrong with a MWBC, as long as its installed correctly.

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