achovanetz Posts: 1, Reputation: 1 New Member #1 Jan 30, 2006, 01:10 PM
4 wire home service entrance wire size
Mobile home requires 4 wire electrical service entrance wire. Distance is 160 foot from meter to breaker panel. 220V service. What size wire do I use? Can I use diff. size for neutral and ground?
 tkrussell Posts: 9,659, Reputation: 725 Uber Member #2 Jan 30, 2006, 02:07 PM
First if you check, I believe your supply voltage is 240 volts, if you are located in the US, this is the nominal voltage used.

I mention this because accurate voltage is considered when performing voltage drop calculations.

The National Electric Code recommends that the voltage drop for feeder not be more than 3%, so your service feeder needs to be sized to deliver at least 232-233 volts at the panel.

There are several other factors that must be considered. One is the wire material, copper is a better conductor than aluminum. Bascially aluminum is the next size larger than copper in ampacity. But copper can be very expensive for long or large feeders and aluminum is chosen very often.

Next is the amperage,or load. A 200 Amp service cannot be loaded more than 160 amps, an 80% derating factor. But to use 160 amps to calculate VD will use a 4.3% VD. More than the NEC allows. I used a more realistic load of 125 amps to arrive at using #250 MCM Aluminum wire with XHHW insulation to get a 3.4%VD.

You will need 3 #250 MCM XHHW conductors for the two hots and one neutral, and 1 # 4 Al XHHW for the equipment ground. All of this needs to be installed in a min 3" Sch 40 PVC conduit, assuming this is an underground run.

If this feeder can be installed as one cable, ALCAN makes a 4 wire cable with two 250 MCM and one #3/0 for the neutral and a #4 for the ground.

As you can see the neutral may be reduced, the cable manufacturer, allows for a #3/0, which is usually close. To reduce your own by pulling individual wires, more detailed calculations must be done, but the #3/0 I am sure is as small as you would want to go.

If you want to at least price a copper feeder, you can use a min of #3/0 THWN or XHHW copper cable, and a # 6 ground. This will give you a 3.1 VD.
And you will need a min of a 2 in Sch 40 PVC conduit.

If you do manage to afford copper, I hope you have some strong friends to help pull the wire. Here is where you will see why electricians get paid so well.

Hope this helps.

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