Service conductor size

[Lanesmith]

300amp service 900 ft. run 480ft. Direct burial 400 overhead! Want to use aluminum triplex type cable to keep cost reasonable. What size conductors will I need 500kcmil?

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[iwire]

300amp service 900 ft. run 480ft. Direct burial 400 overhead! Want to use aluminum triplex type cable to keep cost reasonable. What size conductors will I need 500kcmil?

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What is the calculated load?

What is the voltage?

What is the service supplying?

How much voltage drop are you willing to live with?

If this is a single phase 240 volt service and we say the actual load is 200 amps and we can live with 3% drop you would need

3 conductors per phase utilizing a #600 Aluminum conductor will limit the voltage drop to 2.70% or less when supplying 200.0 amps for 900 feet on a 240 volt system.

Or if you go copper

2 conductors per phase utilizing a #600 Copper conductor will limit the voltage drop to 2.83% or less when supplying 200.0 amps for 900 feet on a 240 volt system.

In general 900' is too far for low (under 600V) voltage.

If it happens to be 3 phase 480 service

1 conductors per phase utilizing a #1000 Aluminum conductor will limit the voltage drop to 2.63% or less when supplying 200.0 amps for 900 feet on a 480 volt system

I hope you have very deep pockets.

 

[Lanesmith]

The power company wants 10k to supply three phase power to site. I suggested 480 three phase when I was first contacted. But after discussing with local power company want to try find alternative maybe. Customer does have deep pockets but wants to save if he can of course. On top of that the power company wanted to come in set 3 to four poles which would enable cutting numerous OK trees down and that is not an option plus they want everything rustic looking on this ranch so no poles running through main entry. If you have suggestions I'm all ears I was thinking maybe setting 3 phase xfmr at switch rack then running 900 ft

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[Lanesmith]

Thanks for your reply sir

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[Lanesmith]

I don't have info to do load Calc at this time was going on verbal by home builder

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[kwired]

find out what POCO will charge to bring the primary voltage closer - but underground. You will be excavating or directional boring either way. If they ever have the need for increased capacity - the underground primary will remain the same, you would just swap transformers and increase what is on the secondary.

 

[NewtonLaw]

300amp service 900 ft. run 480ft. Direct burial 400 overhead! Want to use aluminum triplex type cable to keep cost reasonable. What size conductors will I need 500kcmil?

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Based on this information I assume you are extending a single phase 120/240 volt service. Without specific load details it is a little hard to give you a best answer. I will attache some voltage drop curves, in the mail to you, that I have used for PE and XLP cables for triplex overhead and triplex UG cables. These allow you to select cable base on run length and load. You mentioned 300 amp service, so I assumed cables of at least 4/0 AL or larger as the supply cables. Figure out what load you expect to supply in kW at no worse than 90% power factor, and read the voltage drop you may expect at a given distance.

Hope this helps,

Newton Law

 

[kwired]

Based on this information I assume you are extending a single phase 120/240 volt service. Without specific load details it is a little hard to give you a best answer. I will attache some voltage drop curves, in the mail to you, that I have used for PE and XLP cables for triplex overhead and triplex UG cables. These allow you to select cable base on run length and load. You mentioned 300 amp service, so I assumed cables of at least 4/0 AL or larger as the supply cables. Figure out what load you expect to supply in kW at no worse than 90% power factor, and read the voltage drop you may expect at a given distance.

Hope this helps,

Newton Law

Post 3 he says this is 480 volt three phase.

 

[NewtonLaw]

Post 3 he says this is 480 volt three phase.

I thought he said he suggested 480 volt 3 phase, not that it was 480 volt three phase. Also, he spoke of Triplex cable. For a Utility Engineer, this means 2 phase conductors and one neutral, i.e., single phase, not three phase which would normally be supplied by Quadruplex cables. I guess I missed something.

 

[NewtonLaw]

Based on this information I assume you are extending a single phase 120/240 volt service. Without specific load details it is a little hard to give you a best answer. I will attache some voltage drop curves, in the mail to you, that I have used for PE and XLP cables for triplex overhead and triplex UG cables. These allow you to select cable base on run length and load. You mentioned 300 amp service, so I assumed cables of at least 4/0 AL or larger as the supply cables. Figure out what load you expect to supply in kW at no worse than 90% power factor, and read the voltage drop you may expect at a given distance.

Hope this helps,

Newton Law

Sample of what I was sending to you is below:

 

[Lanesmith]

I thought he said he suggested 480 volt 3 phase, not that it was 480 volt three phase. Also, he spoke of Triplex cable. For a Utility Engineer, this means 2 phase conductors and one neutral, i.e., single phase, not three phase which would normally be supplied by Quadruplex cables. I guess I missed something.

No I was hoping my customer was going to have three phase accessible but power Co . Want 10 thousand just to bring three phase to existing service so trying to figure most efficient alternative if possible . Ty for your reply and input sir.

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[Lanesmith]

Sample of what I was sending to you is below:

Ty this does help I found almost the same type chart earlier today and still trying to figure best way to be cost effective now but in the long run as well Ty for your reply and suggestions for I'm limited on time I have to figure out for my buddy due to not much spare time rt now. I am FACILITY CONTROL MANAGER AT NEW AMAZON FACILITY. EVEN THOUGH OUR PEAK JUST ENDED WE ARE STILL SLAMMED MOVING OVER A MILLION PACKAGES A DAY AT MY FACILITY SO YOUR INPUT IS GREATLY APPRECIATED SIR. HAVE A GREAT WEEK!
Lane smith

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[electrofelon]

300amp service 900 ft. run 480ft. Direct burial 400 overhead! Want to use aluminum triplex type cable to keep cost reasonable. What size conductors will I need 500kcmil?

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For us to offer meaningful help, we really need better information. See Iwire's questions. I am also confused about your OP: is it 900 feet or 480 feet? Is it underground or overhead? Here is a voltage drop calculator you can play around with:

http://www.southwire.com/support/voltage-drop-calculator.htm

The key is to know what value to use for the current. If its a residential application without a bunch of electric heat or AC, I would feel perfectly comfortable using 70 amps for me current and keep that somewhere around 3-5% or less. If that was the case, and assuming it is 900 feet, 500 AL would get you there all day and that would be about 5k for the wire. (Even 350 URD would be about 4% and URD/triplexed USE is usually cheapest - I think 350 is the largest size)

As far as bringing in primary, the best scenario is if your utility lets you run the primary, and they provide the transformer and terminate. We have one utility here in central NY that allows that and its great. A neighboring utility doesnt and they charge about $15/ft to run primary. If the latter is the case, there is always the option of doing you own step up step down, but at 900 feet Ill bet you are better off putting you transformer money into aluminum conductors and keeping it low voltage.

 

[Lanesmith]

For us to offer meaningful help, we really need better information. See Iwire's questions. I am also confused about your OP: is it 900 feet or 480 feet? Is it underground or overhead? Here is a voltage drop calculator you can play around with:

http://www.southwire.com/support/voltage-drop-calculator.htm

The key is to know what value to use for the current. If its a residential application without a bunch of electric heat or AC, I would feel perfectly comfortable using 70 amps for me current and keep that somewhere around 3-5% or less. If that was the case, and assuming it is 900 feet, 500 AL would get you there all day and that would be about 5k for the wire. (Even 350 URD would be about 4% and URD/triplexed USE is usually cheapest - I think 350 is the largest size)

As far as bringing in primary, the best scenario is if your utility lets you run the primary, and they provide the transformer and terminate. We have one utility here in central NY that allows that and its great. A neighboring utility doesnt and they charge about $15/ft to run primary. If the latter is the case, there is always the option of doing you own step up step down, but at 900 feet Ill bet you are better off putting you transformer money into aluminum conductors and keeping it low voltage.

Thanks for your reply and yes I have since this morning downloaded a voltage drop calc. And just to straighten out your confusion it is 480 ft. Direct burial and the second half of the run will be above or overhead. approx. 420'. Running this way due to terrain. I live in the hill country in central Texas and most of the ground is solid flint rock and is very difficult even with a rock saw. Also esthetics plays a big part in why we want it done this way.

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[Lanesmith]

For us to offer meaningful help, we really need better information. See Iwire's questions. I am also confused about your OP: is it 900 feet or 480 feet? Is it underground or overhead? Here is a voltage drop calculator you can play around with:

http://www.southwire.com/support/voltage-drop-calculator.htm

The key is to know what value to use for the current. If its a residential application without a bunch of electric heat or AC, I would feel perfectly comfortable using 70 amps for me current and keep that somewhere around 3-5% or less. If that was the case, and assuming it is 900 feet, 500 AL would get you there all day and that would be about 5k for the wire. (Even 350 URD would be about 4% and URD/triplexed USE is usually cheapest - I think 350 is the largest size)

As far as bringing in primary, the best scenario is if your utility lets you run the primary, and they provide the transformer and terminate. We have one utility here in central NY that allows that and its great. A neighboring utility doesnt and they charge about $15/ft to run primary. If the latter is the case, there is always the option of doing you own step up step down, but at 900 feet Ill bet you are better off putting you transformer money into aluminum conductors and keeping it low voltage.

Yes the Power co. Wants 8k to extend service to destination and wants to put four poles rt through the main house and entrance area. Also oak trees where I'm at are like gold lol the cedars were introduced here some 50 yrs ago and have taken over entire area the power co. Would destroy many oaks if they did this so it's not an option I found 1000 ft. Of 500 mcm triplex for 3500.00 so I'm problem going to do what you were suggesting and stick with lower voltage and going with the larger al. Conductor. I have to get with pwr. Co. Tomorrow and see if I need 300 amp safety switch at meter loop again probly and around same cost as PEC was pushing but no eye sores to look at nor trees to destroy. Ty for your advice .

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[kwired]

Yes the Power co. Wants 8k to extend service to destination and wants to put four poles rt through the main house and entrance area. Also oak trees where I'm at are like gold lol the cedars were introduced here some 50 yrs ago and have taken over entire area the power co. Would destroy many oaks if they did this so it's not an option I found 1000 ft. Of 500 mcm triplex for 3500.00 so I'm problem going to do what you were suggesting and stick with lower voltage and going with the larger al. Conductor. I have to get with pwr. Co. Tomorrow and see if I need 300 amp safety switch at meter loop again probly and around same cost as PEC was pushing but no eye sores to look at nor trees to destroy. Ty for your advice .

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And would need replaced someday if you needed increased capacity. Maybe that isn't a concern for now though.

Bringing primary voltage closer to the facility does future proof it quite a bit, even if you just bury large enough raceway for all three phases yet only pull in single phase for now, I think is worth looking into.