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Subpanel for finished basement: Advice on size, cable, installation please!

Subpanel for finished basement: Advice on size, cable, installation please!

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Old 03-30-20, 11:27 AM
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Subpanel for finished basement: Advice on size, cable, installation please!

Thanks in advance for advice! I just finished framing my basement and am moving on to electrical. Hoping for advice on the subpanel. Main 200A Eaton panel is in the garage. I'll need to run cable up into the attic, cross about half the house, then down into the utility room in the basement. I haven't measured this yet, but I'm guessing about 80' of cable. The basement is about 2200 sf with 2 bedrooms, 2 bathrooms, a wet bar, living room, workout room, utility closet, and large storage area. I haven't finished my drawings yet, but I'm guessing about 15 circuits if I do separate lights and receptacles in most rooms. Mini-fridge, small countertop microwave, and a treadmill are the only notable loads. Everything else will be pretty standard: 2 bathroom GFCIs, bar GFCIs, and a bunch of lighting and receptacle circuits. No heat, range, freezer, AC, etc.

My research is telling me it's much better to "go big" and overdo these things, so I was thinking of installing a 100 amp panel with 24 spaces (48 circuits) from Square D, using a 100 amp breaker at the main panel, and running 1-0/1-0/1-0/2 SER since I'll be crossing insulation in the attic. I also understand the subpanel will need a ground bar installed. Is this overkill for my situation? It's a large basement, but without a fridge, range, baseboard heaters, etc., am I overdoing it? I definitely don't want to run out of space down the road, but I also don't want to spend $2+ per foot on cable (plus wrestle that monster) if half that would do the job. Have been advised that another route would be to spend more on a 200 amp panel with more spaces. In either case, could feed it with smaller cable and a 60 amp breaker at the main since I won't draw anything near 100 downstairs. Opinions?

Anyone have opinions or advice for me? Also, do I sound like I know what I'm talking about enough to attempt this on my own and live to tell about it? :-) Thanks!
 
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04-01-20, 03:31 AM
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Anyone have issues with the outlets?
First-generation outlets did have some issues. I'm sure they are better now.

My only issue is that the AFCI outlets need to be readily accessible. That can be difficult as it seems they are the first box that gets covered with furniture. Having them in the panel makes sure they can be easily reset if they ever trip. We often get posts on the forum with similar issues with GFCI outlets, but they are usually put in more accessible locations.
 
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Old 03-30-20, 11:42 AM
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Sounds to me like a 60A feeder would be quite sufficient. And I'd much rather pull a 4ga cable rather than a 1/0!

I would still use a 100A 20-24 space panel to give you the spaces you need. Since the breaker in the main panel will be sized to the wire (60A), there's no issue with a higher-rated panel being used. You can get a main-lug panel, or a panel with a main breaker (the main breaker panels are usually less expensive).
 
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Old 03-30-20, 12:37 PM
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1-1-1-3 AL SER is 100A as long as you aren't burying it within insulation. 1/0 AL SER is needed if run within insulation. I would use same brand and type of subpanel as the main. (Eaton)
 
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Old 03-30-20, 12:38 PM
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Thanks so much for the quick and helpful reply! I'm now strongly leaning towards a 60A breaker and feed having heard that somebody on another board as well. It'll save me a few bucks and some headache pulling the cable. I just can't imagine a reason to go bigger other than being able to support more capacity down there someday...but I have no plans to install heavy draw devices or a workshop or anything. Thanks again!
 
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Old 03-30-20, 12:41 PM
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Thanks, Pattenp! I won't be burying the cable in insulation, but it'll run across the attic joists, so insulation contact is likely. Would 1-1-1-3 still be allowable? Do you have an opinion on 60A vs. 100A in my situation? Thanks again!
 
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Old 03-30-20, 12:48 PM
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Do a middle of the road ... use 2-2-2-4 AL SER. Breaker it at 60A. The #2 AL gives you headroom up to 80A if needed even taking into account downsizing the ampcapacity for attic heat/insulation.
#2 AL SER is actually 90A if not run within insulation.
 
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Old 03-30-20, 04:25 PM
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Pattenp, that sounds like a great compromise to me. I think I'll go with that suggestion and upsize the breaker down the road in the unlikely event it trips. Can't imagine ever needing to upsize the feed for 100A, but I guess I'd cross that bridge if/when it happens. Thanks for the expert advice and saving me a few bucks (sorely needed these days, lol).
 
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Old 03-31-20, 04:49 PM
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Do you have an opinion on 60A vs. 100A in my situation?
I do! Consider that it hasn't really been so many years ago that many homes only had a 60 amp service for the entire house. Most of those older homes probably had either gas or oil heat, but electric water heaters and electric ranges were very common along with window A-C units and laundry machines too. Your plan as described doesn't have any heavy loads at all. 60 amps would be way more than enough for what you are planning. I seriously doubt you will ever load the subpanel to 50% of 60 amps.
 
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Old 03-31-20, 06:18 PM
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I agree. A 60 amp feeder will be just fine.

The adjustments required by Section 334.80 of the NEC applies to two or more cables run together. The insulation is not an issue.

 
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Old 03-31-20, 07:09 PM
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Appreciate the additional replies, CasualJoe and Tolyn Ironhand! So great to have heard from multiple experts here. You've definitely solidified the decision to run 2-2-2-4 off a 60A breaker to supply the subpanel. I ordered a Square D Homeline 125A Main Lug with 24 spaces/48 circuits due to the Qwik Grip cable system and the fact it comes from the factory with a ground bar and lug.

I finished my drawings today and it looks like I'll be doing 17 new circuits and relocating 2 from the main, so 19 out of 24 spaces. I don't foresee needing many more in the future, but you obviously never know. I'm planning to use AFCI outlets at the start of simple receptacle runs rather than AFCI breakers to reserve the possibility of tandem breakers in the future should the need arise. Anyone have issues with the outlets?
 
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Old 04-01-20, 03:31 AM
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Anyone have issues with the outlets?
First-generation outlets did have some issues. I'm sure they are better now.

My only issue is that the AFCI outlets need to be readily accessible. That can be difficult as it seems they are the first box that gets covered with furniture. Having them in the panel makes sure they can be easily reset if they ever trip. We often get posts on the forum with similar issues with GFCI outlets, but they are usually put in more accessible locations.
 
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Old 04-01-20, 07:26 AM
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I agree. A 60 amp feeder will be just fine.
The adjustments required by Section 334.80 of the NEC applies to two or more cables run together. The insulation is not an issue.
Make sure we're talking apples to apples.
My reference of adjustment to the ampacity was about SER cable, not NM. SER follows installation requirements of Article 334, excluding 334.80 so it can be used at 75deg.C. But if the SER is run within insulation it is to be sized at 60deg.C. See 338.10(B)(4).


 
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Old 04-01-20, 09:04 AM
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You've definitely solidified the decision to run 2-2-2-4 off a 60A breaker to supply the subpanel.
If it were me I'd use 6-3 NM-B cable (aka Romex). It would be a lot easier to pull and terminate. Each lug of HOM260 will accept one #8-#2 AWG aluminum or copper. The smaller copper conductors are much easier to work with than the larger aluminum conductors.
 
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Old 04-01-20, 09:37 AM
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"Anyone have issues with the AFCI outlets?"

I don't know for sure about the requirements so I thought I'd add a reply.
I thought I read that all 15- and 20- ampere branch circuits supplying outlets or devices require AFCI protection. If they are and these are all new circuits would it be easier to use AFCI breakers?
 
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Old 04-01-20, 09:44 AM
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If it were me I'd use 6-3 NM-B cable (aka Romex). It would be a lot easier to pull and terminate. Each lug of HOM260 will accept one #8-#2 AWG aluminum or copper. The smaller copper conductors are much easier to work with than the larger aluminum conductors.
Yes the #6 Cu would be easier to install, but my counterpoint is the #2 Al SER is half the cost and gives some headroom if 60A becomes to close to the actual use. Also #6Cu is 55A and yes it can be protected at 60A. But you are already at the max limit of the potential circuit use. This is hopefully a one time install and plus being 80ft of cable I would do the #2 SER and suffer a little pain now with the install to know I have not cut my self short for any possible future power need, plus saved some $$.
 
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Old 04-01-20, 02:58 PM
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I thought I read that all 15- and 20- ampere branch circuits supplying outlets or devices require AFCI protection. If they are and these are all new circuits would it be easier to use AFCI breakers?
That is correct in the required locations. Right now it is 120 volt 15 and 20 circuits. I would rather use breakers for the reasons I posted above. Even though they are about double the cost of the devices.

I also agree with Joe. Copper is the way to go in my opinion.
 
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