Planning subpanel install in shed

[cj7jeep81]

I'm finally getting ready to install electric to my 16'x16' shed. I already have some left over wire (underground rated 10-2 w/ ground). Is this ok to use for a sub panel? Or would I need 10-3 w/ground?

The total run is approximately 60-70 feet. I used this online calcluators (http://www.csgnetwork.com/wiresizecalc.html), and it looks like for this run with 10g wire I can get away with a 40 amp breaker. However, it looks like at 75 feet I need to step up to 8g, which I don't want to do since I already have the 10g wire. As for electrical load, all I plan to run is 2 or 3 100w bulbs for light, and occasionally a small air compressor (currently runs off an extension cord on a 15 or 20 amp circuit). Occasionally, I'll run my 110 welder, but would run both at the same time.

Any thoughts on running 30 amp vs 40 amp for that length of run? If it turns out to be more than 70', I'll go with 30 amps for sure. Also, I know it will be difficult to pul, but I'm planning on running this in conduit for extra protection.

Thanks for any help.

-Edit. Planning on running 1" or 1.5" conduit to make pulling easier, and allow for me to run bigger wire if I ever need to in the future.

 

[dipper]

it really sounds like you need to install a 60 amp subpanel in the shed. A four wire feeder is what you are going to need, but it may depend on where you live. Typically conduit runs are pulled with thhn/thwn individual wires. It shouldn't be difficult to pull as long as you keep the bends minimal and use nice long sweeps for curves. Having a bigger conduit will help though.

 

[cj7jeep81]

i definitely don't need 60 amps in my shed. its is a 16' square shed that's main purpose is to store my lawn mower and tools. its a pain to have to pull out the extension cords every time i want to use the compressor.

90% of the time, i'll just be using the lights as i'd like to be able to clean my guns out there (wife doesn't like the smell of solvent in the house for some reason), and air up the lawn mower tires. when i build my shop, i'll have a dedicated 200amp panel there.

also, i forgot when i figured in my run length to account for going 2-3 feet underground. that will add another 4-6 feet, and probably push me too far for using 40 amps, so i'll stick with 30.

the 30 amp switch i have takes 2 screw in type fuses (and didn't come wiht any, nor does it have any useful instructions). i'm assuming I use 2 15 amp fuses for this?

 

[ArthurPE]

run 2 20A circuits...

one for lighting and 1 or 2 misc recepts.
one for a dedicated recept. for the welder OR compressor

 

[cj7jeep81]

my plan was to install the subpanel (already have it from a different project and didn't end up needing it), and then run one circuit for the lights, one for some outlets, one for teh compressor, and one to an outdoor plug for welding (wooden shed, so no welding/grinding inside).

after more searching, it looks like my 10-2 w/ground won't work for a subpanel, as I'll need 4 conductors. Is it Ok to use what I have for the neutral, ground, and 1 hot, then buy some red THHN wire to use as the second hot?

 

[Aceman]

I'm going to make this as short as possible, I already typed this and lost it once.

UF cable is a bear to pull in conduit, I would highly recommend pulling individual wires. I'd suggest aluminum if cost is an issue.

You can't add an extra wire in the conduit to get the other phase, it must be in the same cable.

You don't need 4 wires out there if all you want to run is a 120v subpanel, you're UF would work just fine.

You need a disconnecting means and a grounding electrode(typically two grd rods) at the shed as well.

I would also suggest purchasing a subpanel with plenty of spaces, they're cheap. You also mentioned you wanted 4 circuits out there, but you're existing fuse panel only has 2 fuseholders. I don't know how you think you're going to get 4 circuits out of that?

 

[cj7jeep81]

I'm going to make this as short as possible, I already typed this and lost it once.

UF cable is a bear to pull in conduit, I would highly recommend pulling individual wires. I'd suggest aluminum if cost is an issue.

You can't add an extra wire in the conduit to get the other phase, it must be in the same cable.

You don't need 4 wires out there if all you want to run is a 120v subpanel, you're UF would work just fine.

You need a disconnecting means and a grounding electrode(typically two grd rods) at the shed as well.

I would also suggest purchasing a subpanel with plenty of spaces, they're cheap. You also mentioned you wanted 4 circuits out there, but you're existing fuse panel only has 2 fuseholders. I don't know how you think you're going to get 4 circuits out of that?

i had never thought about wiring a 120v sub panel, all the panels i've wired have been 240v. i'll have to think about that some more. as for pulling the wire, that's one reason I was planning on using 1.5" conduit, to make it easier. Also, there will only be 2 90's, so I'm hoping its not too horrible.

as for disconnecting, one of the things i have is a 30amp disconnect switch (might be using the wrong terms). that's the piece that has the spot for 2 fuses that i was confused on what size they needed to be. the panel is a 125 amp main lug panel with 20 spaces.

 

[DekeT]

as for disconnecting, one of the things i have is a 30amp disconnect switch (might be using the wrong terms). that's the piece that has the spot for 2 fuses that i was confused on what size they needed to be. the panel is a 125 amp main lug panel with 20 spaces.

I am glad you are asking that question about the 30 amp disconnect.
I thought I read in another thread that using more than one circuit in an outbuilding requires a minimum 60 amp disconnect no matter how small the feed breaker is. No one disagreed.

I would like to use a main lug box in a yard shed for three circuits but I don't want to buy a 100 amp main breaker box to get a disconnect. I know you can get them cheap and 100 amp main breaker seems to be the smallest main panel I can find. I just wanted to use a mechanical switch disconnect like my water well pump uses. Any advice?

 

[cj7jeep81]

I am glad you are asking that question about the 30 amp disconnect.
I thought I read in another thread that using more than one circuit in an outbuilding requires a minimum 60 amp disconnect no matter how small the feed breaker is. No one disagreed.

I would like to use a main lug box in a yard shed for three circuits but I don't want to buy a 100 amp main breaker box to get a disconnect. I know you can get them cheap and 100 amp main breaker seems to be the smallest main panel I can find. I just wanted to use a mechanical switch disconnect like my water well pump uses. Any advice?

I've never heard about needing a minimum 60 amp disconnect, but I'm no electrician.

I ended up needing more than 30 amps, so I installed a 100amp main breaker panel in my shed, and fed it with a 60amp breaker.

 

[SGKent]

Or would I need 10-3 w/ground?

I am not an electrician but I believe 10/3 is good for 30 amps not 40. My understanding is you will need #8 for 40 amps.

 

[ishiboo]

You've reopened a thread from 2009...

It's not that a 60 amp disconnect is required on 30 amp service, it's that if you have more than 2 circuits in the outbuilding, code requires 60 amp service, which would logically require 60 amp or greater components.

 

[ishiboo]

I am glad you are asking that question about the 30 amp disconnect.
I thought I read in another thread that using more than one circuit in an outbuilding requires a minimum 60 amp disconnect no matter how small the feed breaker is. No one disagreed.

I would like to use a main lug box in a yard shed for three circuits but I don't want to buy a 100 amp main breaker box to get a disconnect. I know you can get them cheap and 100 amp main breaker seems to be the smallest main panel I can find. I just wanted to use a mechanical switch disconnect like my water well pump uses. Any advice?

Code says you must have 60 amp service... safety is another thing.

Ignoring code, you could run whatever size you want... 30, 40, and still be safe. You could back feed a 6 circuit panel using one double-pole breaker for the incoming, and use the remaining 4 spaces for circuits.

 

[SGKent]

Code says you must have 60 amp service...

so - not to hijack - the 30 amp subpanel I have in my shed is a no-no because I am running 4 breakers and each is a seperate circuit? Two compressors each on their own circuit and breaker, a 120 V socket and a light. The shed sub-panel is run off a dedicated 30-amp double breaker at the main panel.

 

[ishiboo]

so - not to hijack - the 30 amp subpanel I have in my shed is a no-no because I am running 4 breakers and each is a seperate circuit? Two compressors each on their own circuit and breaker, a 120 V socket and a light. The shed sub-panel is run off a dedicated 30-amp double breaker at the main panel.

Yup.

Edit: actually, it could be grandfathered in... not sure when this entered the code cycle and when you did it.

 

[SGKent]

and the correct solution if not grandfathered would be to replace the 30 amp breaker with a 60 amp and rewire accordingly? It is only about 10 - 12' of wire so not a big expense as long as the conduit is acceptable in size for the wire size.

 

[ishiboo]

and the correct solution if not grandfathered would be to replace the 30 amp breaker with a 60 amp and rewire accordingly? It is only about 10 - 12' of wire so not a big expense as long as the conduit is acceptable in size for the wire size.

Yes, but I would only do it if you were upgrading anyway. There is no safety issue if the over current protection is correct (same as if it were 60A), the purpose is future expansion/practicality.

 

[SGKent]

Thank you.