Electrical – Options for installing sub-panel


we are thinking about the best way to rewire our kitchen. It had 2 circuits when we moved in. We managed to add 2 circuits using an existing 3/4'' conduit that goes from the basement to our third floor apartment in the back hallway (see pictures below). However, we want to remodel the kitchen next year and our goal is to have at least 6 circuits in a kitchen with gas appliances. What are our best options and how much work do they require? We thought about three possibilities.

  1. Stick with the EMT conduit and use multi-wire branch circuits to maximize the circuits we can get out of it. This is based on a previous suggestion from this forum.
  2. Install 60A sub-panel in the 3rd floor using the EMT conduit with 3x #6 wires plus #8 wire for ground. Run 6/3 mc cable from basement junction box to main panel. A sub panel seems much more future proof. How do people feel about the #6 wires for 60A sub-panel. I read different things about that.
  3. Install 60A sub-panel in the 3rd floor by replacing the EMT conduit with 4/3 mc cable that goes directly from main panel to sub-panel. We would remove the EMT and use the same holes for the mc cable. Maybe I am wrong but it seems relatively easy to run this cable.

In general, I like a sub-panel because it's more future proof and because it avoids the MWBC

Current conduit

The 3/4'' EMT conduit goes from the basement to a third floor junction box in the back hallway (about 30') and currently includes wires for 4 circuits (2 for kitchen, 2 for the living area).

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Best Answer

The subpanel is the way to go. But make it big!

That is our #1 thing on panels - you want lots of spaces. Spaces are cheap, regrets because your panel is full are expensive. And that is a dinky little panel downstairs, you're not going to get much out of it, and I bet you're already double-stuffing that!

Of course you want a small "box size", but that can be had - you just have to look carefully. I have a small space" restriction and I'm looking at an 8-space QO panel barely larger than a sheet of paper. I might put 2 of them there, stacked above each other. You could drop straight down out of that junction box.

Or alternately, I don't know if anything is exiting the back of that junction box or if it's yours to rewire, but you have plenty of room for a full-size 30-40 space panel if the panel overlaps the 3/4" conduit. Have the conduit enter the bottom of the panel and exit the top. Any thru wires can passthru the panel.

You may think "A 60A feeder can only support eight 15A branch circuits, so why do I need more than 8 spaces?" Because of oversubscribing. You are vanishingly unlikely to use all 8 circuits at absolute limits at the same time, so it is normal/healthy to put several times that in breakers. This gives you the elbow room, for instance, to put the fridge on a dedicated circuit, non-GFCI so you don't have nuisance trips from unrelated circuits tripping the fridge. A fridge only draws 1 amp.

30 spaces fed from a 60A breaker is perfectly reasonable. Further, you could bump this to 125A by changing to a 1" pipe and #2 wire.

Conduit, oh yes!

All my work is in conduit and I can't recommend it more highly. Since it's EMT, you don't need to carry a ground wire. Given 3/4" conduit, #3 or #4 wire won't fit. But you can fit three #6 THHN wires in there, and have room for six #12 wires. That's only 3 more circuits (4 total) and you don't hit a crippling derate until 5. So that actually works quite nicely.

Or you could fit the three #6 along with three #10 for powering a dryer or another subpanel.

As far as the other three circuits also in this pipe, consider serving them out of this new subpanel, or another subpanel.

Too-low wires

I am concerned about that gaggle of NM cables running out of that panel. If the panel is low enough to be legal, then that bunch of NM is low enough to need physical protection from damage. The best physical protection I'm aware of is EMT conduit, but you can't put a bunch of Romex into a conduit; only 4 circuits per and for fill reasons you are better off switching to THHN wire.

I would try ThreePhaseEel's idea of flexible conduit. Regardless the point is you need to clean up your wiring so it is Code legal. You don't want to wait til the inspector sees this and suddenly wants everyone to fix theirs and there's contention for conduit space.

I suspect your landlord or council is not aware of the code violation here. The better thing would be for everyone to get together and fix it all.