Feeder Length

[ajayl]

I was asked to do a job wiring a new barn 60ft by 45ft. The utility service is 200Amps 120/240v single phase. The feeder (4/0 aluminum) comes from the service to the main panel 561ft away! This main panel has a feeder that supplies a double wide trailer home and a garage that is 24ft by 36ft. The new barn is 100ft away from the main panel.
If I run a 200 amp feeder (4/0 aluminum) to the barn and the maximum load of 150amps this would have a 12% voltage drop!
What I am asking is do you think a 200 amp service is big enough for the house, garage and barn?
There is another option, I could get a service on the other side of the property that would be 150 ft from the barn and 200ft from the house. If I did this it would solve the voltage drop and I could get a 400 amp service. Is 400 amp service to big?
What would you guys do on a job like this would you settle for a 12% voltage drop and a feeder so far away?
Sorry if this is a confusing explanation I will try to clarify if needed. Thanks for any help.

 

[Smart $]

Whether a 200A service rating is adequate (compliant) cannot be answered without doing a load calculation.. and that will be the only means to make the determination. That said, if the barn has a max load of 150A, it is quite likely that a 200A service rating is undersized for the house, garage and barn.

 

[Little Bill]

I was asked to do a job wiring a new barn 60ft by 45ft. The utility service is 200Amps 120/240v single phase. The feeder (4/0 aluminum) comes from the service to the main panel 561ft away! This main panel has a feeder that supplies a double wide trailer home and a garage that is 24ft by 36ft. The new barn is 100ft away from the main panel.
If I run a 200 amp feeder (4/0 aluminum) to the barn and the maximum load of 150amps this would have a 12% voltage drop!
What I am asking is do you think a 200 amp service is big enough for the house, garage and barn?
There is another option, I could get a service on the other side of the property that would be 150 ft from the barn and 200ft from the house. If I did this it would solve the voltage drop and I could get a 400 amp service. Is 400 amp service to big?
What would you guys do on a job like this would you settle for a 12% voltage drop and a feeder so far away?
Sorry if this is a confusing explanation I will try to clarify if needed. Thanks for any help.

Without checking your numbers, 12% sounds high for only a 100' from main to the new barn. With that said, 561' from Utility to main is a lot especially since 4/0 is only good for 180A.

As to whether the 200A is enough for the house, garage and barn, that would depend on the loads in each.
Did you do a load calculation for this?

 

[ajayl]

I used T310.15(B)(6) for 200amp feeder size which is 4/0 aluminum.
Also 12% I added the 561' plus 100' getting 661 feet. Sorry for the confusion on that.
I have not done a load calculation other than throwing some numbers around my head. I am an electrician at a mine so this stuff is not very familiar. How would you suggest doing a load calculation on a house? could I do 3VA per square foot or do I need to find out what the max load is when everything is turned on or is there another way you guys load calculate?

 

[Little Bill]

I used T310.15(B)(6) for 200amp feeder size which is 4/0 aluminum.
Also 12% I added the 561' plus 100' getting 661 feet. Sorry for the confusion on that.
I have not done a load calculation other than throwing some numbers around my head. I am an electrician at a mine so this stuff is not very familiar. How would you suggest doing a load calculation on a house? could I do 3VA per square foot or do I need to find out what the max load is when everything is turned on or is there another way you guys load calculate?

Did you actually look at the SE conductors from the service to the main panel? I find it hard to believe someone would run 4/0 that distance for a 200A service since 4/0 is only the minimum allowed per Table 310.15(B)(6). If you take into count the voltage drop, that would be marginal at best. Although not against code since the NEC doesn't require sizing for VD.

As I said earlier, 4/0 is only 180A per Table 310.16 for ampacities. Table 310.15(B)(6) can only be used if the conductors serve the entire load for the dwelling. So you couldn't use 4/0 for your conductors to the barn if you put in a 200A panel there. You would have to use Table 310.15 and that would be 250 mcm for 200A.

You probably wouldn't need a 200A at the barn. But again, without a load calculation, we don't know what may be required there.
For the house, you could use 220.82 for the load calc. You could turn all the loads on in the house and garage and check the current draw at the main panel outside. That would give you an idea of how much load you could add at the barn but wouldn't be an approved method should your AHJ require a load calc. prior to adding the barn.

Edit: Unless your main outside panel is a feed through, you wouldn't be able to feed the barn with 200A since the bus wouldn't accept a 200A breaker to feed it with. Also the garage might already have used the feed through lugs.

 

[kwired]

Can you get POCO to get the transformer closer to the load? Sure they may charge the customer more, but secondary is not all that inexpensive either when you have to start increasing size for voltage drop, and even worse if you are using copper conductor.

As others have said, load calculations are necessary here, but even if you don't have a lot of load, you will likely experience noticeable voltage dips when larger motors are starting.

 

[Fulthrotl]

I used T310.15(B)(6) for 200amp feeder size which is 4/0 aluminum.
Also 12% I added the 561' plus 100' getting 661 feet. Sorry for the confusion on that.
I have not done a load calculation other than throwing some numbers around my head. I am an electrician at a mine so this stuff is not very familiar. How would you suggest doing a load calculation on a house? could I do 3VA per square foot or do I need to find out what the max load is when everything is turned on or is there another way you guys load calculate?

you are allowed 5% total voltage drop, feeders and branch combined.
you can fudge that with making the feeders 3% and branch circuits 2%.

the feeders at 561' are poco, correct? so, they aren't part of the equation,
being under the poco's control.

4/0 aluminum with 150 amp load going 100' is gonna give you 2.50% voltage
drop, which is acceptable.

i've got a job coming up where i have a 208 3ph 4w. load at 625'.
it comes out at 750 mcm aluminum, and the wire cost is about $8k.
bumping it to 480 would drop it to 350 mcm. the 120 volts to ground
kills you on voltage drop. i'm looking at feeding it with 480 and dropping
it at the load with a transformer.

but your hundred feet of 120/240 should be fine... i'd clamp on a couple
of amp meters, and turn everything on in the house, with the meters set
to capture peaks, and see where you are at. if you really have a 150amp
load, you are getting thin.

 

[kwired]

you are allowed 5% total voltage drop, feeders and branch combined.
you can fudge that with making the feeders 3% and branch circuits 2%.

the feeders at 561' are poco, correct? so, they aren't part of the equation,
being under the poco's control.

NEC does not set any requirements for voltage drop - only puts in suggestions in informational note - or fine print notes in earlier editions.

Whether or not a conductor is under POCO control or not, voltage drop will still happen and it will not care who controls the conductor.

 

[Sierrasparky]

Don't forget size of ground conductor.

 

[GoldDigger]

NEC does not set any requirements for voltage drop - only puts in suggestions in informational note - or fine print notes in earlier editions.

Whether or not a conductor is under POCO control or not, voltage drop will still happen and it will not care who controls the conductor.

However, if the voltage drop within the control of POCO, up to the service point, puts the delivered voltage to you outside of the POCO specifications, then you have some leverage to get POCO to decrease the voltage drop (or just increase the service voltage if there is room at the top (0 VD) end).

If it is your feeders that are causing the delivered voltage to be out of spec, then you can either accept that (since there are no NEC requirements, just customer satisfaction, involved) or you can increase the wire size where it is under your control or you can take other steps like using a pair of transformers.
There is no reason (except cost) that you cannot use larger feeder wires on your side of the service point.