Critical Loads Panel Install (Extending Existing Circuits)

[ChrisG]

My friend just got a few quotes for installing a critical loads panel (sub panel) directly next to main panel in prep for an inverter to run those circuits via an interlock on sub panel. All three quotes came back with significant swings of cost. I called the contractors with him and learned why they are so different and now questioning how I wired mine (NEC 2020) in North Carolina.

In common: All are using SER #2 feeder between joists and derating subpanel; All are using 1.5" conduit nipple between joists (load bearing wall) to connect sub panels for branch circuits and wire nuts in main panel to extend to sub

1. Quote 1: Lowest Cost - Master Electrician and extends hot legs ONLY to new sub panel
2. Quote 2: Medium Cost - Master Electrician and extending both hot and neutral's to make sure there is no problem with AFCI/GFCI circuits
3. Quote 3: Highest Cost - Non-Master but licensed - extending hot, neutral and grounds to sub panel (I really questioned this one as the panels are already grounded via the SER

Seems like they are all interrupting NEC 300.3(B) differently. When I did mine, I extended both hot and neutral for each branch circuit using wire nuts, wish the in-line waygo were available then. Any ideas which is correct?

 

[Zwy]

Here is an easier way to do it: Make the former main panel a subpanel/critical loads panel and remove any N-G bond. Install a new panel and it becomes the main panel. Install a transfer switch, can be 2 pole depending on inverter and how N-G bond will be done, but I prefer a 3 pole so neutral can be switched and inverters bypassed. With a transfer switch, no need for the interlock.

If instead of transfer switch an interlock is used, a new panel is still installed and the interlock is installed on that new panel. The original panel again becomes the subpanel/critical loads. N-G bond it removed. The new panel has utility power and a backfed breaker with a hold down kit on the backfed breaker. With the interlock, power can only come from one source. A double pole breaker is used to feed the now subpanel/critical loads panel.

If it is desired to not have all circuits in the subpanel, then either reroute the wires or if the wires are short, a wire nut or 2 wire Alumiconn or 3 wire Alumiconn will work to extend wires. I would not use Waygo unless it is a low voltage circuit. I like the Alumiconn, secure with set screws and snap cover.

 

[ChrisG]

Here is an easier way to do it: Make the former main panel a subpanel/critical loads panel and remove any N-G bond. Install a new panel and it becomes the main panel. Install a transfer switch, can be 2 pole depending on inverter and how N-G bond will be done, but I prefer a 3 pole so neutral can be switched and inverters bypassed. With a transfer switch, no need for the interlock.

If instead of transfer switch an interlock is used, a new panel is still installed and the interlock is installed on that new panel. The original panel again becomes the subpanel/critical loads. N-G bond it removed. The new panel has utility power and a backfed breaker with a hold down kit on the backfed breaker. With the interlock, power can only come from one source. A double pole breaker is used to feed the now subpanel/critical loads panel.

If it is desired to not have all circuits in the subpanel, then either reroute the wires or if the wires are short, a wire nut or 2 wire Alumiconn or 3 wire Alumiconn will work to extend wires. I would not use Waygo unless it is a low voltage circuit. I like the Alumiconn, secure with set screws and snap cover.

@Zwy Thanks for the feedback. I think going that route you mention would be way too involved. He has three heat pump outdoor units, three air handlers with electric heat strips, two water heaters, that would need to move to the new ‘main panel’ as they won’t be critical loads. Also the service entrance wires are very short and will need to be extended in the current panel to make enough length for new panel.

Going the original route above to add a sub panel, any thoughts on which option is accurate with todays code. I went with option two on mine but that was a year ago. Feel like there electricians are way disconnected with the proper way to do this for him.

 

[zanydroid]

2 is how I do it.

There is explicitly evidence out there that 1 is wrong since it obviously busts the majority of modern breakers. It is how some transfer switches work (but again this is documented to busy modern breaker).

There is no rule I know of that prevents you from sharing EGC to arbitrary extent for most circuits.

Not all MSP can be converted to subpanel in an easy way. A lot cannot

 

[ChrisG]

2 is how I do it.

There is explicitly evidence out there that 1 is wrong since it obviously busts the majority of modern breakers. It is how some transfer switches work (but again this is documented to busy modern breaker).

There is no rule I know of that prevents you from sharing EGC to arbitrary extent for most circuits.

Not all MSP can be converted to subpanel in an easy way. A lot cannot

Thank you. Weird that a recommended licensed electrician would even quote only moving hots over. Very strange.

 

[zanydroid]

Thank you. Weird that a recommended licensed electrician would even quote only moving hots over. Very strange.

It might save a little bit of money if the house is grandfathered into not needing AFCI. IIRC IF the circuit is only extended a certain distance and no new outlets NEC provides an exemption.

It can lead to some dysfunctional hacks though that would require more work down the line to correct if the exemption is no longer valid (EG some circuits get extended with new outlets, and there is not an easy way to pull over the neutrals, IE if conduits are filled up. While if the neutrals were pulled over up front that problem would have been solved up front.).

 

[zanydroid]

Along these lines, another thing I don’t think most electricians appreciate is how sus it is to install 240V only panels and circuits nowadays. That causes issues with installing 240V GFCI and SPDs, which respectively need 120V to operate or intentionally leak current on ground during normal operation. Leaking current on ground will cause bad interactions with upstream GFCI.

I’ve posted this on a few forums but as a DIY pleb I don’t get traction.

That said, probably what will happen is there will be released 240V only GFCI and SPD compatible with L-L-G wiring. Darwinism.

 

[ChrisG]

Along these lines, another thing I don’t think most electricians appreciate is how sus it is to install 240V only panels and circuits nowadays. That causes issues with installing 240V GFCI and SPDs, which respectively need 120V to operate or intentionally leak current on ground during normal operation. Leaking current on ground will cause bad interactions with upstream GFCI.

I’ve posted this on a few forums but as a DIY pleb I don’t get traction.

That said, probably what will happen is there will be released 240V only GFCI and SPD compatible with L-L-G wiring. Darwinism.

Funny you mention 240v only panel. When I bought my cabin it was a mess. Take a look at this . Has been upgraded since (in mid 2020). Could only get black wire:
Before:


After:

 

[zanydroid]

WTH??

 

[ChrisG]

WTH??

Exactly, The 'home inspector' said all was good when I purchased. I was looking to add an outlet in the basement so I took off the covers. Looks like previous owner intended the sub panel to be 240v ONLY but then started adding some 120v, with small 14awg wires going to main panel for neutral AND ground in one. One of the double pole breakers didn't even have the wires torqued down. So I ripped it out and restarted from scratch with the new panel and did it right.

 

[zanydroid]

LOL home inspector is mostly for completely egregious stuff. In my state they can’t even remove the deadfront. And the report spends 30% of the time saying “maybe this is good or bad, we aren’t allowed /qualified to take a closer look”

IMO unless extremely hard up for cash or manufacturing 10-100 homes (in which case the savings add up) people should just run neutral for feeders, and value engineer the feeder wire type as appropriate to compensate…

 

[ChrisG]

And this saga continues. Buddy had a new critical loads panel put in by #2 option in my first post(extend hot and neutral to sub panel) master electrician. He paid extra for a wire trough rather than cut between studs for new recessed sub panel for future expansion work. Electrician used a 8x8 wire way/trough and it failed inspection. Reason: the plane of the working area starts at the front of the panel (flush with drywall) so the trough sticks out 2” more under the panels.

Inspector failed work and electrician is demanding payment with no intention to resolve. WTF.

Inspector referenced this picture from some site:

 

[Zwy]

And this saga continues. Buddy had a new critical loads panel put in by #2 option in my first post(extend hot and neutral to sub panel) master electrician. He paid extra for a wire trough rather than cut between studs for new recessed sub panel for future expansion work. Electrician used a 8x8 wire way/trough and it failed inspection. Reason: the plane of the working area starts at the front of the panel (flush with drywall) so the trough sticks out 2” more under the panels.

Inspector failed work and electrician is demanding payment with no intention to resolve. WTF.

Inspector referenced this picture from some site:

6x6 trough or move electrical panel out 2 inches.

 

[zanydroid]

And this saga continues. Buddy had a new critical loads panel put in by #2 option in my first post(extend hot and neutral to sub panel) master electrician. He paid extra for a wire trough rather than cut between studs for new recessed sub panel for future expansion work. Electrician used a 8x8 wire way/trough and it failed inspection. Reason: the plane of the working area starts at the front of the panel (flush with drywall) so the trough sticks out 2” more under the panels.

Inspector failed work and electrician is demanding payment with no intention to resolve. WTF.

This can just go straight to state licensing board complaint, right?

 

[ChrisG]

This can just go straight to state licensing board complaint, right?

Yup that’s what we looked up and called the company back. Apparently my friend and I also started a lot of shit in a local forum we have in the area where companies advertise. Company will be going to my friends house to resolve.

I would have expected a company with master electricians would have known better. What a hassle.