Running wire for SUB in attic. The devil is in the details

[robertearl]

Ok I am going to run the wires for my sub panel in the new shop from the house. To get to the shop I will have to run the wires from one end of the house to the other and then down and buried to the shop. The length will be about 110'.

In the attic, there will have to be multiple bends in the PVC to get it to the other side of the house. How do you actually run the wire through the PVC?

1. Do you pull them through one at a time and then cut to the correct length?

2. Do you pull something through that you can measure and cut all of the wires to that length and then pull them all through at once?

3. Do you glue the PVC together or do you leave each piece separate until you get the wire through and then go back and glue it?

4. When you are coming down the outside wall to get to the main panel, do you just cut out a large hole in the sheet rock so that you have room to work and then go back and patch the wall or is there a neat trick to do this that I do not know about?

5. I am going to put in a 100 amp subpanel. I believe that the max I would really see is 60 amps. Would #4 copper be OK for this?

6. What size PVC? 1 1/2" or 2"

Reb

 

[rockwithjason]

push a fish tape thru the pipe and tie on a 1/2" rope. use the rope to pull the wire in. make sure to use plenty of lube or you will find out how hard this job can really be. if you pull the wires one at a time it is very likely that you will not be physically able to pull all of the wires in. it gets pretty tough to do it that way. the best is to pull a string thru the conduit and use it as a measure for the wire. make sure you leave some fat on the wire as it is way better to have too much than not enough. glue up all of the conduit and strap it down. as for working at the main, i would convert to flex and run the flex down the wall into the main. you will have to knock out the correct size hole at the panel, fit a connector to the flex and then pull it down to the hole by use of a string or fish tape.

of course you can avoid all of the conduit all together in the house by using the correct size romex cable. you can convert to separate wire before you enter the ground and you would save yourself loads of hassel and expense. for the underground i would use 2" pipe. #4 copper or aluminum should be ok for this.

 

[ArthurPE]

1 no
2 sort of, you push a fish wire thru, then pull all at the same time with it...
some push a nylon rope with the fish, and use that to pull all the wires...
3 the conduit should be complete before the pull, having pull boxes at strategic locations is a good idea
4 not sure what you mean
5 pull 3#3 AWG (Cu) w/a #8 ground (assuming the feeder CB is 100A)
if you use a 80A CB 3#4 and a #8 gnd is fine, but I'ld go with the 100A
6 I'ld use 1-1/2, although this depends on specific wire and conduit type

 

[ddawg16]

I would go at least 1 1/2"....makes pulling the wires a lot easier.

There is a limit on how many 90's you can have....I believe it is 4....over that, you have to have pull boxes....basically, this is a box or LB that the conduit goes into that allows you to pull the wire up to that point....you then send it on to the next leg from there.

So...in your case, I'm going to assume you have at least 3-4 90 deg bends in the attic...which means you want a box maybe at the point where it goes from the attic to outside....then your conduit goes from there onto the garage....which may end up having at least 2 90 deg bends....

If you don't have a fish tape....a foam ball, string and a vac work well. Get a small foam ball, like a clowns nose....tie a string to it...and **** that through the pipe with the vac. I have also had good success just using a piece of cloth...

String is cheap....so pull a lenght all the way through the pipe....cut to length leaving a couple of extra feet just in case....then tie another string or rope to the end and pull that through...the rope becomes your pull rope and the string will tell you how long to cut the wire.....which of course you are going to add a couple more feet to just in case.....and if in doubt...add a few more....nothing worse than pulling a bunch of wires in to only find out that you are about 6" short.....might as well be 100' short because the wire is basically useless....ask me how I know....

When you get ready to pull the wire....strip back the insulation on the end that is going in first....you want at least about 4"...Bend this around your rope and then tape it well...making sure that none of the strands can get caught on any thing. You want a nice tapered end that will fit in the conduit...

One of the things that makes it hard to pull wire is that when you get into the larger stuff....(#6 and larger), the stuff has a hard time bending around the corners....those long straight runs are easy.....this is why you want lub.....you can buy some at HD that works fine....but liquid soap works as well....the only downside to it is that it will start to make the electrical tape start to come off....the wire lube will not do that...plus it will eventually evaporate.

I would avoid using oil or grease....it is not kind to PVC and insulation.......

 

[robertearl]

of course you can avoid all of the conduit all together in the house by using the correct size romex cable. you can convert to separate wire before you enter the ground and you would save yourself loads of hassel and expense. for the underground i would use 2" pipe. #4 copper or aluminum should be ok for this.

I did not know that I could just run romex from the main to the other end of the house and then go to individual wires. Isn't romex that large rather a ***** to bend!? or do they make a stranded romex for applications like this.

Reb

 

[rockwithjason]

everything over #8 is stranded unless it's a special purpose wire. if you mount a deep jbox half in and half out of the wall you can get to the outside of the house easily. just run your underground pvc up into the box. make sure the box is 3r rain proof rated.

 

[hobie1dog]

and I thought you were talking about a real SUB

 

[tfi racing]

This project calls for cable,conduit PVC or EMT would be a major and unnecessary hassle.3/3 NMD thru the house,then make a transition to PVC and RW90 conductors for the exterior and underground.On this side of the border,PVC is not allowed to be buried in insulation,so running it thru the attic wolud be a no-no.

 

[nadogail]

You have received some very good advice.

 

[robertearl]

Thanks guys.

Reb