Upsizing wire run to generator inlet ?


Old 05-10-16, 09:38 AM
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Upsizing wire run to generator inlet ?

From the Transfer Switch out, it's approx 125-140 run between the inlet + cordage of the generator.

I was thinking about upsizing the wire to 8 AWG. However, the transfer switch *reliance 10 breaker*, has #10 wire feeding their bus bar.

Will I still get the benefit of using 8 wire, or will it need to be 8 Wire from Gen - all the way back to the bus bar
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Old 05-10-16, 10:11 AM
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You will get the reduced resistance/voltage drop by running larger wire but if your wire is sized properly to begin with the reduction might not be noticeable.
Old 05-10-16, 10:23 AM
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I'm not clear.
Is V drop mitigated with any larger wire in the run, or does it need to be ~larger~ from point a- b. Meaning the entire run from the generator back the wire that connects the bus bar on the transfer switch.

That's where I'm seeking clarity.

Hell, even reliance said, that my inlet cord could be 10 wire, and the long length run from the inlet to the switch can be my 8, and the small wire from that to the bus bar is 10 already, they we're saying I will still see benefit if it's a longer run.

I was the impression that it needed to be from ~endpoint to endpoint~
Old 05-10-16, 10:44 AM
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Voltage drop is a function of amperage flow, wire size and wire length. Increasing the wire size WILL reduce voltage drop proportional to the length of the wire where the size has been increased.
Old 05-10-16, 12:33 PM
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This is a simple to use voltage calculator. voltage drop calculator
Old 05-10-16, 12:37 PM
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A general rule of thumb without running a formal calculation suggests that circuits greater than 100' length will see a benefit from upsizing the wire. If you want to know exactly, we need the cable length, load in amps and voltage.

You also may see some stability benefit on the generator -- small units tend to have trouble regulating engine speed when a long cord is used.
Old 05-11-16, 06:20 PM
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A short length e.g. pigtail of thinner wire used to fit the terminal hole or screw on the breaker or lug or bus bar will not impair the benefits of the fatter wire used on the long run to combat voltage drop.

The thinner wire just has to meet the "normal" size requirements for "normal" length runs such as 10 gauge copper for 30 amps.

If you really wanted to, you could figure the voltage drop over the portion of the circuit with the fatter wire and figure the voltage drop over the portion of the circuit with the thinner wire and add the numbers together.

Last edited by AllanJ; 05-11-16 at 06:50 PM.
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