Best way to run this wiring

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  #1  
Old 08-07-15, 08:42 AM
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Best way to run this wiring

EXISTING CONDITIONS:

From the utility room I have a main panel and it has two PVC conduits that runs down, then exit the 8" concrete block wall, the 3/4" conduit runs about 35' underground to a shed where the washing machine and dryer are. This conduit right now has six individual conductors in it, four #10 and two #12 stranded conductors for the dryer and washer. The 1/2" PVC conduit is abandoned, has nothing in it.

Here are some pictures to make it easier to visualize.





I would like to add a small 1000W gallon water heater in the shed for the washer which would need another 15A circuit. To do that all I really should need is another #12 conductor, I can share the neutral with the washer by putting the two breakers on opposite legs. However, the 3/4" seems too congested to even try.

On top of that, I have in my garage, sitting and collecting dust, five 10' long 1.5" PVC electric conduits. Also collecting dust a coil of NM 6-3 about 60' long. and also about half a dozen of 60A breakers.

So I am thinking, why not dig a new trench, and run a new 1.5" conduit to the shed? I already have the conduits, I already have the breakers, I already have the wires. Run the #6 to the shed and put in a 60A subpanel, and from there, washer, dryer, water heater.

The issue I see is, I don't have the room (as you can see from the picture), to run a 1.5" conduit from the panel through the concrete wall, the wall is very close to the door, and I have other pipes in the way. So I am thinking to reuse the existing 3/4" and 1/2" as pictured above.

Basically, it means on the outside of the wall, I would like a weatherproof (most likely PVC) box, that I would mount onto the wall where the two pipes currently exit. The two existing PVC conduits would tie in on the back side, then from there, I would connect to the 1.5" PVC pipe at the bottom then run underground for 35'. The only thing in the 1.5" conduit is the 6-3 NM cable. But in the future, I can add more wiring if necessary. Does that sound reasonable? Something like this?



I can't find any weatherproof junction box that has a 1.5" KO at the bottom, and two 3/4" KO holes on the back. Does this mean I will need to get a deep box and drill my own KO holes? Or is there a better way?
 
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  #2  
Old 08-07-15, 09:02 AM
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The 3/4" conduit you have is big enough to contain (3) #6 THHN (black,red,white) + (1) #10 THHN (green) conductor -- enough for up to a 70A subpanel in the shed. If you use #8 THHN, up to 50A. The shed should already have a subpanel as code allows for only one feed per building, and the shed already has two.

It should be a simple job of adding a panel on the shed side, and using the old wires to pull through new wires. A ground rod will need to be added at the shed and bonded to the ground bar with #6 copper.

The NM cannot be used underground.
 
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Old 08-07-15, 09:21 AM
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You mean I cannot feed the NM through the 1.5" conduit buried underground but I can do so with individual conductors?

There is no subpanel in the shed now. Well, I don't know if it's shed technically, it's probably more like a "lean to". It's not standalone.
 
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Old 08-07-15, 09:28 AM
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Never mind. I just saw a reference that says you can't run NM cable in outdoor conduits, buried or not. So I guess that's out.
 
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Old 08-07-15, 09:29 AM
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Correct. NM is for indoor, dry locations only.

Outdoors requires either UF (underground feeder) cable, which is very sitff and difficult to using in conduit, or THHN/THWN individual conductors which are rated as waterproof (the W in THWN).

By not standalone, do you mean it's part of the house?
 
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Old 08-07-15, 09:32 AM
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NM is not allowed outside at all and that includes underground.

Edit: Looks like Ben is faster than me....
 
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Old 08-07-15, 09:46 AM
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"By not standalone, do you mean it's part of the house?"

It's a lean-to shed. Meaning there is no "back wall" or the back is actually the exterior wall of the house. Something like this.



It is not a standalone structure 40' away from the main house. I don't know if you call it a "separate building".
 
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Old 08-07-15, 09:53 AM
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I think it's fair to call this part of the house. Meaning you can run as many circuits as you want to this area from the main panel without a subpanel being required. If it is more convenient to do so, you could install a panel here. To address the immediate need with the least cost, reusing the abandoned 1/2" conduit with #14 THHN in black, white, green would be adequate for the 1000W heater.
 
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Old 08-07-15, 11:57 AM
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I would look at relocation of the laundry room. I would not want to take the clothes outside to wash them.
 
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Old 08-07-15, 01:12 PM
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I might not mind if my back yard had that kind of weather.
 
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