Sub-Panel wire size and type (etc)

[fordluver4x4]

So this is for a sub-panel in the basement not the garage, but the wires will have to run through the attic of the garage... so I'm posting it here because I've got lots of good info from this site in the past.

I’m running wires to the basement for future basement finishing. I’d like to add two circuits of outlets (one on the finished side and one on the unfinished side of the basement), baseboard heaters (I’m also open to other heating options, the basement stays in the low 60’s in the winter, so I only need to raise the temp 5-10 degrees), and possibly an extra circuit for future use if needed. I figured on 6000 watts for the heaters (four 1500w heaters), and 3600w for the outlets (1800w x two). The run to get to the basement is about 60’ including up through the garage wall, across the garage attic, down the joining wall, and across the basement. I’ve considered individual runs for the two outlet circuits and the heat circuit (three runs total), or just running a larger wire to a sub panel in the basement. I lean toward the sub-panel for versatility and because I can install that now and then wire off it when I get around to finishing the basement, but I don’t know what wire to use. With my above estimates I’d need 9600 watts, which should be 40 amps at 240v. I’ve heard of an 80% rule where you can only use 80% the capacity of the wire, so do I need a wire rated for 50 amps? I also wouldn’t mind a little extra capacity in the panel in case I need it, but I think above 50 amps I’m starting to need a pretty hefty cable. So I guess my questions are:

1. Is there a better option than baseboard heat for the basement that would take less current (I don’t want to cut into the central air)
2. Do you think a sub panel is a better option than individual wires running to the basement?
3. If individual runs are best, what gauge do I need for the four 1500 watt 240 volt heaters (6000w @240), and how do I terminate that wire in the basement until I install the heaters?
4. If a sub panel is the best option, what size/type of wire do I need for 40 amps, and what if I want a little extra capacity (50 amps)?
5. Is it best to stay away from aluminum cable due to the extra size and trouble running through walls etc along with needing the goop to keep it from corroding?
6. Can a sub-panel have more amperage of breakers in it than the breaker/wire supplying it? IE: my main panel is 200 amp, but there it probably 4-500 amps worth of breakers in it (they obviously won’t all be at capacity at once).
7. Could I run 6/3 romex off a 50 amp breaker, to a sub-panel with a 50 amp main breaker, and have 12,000 watts (50 amps) total wired off it, or does that violate the 80% rule? (this would be two 15 amp outlet circuits, one double pole 30 amp breaker with the 6000 watts (25 amps) of heaters, and one 20 amp breaker left for future expansion).
8. If I don't want the extra capacity, could I do 8/3 romex with 40 amp breakers for my 9600w need, or again, does this violate the 80% rule?

Thanks for any help. Also, if there is an electrician in south central PA that would like to come talk over my projects, then double check them and hook them up once I’ve got everything run, I’d be interested in that.

 

[mm08822]

1. May want to consider a minisplit or 2. Good for dehumidification in summer.
2. A sub panel keeps things close to point of use.
3. N/a
4. Use SER Aluminum cable. 2-2-4-6. Good for 90 amps. (Minor cost increase, but 1 and done. Put in a 24 space panel (or larger...they're cheap.)
5. AL cable is perfectly fine today. Different alloys than late 60/70's . Oxide inhibitor not always needed today but can still be used.
6. Do not add up cb ratings for load estimation. That gives a useless answer. It's about simultaneous usage. These numbers can be surprisingly low.
7. See reply #4, use 90a cb.
8. Do reply #4 and you wont ever have a problem. Copper is about 3x AL. So buy the flexibility/future-proofing by using AL.

 

[theoldwizard1]

1. May want to consider a minisplit or 2. Good for dehumidification in summer.

Electric heat is the MOST EXPENSIVE cost to operate (except in a few locations).

A mini split will cost more to install, but less to operate. You will get paid back. The bonus is AC/dehumidification

 

[fordluver4x4]

Thank you for the thoughts.

I know electric heat is the most expensive, I just wasn't sure it would be worth the cost/install/maintenance of a mini-split. the basement is 884 sq ft, once you subtract the concrete and stud walls etc the actual area is closer to 700 sq ft, and I'm only planning to finish 1/2 of that. so my assumption was that the cost to raise 350 sq ft from 63 to 69 wouldn't be a lot even with baseboard, and that it wouldn't make sense to buy/install/maintain a mini-split for that. Does that sound right or would you still suggest a mini-split?

If I plan for a mini-split, that reduces my electrical load significantly, to the point that I'm thinking it may make more sense to skip the subpanel and just run 12/2 (that I already have) for the outlets (x2), and a wire for the mini-split (12/2 if I remember correctly from what I ran for the future mini I'm hoping to put in my garage). I still like the idea of a subpanel in the basement, but the sump outlet and the basement lights would still be run from the main panel, so it may actually be a cleaner install to have all the basement circuits in the main panel.

Thoughts?

 

[mike93lx]

You can buy a lot of power for the cost of a mini.

In a space that small, a couple baseboard heaters should be plenty and run a separate dehumidifier if needed

 

[fordluver4x4]

Also, in the winter I don't need dehumidification, and in the summer the basement stays under 70, so the mini probably wouldn't run enough to work as dehumidifier.

one other note: I'm planning to eventually switch my water heater to a heat pump style, it would be in the unfinished side of the basement, but I guess theoretically it could be stealing heat from the baseboard heaters... however I still lean toward baseboard being the simplest/easiest way to keep the basement 5-6 degrees warmer than it naturally stays.

 

[theoldwizard1]

I know electric heat is the most expensive, I just wasn't sure it would be worth the cost/install/maintenance of a mini-split.

If you are NOT going to use it a lot, then you may be correct. However, remember that heat rises, so if the basement is kept at 68°F - 72°F with your mini-split, that heat is NOT wasted. It will warm the floor(s) above.

If I plan for a mini-split, that reduces my electrical load significantly, to the point that I'm thinking it may make more sense to skip the subpanel and just run 12/2 (that I already have) for the outlets (x2), and a wire for the mini-split (12/2 if I remember correctly from what I ran for the future mini I'm hoping to put in my garage).

Yes !

I never understand why people use 12/2 when 14/2 is adequate and they are using a 15A breaker.

 

[fordluver4x4]

I talked to an HVAC tech who thinks I'll be ok splicing into existing duct work. So I'm now thinking of just running two 20 amp circuits for outlets (this is already probably overkill) and then a spare circuit just incase I needed a little extra heat, or it could power a mini-split if I decided to go that route. Both baseboard and mini-splits only need 2 wire (plus ground) 240v, So I'm thinking of either running 12/2 (which I already have) to a simple disconnect, or 10 gauge romex to a "load center" (6 space mini panel) where I could branch off into two baseboard circuits if I went that route. Does anyone know if the "load center" would be ok, or being remote from the main panel would it need to have a main breaker? also would I need to run 10/3 and include a neutral in the load center even though the heating equipment doesn't need the neutral?

Load center https://www.lowes.com/pd/Square-D-100-Amp-6-Spaces-12-Circuit-Main-Lug-Load-Center/3134331
Disconnect https://www.lowes.com/pd/Square-D-6...e-Enclosed-Circuit-Breaker-Disconnect/3364886

This seems much simpler to me than 2/2/2/4 with a sub panel etc. And the two 20 amp outlet circuits leave room for expansion if needed.

Thanks for the help so far.

 

[sparky 1971]

I talked to an HVAC tech who thinks I'll be ok splicing into existing duct work. So I'm now thinking of just running two 20 amp circuits for outlets (this is already probably overkill) and then a spare circuit just incase I needed a little extra heat, or it could power a mini-split if I decided to go that route. Both baseboard and mini-splits only need 2 wire (plus ground) 240v, So I'm thinking of either running 12/2 (which I already have) to a simple disconnect,

You don't need a disconnect for the heaters. The thermostat is enough

or 10 gauge romex to a "load center" (6 space mini panel) where I could branch off into two baseboard circuits if I went that route. Does anyone know if the "load center" would be ok, or being remote from the main panel would it need to have a main breaker?

You don't need a main since it's the same building

also would I need to run 10/3 and include a neutral in the load center even though the heating equipment doesn't need the neutral?

You can do it with 10/2 but that will limit you to 240 volt loads and you might kick yourself in the future if you wanted to add something 120. Why not run 8/3 for the sub panel, put it on a 40 amp breaker (or 6/3 and a 50)? Use four spaces for the two baseboard heaters and the other two spaces for the 120 loads? You can still use the 12/2 that you have, and if you needed to add something in the future, you could use tandem breakers.

Load center https://www.lowes.com/pd/Square-D-100-Amp-6-Spaces-12-Circuit-Main-Lug-Load-Center/3134331
Disconnect https://www.lowes.com/pd/Square-D-6...e-Enclosed-Circuit-Breaker-Disconnect/3364886

This seems much simpler to me than 2/2/2/4 with a sub panel etc. And the two 20 amp outlet circuits leave room for expansion if needed.

You won't be able to expand to anything 120 volt if you feed it with a 10/2.

Thanks for the help so far.

 

[75gmck25]

If you insulate your basement well, including something on the floor to reduce cold from below, it won't take that much heat to raise the temperature in your basement. I have an old 1940 home and I used 1" foam, glued to the wall and taped to prevent air infiltration, then framed a 2x4 wall and laid in mineral wool bats and installed drywall. I had no easy way to insulate the old floor without reducing headroom too much, so I just have a pad and area rug on top of the painted concrete floor.

With no heat source, the basement stabilizes at about 65-66 degrees, and I can use a simple roll-around space heater (the ones that look like a little radiator) and it will raise the temps to 70+ degrees in about 15 minutes or less. I made sure I had plenty of 20 amp wall receptacles so that I can plug in one or more of the heaters in just about anywhere. With the walls well-insulated, and the rooms above already heated by my primary heating system, it takes very little to heat the basement.

 

[theoldwizard1]

I talked to an HVAC tech who thinks I'll be ok splicing into existing duct work.

You will never be happy (warm) with this solution !

If you want a COMFORTABLE area, you need a heat source with it's own thermostat.

 

[theoldwizard1]

... "load center" (6 space mini panel) where I could branch off into two baseboard circuits if I went that route.

Do this !

If you feed that load center from a 40A-60A breaker in your main load center then you can use 6-6-6-6 SER. They make 6/3 NM-B but I would not want wrestle that.

 

[fordluver4x4]

Thanks for all the help. The basement has R11 blanket insulation on the walls, I'm planning to stud inside that with insulation in the stud wall, so it should be east to heat. My calculation is that I would need 6000 watts of baseboard heat for the whole basement, which I actually think is overkill since I only need to bring the temps up 5-6 degrees and the calculation was based off that being the main heat source. Could I do 6000 watts (25 amps) on 10 gauge romex, or would I need to stay under 5760 watts (24 amps) to be under the NEC 80% rule? I don't think staying under the 24 amps would be a problem.

My plan at this point is: Two 20 amp outlet circuits run off 12/2 romex (x2), and 10/3 romex to a Load Center for future expansion. That would give me the ability to do baseboard or wall mount electric heaters or run to a heat pump, etc.



Different question (I guess it's ok to hijack my own thread?)
I'm running wire to a 50 amp welder outlet in the garage. The welder uses a 6-50r which is two hots and a ground, I'd like to run 6/3 w/G in case I ever want to install a 14-50r for an RV or electric car. Is it ok to just wire nut the unused neutral in the receptacle box? and if so, should I also wire nut it inside the panel, or wire it to the neutral bar in the panel? (I know I could just install the 14-50r and use a 14-50p to 6-50r pigtail, but I don't like unnecessary pigtails/adapters)

 

[mike93lx]

I'm running wire to a 50 amp welder outlet in the garage. The welder uses a 6-50r which is two hots and a ground, I'd like to run 6/3 w/G in case I ever want to install a 14-50r for an RV or electric car. Is it ok to just wire nut the unused neutral in the receptacle box? and if so, should I also wire nut it inside the panel, or wire it to the neutral bar in the panel? (I know I could just install the 14-50r and use a 14-50p to 6-50r pigtail, but I don't like unnecessary pigtails/adapters)

Yes, fine to wirenut it in the box. I would land the neutral in the box though, no reason not to. That way if you go to use it, the panel side is done.