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i_need_help 02-01-2011 09:10 AM

Long Run Voltage Drop
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I want to keep the voltage drop within acceptable limits on a long feeder run. 240v Single Phase @ 200amps for 500' underground. The lugs at each end can accommodate 4/0 max. Can I connect 4/0 at each end and then have 500 mcm for the majority of the run?

brric 02-01-2011 09:26 AM

Provided they are available in the sizes you need, you could use pin terminals to reduce the 500 to 4/0. A Burndy AYP500 will terminate to 500MCM and provide a pin .68 inch in diameter. You will need the proper compression tool to install these connectors. Some electrical supply house will loan you the tool when you purchase the terminals.

oleguy74 02-01-2011 10:24 AM

250mcm will give you 4.9% drop or 10 volts.

J. V. 02-01-2011 11:00 AM

Sfeyelectric 02-01-2011 11:08 AM


Originally Posted by oleguy74 (Post 582431)
250mcm will give you 4.9% drop or 10 volts.

Yes but that is above the 3% or 7.2volts that are acceptable

oleguy74 02-01-2011 11:19 AM

then go 350kcm.that is 3%.i would do a cost check.

CheapCharlie 02-04-2011 07:27 PM


Originally Posted by oleguy74 (Post 582458)
then go 350kcm.that is 3%.i would do a cost check.

You said feeder circuit right? Are you talking from the pole, throught your meter to the panel? If so, you can only have 2% VD

LyonsElecSupply 02-04-2011 10:45 PM

Branch circuits are maximum of 5%, preferably 3%.....DC is maximum of 3%

Even if he uses 250 or 350 his lugs still arent big enough.........You can just bring the 500 mcm into a "tangle box" such as a 8x8x6 PVC box and make junctions inside with splicers or split bolts.....tape em up and you are good......

as long as your overcurrent device is rated, i dont see why not.

SD515 02-05-2011 07:16 AM

I'd hate to be the one having to make joints with 500 MCM in a 8X8 box. One maybe...but 4? Not my idea of fun...

CheapCharlie 02-05-2011 07:56 AM

I realized the OP is from the states. Here in canada FYI the VD allowable is 5% from meter to end of branch circuit. No more than 3% from your main to the end of a branch circuit. That's to say if you only have 1% from your meter to the panel, it doesn't mean you can have 4% on a branch circuit. I hope that makes sense

LyonsElecSupply 02-05-2011 10:53 AM

Obviously you would have to do a cubic inch calculation for the used wires. I was making a suggestion using an example. Common sense dictates you would use a bigger box if it didnt fit.

FYI: to the OP, you can reduce your neutral down, I *think* 70% of the rated capacity of the OCPD. Also you can reduce your ground. I would say a 4/0 ground is fine. Grounds are not Current carrying so you dont have to worry as much about ampere rating.

Note: i do not have the code in front of me, but if i remember right there is a provision for reducing the neutral in feeder circuits.

Also OP, why do you HAVE TO HAVE this capacity? im guessing 200A......Derating and biting the bullet may be in your best interest.

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