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We recently bought a 1950s 1700 square foot house with 3 bedrooms and 2 bathrooms, and a largely unfinished basement. We want to renovate the basement into a modern main bedroom/bathroom suite.

We have 200 Amp service with a recently updated panel that has 20 slots. We also want to use this opportunity to update the electrical wiring in other parts of the house, including the kitchen, which we want to renovate down the road. However, I'm having a hard time coming up with a plan that allows us to fit everything we want on the existing panel.

Are there circuits that we can combine in the following plan? Or should we just bite the bullet and have a sub-panel installed? Similarly, on the current plan, are there combined circuits that really should't be combined? We have done quite a bit of research to ensure that this will meet current code.

Also, I welcome any other feedback. Thanks very much for any assistance!

Planning Diagram

Work area

Inside Panel

Label

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    Double-breaker was a typo. It is the oven/range (now fixed). The two at the bottom are the circuits that I can't currently fit on the existing panel. If we do a sub-panel, I think I would like to try to place it nearer to the kitchen to simplify future work that we do there. – David Jan 28 at 4:11
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    Also updated with more photos. Yes, mini-split is a heat pump. Note that the screen capture doesn't align with the current panel breaker placement. I'm just trying to figure out if there is a way to fit all future runs on the existing panel right now. Hope that helps. Thanks again. – David Jan 28 at 4:29
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    Or you could identify the "box" (panel outer case) and then identify a Square D "QO" panel that uses that same box. Unbolt the whole bus assembly (basically everything that isn't the steel box) which comes out with 3-4 screws. Bolt it into this panel. It's now a QO panel with ~30 spaces. – Harper - Reinstate Monica Jan 28 at 9:46
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    Unfortunately, it looks like @Harper-ReinstateMonica's "Mr. Snippy" has been in your panel making a very neat looking install that makes it difficult to rearrange the breakers (the wires aren't long enough to reach a new location). This will make moving breakers to create space difficult. – FreeMan Jan 28 at 13:32
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    @FreeMan Not difficult, just messy. The wires can be extended with a wire nut and pigtail. The festoon of wire nuts (or is it a gaggle? swarm? school?) defeats the purpose of the "neat"... – Harper - Reinstate Monica Jan 28 at 19:20
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You have enough room to get what you want, but nothing more than that

The good news is that your panel can accept double-stuff (tandem/quadruplex) breakers at all positions, which means you can free up just enough room for the two new circuits in your panel and a feeder to a subpanel, but nothing more without compromising your ability to retrofit AFCI protection into your panel.

I would start by getting a HOMT230240 to put in spaces 5 and 7; this consolidates your range and dryer circuits into those two spaces, replacing the HOM240 and HOM230 that currently serve them. We then move onto the wall heater and heat pump (mini-split) circuits, which get moved onto a HOMT215220 in spaces 1 and 3 to replace the existing HOM220 and HOM215, respectively. This leaves spaces 2, 4, 16, and 19 open for the four new branch circuits you have planned; once those are in, you can put up to a 125A feeder in, with the feeder breaker on spaces 18 and 20 in the panel.

But you have a problem with that extra framing in front of the concrete

The bad news, though, is that extra framing furring out from the block wall the panel's mounted on already violates Code. In particular, it infringes on the clear working area in front of the panel required by NEC 110.26(A); as a result, you'll need to either trim that frame back so you have a 30" wide space in front of the panel clear of errant framing bits or other obstructions, or frame up from the low wall to provide a bay to mount the panel into, then move the entire panel forward into the new bay.

(If you need a visual aid, think of a fridge-sized box in front of the panel that needs to be kept absolutely clear of fixtures, obstacles, tripping hazards, and so on.)

Worse yet, the original builder didn't foresee this coming

The other problem with your situation is that your panel was mounted in a spot that while legal modulo the knee-wall, is not wise. You see, multiple pieces of electrical equipment are permitted to share a single 30" "bay" of clear working space, but the window and perpendicular wall in your picture are both rather awkwardly placed, making it rather impossible to get a second panel into that space, especially with the transition from frame to block involved. Worse yet, while you theoretically could put the panel in the frame wall around the corner, that's practically a no-go due to the corner framing at the end of that wall blocking any effort to run wiring through it.

So, when you do put the subpanel in, you'll have to find room somewhere else for it. This is further aggravated by the fact conduits fat enough for fat feeders don't fit well into 2x4 stud walls, which means you'll be stuck pulling a 4-wire SER cable over for the feeder instead. The good news is that since you're constrained to a 125A feeder breaker by panel spaces, you can pull a 1/0-1/0-1/0-2 Al SER cable and have it be good enough for a reasonably sized subpanel installation, with a 24-space or 30-space, 125A, main lug panel fed from the feeder breaker in the main panel.

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Many manufacturers make tandem breakers that take up a single slot but provide two independent circuits (or take up two slots and provide 2 120V and 1 240V circuit).

single tandem breaker double tandem breaker

Whether this is practical in your case depends on several things:

  • If your brand of panel has tandem breakers available
  • If the panel physically has enough space for the wiring
  • If the existing wiring can be moved in a way to accommodate this
  • Limitations that prevent tandem breakers in some cases (eg, GFCI breakers, or AFCI required in bedrooms)
  • If doing this gives you enough space (hopefully with a bit of spare room)

You'd also have to consider cost compared to a subpanel or even just replacing the entire panel with something bigger.

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    Thanks for this info. Our panel is HOMC20UC Homeline. Seems that there are tandem breakers available for this line of products. I think using them for the time being may be our solution, though while we have the basement walls open, will look at running the wire to support a future sub-panel near the kitchen when we get to doing that work. – David Jan 28 at 5:44
  • Yeah this will maybe meet your immediate need, but I'd strongly recommend planning for a future subpanel. In particular, you can only get regular breakers as tandem, not AFCI or GFCI, and as of the 2020 code, most new circuits need to be one of those. – Nate S. Jan 28 at 22:38

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