Question on sub-panel feeder wire and conduit

[ehjorten]

I am going to be calling my local L&I, but what size conduit would be required to run 100 A or 200 A service to my shop. Feeders are underground and coming from a 320 A CSED. I don't need 200 A, but want to know the difference in conduit size just in case. Feed will probably be 100 A, but just in-case I get crazy or sell the place and someone else wants to get crazy the conduit will be sized for it.

Oh...and the run is about 175'.

I am asking because I have 3" conduit in the ground, but if I can bush it to a smaller size at the ends, then it won't be such a massive pipe running up the side of the house and side of the shop.

 

[ddawg16]

Assuming you use THN wire, you would need #2 AWG and a min of 1" conduit.

But trying to pull #2 wires through a 1" conduit will not be easy....I would go 1 1/2" or even 2"....not a big difference in price.

 

[PAToyota]

I have a similar setup - C320 meter to feed the house and shop 200amp panels. I used 3" conduit for the straight part of the run, but went up to 4" for the bends to come up to the meter and panels. That made it a heck of a lot easier to pull the wire.

 

[kbs2244]

Amen to PAT.
You can be legal and then you can be smart.

 

[Aceman]

We run 1.25" for 100 amp and 2" for 200 amp feeders. Price difference isn't much so I'd just run a 2" conduit. 3"+ is overkill, plus you'd have to use reducer couplings to neck it down to 2-2 1/2" just so it'll fit the knockouts.

 

[Ezzie]

200A secondary at 175' is really pushing it - my utility wouldn't let me go over 150' (at 100A they would!!) so I had to bring the primary service in from the road to a xformer pole. I'm using a 4" drainage tile duct (solid no perfs) at 130 feet between the meter and the spot where I'm installing the pole. From there to the meter base underground in the duct we'll be using 3 conductors of 250 MCM (AL) to feed through 2-1/2" PVC from the ground up into the meter base.

 

[Aceman]

I'm using a 4" drainage tile duct (solid no perfs)

Diyer's.....

Ezzie, his run is between the meterbase and panel, not the meterbase and transformer.

 

[Graham08]

I second the recommendation to go with at least 1 1/4" for a 100A run. I just recently did mine in 1", and it was a royal PITA. The minimal difference in the conduit cost is repaid 100 times in reduced aggravation!

 

[Ezzie]

Diyer's.....

Ezzie, his run is between the meterbase and panel, not the meterbase and transformer.

175' between a meterbase and a sub panel?? Wow!! That's a long run. In that case, any losses are on his dime and not the utility co. so I can see they probably don't care.

 

[Stuart in MN]

175' between a meterbase and a sub panel?? Wow!! That's a long run. In that case, any losses are on his dime and not the utility co. so I can see they probably don't care.

For a run that long it's a good idea to check the voltage drop, just in case. Using the calculator at http://www.csgnetwork.com/voltagedropcalc.html (there are a lot of them out there, this is just the first one that pops up in a Google search), and plugging in #2 copper, 175 feet, 240vac and 100 amps from the information given above the voltage drop comes out to 2.8%, which is good - you want to keep it under 3%. If any of the parameters are changed, run them through the calculator again.

As long as you make the wire large enough (and can afford it), you can have ridiculously long runs without any significant voltage drop.

 

[LoneGunman]

175' between a meterbase and a sub panel?? Wow!! That's a long run. In that case, any losses are on his dime and not the utility co. so I can see they probably don't care.

LOL that is not a long run at all and it was from the meterbase to PANEL not meterbase to sub panel.
I'll be doing a 500' from meterbase to panel run in the next few weeks.