• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Conduit Conundrum

Gaijin2

New Member
Joined
Oct 25, 2024
Messages
79
Location
Texas
Hey all,

I'm trying to wire in a smart home panel (basically a subpanel) to my house. Unfortunately the main power panel is outside, and the subpanel is for indoor installation only, so that's opened up a rat's nest of code compliance issues, cable derating, counting current-carrying conductors and having to add more conduits, conduit sizing, and everything else. I've tried several ways to plan this out and I keep running into various roadblocks, so I thought I'd ask you folks for a fresh take on it, if that's okay.

There are 12 circuits that will be moved over to the subpanel. Wire is 90c THWN-2, #2 for main power and circuit wire is all six circuits of 10-gauge and six circuits of 12-gauge (oversized for derating reasons). Wall is 6" thick.

Here's a pic of the main panel. All the main panel's knockouts are on the bottom, except for one on the left connected to the meter and a similar (unused) one on the right. Notice where the top of the window is; there's about 4" from the top of the window to the top of the wall, where the soffits begin.
Main panel and STS proposed layout - exterior.jpg
Now in this photo, you can see a purple overlay of where I'm trying to mount the subpanel. It's basically just on the opposite side of the wall from the main panel, and the closest edge is left of the center of the main panel by about 36 inches.

And here's a shot of the desired interior mounting location:
Main panel and STS proposed layout - interior.jpg
Notice the top of the window -- that's the same window that was outside, but now there's about 14" of space up above it to the ceiling. This is due to the steep rake of the roof; the soffit is about 18 inches deep outside.

Seemed like it should be a relatively simple install originally. But there are several complicating factors.
1. You can't connect cables to the subpanel from the bottom or back, it can only be penetrated from the upper sides or the top.
2. The sides are between a stud (for the cabinets) and a window, so there's framing wood there that eats up some of those five inches on each side.
3. There's only about four inches above the subpanel's top before we reach the level of the outside soffit bottom
4. Moving the subpanel down is somewhat complicated by there being the existing light switch.

I'm happy to provide any more details or answers. Looking for new ideas and a fresh take since I've driven myself batty trying to figure this out. So - what's the recommended best practice for running the conduits for this situation? Thanks!
 
What difference does it make if you go above the soffit bottom?

Your indoor picture shows the panel higher than the outdoor picture.
 
1. Why can you not connect wires to the bottom of the sub?
4. Your light switch wires may be a complicating factor when cutting in the sub panel. Especially so if that switch box is attached to a stud. Would a surface mount load center be possible with wires exiting/entering behind it?
 
What difference does it make if you go above the soffit bottom?
I don't believe it causes any issue. I was just pointing it out because the photo didn't make it clear where the wall stopped and the soffit bottom stuck out.

Also, if there were suggestions forthcoming to use (for example) LBs to penetrate the wall, I don't think that would be allowed if the LB is up in the soffit and therefore isn't accessible, but am open to any and all ideas.

Your indoor picture shows the panel higher than the outdoor picture.
You're right, it is. Oops. The indoor picture is the accurate one; the outdoor picture is not to scale, it's just to give the idea of how it's supposed to work. I can update it to be more accurate if it confuses people.
 
Last edited:
1. Why can you not connect wires to the bottom of the sub?
It's a power station "smart panel", and there's all sorts of electronics in the bottom and back. The permitted entry points are strips about 2.1" wide on the sides, and about 2.3" wide on the top. Here's a diagram they included; the gray shaded areas are the permissible entry points:
STS-entry-points.jpg

Which also means that the conduits can't be flush against the wall when they enter the subpanel. They have to be about 3 3/4" away from the wall to clear that reserved area, 94.5mm at the top or 89.5mm on the sides.

For more information, the overall subpanel's dimensions are approximately 14.7 wide x 22" tall.
STS dimensions.jpg

4. Your light switch wires may be a complicating factor when cutting in the sub panel. Especially so if that switch box is attached to a stud. Would a surface mount load center be possible with wires exiting/entering behind it?
Sorry, should have clarified that this panel is designed to be surface mounted. It's not meant to be inset into the wall.

I knew the light switch could be a problem, and I am willing to relocate it if necessary. The good thing about it is that the lights that it controls are also controlled by other switches too, so even if I had to lose the switch entirely we'd still have other switches to control those lights. But of course I'd rather keep it there as-is if possible.

I have been assuming I'd have to mount some sort of junction box in addition to the transfer switch; the way I've been thinking about it would be a junction box could receive the wires from behind it and then have to have to change the wire directions so they could come out of the bottom or side of the junction box or gutter or whatever it needs to be, so that they could enter the subpanel from above, or they could be 90 degree sweep elbows coming in, or LBs or something, but nothing seems to fit well in the available space. However, I am new to conduit and very open to changing the plan!
 
Last edited:

diy solar

diy solar
Back
Top