Another Subpanel Feed Question

[exranger06]

I feel like this question has been asked a million times before, and I feel kind of dumb for asking, but I'm getting a little overwhelmed reading through dozens of threads, some with conflicting information, and getting confused.

So, I'm trying to decide which type of wire to use to feed my subpanel. Subpanel is in attached garage, I ran 1.5" PVC conduit from main panel to subpanel. Part of the conduit run is underground, not sure if that matters. Total conduit run is less than 20 feet. Subpanel is a 100A panel and I already have a 90A breaker to go in the main panel.

I know I can use 2-2-2-4 MHF, but was wondering if there are any better choices, maybe something that would be easier to pull through the conduit. #3 Cu THWN? If I went with THWN, which size ground should I use? Cost isn't much of an issue, since I only need about 20 feet of it. Just wanted to know what would be easiest to install and be code compliant.

 

[Stuart in MN]

#3 copper THWN will work fine. Your ground wire can be #8.

 

[sberry]

How many turns is in it? Agree, at 20 ft it isn't a big deal.

 

[pattenp]

The underground part limits you to using wire that is rated for wet locations and can be placed underground. That means no NM-b(no wet locations) or SER(wet locations above ground, but not underground).

 

[Bretny]

Usualy you pick a wire size before you burry/install the conduit so you know it will fit and can even run the wire while your putting the conduit in.

 

[b-boy]

I'm going through this now. I had a 200 ft run. I went with 4-conductor #2 Cu THWN. #4 Cu for the ground. It's running through 2" conduit. I will be running 90A to a 100A sub panel. Right now I have a 60A breaker in place.

All I can say is Cu is crazy expensive.

Are you sure you can use #3 for 90A? All the calculator I used said #2 AWG for 90A.

 

[exranger06]

How many turns is in it? Agree, at 20 ft it isn't a big deal.

I have an LB attached right to the main panel. Then I have a 45 degree elbow and two 90 degree elbows before it gets to another LB. Then it goes through another 90 elbow into the subpanel.

The underground part limits you to using wire that is rated for wet locations. That means no NM-b or SER.

Yes, I knew that. I'm pretty much just trying to decide between MHF or THWN, and which gauge THWN if I decide to go that route.

Usualy you pick a wire size before you burry/install the conduit so you know it will fit and can even run the wire while your putting the conduit in.

Yes, I know that too. I've been trying to get this project finished for the last 3 years and it's undergone several design changes. I started running this conduit over 2 years ago and am just now finally finishing it. I decided to stick with this size since I already had half of it done in this size.

 

[MattT]

With two LBs in the run I'd use THWN. You'd be fighting MHF through those.

 

[pattenp]

I'm going through this now. I had a 200 ft run. I went with 4-conductor #2 Cu THWN. #4 Cu for the ground. It's running through 2" conduit. I will be running 90A to a 100A sub panel. Right now I have a 60A breaker in place.

All I can say is Cu is crazy expensive.

Are you sure you can use #3 for 90A? All the calculator I used said #2 AWG for 90A.

#3Cu is 100A @ 75C. Don't know why the calculator you're using is saying #2 being that it's only 20ft. Are you using 60C temp rating?

 

[Skiff Builder]

I recently ran about 120' 2-2-4-6 mhf. 3 LB's, 2 90's. Panel to panel. Quite slippery, no probs pulling solo with no lube. Priced right and working as well as the old copper.

 

[b-boy]

#3Cu is 100A @ 75C. Don't know why the calculator you're using is saying #2 being that it's only 20ft. Are you using 60C temp rating?

You are correct. I used a different calculator and got 3AWG for 20 ft.

The one I was using didn't account for insulation temp rating. It must be using 60C as a default. I bookmarked the new one.

Good news is that my 200ft run using 2 AWG still stands, so I didn't waste a bunch of $$$ on oversized wire.

 

[Bert_]

For pulling into a conduit I like to use XHHW. Similar to THHN but it is commonly available in aluminum. It pulls easier than the MHF type wire since it isn't twisted. Price is about the same.

 

[pattenp]

The XHHW is lighter weight and smaller than MHF because the insulation is thinner not being direct bury rated.

 

[exranger06]

The XHHW is lighter weight and smaller than MHF because the insulation is thinner not being direct bury rated.

I think I might go with XHHW aluminum #2 with a #6 ground. Looks like it's about half the price of #3 copper.

 

[pattenp]

I think I might go with XHHW aluminum #2 with a #6 ground. Looks like it's about half the price of #3 copper.

90A is the max breaker size for #2 Al, not 100A if that's your thinking.

 

[exranger06]

90A is the max breaker size for #2 Al, not 100A if that's your thinking.

I know 90A is the max for #2 Al. Like I said in my first post, I already have a 90A breaker to feed the subpanel. Even if I use #3 copper, I'm still going to use the 90A breaker I have.

 

[pattenp]

I know 90A is the max for #2 Al. Like I said in my first post, I already have a 90A breaker to feed the subpanel. Even if I use #3 copper, I'm still going to use the 90A breaker I have.

Forgot you said you had a 90A breaker to use.

 

[wyliesdiesels]

The underground part limits you to using wire that is rated for wet locations. That means no NM-b or SER.

To clarify this, SER/SEU is permitted in wet locations, just not underground.

 

[pattenp]

To clarify this, SER/SEU is permitted in wet locations, just not underground.

Ooops… I knew that, my wording was not quite right. Thanks for clarifying. Will fix.

 

[strutaeng]

I ran about 40 feet of AL #2 XHHW (2 hot, 1 neutral and #6 ground) for my detached garage subpanel 6 months ago.

I ran it in 1 1/4 schedule 40. I did it the other way around by mistake. I bought the conduit first. I had 2, 90s that went down and up from grade, then 2 "large radius" bends that I heated with a torch, I'd say like 5 ft radius. One was like 70 degrees and the other like 110 degrees.

I used lube a had no problem feeding through the conduit.

You should be fine. I used a stringline to pull and pushed the cables. I know it's not pro. but I hesitated to buy a fish tape for a one time use. Fish tape and helper would be piece of cake.

Power on!

 

[larry4406]

For pulling into a conduit I like to use XHHW. Similar to THHN but it is commonly available in aluminum. It pulls easier than the MHF type wire since it isn't twisted. Price is about the same.

Bert - are you saying then if you have a preference you would pull separate strands of XHHW vs the pre-made bundle of MHF? I assume you are pulling all the strands at once?

I still need to buy my wire for my barn and am looking at XHHW vs MHF. I will be running 2" conduit.

 

[Bert_]

Bert - are you saying then if you have a preference you would pull separate strands of XHHW vs the pre-made bundle of MHF? I assume you are pulling all the strands at once?

I still need to buy my wire for my barn and am looking at XHHW vs MHF. I will be running 2" conduit.

Absolutely, and yes you pull all the wires at once. It pull so much better than the twisted cable intended for direct bury. It ends up being more flexible and some of the XHHW out there is very slippery.

I ran about 40 feet of AL #2 XHHW (2 hot, 1 neutral and #6 ground) for my detached garage subpanel 6 months ago.

I ran it in 1 1/4 schedule 40. I did it the other way around by mistake. I bought the conduit first. I had 2, 90s that went down and up from grade, then 2 "large radius" bends that I heated with a torch, I'd say like 5 ft radius. One was like 70 degrees and the other like 110 degrees.

I used lube a had no problem feeding through the conduit.

You should be fine. I used a stringline to pull and pushed the cables. I know it's not pro. but I hesitated to buy a fish tape for a one time use. Fish tape and helper would be piece of cake.

Power on!

Fish tapes don't work that well in large conduits anyway. You did it the best way. I usually **** a string through with a plastic bag tied to the end and a shop vac. Use the string to pull in a larger rope if necessary.

 

[James-W]

So, I'm trying to decide which type of wire to use to feed my subpanel. Subpanel is in attached garage, I ran 1.5" PVC conduit from main panel to subpanel. Part of the conduit run is underground, not sure if that matters. Total conduit run is less than 20 feet. Subpanel is a 100A panel and I already have a 90A breaker to go in the main panel.

I know I can use 2-2-2-4 MHF, but was wondering if there are any better choices, maybe something that would be easier to pull through the conduit. #3 Cu THWN? If I went with THWN, which size ground should I use? Cost isn't much of an issue, since I only need about 20 feet of it. Just wanted to know what would be easiest to install and be code compliant.

Just a question here, how do you run conduit underground when going from your house to an attached garage?

 

[Norcal]

Just a question here, how do you run conduit underground when going from your house to an attached garage?

It may because of the way the house is built, or a typo in the post, the reasons are almost endless.

 

[exranger06]

Just a question here, how do you run conduit underground when going from your house to an attached garage?

Main panel is in my finished basement, flush mounted with drywall all around it. Also right next to it is a brick hearth for a wood stove. I didn't want to hack any of that up to run wire, so I ran the conduit out the back of the main panel, outside. It then goes down, underground, along the foundation of the house a few feet, and back up the adjacent garage wall, through the wall into the garage.

 

[exranger06]

Attached pictures should explain it a little better.

 

[exranger06]

And attached here is a pic of my main panel. I would've had to run the wire to the left, behind that brick hearth somehow. Didn't want to deal with that. Someday, that hearth is getting ripped out, but not for at least several more years. This is also why I installed a subpanel in the first place: I only have to deal with running wire to the main panel once, then I never have to touch it again. Now I can easily add circuits and outlets in the garage whenever I want and just connect them to the easy-to-access subpanel.