Correct Wire sizes to be used with a generator

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  #1  
Old 09-22-05, 08:14 AM
midjack
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Correct Wire sizes to be used with a generator

I have a 5550 watt generator (4 20 amp sockets) and need to know the correct gauge wire for the extensions. I would like to find a chart showing: wire gauge, length of wire and maximum wattage for each length and gauge. I know that longer wires lose their ability to transmit current.

Kinda like this:

Gauge Length Maximum Wattage Length Maximum Wattage
12 50' 1800 (?) 100' ?
14 50' ? 100' ?


Anybody know of such a chart?

Thanks
 
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  #2  
Old 09-22-05, 09:49 AM
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Longer wires do not lose their ability to transmit current. Voltage drop increases in relation to the distance. Voltage drop is a function of the current, the distance and the wire size. You can find calculators on line by googling the term "voltage drop calculator". The longer the distance, the larger the wire size (smaller gage) needed to carry the load. Generally you look for a voltage drop of a few percent or less, but it depends on the actual load.

In your case you haven't provided enough information. How are these receptacles protected? Is each pair protected by a 20 amp circuit breaker? Does each receptacle have a single 20 amp breaker? Are all four on the same breaker? What load do you intend to run? Do you have a specific use in mind, or are you looking to understand the rules, so that you can apply them to each case as it is presented to you?
 
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Old 09-22-05, 11:41 AM
midjack
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Correct wire sizes to be used with a generator

Thanks so much for your reply.

1. Each pair is protected by a 20 amp circuit breaker so there are two circuit breakers for the four sockets.

2. Load: 110-120 volts

3. You hit the nail on the head, I'm looking to understand the rules, so that you can apply them to each case.
 
  #4  
Old 09-22-05, 12:38 PM
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Have a look at the voltage drop calculator:

http://www.electrician.com/vd_calculator.html

The voltage drop depends on the wire gauge, the load (in amps), the voltage and the wire length. Acceptable voltage drop is considered to be 5% or less. You could fudge that a little higher since a generator is for temporary emergency use only, but your appliances -- especially anything with a motor -- will run best with minimal voltage drop.

To find the correct size extension cord to reach from the generator to your refridgerator, for example, you know (or can determine) the length, load amps, and voltage. You need to then adjust the wire size so that the voltage drop is 5% or less.

EDIT: One additional point. Conductor ampacity always trumps voltage drop. If a cord says "13A" on the package, never exceed 13A even if the calculator says the voltage drop is okay.
 
  #5  
Old 09-23-05, 05:09 AM
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I suggest that you use a voltage calculator like the one ibpooks suggests, or another, and make your own chart. You could use Microsoft Excell to make the chart and it wouldn't take long at all.
 
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