Want to run generator from shed... This what I need?

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Old 08-28-17, 12:00 PM
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Want to run generator from shed... This what I need?

Hi all

So, I have a 10x12 shed with gable vents and a window that can open/close. I am thinking I want to make it so I can safely store and run my generator from this shed. (I assume, between window and vents, I have adequate ventilation?)

My plan is to rent a trencher, and run a (100'?) trench from the existing inlet (electrician installed complete with panel lockout) and an existing outdoor 20 amp outlet (to power trickle charger in the shed) and run:

  1. Trench 18" deep
  2. Run two 3/4" conduits
    • Conduit #1: Run three #10 wires for hots/neutral for inlet PLUS a #12 ground wire (green insulation). Plus a tracer wire?
    • Conduit #2: Run three #12 wires for the 20amp circuit to power trickle charger.. Plus another tracer wire?

Do I need any gravel or anything in the trench? Am I using the proper gauge wire?

Dont know if this helps at all, but this is the generator I have: https://www.lowes.com/pd/Troy-Bilt-X...Engine/3192419

Thanks for any and all advice!
-k
 
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Old 08-28-17, 12:12 PM
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Are you going to be installing a exhaust system to vent the engine's exhaust outside?

How much open area does your gable vents provide? Do you have the door and window on opposite ends of the shed? I'm concerned about there being enough fresh air for engine cooling. If you don't have enough ventilation the engine will quickly heat the inside of the shed and could cause it to overheat.
 
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Old 08-28-17, 12:37 PM
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Hi! I have two 8x10 gable bents (I am estimating--have to measure). I have a single window (18x36, I think)

With all that, I'd STILL have to fabricate an exhaust solution? That would be a bummer...
 
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Old 08-28-17, 12:37 PM
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Am I using the proper gauge wire?
Wire size depends on the output of your generator. #10 limits you to 30 amps. Probably marginal to run only a central A/C or only a water pump or only an electric water heater with very little left over for other things. I'd suggest 1" conduit and #6-H, #6-H, #6N, #8G.* (¾" conduit will barely work for #6 but 1" will make things easier.) You could still go with 30 amp generator using the #6 but you would be future proofed if you ever need more power.

With all that, I'd STILL have to fabricate an exhaust solution? That would be a bummer...
Old B&S engines use to use standard pipe thread for the exhaust. I can't say for modern engines on generators.

Do you plan to run natural gas to the shed?

*I changed and #6-H, #6-H, #6N, #10G to and #6-H, #6-H, #6N, #8G because it may be considered upsizing for voltage drop. However if not considered up sizing 10 ground is okay for 60 amp.
 

Last edited by ray2047; 08-28-17 at 10:06 PM.
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Old 08-28-17, 02:52 PM
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I do not currently plan to run gas to the shed. lol... Maybe I should put some pipe in while I have the trench dug? I dont envision ever converting to natural gas, but you never know what the future holds.

I'll check the exhaust when I get home, but I dont recall seeing threads (that would have been amazing)...

The generator feed is currently on two 15 amp breakers (with a lockout). I am tying in to the existing inlet on the outside of my house (basically converting that to a junction box). I do know that, as I have all LED lighting, I can power pretty much the whole house minus the central air. That said, I did NOT test with the two sump pumps running...

Does that change the recommendation for the wire gauge?
 
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Old 08-28-17, 03:00 PM
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At the very least..... change out the #10 for #8.
It will allow for less voltage drop over that fairly long distance.
 
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Old 08-28-17, 04:17 PM
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#8 at least but if you can afford it I say go for #6 in 1" conduit. It gives you more future flexibility.

Conduit #2: Run three #12 wires for the 20 amp circuit to power trickle charger.
If you already have power to the shed you can't by code run another circuit.
 
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Old 08-28-17, 08:55 PM
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Yes you need another circuit, whether or not run in a second conduit.

If you are going to run the generator from inside or near the shed then you need a conduit or cable run (usually hot, hot, neutral, ground) with the generator inlet or hardwire as the source and the main house backfeed breaker set or transfer switch as the load. Also a separate feed (optimally hot hot neutral ground) with one of the regular side breaker sets in the house panel as the source and the shed subpanel (lights and receptacles in the shed may be wired directly with no subpanel if 20 amp or less) as the load.

If you run separate wires all in one conduit then just one ground wire, sized for the larger of the two hot-hot-neutral sets, is needed.

The existing run from interlocked breaker to the inlet on the side of the house can be a portion of the first feed. The existing circuit from the panel to the ordinary receptacle near the inlet can be a portion of the second feed.

The same cable or set of wires cannot serve both of these functions.

Hot and neutral conductors sized 6, 8, or 10 chosen simply to carry X amperes take a 10 gauge ground. Six and 8 gauge hot and neutral chosen taking into account a one size upgrade to combat voltage drop take an 8 gauge (also a one size upgrade) ground.
 

Last edited by AllanJ; 08-28-17 at 09:11 PM.
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Old 08-29-17, 08:17 AM
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As always, terrific advice on this forum!

@ray2047: I am confused. What would not be allowed? I have no existing power in my shed. I want to move the inlet on my house to my shed and convert the old location to a junction box. I also want to install a single 20amp circuit to the shed to power the trickle charger and/or an occasional tool if I want to do a project and need use a saw (for example)

@Allanj: thanks for the detailed info. Two things I am not clear on: 1) are you advocating for a single conduit with 3 #6 wires (hot-hot-N for inlet) and 4 #8 wires (H-H-N+ SHARED GROUND)? 2) why two hots for a 20 amp 110v circuit? Dont I only need Hot-Neutral-Ground? What is the extra Hot for? Future-proofing?

To all: THANK YOU again. General question: so it seems that my plan to have only a single 20 amp circuit will be code compliant (assuming @ray2047 is talking about something different?)... I dont have crazy amounts of money for this project... BUT... if I wanted to run wire to EVENTUALLY put a subpanel in the shed... Is it as 'simple' as running an extra conduit? Or *should I* pull wire that will handle a future subpanel, but use for now as that single 20amp circuit...? What size wire would that mean to me?
 
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Old 08-29-17, 08:47 AM
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Code only allows one power feed per building, so if you already had one you couldn't add another. Given that you only want to add one, it's OK.

You can use one conduit or two -- not too much difference in materials cost but it's up to you. You only need one hot, one neutral, one ground for a single 120V circuit. The second hot would be for future expansion to a multiwire circuit or subpanel.

If you think you might want a subpanel in the future, I'd run a 3/4" or 1" conduit for it. You can pull your single #12 wires in it today and if you ever want to do the upgrade, pull those out and pull in bigger ones. If you only think you'll want just the one 20A circuit, use one conduit shared with your generator inlet feed.
 
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Old 08-29-17, 09:36 AM
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I am trying to start to put together this shopping list. I have an electrical supply shop near me who will sell to consumers provided they know EXACTLY what they need ahead of time (vs home depot)..

Is this what I would use for the wire in the conduit? What does the '-2' on THWN-2 mean?

For Inlet
  • [*]
  • [*]
  • [*]
  • [*]
For 20 amp circuit:
 
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Old 08-29-17, 09:50 AM
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The second hot does not need to be red. Both can be black. Sometimes it is cheaper to buy a whole roll of black and cut it in two.

You don't need #6 for ground. #8 will be large enough.

#10 would be large enough to compensate on a 120v/20 amp circuit to the shed.

If you put it all in conduit you do not need a separate ground for the 120/20 amp feed. It can share with the generator. If you use separate conduits you only need a #10 ground.

If you share conduit for those sizes 1¼" would be a good size. Otherwise 1" and ¾" conduit.

If the shed is less than 100 feet from the home panel upsizing isn't needed and wire size can be reduced.
 
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Old 08-30-17, 08:33 AM
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Got the measurements!

Finally took 10 minutes to measure this out

I also realized that I really have two options:
  • Option 1: original plan. Run new wire from exiting inlet and outlet on patio to shed. This is approx 58' (+/- 2 ft due to running through shrubs in a planting area) to the front corner of the shed. I may decide to put the inlet/outlet in the rear of the shed, though. In that case, its approx 64'
  • Option 2: instead of relying on existing inlet/outlet, I can just run this as a completely new run from the panel (located in garage). This would be roughly the same distance to the front corner of the shed (58'), or it would be approx 70' to back corner.

If I go with option 1, the run is 58 or 70' PLUS whatever they used in the garage (figure another 30-40' of wire to run around perimeter of my single car garage?). With option 2, the length is the length.

Questions:
  • Is there an obvious 'winner' apparent to anyone, between option 1 and 2? Only thing I can think of is that the 20amp circuit will be dedicated with Option 2, versus sharing an outdoor outlet circuit with option 1. That and the shortening of the run by not using existing perimeter run inside garage...
  • If I go with Option 2, if I have the wire enter garage just above foundation, do I need metal conduit inside the garage to protect the THWN wires into the panel? I assume it would be against code to try to have the cables enter the panel directly from outside, so any option would require come kind of protection... (point for Option 1 here?)
  • Does anyone have advice on how to get the conduit/wires to 'pop up' on the shed side? I have a railroad tie border and 4" of gravel for the base... Do I just trench all the way to the tie and try to poke a coat hanger up and under the tie/gravel? Any pro tips appreciated
  • I am also interested in what tools I 'need' for working with conduit and any tips on pulling such a long run of wire... I am not sure if its just a matter of running the wires through a length of conduit, with a coupler glued on, then pulling through another conduit length and then gluing/attaching to the first length, etc... Versus if there is an extra long fish tape that makes life easier
  • Do the more official measurements change the gauge recommendations? I am currently at 8 gauge for the inlet / 10 gauge for the 20 amp circuit, plus ground one size higher gauge (10 gauge/12 gauge), I think...

Here is a picture of the shed side of the equation
 
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Old 08-30-17, 09:28 AM
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You are under 100 feet so no upsizing needed. #12 for a 20 amp receptacle circuit and #10 for a 30 amp generator circuit. Use at least ¾" conduit but I'd suggest 1" if both circuits in the same conduit. If both in the same conduit you can share the inlet circuit #10 ground with the receptacle circuit so only one ground wire needed.

Simplest would be to run from the existing inlet and receptacle on the patio.

Using PVC conduit all you need is a hack saw and emery cloth or sandpaper to smooth the cut.
 

Last edited by ray2047; 08-30-17 at 12:06 PM.
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Old 08-31-17, 09:11 AM
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thanks again! I'll price conduit and then make decision. I am leaning toward a single 1" conduit for now. Hopefully i'll be able to use this for a subpanel in the future, if I ever decide thats what I want. Maybe I'll put a spare conduit in just in case, with a single wire in to help for pulling wire later...

Any tips for how to bring the wire up to the shed, given that gravel/railroad tie situation? A colleague suggested just going up and over it-- but I dont think I like that aesthetic...

I am wary of digging out the stone... I dont want shed to shift. Is poking around with a fish tape the best approach?
 
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Old 08-31-17, 09:32 AM
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with a single wire in to help for pulling wire later...
Mason's twine is cheaper.

The shed won't shift if you just dig a narrow trench less than a foot wide 18" deep through gravel. I'd use a post hole digger. It will keep the trench narrow.

Off topic but why did you put the shed on gravel instead of concrete blocks. Oh well too late now.
 
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Old 08-31-17, 11:50 AM
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The shed company recommended it, for warranty purposes. Less settling, better drainage, etc.

thanks for the reply! great info
 
 

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