120v Subpanel to shed, could use some advice.

[tojoski]

With my wife working from home, we are setting up a shed in the back yard for her to use for an office.

I have a panel on the side of the house that I will add a single 120v breaker to, then run some #4-3 aluminum direct burial out to the shed. (H, N, G)

I bought a 2 space Subpanel for the shed, and I had planned on putting (2) 15a breakers out there. One for the window AC and one for the outlets and lights.

What I hadn't considered, was that the two hot sides of the panel of course aren't bonded.. Is there any reason I can't just run a jumper between them? Being just a tiny office, theres no way I will ever need 240v out there.

Originally I had planned on just relying on the ground rod at the house, but I have since decided that I probably need a separate one out there.

 

[Terry D]

I definitely would have at least 2 circuits out there. The AC should be on its own circuit. How far is the shed away. #4 seems over kill. #12-3 or #10-3 UF should be plenty. I like conduit myself, but direct burial is fine also. Do you have space for a 2-pole breaker in your outside panel

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[tojoski]

I remembered incorrectly, it's actually #6-3, and although it's direct burial, I plan to put it in conduit anyway.

Yes, I have room for a double pole breaker, but that would only be used if I ran 240 out there right?

 

[Terry D]

Trying to put that in conduit will be a PITA. Plus, if its just regular Romex, you cant put it underground even in conduit. I would just pull in separate THHN/THWN conductors.

Yes, you would need a 2-pole breaker for 240 volt to feed your subpanel. I would do (2) separate circuits

 

[mike93lx]

Is it URD? If so, it can't go inside either structure, at all. Not even a right angle directly into the box.

If you are doing conduit, THWN (copper) or XHHW (Aluminum) are much better, but it sounds like you already own the wire.


I would return the panel and grab a small main breaker panel. Won't cost much and you'll probably get at least a 6 space, so no jumpering between buss bars. Most breakers aren't rated for double tapping, so jumpering won't work. I also prefer having a main breaker anyway to easily shut off the panel

 

[wyliesdiesels]

I remembered incorrectly, it's actually #6-3, and although it's direct burial, I plan to put it in conduit anyway.

Yes, I have room for a double pole breaker, but that would only be used if I ran 240 out there right?

As said above, I would put the AC on a separate branch circuit off of a 120/240v panel/ feeder

The large draw on startup will cause a voltage sag and some electronics dont like that.

In regards to the 6/3 UF-b, that will be a royal pain in the *** to pull through conduit since its flat.

There isnt much of a cost difference to go with 120/240v vs 120v only. Plus with 240v, you can put the AC on the opposite leg and not have to worry about voltage sag

As others have said, just get individual conductors. you will need white and green jacketed conductors for the neutral and ground if theyre smaller than #4, because those cannot be phase taped...

 

[mike93lx]

Didn't think of UF... I hate that **** and can't imagine pulling it through conduit. That would **** royally

 

[pattenp]

For the power you need 10-3 UF would be more than enough. That's two 120V 30A legs. Using 3/4in conduit would be a fairly easy pull. It will give you 240V at the shed but you don't need to use it. I imagine your wife may also want a small frig out there.

 

[sberry]

Could use 12 and not need a panel. Would need a dp switch though.

 

[tojoski]

Yes, it's URD and I know you technically aren't supposed to run it inside a structure, but I live out in the county and there aren't any code or inspection requirements.
It will be in a pvc conduit all the way to the inside box.

My understanding of the URD restriction is because the jacket isn't fire rated. If it is properly protected at the main panel, would this be sort of mute? Especially for an outbuilding?


As far as surge wattage goes when the AC kicks on, that was my thinking for over sizing the wire a bit. That being said, the window unit we got for it is one of those super efficient inverter types.

I suppose I could also get a couple of the slim 15a breakers for that panel and just leave one side dead.

If I were to run 240 out there, and I used the URD that I already bought, that would leave me without a ground back to the main panel. Would a separate ground at the shed suffice?

 

[wyliesdiesels]

Yes, it's URD and I know you technically aren't supposed to run it inside a structure, but I live out in the county and there aren't any code or inspection requirements.
It will be in a pvc conduit all the way to the inside box.

My understanding of the URD restriction is because the jacket isn't fire rated. If it is properly protected at the main panel, would this be sort of mute? Especially for an outbuilding?


As far as surge wattage goes when the AC kicks on, that was my thinking for over sizing the wire a bit. That being said, the window unit we got for it is one of those super efficient inverter types.

I suppose I could also get a couple of the slim 15a breakers for that panel and just leave one side dead.

If I were to run 240 out there, and I used the URD that I already bought, that would leave me without a ground back to the main panel. Would a separate ground at the shed suffice?

what do you mean by properly protected? PVC conduit will not stop the insulation from burning which is toxic smoke...

 

[mike93lx]

Yes, it's URD and I know you technically aren't supposed to run it inside a structure, but I live out in the county and there aren't any code or inspection requirements.
It will be in a pvc conduit all the way to the inside box.

My understanding of the URD restriction is because the jacket isn't fire rated. If it is properly protected at the main panel, would this be sort of mute? Especially for an outbuilding?


As far as surge wattage goes when the AC kicks on, that was my thinking for over sizing the wire a bit. That being said, the window unit we got for it is one of those super efficient inverter types.

I suppose I could also get a couple of the slim 15a breakers for that panel and just leave one side dead.

If I were to run 240 out there, and I used the URD that I already bought, that would leave me without a ground back to the main panel. Would a separate ground at the shed suffice?

Another "code doesn't matter because reasons" guy.

Code matters. Will you ever have a problem with the URD? Probably not. Do you want an insurance claim to be denied or someone to get injured if something goes wrong? I know I wouldn't.

It isn't the end or the world. Just put a box on the exterior, transition to XHHW and go in with that.

 

[tojoski]

what do you mean by properly protected? PVC conduit will not stop the insulation from burning which is toxic smoke...

I was referring to protection via a breaker at the main panel.

Another "code doesn't matter because reasons" guy.

Code matters. Will you ever have a problem with the URD? Probably not. Do you want an insurance claim to be denied or someone to get injured if something goes wrong? I know I wouldn't.

It isn't the end or the world. Just put a box on the exterior, transition to XHHW and go in with that.

Not saying it doesn't matter, just that I'm not going to get called out on it specifically. On the other hand, I'm usually the type to overthink these types of projects.

For the sake of conversation, would it be acceptable to use just a sealed outside enclosure under the building to transition to XHHW? Basically in what amounts to the crawlspace of the shed? The wife would probably prefer not to have the conduit visible.

Oh and I was right the first time, it's #4 URD

http://www.kingwire.com/product-catalog/600-volt-ud/triplex

 

[wyliesdiesels]

I was referring to protection via a breaker at the main panel.

Breaker protection has nothing to do with insulation ratings..

 

[mike93lx]

I was referring to protection via a breaker at the main panel.



Not saying it doesn't matter, just that I'm not going to get called out on it specifically. On the other hand, I'm usually the type to overthink these types of projects.

For the sake of conversation, would it be acceptable to use just a sealed outside enclosure under the building to transition to XHHW? Basically in what amounts to the crawlspace of the shed? The wife would probably prefer not to have the conduit visible.

Oh and I was right the first time, it's #4 URD

http://www.kingwire.com/product-catalog/600-volt-ud/triplex

Under the building is not outside, in my opinion.

How long is the run? I get you have URD already, but AL XHHW is not expensive at all. I would just to it right and chaulk up the expense to a mistake

I am also very confused as to why you are running #4 for a pair of silple 120v circuits.

Also, if you want 240v,you HAVE to run 4 conductors. You could use the URD and add a 4th wire. Ground rods at the shed are not the same. Read wylie's sticky

 

[pattenp]

You can jumper the two lugs in the panel to utilize both legs just for 120V. Do not put two wires in one lug. Use two pigtails and a connector to the one 120V feeding conductor. Lugs in the panel are rated only for one wire to be connected.

 

[tojoski]

My original intention was just to have a single 120v leg out there as there will be absolutely no use for 240v..

I basically was just going for overkill and as little voltage drop as possible and I wanted to make sure I had the capacity to run the two 15a circuits.

The run is about 120ft.

Is URD the only type that is expressly forbidden to run inside a structure?

 

[tojoski]

You can jumper the two lugs in the panel to utilize both legs just for 120V. Do not put two wires in one lug. Use two pigtails and a connector to the one 120V feeding conductor. Lugs in the panel are rated only for one wire to be connected.

Thanks, I suspected so..

This is the panel:

https://www.homedepot.com/p/Square-D-Homeline-70-Amp-2-Space-4-Circuit-Indoor-Flush-Mount-Main-Lug-Load-Center-with-Cover-HOM24L70FCP/100125358

 

[pattenp]

The NEC disallows any wire that only has a USE rating to enter a structure, it must be terminated on the outside.

 

[mike93lx]

My original intention was just to have a single 120v leg out there as there will be absolutely no use for 240v..

I basically was just going for overkill and as little voltage drop as possible and I wanted to make sure I had the capacity to run the two 15a circuits.

The run is about 120ft.

Is URD the only type that is expressly forbidden to run inside a structure?

It is the only wire I am aware of that cannot go inside.

Most people here recommend MHF instead of URD as it is direct burial and it can go inside (in conduit).

You could do 3 pieces of #6 xhhw for $0.60/ft (total, plus shipping). For less than $100,you would have the right wire to go end to end in conduit and be code compliant.

At that cost, I wouldn't bother with UF (although 10/3 would get it done for what you want) if you want to run conduit anyway

 

[Terry D]

My original intention was just to have a single 120v leg out there as there will be absolutely no use for 240v..

I basically was just going for overkill and as little voltage drop as possible and I wanted to make sure I had the capacity to run the two 15a circuits.

The run is about 120ft.

Is URD the only type that is expressly forbidden to run inside a structure?

You can not have 2 15 amp circuits with only 120 volt going out there. You need 2 hots sharing a neutral. Yes, you will have 240 volt out there, but that doesn't mean have would have to have any 240 volt loads

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[mike93lx]

You can not have 2 15 amp circuits with only 120 volt going out there. You need 2 hots sharing a neutral. Yes, you will have 240 volt out there, but that doesn't mean have would have to have any 240 volt loads

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Why not? A 30a feed to a subpanel, split into two 15a circuits

 

[CJ7VFR]

You can also do a search of this website for a multi wire branch circuit, or MWBC. That will give you another option to allow you to run the AC on one branch, and the lights and other receptacles on another.

There are many examples on this site of people running a MWBC out to their sheds, or other out buildings, for running higher amp rated power tools on one branch and lights on the other so that you don't pop the breaker.

Jim

 

[pattenp]

You can not have 2 15 amp circuits with only 120 volt going out there. You need 2 hots sharing a neutral. Yes, you will have 240 volt out there, but that doesn't mean have would have to have any 240 volt loads

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That's just wrong. The only thing he can't have is 240V.

 

[tojoski]

That's just wrong. The only thing he can't have is 240V.

I'm a noob but it doesn't make sense to me either.. ordinarily you would have multiple breakers on a single leg.

If I had a panel with 8 spaces, 4 of those would be on one leg, and the other 4 on the other leg.

I called all my local suppliers this morning and none carry #6 XHHW in aluminum.

I suppose since I'm re-thinking this, I could just do 10-3 with ground, and go ahead and make both legs hot, but at 130' would the voltage drop be too high?

I would need direct-burial correct? Romex is not allowed in conduit?

 

[mike93lx]

I'm a noob but it doesn't make sense to me either.. ordinarily you would have multiple breakers on a single leg.

If I had a panel with 8 spaces, 4 of those would be on one leg, and the other 4 on the other leg.

I called all my local suppliers this morning and none carry #6 XHHW in aluminum.

I suppose since I'm re-thinking this, I could just do 10-3 with ground, and go ahead and make both legs hot, but at 130' would the voltage drop be too high?

I would need direct-burial correct? Romex is not allowed in conduit?

Wireandcableyourway.com has good prices.

10/3 would do a pair of 15a circuits fine at that distance (3.25% voltage drop). Romex is allowed in conduit but it can't be in a wet location and underground is wet. You do not need direct burial if doing conduit.

You could also run four pieces of 10 thwn

 

[pattenp]

For a 120V only panel you jumper the legs. That way both sides of the panel is used but you can't get 240V. I commented about this in post #16.

 

[mike93lx]

For a 120V only panel you jumper the legs. That way both sides of the panel is used but you can't get 240V. I commented about this in post #16.

Would you have to maintain wire gauge in the pigtails?

So something like a polaris connector two two pieces of wire?

 

[tojoski]

Thanks for all the input. I'm still weighing options..

Wireandcableyourway.com has #6 XHHW for $.20 per ft, so that would make a 120v run $.60 per ft. VS $1.11 for 10-3 UF.

 

[mike93lx]

Thanks for all the input. I'm still weighing options..

Wireandcableyourway.com has #6 XHHW for $.20 per ft, so that would make a 120v run $.60 per ft. VS $1.11 for 10-3 UF.

If you do UF, it doesn't have to be in conduit, except when it is subject to damage. Xhhw will require conduit the whole way.

Probably a wash when you look at the total cost.

 

[tojoski]

I like the extra protection that the conduit provides, so even if I went with the UF, I would probably put in conduit.

 

[Terry D]

That's just wrong. The only thing he can't have is 240V.

I understand what your saying. Its not common practice to do that, just run run a MWBC and be done with it. If you ran a 10-3 out there, and down the road if you wanted to make those 20 amp circuits, you could still do that without the fear of overloading the neutral


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[tojoski]

I understand what your saying. Its not common practice to do that, just run run a MWBC and be done with it. If you ran a 10-3 out there, and down the road if you wanted to make those 20 amp circuits, you could still do that without the fear of overloading the neutral


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Isn't #6 AL good for 50A though?

 

[mike93lx]

Isn't #6 AL good for 50A though?

At that distance, yes.

If you are running conduit, there is no reason to use UF. The stuff ***** to work with. Run the xhhw, IMO

 

[Terry D]

Isn't #6 AL good for 50A though?

Yes, i guess i havent been following on exactly what wire you are installing. It sounds like you are running #6 XHHW in conduit. You can go up to a fifty amp breaker feeding the sub panel. I would not jump both sides of the panel to one hot. Since you are trenching and installing conduit, run the extra wire and have both legs out there. If for some reason, down the road you would need 240 volt, it would be there. What about heating this structure




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[tojoski]

Yes, i guess i havent been following on exactly what wire you are installing. It sounds like you are running #6 XHHW in conduit. You can go up to a fifty amp breaker feeding the sub panel. I would not jump both sides of the panel to one hot. Since you are trenching and installing conduit, run the extra wire and have both legs out there. If for some reason, down the road you would need 240 volt, it would be there. What about heating this structure




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It's a 12 x 18 building, so we had planned on running an electric heater on the same circuit that the window ac is on.. basically that circuit will be dedicated to hvac..

but you are right, for another $26 I can run another #6 AL and be done with it, hardly even worth thinking about.

 

[pattenp]

I understand what your saying. Its not common practice to do that, just run run a MWBC and be done with it. If you ran a 10-3 out there, and down the road if you wanted to make those 20 amp circuits, you could still do that without the fear of overloading the neutral


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No it's not common but it can be done. I do not advocate doing a 120V only panel because the cost of the additional conductor is minimal. Also providing that the serving panel has space for a 2pole breaker.

 

[mike93lx]

Where did you land on the panel? I would never install one that is already maxed out. My preference would be at least a 6 space, Main breaker

 

[pattenp]

Would you have to maintain wire gauge in the pigtails?

So something like a polaris connector two two pieces of wire?

The pigtails need to be sized the same as the feed. And yes to the polaris example.

 

[mike93lx]

The pigtails need to be sized the same as the feed. And yes to the polaris example.

Thanks. I assume running out of one breaker and into another on the other buss is not kosher?