What is the best way to wire this panel?

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Coppersmith

Coppersmith

Senior Member
Location
Tampa, FL, USA
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Electrical Contractor
I've been hired to do a panel change. The existing panel is behind the washer and the washer cannot move. All of the branch wiring enters the panel at the top. Since this is a working space violation and there isn't another good spot for the panel inside, I plan on installing the new panel outside on the opposite side of the wall from the existing panel (next to the meter).

The issue I have is how to reasonable connect the branch wiring. If I leave the existing cabinet as a junction box I can bring conduit out the bottom, penetrate the wall and pipe into the bottom of the new panel. I've got 38 CCC's plus I need some reserve. This would require a bunch of conduits (probably 6 x 3/4") to avoid derating below 70% per 310.15(B)(3)(A). The MWBC trick doesn't help here since it all existing wiring.

I'm wondering if it would be code compliant to connect the branch together with individual UF cables. If they exit both the new panel and the old from the bottom, I could run them through a row of small penetrations and then cover them with a sheet metal cover for physical protection and also secure them to the wall. Thoughts?

Am I allowed to use standard (non-weatherproof) NM connectors outside if on the bottom and covered?
 
masterinbama said:
Can you put a 2.5" nipple between the 2 panels? No creating in a short nipple.
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I assume you meant derating. How long can a short nipple be without derating? It would have to have two LB's in it as well since the panels are not back-to-back.

Also a code reference for this no derating of nipples would help me.
 
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Do you have any pics?
Could you put the junction boxes in the attic? Then run romex into the back of the outside panel from the wall.
Some circuits may be just as easy to run a new circuit to that location. Such as the range, dryer, water heater or AC.
Is their a crawl space?
Code allows you as you know to leave the old panel and use it as a junction box. It's been my experience that HOs don't like that. Pull it off and install a 4x4x12 box.
Their is more then 1000 ways to do this panel change out.
Keep in mine, most of the time you derate on general wiring residentiall you still end up with the same wire or breaker size.
 
If your installation is nipple out of old panel - LB - nipple through wall - LB - nipple to new panel; then you have 3 nipples each of which can be up to 24" long without de-rating the conductors.

An LB is a conduit body covered by 314, not a raceway and does not require de-rating of the conductors within. 310.15(B)(a)(3) specifically says "Where the number of current-carrying conductors in a raceway or cable exceeds three".

If you think this is stretching the code - then here it your alternative method.

Install multiple nipples out of old panel into NEMA 1 junction box directly below old panel. Now install nipple through wall - LB - nipple to new panel; which according to your measurements the single raceway length should be about 16".
 
Coppersmith said:
I've been hired to do a panel change. The existing panel is behind the washer and the washer cannot move. All of the branch wiring enters the panel at the top. Since this is a working space violation and there isn't another good spot for the panel inside, I plan on installing the new panel outside on the opposite side of the wall from the existing panel (next to the meter).
Click to expand...

Not sure about Florida, but here in Michigan, we're allowed to install new panels in the same location as existing ones for a replacement, even if it would be a working space violation in a new house. But if we relocate it, then it has to comply with today's Code. Most panels here are located in the basement directly under the location of the meter. Is that where yours is?
 
Nuber said:
If your installation is nipple out of old panel - LB - nipple through wall - LB - nipple to new panel; then you have 3 nipples each of which can be up to 24" long without de-rating the conductors.

An LB is a conduit body covered by 314, not a raceway and does not require de-rating of the conductors within. 310.15(B)(a)(3) specifically says "Where the number of current-carrying conductors in a raceway or cable exceeds three".
Click to expand...

This would work fine. I'm just not sure you are correct about the LB's resetting the nipple length. Can anybody confirm Nuber's analysis here?
 
jeff48356 said:
Not sure about Florida, but here in Michigan, we're allowed to install new panels in the same location as existing ones for a replacement, even if it would be a working space violation in a new house. But if we relocate it, then it has to comply with today's Code. Most panels here are located in the basement directly under the location of the meter. Is that where yours is?
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The panel is back-to-back with the meter. I push the envelope with the inspector's here frequently. This is one battle I want to avoid.
 
Coppersmith said:
The MWBC trick doesn't help here since it all existing wiring.
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Sorry, why is that? If you aren't required to install AFCI (or if you use a non-GF detecting AFCI), then couldn't you use one MWBC from the new panel to the old panel/junction box to feed two existing 2-wire circuits?

Cheers, Wayne
 
Rather than quoting, I'll just say:

Definitely check whether you can install the new panel where the existing one is. We can generally replace like-with-like where-is because we're not "increasing the risk" to do so.

You absolutely can use MWBC wiring between old and new panels. If you use a conduit method, you can even use one (or a few) single EGC(s) sized for the largest circuit connected.

If you happen to have an odd number of 15a and 20a circuits, you can even share a #12 neutral (or the neutral in 12-3 cable, if you use NM), as long as you breaker each properly.
 
LarryFine said:
Definitely check whether you can install the new panel where the existing one is. We can generally replace like-with-like where-is because we're not "increasing the risk" to do so.
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Sure, why not. It's not that big of a deal, I have to move things all the time to get near a panel. There are apartments around here where all the panels are in laundry closets.

List it on the permit as a repair job.
 
Coppersmith said:
That would be very tight I think. 8" through the block, then 8" on each side of wall. What if i use trough instead of conduit? Does derating apply to trough?
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If you can't get to less than 24" then run enough raceways so you have no more than 20 CCC's per raceway. Still need to adjust conductor sizes, but not any more than 50% ampacity adjustment. 10 AWG still good for any 20 amp circuit in this case. If you go beyond 20 CCC's you may need 8 AWG or even 6 AWG conductors for 20 amp circuits.
 
I don’t know if it’s required to be moved to bring it up to code (working space) but if it wasn’t required by the local building department I would just leave it in the current location facing the interior.
 
Coppersmith said:
This would work fine. I'm just not sure you are correct about the LB's resetting the nipple length. Can anybody confirm Nuber's analysis here?
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No one want to play with this one - so... I would add additional layman's justification is that an LB, junction box, or panel in any raceway path has significantly more air space than the raceway itself. LB's are specifically designed to have at least twice the cross sectional area of a similar sized raceway. The LB is acting like a heat sink and dissipating the heat buildup in the nipple.

Additionally you can ignore the neutral in a multi-wire branch circuit, so you could "create" some between the new panel and old saving some CCC's. This might lower your raceway needs if you haven't accounted for this yet. see 310.15(B)(5)

Do what you will - good luck.
 
I can't see you sitting on top of the washing machine to push wires through the wall to the new panel. No matter how you do it, that machine's gonna have to move, at least while you're working!

Let the 'laundry technician' of the household know that the machine will be out of service while you work.

That'll make replacing the box in-place manageable, without a lot of finagling with nipples, bodies, conduits, or whatever!
 
Coppersmith said:
I've been hired to do a panel change. The existing panel is behind the washer and the washer can not move. All of the branch wiring enters the panel at the top. Since this is a working space violation and there isn't another good spot for the panel inside, I plan on installing the new panel outside on the opposite side of the wall from the existing panel (next to the meter).
Click to expand...

PaulMmn said:
I can't see you sitting on top of the washing machine to push wires through the wall to the new panel. No matter how you do it, that machine's gonna have to move, at least while you're working!

Let the 'laundry technician' of the household know that the machine will be out of service while you work.

That'll make replacing the box in-place manageable, without a lot of finagling with nipples, bodies, conduits, or whatever!
Click to expand...

They would probably have trouble trying to use the washer while the panel is being changed anyway (temp power outage).

When the OP says the washer can't be moved I think he means to a different laundry area (permanently). He is worried about the code violation when he puts the washer back in place.
 
growler said:
When the OP says the washer can't be moved I think he means to a different laundry area (permanently). He is worried about the code violation when he puts the washer back in place.
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Correct.

Update: The panel change is in full swing. I placed a 4x4x36 trough between the old panel and the ceiling to intercept all the cables. It's on standoffs so I don't have to disconnect power until I'm ready. Two 1.25" PVC conduits enter the trough from the back and go to the new panel outside. I have been standing on the edges of the washer to perform this work. Eventually I will have to move the washer, but since this is a multiday panel change I didn't want to take it out and then put it back.

It's amazing the number of additional rules I had to abide by to do this panel change. Since I used a trough, I had to avoid more than 30 CCC in any cross sectional area. Brought the cable in the top on both sides of the conduit to avoid. Since I used conduit outside, I had to worry about derating in one conduit (it's long than 24") but not in the other (shorter than 24"). The shorter one can have 60% fill while the longer one is limited to 40%. Had to keep the wire count at 20 max too. Of course I can't use NM (not weatherproof), so THWN.

Also, punched a new KO in a tiny old hot meter can (wearing arc flash gear of course.)
 
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