Ask Me Help Desk - 70 amp 2 pole subpanel

70 amp 2 pole subpanel

Hi, I'm looked 70 amp Homelite subpanel with 2-spaces-- so 2 20-amp breakers or 1 20-amp breaker and split 15-amp breaker --- and plan to run #8 or #6 off 40-amp two pole breaker in my main panel so,

8-8-10-12awg or #6-6-8-10awg ground through 1-1/4" 1-1/2" or 2" schedule 40--- sch-80 under driveway ---PVC( gray ) to the 70-amp panel, with NO main in the subpanel, however, when I got home and look at this 70 amp Homelite subpanel, on web page Iread the following;

"1 Phase, 3 Wire, 120/240VAC"

Ohh, I remember now, the 3 -wire will handle 2 hots neutral and ground... duhh.. so no question, rather, maybe just verification by more of expert for my plans.

I see now better to use THWN in case wire ever got wet, and not THHN.

As of now the load at this small cabin 150' away from my main, will have a window air conditioner--- 7.5 or 15 amps I don't know yet ---and another20 amp circuit for lights etc but actually/maybe there will be tiny fridge-- amps unknown --so for that 2nd space in panel I would use split 15-amp ergo 15 for tiny fridge and 15-amp for lights, computer etc...

I know to NOT bond the ground bus to the neutral bus. I will run ground wire in PVC to a ground rod.

I know there will be voltage drop and if I were really concerned for optimum supply of voltage I would use #4 awg, however, this cabin is likely to only get used once or twice a year for a few days.

I plan to use a junction box under my house when coming out of the PVC and run romex 8/3 or 6/3 to my panel.

Lets see now, what info did I leave out above if any? Thx for any experts help.

rr6

I'm a bit confused with your jumping around, but I'll try.

No way I'd have only a two space panel. If you don't want to bother with having a main breaker then go to a six space panel. This way you have a bit of room and are still legal. If it were me I'd go with at least a 12 space 100A main breaker panel in the cabin.

Also, most all new THHN is dual rated THWN, so this is not a worry. But an underground conduit is considered a wet location.

I'd stay with #6cu and a 50 or 60A feeder breaker.

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stanfortyman--No way I'd have only a two space panel. If you don't want to bother with having a main breaker then go to a six space panel. This way you have a bit of room and are still legal. If it were me I'd go with at least a 12 space 100A main breaker panel in the cabin.

Hi Stan and thanks for quick reply. Sorry for confusion but I did try to convey all needed information for consideration.

I don't understand do you think a 70-amp 2-space panel would not meet my codes?

My reason for this panel was;

1) small cabin, rarely used, and probably never more than 40-amp load( guessing ),

2) $14.00 panel vs $25. Or $37. Panel when not needing 6 or 8 spaces for such a small rarely used cabin.

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Also, most all new THHN is dual rated THWN, so this is not a worry. But an underground conduit is considered a wet location.

Thx for that verification, as I called Lowe's back and they do not even carry the THWN and he stated the THHN is commonly used in conduit even underground.

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I'd stay with #6cu and a 50 or 60A feeder breaker.

I was originally thinking of coming off a 50 amp 2-pole breaker but then got to thinking if the load would ever be that much, but I think your thoughts of 50 are probably best and match #6.

I was only thinking of 40-amp 2-pole if I was only going to use the #8 i.e. trying minimize the costs if possible for at most a;

1) 15 amp window air conditioner,

2) 7.5 amp tiny fridge,

3) 3 lights, computer, etc...

Probably will do #6, 50-amp, 2-pole as my original plans called for.

Stan, do you see any problem in using junction box to go from THHN to romex 6/3 that last 40'?

Someone on another forum was telling someone else to not use a junction box and I can't understand any problem in using a junction box.

Oh yeah, what does "cu" after the # of wire and gauge mean? Never mind, I bet it is copper wire( cu ). Yeah I would never use aluminum wire.

Thx again. Rr6

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Thx for that verification, as I called Lowe's back and they do not even carry the THWN and he stated the THHN is commonly used in conduit even underground.

He was wrong as usual.

Please do not believe anything you hear from the aisle monkeys at home centers.

Quote:

Originally Posted by stanfortyman

He was wrong as usual.
Please do not believe anything you hear from the aisle monkeys at home centers.

Ok Stan, so it you believe that I should use THWN for undeground in conduit. Lowe's does't carry that so it is off to another store. That may be for the best since there wire was more expensive than same wire I priced at a smaller electrical supply house and I don't know if there's was THWN either.

I think THWN is best. Just read in another forum that the Lowe's THHN probably is dual rated and printed on the cable itself and the employee does not realize this and is just going by the signs above the cable, as that is all I was going by also.

I will call Lowe's employee back and ask to read what is on cable. Thanks again

Ha, I called him and sure enough it is printed on the cable dual rated as THHN/THWN so he and I both learned something today. He stated that he even worked at electrical plumbing supply house for 6 years and had never noticed that.

rr6

Spend the extra $11 or 13. One day you will want some outside power, maybe a window AC or extend the cabin.

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I think THWN is best. Just read in another forum that the Lowe's THHN probably is dual rated and printed on the cable itself..

Actually I said this in my first reply.

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Originally Posted by ma0641

Spend the extra $11 or 13. One day you will want some outside power, maybe a window AC or extend the cabin.

Already considering window with plans I listed, however, your mentioning of outside power is a good thought indeed. Yeah, I think owner of the cabin will like that idea of 6 - 8 spaces more than the minimal 2 because of having and outside power source,

Although I suppose I could go through window or door to plug into the split 15 amp circuit-- in the 2 space panel --- to run skillsaw for doing work or electric leaf blower for future maintenance of cabin. She has no plans to ever have water/plumbing here.

My closest supply house does not even carry any subpanels under 125 amps and that is bigger than my old house with a 100-amp main.

rr6

Quote:

My closest supply house does not even carry any subpanels under 125 amps and that is bigger than my old house with a 100-amp main.

The maximum rating of the panel means nothing. It's the number of circuit sand the breaker feeding it that matter.

Even if you use a 100A main breaker panel as a sub-panel, the 100A main is only serving as a disconnect.

Quote:

Originally Posted by stanfortyman

Actually I said this in my first reply.

Yes and you were correct, but that was not obvious in Lowe's to me or the employee, ergo my call to verify. That is what this thread has been about, to verify my plans are reasonbaly safe if not exactly meeting some codes, though so far I don't see where I might be violating any codes with my plans.

Thx again. rr6