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Discussion Starter #1
Below is my plan for running a sub panel to my exterior shed. I already dug and ran the conduit, but want to confirm the wire gauge and panel size necessary for the project. Originally I was thinking of using #4 and doing a 75 AMP sub, but since #6 is much more readably available at the local big box stores I was wondering if I could get away with that and maybe a 50 or 60 AMP sub panel.

The items I will be running out in the shed are a computer, 5' electric baseboard heater, and then some lights and outlets.

I know the common suggestions are to go bigger in case you want to add anything else in the future, but I don't see this shed need anything else. Also, if there's any recommendations for online stores to order wire from I'm all ears.


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From what you have posted, I think a 50 or 60A supply would serve you well for planned and future needs. Just make sure you get a panel with sufficient breaker spaces for those future posibilities.

I can't tell from your picture and don't know if you are in a hurry but if it is at all difficult to run through the house from the panel to the garage I would consider leaving the #4 run to the garage so you don't have to go through it all again in the future if you need to upgrade. Also, a garage is often a place where extra circuits are required. Have you thought about a panel instead of a junction box in that location?
 

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Discussion Starter #3
From what you have posted, I think a 50 or 60A supply would serve you well for planned and future needs. Just make sure you get a panel with sufficient breaker spaces for those future posibilities.

I can't tell from your picture and don't know if you are in a hurry but if it is at all difficult to run through the house from the panel to the garage I would consider leaving the #4 run to the garage so you don't have to go through it all again in the future if you need to upgrade. Also, a garage is often a place where extra circuits are required. Have you thought about a panel instead of a junction box in that location?

Thanks for the information. The basement is all open, so it's relatively easy to run the wire. If I was to do your suggestion, you are saying I could run a #6 from shed to garage, and #4 from garage to panel?

Also, an recommendations where I might be able to purchase 4/3 wire online? Hard to find at my local big box store.
 

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You have conduit from the garage to the shed. I thought that would be relatively easy to repull larger conductors if you wanted to. I assume you are using PVC. I thought if you were opening drywall/fishing in the house it's better to do it once than twice.

Also, 1-1/2 or even 2" PVC to the shed is not much more expensive than 1-1/4". Just saying.

One 1" PVC for data? Another consideration while the trench is open.:)

Any supply house should be able to help you with wire. I'm not from the US so I'll let someone else give you recommendations for that.

Oh, #4 to #6 is fine.
 

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Discussion Starter #5
You have conduit from the garage to the shed. I thought that would be relatively easy to repull larger conductors if you wanted to. I assume you are using PVC. I thought if you were opening drywall/fishing in the house it's better to do it once than twice.

Also, 1-1/2 or even 2" PVC to the shed is not much more expensive than 1-1/4". Just saying.

One 1" PVC for data? Another consideration while the trench is open.:)

Any supply house should be able to help you with wire. I'm not from the US so I'll let someone else give you recommendations for that.

Oh, #4 to #6 is fine.

Conduit is already buried, but I did also run a 1" data conduit. And I actually did run a larger conduit once I saw the small price difference.
 

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You mentioned big box stores.
Call any electrical supply house near you for pricing.
I would think you could buy that #4 cheaper from a supply house than you would pay for the #6 at a big box.
I have also had success online with wire purchases. I bought some #8 cut to length, shipped to my house cheaper than Home Depot or Lowes.
I would not reduce the amperage just because of wire availability.
You may want air conditioning, an air cleaner of sorts and so on.
 

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Red Seal Electrician
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You mentioned big box stores.
Call any electrical supply house near you for pricing.
I would think you could buy that #4 cheaper from a supply house than you would pay for the #6 at a big box.
I have also had success online with wire purchases.
As a small-time guy, I can't buy anything at a wholesaler cheaper than a big-box store. What the wholesaler does let me buy is all the stuff the big-box doesn't carry (i.e. Aluminum conductors).

Online is looking increasingly good. So far I've been able to buy circuit breakers and 4' fluorescent lamps cheaper online than big-box stores.
 

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I didn't say wholesaler.
Any electrical supply shop that sells retail will sell to you....and always lower than the big box or hardware stores.
You just have to call and ask if they sell retail.
 

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I didn't say wholesaler.
Any electrical supply shop that sells retail will sell to you....and always lower than the big box or hardware stores.
You just have to call and ask if they sell retail.
In Canada (out west anyway) we call the "electrical supplier" a wholesaler. They all sell retail around here (even to non-electricians) but its not cheaper.

EDIT: The point being to shop around instead of taking blind advice... :)
 

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My 2 cents...
I did something like this recently. Used 2" grey elect. conduit...#6awg , needed 1 fancy pvc sleeve that moves with sunlight instead of breaking. Could not find a 60A sub panel anywhere so got a 125A panel and used 60A breaker in 100A main panel. Then realized i really wanted a sub panel with main breaker disconnect included instead of a main lug panel. This mistake forced me to hunt down a special double pole breaker retaining clip that is required when one backfeeds a main lug sub panel like I did with another 60A breaker.

If you can find a 60A subpanel (good luck) try to get one that is a main breaker variety because the main lug variety is really for a sub panel within a few feet of the main panel. You need a main disconnect at the new panel in your office due to distance from previous panel. The backfed approach works as an alternative but was a real drag to assemble the pieces via mail order...and it used 2 slots on my panel!

The lesson I learned is that there is no such thing as a generic "sub panel". Once you figure out amperage demands then you either want a main lug load center or a main breaker panel...with included main breaker which looks nothing like an ordinary double pole breaker since they actually bolt onto the phase legs...and are also not easily found at a big box store so be sure it is included. I think there are main lug load centers that are "convertible" to main disconnect but those types of breakers are not something easily bought at ace hardware so be careful. They are also expensive. Really, there is no such thing as a generic "panel" nor a generic "breaker". I may as well say Tom Brady plays a "Sport". The details about the panel and disconnect are hugely important...including the manufacturer, type, AFCI, neutral pigtails, etc.

It was the one detail I was caught off guard by when adding power to a garage and it is important enough to bring it up even if I do not know as much as the other fellas since I'm seeing a lot of generic "subpanel" terminology being used.

There is also a detail about how the neutral and ground buss on the sub panel is or is not bonded to the subpanel box for some reason. Look it up.

Oh, there are a TON of details to this project. Not at all easy or fast for a novice. But within the abilities of someone with very good research skills and reading comprehension and "more time than money".
The physical part is nothing compared to the research. The easy part is digging the trench deep enough without hitting an unmarked gas line. Then it gets complicated.
 

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Discussion Starter #13

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The reason I wasn't considering a supply house was because I was worried they would only sell the wire to licensed electricians. Is that not true? Will they sell to a home owner?
Only one way to know... contact them. There's no consistency in my experience.
 

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I am getting this panel
Yes that panel is more plug n play....although it does raise the issue of having a 100A main breaker in the sub panel fed by a 60A breaker in the main panel...not sure that is allowed. Obviously you can't exceed 60A in load but your main panel breaker feed will trip before your sub panel breaker? Hmmmmm.:unsure:
do you have 200A service? Some of these details are beyond my experience level. What #Amp breaker will feed your new sub panel?
 

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You can have a 100 amp main breaker fed with a 60 amp feed. The main will just be a means of disconnect.

A 100 amp main breaker is the smallest you will find.
 
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I have also had success online with wire purchases. I bought some #8 cut to length, shipped to my house cheaper than Home Depot or Lowes.
Oh, I'd really like to hear about that! I've seen nothing but "beats you to death on shipping".


Any electrical supply shop that sells retail will sell to you....and always lower than the big box or hardware stores.
I wouldn't go so far as to say "always"... every sort of odd-and-end, absolutely, 4-11/16" boxes are like $2.50 vs $7. EMT fittings, etc.

But not on bulk commodities like Romex spools. On #12 stranded THHN I pay 2% to 25% more at the electrical supply, but my time is valuable and I want a choice of a dozen+ colors.

I'm just a walk-in retail customer, don't set up accounts. Do not like accounts, just have a fair price.


Could not find a 60A sub panel anywhere
They're not made anymore. Utilities do not offer 60A services anymore, and haven't for years, so the only reason to have a panel that small is as a subpanel, and 60A is an awkward size there, because #8 THHN gives 50A and #6 THHN breakers at 70A.

If you can find a 60A subpanel (good luck) try to get one that is a main breaker variety because the main lug variety is really for a sub panel within a few feet of the main panel.
You mean "in the same building". Disconnect switches are not needed for subpanels in the same building.


Square D by Schneider Electric HOM816M100PC Homeline 100 Amp 8-Space 16-Circuit Indoor Main Breaker Load Center with Cover (Plug-on Neutral Ready), - - Amazon.com
I didn't know they mad "main breaker" panels that small. Compare the price of this to a 12-space and a 16-space. If it's only a couple of bucks, step up - nobody ever complained about having extra breaker spaces, but they're lined up 'round the block to complain about the other thing.


Yes that panel is more plug n play....although it does raise the issue of having a 100A main breaker in the sub panel fed by a 60A breaker in the main panel...not sure that is allowed.
It's totally allowed. Subpanels do not need main breakers at all. Not at all. Seriously.

Subpanels in outbuildings need disconnect switches, and they can be indoors. If you're searching the marketplace for the cheapest way to get a disconnect switch, you come upon a clever "hack" of simply using a panel with a main breaker, not using the breaker for a breaker at all, but just as a disconnect switch. Cheap and easy lol.

That hack has become so mainstreamed that a false "meme" popped up, people believing subpanels need main breakers. Nope, never did, never will :)

When you use a main breaker that way, size does not matter in either direction. The supply breaker must be sized to protect the feeder wire, is the only rule. If the feed wire/breaker > the subpanel's bus, the subpanel's main breaker will protect its bus.


Obviously you can't exceed 60A in load but your main panel breaker feed will trip before your sub panel breaker? Hmmmmm.:unsure:
Why not :) It doesn't matter. The farther-away (supply feed) breaker is always going to trip first anyway. First because the far breaker is a branch/feeder breaker, not a main, and those tend to have less forgiving trip curves. Second because of Murphy's Law :)
 

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Discussion Starter #19
@joe-nwt So I'm still debating whether or not I should go with the #4 or #6 gauge. It really is a lot of savings to go with the #6. I'm just concerned of voltage drop. Do you think if I did a 50AMP panel I would be fine with #6 at that distance? If not what size panel would I be fine with #6.

Also, what size thhn ground wire would I need? I thought I would need the same size as the other wires, but it seems that most of the time the ground is smaller. Thanks again for you help!
 

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@joe-nwt So I'm still debating whether or not I should go with the #4 or #6 gauge. It really is a lot of savings to go with the #6. I'm just concerned of voltage drop. Do you think if I did a 50AMP panel I would be fine with #6 at that distance? If not what size panel would I be fine with #6.

Also, what size thhn ground wire would I need? I thought I would need the same size as the other wires, but it seems that most of the time the ground is smaller. Thanks again for you help!
I think if you ran #6 and supplied it with a 50A breaker you would be fine. Your planned heater is the only significant load so far and even that's nothing, just make sure you get a panel with some extra spaces for the future. in a worst case scenario, you could always pull bigger wire into the conduit at a later date. That's the benefit of installing a bit bigger conduit at the start.:)

Voltage drop will be almost negligible at 50' from your house.

Ground wire to your subpanel and ground rods has to be #6 regardless of what size of a panel you install.
 
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