[FloridaMan]

Hi, I have a newbie question. I just got a shed (so excited). I wired it up just the way I want it using 12-2 romex. Everything goes to a brand new Eaton 125 amp subpanel. Yesterday I installed the ground rod with 6 AWG bare wire. Today I dug the trench to the house. I'm so close to being done - expect I have no idea where I should pull my feeder wires from, let me explain.

Our main panel is a 125 amp panel in the laundry room. Outside is a 100 amp panel with a 2-pole 100 amp circuit that is connected to meter. Connected to that is a 100 amp sub panel with a 2-pole 40 circuit and a single 20 circuit. This subpanel is for the closed in lanai (porch)

Can I put a breaker in the "porch" subpanel outside and just run that to my subpanel in the shed? That would make things pretty easy.

 

[Jim Port]

There is no sense in adding a panel to something that can only supply 20 amps of power. Secondly, NM is not for use outside.

 

[NCmountainCabin]

what is the 'purpose' for the shed? what electrical needs do you have for it?

 

[NCmountainCabin]

deleted, duplicate

 

[NCmountainCabin]

https://www.homedepot.com/p/Eaton-B...th-Cover-BR24L70RP/100128514?modalType=drawer
or this one:
https://www.homedepot.com/p/Eaton-B...d-Center-BR24L70SP/100184409?modalType=drawer

you are installing a 'sub-panel' that is larger than the breaker panel it is pulling from, so no - but you can easily install the above 'sub-panel' made especially for situations like yours - a small shed, etc. Since your house panel you are connecting to is only rated for 100amps, you can't install a downstream 'sub-panel' that is LARGER than that - it must be smaller since you are already USING much of the amps in the main panel for the porch.
Keep it simple and only use this small one, only needing MUCH smaller wires to the shed, and for only a few circuit breakers, probably only a 15amp and/or 20amp for 'normal' usage for lights, outlets, power tools, etc.

 

[NCmountainCabin]

you'll also want to add a ground bar for this panel, since Eaton only provides the neutral bar, and the grounds and neutrals need to be separate within the new panel.

the nice thing about this 'main lug' sub-panel is that it does not require it's own 'main 240v breaker' since it uses the main breaker you already have on the house's panel, for it's cut off. You only need two individual circuit breakers within this panel, or you could use 4 'tandem' breakers, which would also fit on the two slots provided, giving you four circuits, if you need them.

these types of 'main lug' panels are simpler than 'main breaker' panels, and are designed to be an easy 'extension' of your existing panel. Since you're not wiring in a 240v 'main breaker' for it, you only need the wire size that fits the amount of circuit breakers you'll be using. For example, if you have two 20amp circuits within the new panel, you can easily pull 12/3 wire to it, since #12 is designed to easily handle 20 amps. The black wire to one lug, the red wire to the other lug, and the white to the Neutral lug, and the ground to the installed ground bar lug. Since the hot wires are each only serving ONE circuit, neither circuit will need anything larger.
If this sub-panel was being used for a double-pole 50 or 60amp breaker circuit, then you'd need larger wiring, like #6, but that would be more for a 'cut off' for a spa, hot tub, air conditioner, etc, and not as a simple sub-panel for several lights and outlets as you may be planning. Yours are also only single 120v power needs, I assume, so your main wiring doesn't have to be nearly as large.
Some may suggest that just because it is 'rated' for 70amps that you must then wire it with the size that can handle that, maybe #4, which is a little overkill if that's not the plan for the panel. If anything, make a note on the panel itself that it has been 'wired only for up to 20amps per side, with 12/3 wire' as a caution for down the road.

 

[rjniles]

He already has a 125 amp sub in the shed and he certainly can use it. He does not say if it is a main lug or main breaker but either can be used. If he uses a main lug, it will require either having 6 or less handle throws or a back fed main breaker.

Poster needs to determine how much power he needs in the shed to figure out wire size and breaker size. Feeding from his porch sub is fine.

Poster, you need a second ground rod at shed. Is this work have a permit? If not I suggest you get one so an inspector can verify your work.

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[FloridaMan]

what is the 'purpose' for the shed? what electrical needs do you have for it?

The shed is an 10x20 that I've split into two sections. The office which is 10x8 and the garage which is 10x12.

The office has a switch/light. Will also have a window A/C (own circuit) which might house a 6-GPU mining rig later down the road. Then 3 receptacles for a gaming PC/TV (these 3 are on one circuit). Then a 3D printer which is on its own circuit.

The garage section is 3 receptacles own its own circuit. Another receptacle for an air compressor on its own circuit and then a receptacle/switch (for swag led shop light) which taps into the switch in the office section via junction box.

He already has a 125 amp sub in the shed and he certainly can use it. He does not say if it is a main lug or main breaker but either can be used. If he uses a main lug, it will require either having 6 or less handle throws or a back fed main breaker.

Poster needs to determine how much power he needs in the shed to figure out wire size and breaker size. Feeding from his porch sub is fine.

Poster, you need a second ground rod at shed. Is this work have a permit? If not I suggest you get one so an inspector can verify your work.

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I have attached pictures of the panel in the shed. Also, I have a grounding rod at the shed.

Yes, it will be permitted and inspected but probably sometime next year. My county is shut down and back logged due to pandemic.

 

[carmusic]

you need connectors for each cable on that subpanel, you need at least 40 amp power, the rig itself needs it own 15-20amp circuit, the ac needs a 15-20 amp circuit and another 15-20 amp circuit for other computers/tv lights

 

[rjniles]

You are really stretching your 100 amp service. You need to seriously consider an upgrade to a 200 amp servive. Bit coin mining takes a lot of power. More than you will have without an upgrade.

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[roughneck]

Are there any service connectors on that panel? Or did you run the wires straight through the knockouts?
That panel needs cleaned up a bit. Wiring is a bit haphazard.

 

[roughneck]

Duplicate post.

 

[FloridaMan]

I just need to know if I should run the feeder wire to the subpanel on the outside of the house that powers the porch or if I should go into the main panel in the laundry room.

 

[rjniles]

I just need to know if I should run the feeder wire to the subpanel on the outside of the house that powers the porch or if I should go into the main panel in the laundry room.

It really depends on what you are planning to about an upgrade. Personally I would do a new 200 amp service and run your shed feed to the meter location and use neither the laundry room panel nor the porch panel. This will call for a new meter main panel to feed the shed and the laundry room panel.

 

[FloridaMan]

It really depends on what you are planning to about an upgrade. Personally I would do a new 200 amp service and run your shed feed to the meter location and use neither the laundry room panel nor the porch panel. This will call for a new meter main panel to feed the shed and the laundry room panel.

Thank you.

I'll do some research on that and let you guys know how it goes.

 

[FloridaMan]

Are there any service connectors on that panel? Or did you run the wires straight through the knockouts?
That panel needs cleaned up a bit. Wiring is a bit haphazard.

Was waiting for the right size connectors to be available at my local Lowe's. Everything came in this afternoon. I added the connectors and cleaned up the wiring.

 

[seharper]

That panel needs cleaned up a bit. Wiring is a bit haphazard.

You only say that because you don't see all the neutrals runted off to barely make the neutral bar, and the hots runted off to barely make the breaker they're on now, with that cute little 90 degree bend. I follow a different rule. Hot and neutral of every circuit can reach any space in the panel. That way you can move things around, add GFCI/AFCI when the inspector writes you up for forgetting all those, etc.

OP may regret following your advice.

you are installing a 'sub-panel' that is larger than the breaker panel it is pulling from, so no

You keep repeating this, and it's completely wrong. It is a huge misconception about how panels work and are specced.

And it drives people into the serious mistake of using far-too-small panels. The ones you linked aren't even panels, they're basically fused disconnects that use breaker hardware. I wouldn't even put one on an air conditioning unit because you need a third space for the serviceman's receptacle. That's where a 6-space would come in, that way when the guy comes back and says "I also want to power a mini-split here" you say "Gotcha covered" instead of saying "Well gosh, you'll need to replace that subpanel".

For the price difference ($10?) It's very cheap insurance.

Running out of space is a pain in the keister. I can't tell you how many questions I've fielded that start out with "My panel is full, and I need to add------" It's so stupidly unnecessary to have that problem.

And no, it's not about the $40 panel. It's about the hours you spend swapping it.

Since your house panel you are connecting to is only rated for 100amps, you can't install a downstream 'sub-panel' that is LARGER than that

Again that is the thing you are wrong about. What you say is simply not an issue.

The way your brain is working on this, if you bought HR rated tires, you'd feel *obliged* to drive 112 mph.

SUBPANELS DO NOT HAVE A SIZE. THEY HAVE A BUS RATING. You are misunderstanding what that number is. Look, a 225A panel does not draw 225A. Suppose you install a 20A and I install a 225A. We both put 13A loads on our panels. How much load does your panel actually draw? 13A, not 20A. How much does mine actually draw? 13A, not 225A.

The draw is decided by the load, not the panel.

Now suppose both our subpanels have 20A feed breakers in the main panel because we are power-limited like OP. What happens if you put 40A of load in your panel? The feed breaker trips. What happens if I put 40A of load in my panel? The feed breaker trips.

We both plug in a load that has a problem and pulls 150A. After 3 seconds, our feed breakers trip. My subpanel's "main breaker" doesn't even notice it. Your panel is on fire because of the cheap 20A busing.

Get it? In a current-limited situation like OP's, the thing that matters is the feed breaker that supplies the current to the cable run to the outbuilding. The size of the wire does not matter. (as long as it >= feed breaker).
The size of the "main breaker" in the sub does not matter.
The bus rating of the sub does not matter. (as long as it >= feed breaker).

Keep it simple and only use this small one ... and for only a few circuit breakers, probably only a 15amp and/or 20amp for 'normal' usage for lights, outlets, power tools, etc.

Painting yourself into a corner is not simple at all. It creates a big mess in the future.

only needing MUCH smaller wires to the shed

Look. If you have a 20A feed breaker supplying a 225A subpanel, the wires only need to be #12. Really. Because the feed breaker is 20A. You're always welcome to use larger wires than are required, so feel free to run #1Al feeder wire. Then when your service is upgraded you can just pop the #1 onto a 100A breaker. Really. It's that easy.

You make it much harder than it is. You keep thinking that's cheaper, and it's not.

the nice thing about this 'main lug' sub-panel is that it does not require it's own 'main 240v breaker' since it uses the main breaker you already have on the house's panel, for it's cut off.

No. The disconnect switch has to be at the outbuilding. The cheapest way to do that is select a subpanel that has a main breaker, and you just use the main breaker as a disconnect switch. However since OP did not get that kind of panel, OP will need a separate disconnect switch.

Those 2-space "panels" you linked will suffice, just put a breaker in them >= the feed breaker. Or < the feed breaker. It really doesn't matter, the feed breaker in the main panel is responsible for overcurrent.

NEC 2020 now requires an external disconnect at services. It does not require an external disconnect at outbuildings with subpanels.

You only need two individual circuit breakers within this panel, or you could use 4 'tandem' breakers, which would also fit on the two slots provided, giving you four circuits, if you need them.

2 years later: Help! I need to add a circuit and my panel is out of space. Also, if you have any 240V loads, your "tandem/quad" plan won't work. 240V loads will need GFCI protection, and that can *only* happen at the breaker.

And here's a thing you don't know. You're not allowed to run 2 same-voltage circuits to an outbuilding. Your logic is "when I need 2 more circuits I'll just run another 12/3 with another pico-panel". No you won't You'll have to replace the kaboodle with a new #8 run, and have a proper panel.

For example, if you have two 20amp circuits within the new panel, you can easily pull 12/3 wire to it, since #12 is designed to easily handle 20 amps. The black wire to one lug, the red wire to the other lug, and the white to the Neutral lug, and the ground to the installed ground bar lug. Since the hot wires are each only serving ONE circuit, neither circuit will need anything larger.

Why on earth would you do that, when you could just run a MWBC. Then you wouldn't need a subpanel, outbuilding disconnect switch, nor ground rods!

Isn't this supposed to be about being economical?

You'll also be dead-ended, but you don't seem to mind that.

 

[seharper]

OP you are going to need a disconnect switch, because the shed is an outbuilding. You are not required to put the disconnect switch outside, but firemen might appreciate it if you did.

Also your pictures have been posting at odd angles. I hope your panel is mounted vertically so the switches throw sideways. It's a codevio in the US to have breakers oriented where "down" is "on".

Also I see 3 missing knockouts, you'll need to patch any unused ones to complete the job. Knockouts plugs are dirt cheap and just snap in.

Those 2-space pico-panels/disconnect switches that NCMountainCabin are worth pricing (add a breaker). Another neat thing you can do with those pico-panels, once you get written up for no GFCIs, is stick a 2-pole GFCI breaker there and let that protect the entire shed in one swell foop. It's $80 but that's cheaper than what, five GFCI receps?

 

[rjniles]

Ditto on using a large sub panel. All the big apron stores sell what they call a 100 amp value or contractor pack in the $60-70 range. They are 20 space, 20 circuit panels with a 100 amp main and several branch circuit breakers included. Usual brands are Siemens, Homeline, GE and others.

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[FloridaMan]

Also your pictures have been posting at odd angles. I hope your panel is mounted vertically so the switches throw sideways. It's a codevio in the US to have breakers oriented where "down" is "on".

LOL. You still have one of those flip phones don't ya?