# Block heater/extension cord ?'s



## JD4755

Needing to plug my truck in, and am worried about tripping the breaker.. its a 20A breaker, the heater draws 15 A. How much extension cord (12ga) can i use before i overload it? I know theres a formula for it but i cant find it. Thanks


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## BCFENCE

I plug up the truck and tractor on 20 amp , Just use regular cord, dont what it is, could be 12 or 14 gauge , thats allways worked for me , just my 2 cents,


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## Production Acres

looks like about 25' is all you can use - go to www.csgnetwork.com/wiresizecalc.html
try this link


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## Byron Seeds

It's more important to the wire size not the length. The only time that length really comes into place is for voltage drop. Low voltage will increase your current draw but won't hurt the heater. The outlet that you plug into will probably only be rated at 15 amps and what size wire attaches to that? Your cord will also be outside so the cold weather will actually increase the ampacity. You probably already have a few hundred feet of wire between the transformer and the receptacle. For heating elements you can only draw 80 percent of rated capacity, so a 20 amp circuit can only draw 15 amps.
If you have extra cord don't keep it coiled up. This generates more heat. Measure the voltage at the end of the cord and if you have 115-126volts you should be in good shape. If the ends of the cord get hot then the ends need replaced. Cords typically go bad at the ends not in the middle.

Hope this helps


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## JD4755

Thanks for all your help guys, the receptacle is on a pole not far from the transformer, and i used up to 75' of cord and it never tripped, but am using 50 feet right now. Thanks again


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## mmaddox

14 gauge wire is rated for 15 amps, 12 gauge for 20. There are lots of factors to include in figuring volt drop and capacity. As mentioned before, the plugs and sockets are often the weakest links and will show heat first as a result of the poor conductivity. Make sure you keep an eye on these, and use only first class equipments, up to and including hospital grade recepticles. Depending on the rating of your block heater, usually the largest are 1500 watts, your figures would indicate an 1800 watt unit, with good equipment and a 12 gauge cord, you should be alright with 100' of cord. That being said, the shorter the cord the better. Don't forget to make sure your grounds are good.
Also watch where the cord attaches to the heating element this is the failure is most common, a little dielectric grease is a big help there.


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