moving house panel to new location

[howardrichman]

I'll be moving a (main) 30ckt. subpanel 15+ft out of a laundry area in a kitchen to a new area. The feeder will be plenty long. They'LL be many 220V heat,stove,oven, and dryer ckts, w/ many lighting circuits(30+ckts). I figure I could either splice all those cables out of a trouph in an attic, or from trouph using thhn wire in conduits and account for proper derating. Would attic heat affect splicing? Would using shared nuetrals in a 3w cond. be ok to use? What size trouph?

Thanks;
Howie...

 

[Pierre C Belarge]

Will the construction of the existing location provide for the existing panel enclosure to be left in place and used as a splice point?

 

[infinity]

Splicing in the attic isn't a problem but you might need to make an ambient temperature adjustment for the conductors in the raceways. I would use a pull box to avoid the potential for derating in the wireway if you exceed 30 CCC's at any cross section. MWBC's are fine and will help you cut down on the number of CCC's in each raceway by up to 1/2.

 

[shockin]

MWBC's are fine and will help you cut down on the number of CCC's in each raceway by up to 1/2.

Can you explain this to me. I don't understand how a MWBC reduces anything assuming you are under the 2008NEC which requires a neutral for every hot. Unless you use 2 pole breakers but that would be a bad idea IMO.

 

[Dennis Alwon]

Can you explain this to me. I don't understand how a MWBC reduces anything assuming you are under the 2008NEC which requires a neutral for every hot. Unless you use 2 pole breakers but that would be a bad idea IMO.

Trevor is saying that if you use conduit then a MWBC will reduce the number of conductors in the conduit lowering the derating issue. True you would need a DP breaker and I agree it's undesirable.

 

[howardrichman]

Will the construction of the existing location provide for the existing panel enclosure to be left in place and used as a splice point?

No; it's presently in a laundry area in a kitchen to be removed. I suppose I could swing the panel in the attic, but may not be listed for that purpose for inspection. That sure would be easier.

Howard

 

[Dennis Alwon]

No; it's presently in a laundry area in a kitchen to be removed. I suppose I could swing the panel in the attic, but may not be listed for that purpose for inspection. That sure would be easier.

Howard

If you have the proper clearance I believe you could put the panel in the attic.

 

[infinity]

Can you explain this to me. I don't understand how a MWBC reduces anything assuming you are under the 2008NEC which requires a neutral for every hot. Unless you use 2 pole breakers but that would be a bad idea IMO.

Let's assume 8-20 amp (#12 AWG) circuits in one raceway. By using MWBC's you would have 8 CCC's which would require a derating of 70%.

30 amps * 70% = 21 amps so you're still good.

Now use the same 8 circuits with separate neutrals which equals 16 CCC's and would require a derating of 50%.

30 amps * 50% = 15 amps so your 20 amp circuits with #12 conductors are no good.

When using separate neutrals you could only get 4 circuits in the raceway (only 1/2 of the number you would with a MWBC setup) and still maintain the 20 amp rating for the #12 conductors. Not to mention the MWBC would save you on conduit fill as well.

 

[shockin]

Let's assume 8-20 amp (#12 AWG) circuits in one raceway. By using MWBC's you would have 8 CCC's which would require a derating of 70%.

30 amps * 70% = 21 amps so you're still good.

Now use the same 8 circuits with separate neutrals which equals 16 CCC's and would require a derating of 50%.

30 amps * 50% = 15 amps so your 20 amp circuits with #12 conductors are no good.

When using separate neutrals you could only get 4 circuits in the raceway (only 1/2 of the number you would with a MWBC setup) and still maintain the 20 amp rating for the #12 conductors. Not to mention the MWBC would save you on conduit fill as well.

So I assume you are installing the MWBC on double pole breakers. I'm not sure that is a good design in a home. (Or commercial) But your example is correct. Just not the way I would do it.

 

[infinity]

So I assume you are installing the MWBC on double pole breakers. I'm not sure that is a good design in a home. (Or commercial) But your example is correct. Just not the way I would do it.

I agree not the best design but code compliant. If it were up to me the multi-pole/handle tie section for MWBC's would be removed from the NEC.

 

[Pierre C Belarge]

I agree not the best design but code compliant. If it were up to me the multi-pole/handle tie section for MWBC's would be removed from the NEC.

I believe that may happen in the 2011 cycle.....

 

[infinity]

I believe that may happen in the 2011 cycle.....

Well the book is out so is it removed or isn't it?

 

[Dennis Alwon]

210.4(B) is the same & 240.15 (B)(1) is pretty much the same.

210.4(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
Informational Note: See 240.15(B) for information on the use of single-pole circuit breakers as the disconnecting means.

 

[Pierre C Belarge]

I have not purchased the '011 yet. I may have mistaken it, but I thought I heard comment about this from the CMP during the Eastern Section Meeting. That is why I did say "may" in that post..



Thinking a little more about this, it may be discussion that has been held over for more discussion in the '014 cycle. I will go back over my notes and see what I can find.

 

[Pierre C Belarge]

Okay, I found it.

" Revisions were made to the requirements for circuit breakers used as overcurrent devices. Circuit breakers used to provide overcurrent protection for multiwire branch circuits also provide the disconnect means for those circuits. The circuit breakers would generally be required to open all ungrounded conductors manyally and automatically. for multiwire branch circuits, the previous language at 240.15(B)(1) did not require automatic opening of the circuits (common trip). Based on the changes in NEC-2008 at 210.4(B) which states that all multivwire branch circuits must be provided with a means to simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates, the manual opening (common disconnect) is now required. Section 240.15(B) permitted the use of identified handle ties on several systems that were excluded by the UL 489 Product Standard, Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures.
While 110.3(B) ["Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling"] limited the applications, providing correlation in 240.15(B) will add clarity for NEC users that might not have ready access to UL Standards or even UL White Book guide information.
This revision will bring the NEC into agreement with the UL White Book guided information (see category DIVQ). The revisions should help prevent the misapplication of circuit breakers, particularly in light of the availability of three-pole handle ties which have become available in response to the addition of 210.4(B) in the 2008 NEC.


After reading this as I typed it, I see I misunderstood the comments made at the meeting. It would seem that handle ties are permitted.

 

[Dennis Alwon]

Here is the entire 240.15(B)

(B) Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit both manually and automatically unless otherwise permitted in 240.15(B)(1), (B)(2), (B)(3), and (B)(4).
(1) Multiwire Branch Circuit. Individual single-pole circuit breakers, with identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.
(2) Grounded Single-Phase Alternating-Current Circuits.
In grounded systems, individual single-pole circuit breakers rated 120/240 volts ac, with identified handle ties, shall be permitted as the protection for each ungrounded
conductor for line-to-line connected loads for single-phase circuits.
(3) 3-Phase and 2-Phase Systems. For line-to-line loads in 4-wire, 3-phase systems or 5-wire, 2-phase systems, individual single-pole circuit breakers rated 120/240 volts ac with identified handle ties shall be permitted as the protection for each ungrounded conductor, if the systems have a grounded neutral point and the voltage to ground does not exceed 120 volts.
(4) 3-Wire Direct-Current Circuits. Individual singlepole circuit breakers rated 125/250 volts dc with identified handle ties shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for 3-wire, direct-current circuits supplied from a system with a grounded neutral where the voltage to ground does not exceed 125 volts.

 

[growler]

I'll be moving a (main) 30ckt. subpanel 15+ft out of a laundry area in a kitchen to a new area. The feeder will be plenty long. They'LL be many 220V heat,stove,oven, and dryer ckts, w/ many lighting circuits(30+ckts).

The first thing I look at is what type of house I'm working at. Is this a cheap rental property, a house that's beign flipped or a house where the homeowner cares about the quality of work being performed.

If there is a kitchen remodel going on then I may wish to run new home runs for the kitchen circuits and avoid splices in these circuits. I try and see how many new home runs can be run with a minimum of time and materials used and then see what method of splicing would be best.

Try to up-sell as much as possible for a quality job.

 

[ActionDave]

So I assume you are installing the MWBC on double pole breakers. I'm not sure that is a good design in a home. (Or commercial) But your example is correct. Just not the way I would do it.

Not exactly the way I would do it either. I would use handle ties rather than a two pole breaker.

If it were up to me the multi-pole/handle tie section for MWBC's would be removed from the NEC.

Agreed, agreed, and agreed. One of the worst code changes ever.

 

[howardrichman]

Thanks for the replies. What i may do is to try to find a new location to reuse as many lines as possible, and replace and extend the main feeder to the new panel location; better job if possible.

Howie...

 

[Pierre C Belarge]

Are any of the cables entered into the existing panel coming from the top? If so, bring them into the attic and either mount a panel or enter them into a junction box.

If you have the clearances in the attic, and access to the attic, you can mount a panel there.