Sign In to join the community | Help

Extension cord gauge needed for 240 volt service

I have a 4000 watt generator with a 240 volt outlet on a 15 amp breaker. I want to use it in emergencies to power a 240 volt heater that pulls 12.5 amps. For a 25 foot extension cord, what gauge do I need? What letters should I look for on the cord if the gererator will be outside and the heater inside the house? If I want a 50 foot cord, would I need a heavier gauge?
Not what you were looking for ? Try posting a question
Posted 2018-12-04T19:54:24+0000  by Retiree Retiree
Hello Retiree.  Welcome to the Community!

You will want to find a 12 gauge outdoor rated extension cord which has 240 volt, 15 amp plugs.  Ideally the cord should be marked SJOOW, and be rubber coated.  Whether you use a 25 footer or a 50, I would still go with 12 gauge.


Posted 2018-12-04T20:36:48+0000  by Chris_HD_CHI
I would agree with Chris, go with a 12 gauge cord.  As long as the packaging says outdoor, then you'll be fine.  If you are making your own cord, then the only letter designation that really matters for you is W (weather resistant).  There will likely be S (service, 600 volts) or SJ (service junior, 300 volts), an O or OO (for varying degrees of oil resistance), and maybe a E (flexible jacket in low temps).
Posted 2018-12-04T21:43:26+0000  by Adam444
Not what you were looking for ? Try posting a question