220 conduit size?

[Arizonarob]

I’m about to start on a concrete project that requires some electrical conduit run. I need to know the proper size conduit to run for a 220v line from a 50 amp sub panel mounted on the side of the house, to its final destination approximately 25 feet away.
The conduit will be buried 18” below grade, and I’ve been told 3/4” will be “fine”. I know air space around the wire is what sets the minimum requirements, but I’d like to make sure that it will be good in the heat we get here in the desert.
What’s your thoughts?

 

[ajw22]

I don’t think Arizona heat makes a difference.

Conduit Fill Table

www.constructionmonkey.com

You running #4 or #6 wire? Copper?

Why not run 1” conduit and make it easier to pull wires?

 

[JamesW]

I need to know the proper size conduit to run for a 220v line from a 50 amp sub panel mounted on the side of the house, to its final destination approximately 25 feet away.

What is the line going to be used for?

Is the line going to the subpanel from the house or from the subpanel to some piece of equipment?

What amperage is the line going to be?

 

[crushkittykitty]

Are you running alum wire or cooper ?
alum wire would be 4 THWN
cooper wire would be 6 THWN
here is the chart I use here
I would use 1 inch but I hate pulling wire the smaller the conduit the harder the pull.
I also used pvc instead of metal try to limit bends and I just bent the pvc with a heat gun. also use plenty of wire lube.

 

[crushkittykitty]

lol better people then I are here. I will watch from here out

 

[Arizonarob]

I don’t think Arizona heat makes a difference.

Conduit Fill Table

www.constructionmonkey.com

You running #4 or #6 wire? Copper?

Why not run 1” conduit and make it easier to pull wires?

What is the line going to be used for?

Is the line going to the subpanel from the house or from the subpanel to some piece of equipment?

What amperage is the line going to be?

Are you running alum wire or cooper ?
alum wire would be 4 THWN
cooper wire would be 6 THWN
here is the chart I use here
I would use 1 inch but I hate pulling wire the smaller the conduit the harder the pull.
I also used pvc instead of metal try to limit bends and I just bent the pvc with a heat gun. also use plenty of wire lube.

Sorry guys, I should have given a little more info.

Main line will be pulled from the panel through the attic to an outside wall mounted 50amp sub panel. From there, run down through the ground under a concrete slab and stub out at the pad. This service will be running a spa. Here is the wiring diagram.

 

[tim5055]

As crushkittykitty noted, the pull through the conduit is a big deal. For the few pennies you will save on conduit, I'd move up to 1 1/2" myself.

Anytime i have ever done slab work I alwasy add an extra conduit here and there under the slab for later use should then need arise.

 

[ajw22]

Ok, so you have a run from main panel to subpanel of 4 #8 and subpanel to spa of 5 #12/10.

3/4 conduit is ok and 1” will make pulls easier.

 

[Bama Rambler]

In order to give you an accurate answer we need to know a couple of things;
1) How many amps are you expecting? (we know that's 50 amps from your write up)
2) How far is the total wire run from the house panel to the sub panel?

The total run is needed in order to figure the wire size, and from there we can figure the conduit size.
The installation manual gives you a general rule of thumb, but it could change if the run is longer or the voltage drop is higher than recommended. I personally don't want the voltage drop to be more than 3%.

 

[Arizonarob]

In order to give you an accurate answer we need to know a couple of things;
1) How many amps are you expecting? (we know that's 50 amps from your write up)
2) How far is the total wire run from the house panel to the sub panel?

The total run is needed in order to figure the wire size, and from there we can figure the conduit size.
The installation manual gives you a general rule of thumb, but it could change if the run is longer or the voltage drop is higher than recommended. I personally don't want the voltage drop to be more than 3%.

Dave, not sure on the amount of run feet from the main to the sub panel, but I do know from the sub panel to the spa is approximately 20' away. I'm having an electrician do all the wiring, so I was just trying to figure out conduit size so everything is in place when he shows up to do the work.

Thanks guys for all the responses, I think I'm going to go with 2 1" runs under the slab. 1 for the spa, and one for later use if needed.

 

[crushkittykitty]

A+ bigger is always better :/

 

[Bama Rambler]

You can easily get 4 #6awg THHN in a 1" conduit, so your thinking is good. If you run 1" you won't have a problem.

 

[Randrx2]

I was an electrician and still carry a license. Always go bigger with the conduit if you can! Don’t go too big though. It costs more and your panel may not have the right size knockout for a larger conduit.

For future reference for others:
1. I am assuming based on your circuit size of 50A you are using #6 THWN copper. You can use #8, but standard is to use #6 for 50A circuit based on temperature rating. FYI, underground conduit is considered a wet location, need to use wet rated wire.
2. Technically, 3/4” is allowed. It will be a bear to pull through unless the run is straight with no bends. Upsize to 1”.
3. Minimize your bends. You can only have a max of 360 degrees of bends. But if you have that many, your pull is going to be hard.
4. Don’t be afraid to be generous with the wire lube when pulling.
5. Label your wires before pulling. Better to use colored wire (black, red, white, green).
6. Most times for underground, assume you are using SCH 40 PVC. If you are using something else, like SCH 80, you cannot use the same amount of conductors (due to thicker walls of conduit).
7. The ground wire does not have to be full sized. For a 50A circuit, you can use #10 copper.
8. Does not matter if circuit is 120V or 240V, wire size depends on amps.

If your electrician is licensed, and a permit is pulled, the inspector will also be checking wire, conduit, and ground size.

Have fun on your build!