voltage drop

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Robo

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I have a friend that wants to have a 200 amp 120/240 volt 1 phase service 1000 feet from the meter base that the utility is installing. How do I calculate the line loss and or correct wire size to use for this run. We are planing in installing direct burial - think it is called - URD cable.. aluminum, 3 wire - twisted together cable. :)
 
Re: voltage drop

Need to know what you are going to be drawing for current? Do you want to calcuate voltage drop on 200 amps or maybe 150 amps. Wire size will be different for each. Also if at the meter base you have your disconnect there you will need 4 wires to your 200 amp panel.
Jim
 
Re: voltage drop

With 1,000 ft there will be lot of voltage drop . You may need several conductors in parallel.
Do your friend a favor and get an electrician to help out. you may need to have parallel runs and this is beyond the scope of you or your friend to install.
My first suggestion is to have the POCO run primary to within 100 ft of the house.
 
Re: voltage drop

I ran some numbers. 250 mcm at 100 amps is about 16 volts drop. Your limit is 3% or 7 volts.
go to plan b
 
Re: voltage drop

Originally posted by james wuebker:
Ryan, you should know by now that the 3% is a rule of thumb. It's not in the book but most of us use it.
Jim
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I agree however I also agree with Ryan that 3% or 5% should not be presented here like it is a formal rule when in most cases it is just a design decision. :cool:
 
Re: voltage drop

Yes you are correct, it should be "a suggested limit is 3%. Mike Holt tells of an installation of overhead 480 for three miles that is 120 at the far end which is what they want.
 
Re: voltage drop

Originally posted by tom baker:
Yes you are correct, it should be "a suggested limit is 3%. Mike Holt tells of an installation of overhead 480 for three miles that is 120 at the far end which is what they want.
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I guess the load would be constant, if not the voltage would really fluctuate.
 
Re: voltage drop

Also if at the meter base you have your disconnect there you will need 4 wires to your 200 amp panel.
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Can anybody elaborate on that, regrading NEC requirements?
 
Re: voltage drop

Doing a quick calculation for a load of 160 amperes on the 200 amp panelboard, supplied by 1000 ft of aluminum conductors, and allowing a VD of about 7+ volts (about 3 % of 240) you could use two sets of 500 kcmil aluminum in parallel.
 
Re: voltage drop

By Tom: it should be "a suggested limit is 3%.
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I have always thought that the 3% was for branch circuits and 5% was over all. (both the branch circuits and feeders, which would be saying that the feeders (or in the Case of 547.9(B)(2) FPN service conductors) would be suggested to only have a 2% drop leaving 3% for the branch circuits, I know this article doesn't deal with this issue but the FPN to 547.9(B)(2) seems to follow this also?
 
Re: voltage drop

One of the energy codes (either Ashrae 90.1 or the IECC) requires less than 3% drop for branch circuits and 2% for feeders. I don't think the install in this thread falls under either of these codes but there are some hard and fast rules for commercial construction.

As for 4 wires, If your service entrance disconnect is at the meter, you have to run an equipment grounding conductor to the panel. Two hots, neutral, and ground thats 4 wires.

Is it just me or does this really sounds like a DIYer?
 
Re: voltage drop

Originally posted by tom baker: Mike Holt tells of an installation of overhead 480 for three miles that is 120 at the far end which is what they want.
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I heard him describe that as well. Just to be clear, there is no transformer at the end to convert 480 to 120. It just has enough VD along the line to permit them to power a 120 volt receptacle at the end.

Code Question of the Day: Is there a code violation in that installation? If you think so, please cite the article.
 
Re: voltage drop

Code Question of the Day: Is there a code violation in that installation? If you think so, please cite the article.
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I don't think so.

In addition, submersible crude oil pumps (up to 4000 ft deep) use the voltage drop for soft start and to achieve nominal voltage thereafter.

Same design approach is applied in the shipbuilding industry for a bow thruster motor (~500 HP) on very long supertankers.
 
Re: voltage drop

How about 110.4? You have a receptacle that is rated for 120 volts being connected to a branch circuit that is rated for 480 volts.
 
Re: voltage drop

The Voltage Drop utilization has nothing to do with a sloppy implementation.

480 volts to a 120 volts rated device for sure is not a sound practice.
 
Re: voltage drop

I may be a little rusty, but is it not permissible anymore to treat the house in this topic as an outbuilding and use three conductors without a grounding conductor?
I did this at my house. I, originally, had my service entrance at my house. The utility pole was next to my barn 250 feet away. When it came time to electrify my barn, I intercepted the 4/0,4/0,2/0 URD aluminum and rerouted it to the barn where I re-established my service entrance. Then I subfed my house as an outbuilding from the barn utilizing the existing feeder. Authority having jurisdiction agreed with my approach and approved it so long as I had a ground rod at the house and was bonded at the panel. My only problem with the installation is that there is likely a tiny bit of imbalance load that flows through the earth between the two bonding points!
Thoughts?? (edited for clarification and spelling)

[ November 17, 2005, 02:10 PM: Message edited by: ramdiesel3500 ]
 
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