Subpanel for a farm

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KG1321

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Howdy!

I recently retired from the trade and wanted some advice for a small job I want to do on my property. I want to install a 100 amp panel in a barn about 250' from the main panel that feeds the rest of my property. I figured on using #2 copper with an equipment grounding conductor in 1 1/4 PVC underground.

I know for most of yous guys this seems like "old hat" , but I want to get this right - and there aint no foreman I can blame!!:lol:

Thanks!
 
KG1321 said:
Howdy!

I recently retired from the trade and wanted some advice for a small job I want to do on my property. I want to install a 100 amp panel in a barn about 250' from the main panel that feeds the rest of my property. I figured on using #2 copper with an equipment grounding conductor in 1 1/4 PVC underground.

I know for most of yous guys this seems like "old hat" , but I want to get this right - and there aint no foreman I can blame!!:lol:

Thanks!
Click to expand...

Howdy back acha Tex!

Welcome to the forums :thumbsup:

So those conductors will be about 270' in length?

Have you done load calculations on the main service to make sure you're not going to overload it?

Is this a bona-fide farm? Or just a Texas sized homestead?
 
You don't mention whether this is 3-phase, but I will presume it is. You also don't mention your selected size of the EGC. My calculation tells me that a #2 wire will result in a 4% voltage drop over the 250 foot distance, presuming a full load of 100 amps. Of course, it may be unlikely that the load will ever actually get that high. But you didn't tell us what loads you intend to serve, so I will presume the load really is 100 amps. Most people would say that 4%VD is excessive. So I would suggest going with #1 wires or larger. With a #1, my calculation results were at 3% VD. Please note that this would require bumping up the conduit to 1-1/2 inch, due to conduit fill restrictions. The EGC would need to be #8, if you stayed with the #2 ungrounded conductors. If you increase the ungrounded to #1, per my suggestion, then you need to upsize the EGC to #6, per 250.122(B).
 
KG1321 said:
Howdy!

I recently retired from the trade and wanted some advice for a small job I want to do on my property. I want to install a 100 amp panel in a barn about 250' from the main panel that feeds the rest of my property. I figured on using #2 copper with an equipment grounding conductor in 1 1/4 PVC underground.

I know for most of yous guys this seems like "old hat" , but I want to get this right - and there aint no foreman I can blame!!:lol:

Thanks!
Click to expand...

that's a lot of trench. hope you have an apprentice to do the shovel work.

:)
 
charlie b said:
You don't mention whether this is 3-phase, but I will presume it is. You also don't mention your selected size of the EGC. My calculation tells me that a #2 wire will result in a 4% voltage drop over the 250 foot distance, presuming a full load of 100 amps. Of course, it may be unlikely that the load will ever actually get that high. But you didn't tell us what loads you intend to serve, so I will presume the load really is 100 amps. Most people would say that 4%VD is excessive. So I would suggest going with #1 wires or larger. With a #1, my calculation results were at 3% VD. Please note that this would require bumping up the conduit to 1-1/2 inch, due to conduit fill restrictions. The EGC would need to be #8, if you stayed with the #2 ungrounded conductors. If you increase the ungrounded to #1, per my suggestion, then you need to upsize the EGC to #6, per 250.122(B).
Click to expand...

Wouldn't he also need 2 ground rods or the building steel and one ground rod since it is detached?
 
KG1321 said:
Howdy!

I recently retired from the trade and wanted some advice for a small job I want to do on my property. I want to install a 100 amp panel in a barn about 250' from the main panel that feeds the rest of my property. I figured on using #2 copper with an equipment grounding conductor in 1 1/4 PVC underground.

I know for most of yous guys this seems like "old hat" , but I want to get this right - and there aint no foreman I can blame!!:lol:

Thanks!
Click to expand...
I would likely install 1/0 aluminum in 2 inch conduit, unless voltage drop dictates even larger. Will cost a lot less then the copper.

If this is service conductors you only need a single grounded conductor, if it is a feeder you need a grounded and an equipment grounding conductor. A grounding electrode system is needed either way.
 
Just wanted to thank everyone for their responses

Just wanted to thank everyone for their responses

I'm still mulling over my "project." I've got some existing sub panels that are being feed with aluminum so I'm thinking about the 1/0 aluminum in a 2" pvc. Oh BTW this is not 3 phase but Single phase 120/240. Only two wires on the pole! :D

Again, thanks to all of yous guys!:bye:
 
KG1321 said:
I'm still mulling over my "project." I've got some existing sub panels that are being feed with aluminum so I'm thinking about the 1/0 aluminum in a 2" pvc. Oh BTW this is not 3 phase but Single phase 120/240. Only two wires on the pole! :D

Again, thanks to all of yous guys!:bye:
Click to expand...

Well if you have (2) wires on the pole then you have an even bigger problem. Chances are you have (3) conductors from the XFMR on the pole but I think you knew that and simply omitted the grounded conductor...no worries.

Keep in mind some subtle points in Charlie B's advice (even if it was based on 3-phase thoughts) in that 1/0AL for 250' would give you 4% VD, and by chance you need it to be the 270' from termination to termination as someone else stated....using that same 1/0 AL would result in 4.3% VD. While VD is not mandated in your case (might require an ointment or medication that's another thread) it is always something to be considered in the design. So since we are basing it on the entire load (due to nothing stated otherwise) my opinion would be that IF you are going to use AL instead of CU...that you increase It to 2/0AL at the least....but then again you have to way the cost of AL versus CU, the actual load your supplying, and increasing the raceway size cost in your overall cost analysis model.
 
MasterTheNEC said:
Well if you have (2) wires on the pole then you have an even bigger problem. Chances are you have (3) conductors from the XFMR on the pole but I think you knew that and simply omitted the grounded conductor...no worries.
Click to expand...

Could have been saying there is only two wires on the primary side of the transformer;)
 
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