Wire size for 250' to garage?????

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I am trying to find out the wire sizes needed for a 250' underground feeder from the main panel, to a sub panel in the garage. I would like a 220, 50 or 60 amp service. What type wire would be the least expensive/
Thanks, cliff
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At that distance, for the neutral and the two hot conductors, minimum of 6AWG copper for 50A or 4AWG copper for 60A, and for the ground, minimum of 8AWG copper at either 50A or 60A.
Grounding requirements are different in subpanels. You must make sure that: - the subpanel has two separate bars for ground and neutral - the two bars are NOT connected to each other (they ARE in the main) - the neutral bar is insulated from the panel chassis - the ground bar is NOT insulated from the panel chassis
You may also need a separate ground rod at the garage; check with your local building inspector.

You'll need to make a few phone calls to find that out.
--
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Doug Miller (alphageek at milmac dot com)
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wrote:

There will be a trade-off: more investment in copper will result in reduced resistive loss in line over time.
J
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snipped-for-privacy@aol.com wrote:

There are two issues here for wire size: 1) Minimum code required size for the current, regardless of length. That would be 8AWG for copper and 6AWG for Aluminum, for either 50 or 60A.
2) Acceptable voltage drop at maximum current for that length: My old 1990 NEC does not specify, but only recommends a voltage drop percentage of 3% for the feeder or 5% including the branch circuit. This would be based on the actual load, not the subpanel rating. Also, if you will always have a balanced load, you can compute it based on percentage of 240 V, and you may be able to get away with a lesser wire for the neutral, if you may have a way unbalanced load, you would have to compute it based on a percentage of 120 V. Here is a bit of data:
AWG ohms/500' V drop @ 50A % of 240V 6 Cu .25 12.5 5.2 4 Cu .154 7.7 3.2 2 Cu .1 5.0 2.1
6 Al .404 20.2 8.4 4 Al .254 12.7 5.3 2 Al .16 8.0 3.3 1 Al .13 6.3 2.6%
You may find Aluminum to be cheaper for those wire sizes even though you need a larger size for Al.
If you need to ask these questions, you probably should be talking to you local building inspector because there are many other code issues to do this right.
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M Q wrote:

Possible typo: #8 Cu won't do it for a 60 Amp feeder.
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Speedy Jim wrote:

...
Oops -- thanks for catching that. I was looking at the table on the wrong side of the page. For underground UF, #8 Cu will only do 40 A.
#6 Cu 55 A #4 Cu 70 A
#4 Al 55 A #3 Al 65 A
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wrote:

Are you up on NEC?????
First, your amp ratings do not account for voltage drop at 250'.
Secondly, if you are suggesting that he use UF for a service entrance, read NEC 340.12 (it shall not be used as a service entrance cable)
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wrote:

Are you?????

A feeder to a garage is not a service entrance as defined in the NEC.
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Doug Miller (alphageek at milmac dot com)
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read
Where's this stated in the NEC2005?
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kjpro @ usenet.com wrote:

In the "definitions" section at the beginning:
Service: The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
If the garage is being fed from the main panel, then by definition that feed is not a "service".
Chris
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wrote:

Article 100, Definitions
"Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served."
"Feeder. All circuit conductors between the service equipment ... and the final branch circuit overcurrent device."
What the OP has is a feeder, not a service.
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Doug Miller (alphageek at milmac dot com)
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the
Two examples...
#1 HV lines to transformer, trans to house meter, meter to panel, panel to garage.
#2 HV lines to transformer, trans to meter on pedestal, meter to distribution panel on ped, d-panel to house - d-panel to garage.
Using the two examples, please list the feeders and service conductors for each.
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wrote:

Which is the situation the OP has.
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to
So, for clarification, Ex #2 as posted earlier...
#2 HV lines to transformer, trans to meter on pedestal, meter to distribution panel on ped, d-panel to house - d-panel to garage.
Can you run UF from the d-panel to a house/garage?
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wrote:

Not relevant.
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Doug Miller (alphageek at milmac dot com)
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panel
It's a question, so yes, it *is* relevant.
So, for clarification, Ex #2 as posted earlier...
#2 HV lines to transformer, trans to meter on pedestal, meter to distribution panel on ped, d-panel to house - d-panel to garage.
Can you run UF from the d-panel to a house/garage?
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wrote:

It's not relevant to the question raised by the OP.
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Doug Miller (alphageek at milmac dot com)
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Ok, just admit you *can't* or don't *want* to answer the question.
Third times a charm...
So, for clarification, Ex #2 as posted earlier...
#2 HV lines to transformer, trans to meter on pedestal, meter to distribution panel on ped, d-panel to house - d-panel to garage.
Can you run UF from the d-panel to a house/garage?
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wrote:

It's not relevant. Go away.
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Doug Miller (alphageek at milmac dot com)
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panel,
Ok, so you *can't* or don't *want* to answer the question.
That's just what I thought... all mouth and no answers.
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