Connecting A Portable Generator To Your Home
July 28, 2006
Q: I need a 25ft. 220v extension cord for my generator. Outlet on generator is 120/240v, four plug adaptor? Opposite end will be a dryer type plug. Need to know what type of plugs and wire to purchase, and where to purchase, so I am able to make the cord.
A: You CANNOT do this. It sounds to me like you are going to backfeed into your dryer receptacle to provide limited power to your home during an emergency. This is illegal, unsafe and will end up killing someone.
This is a National Electrical Code (NEC) violation. NEC article 406.6(B) states “Connection of Attachment Plugs. Attachment plugs shall be installed so that their prongs, blades or pins are not energized unless inserted into an energized receptacle. No receptacle shall be installed so as to require the insertion of an energized attachment plug as its source of supply.”
This is unsafe because the dryer type plug end of the cord that you want to make will have live prongs or blades with either 20 or 30 amps at 240 volts. This will easily electrocute and kill someone.
You need to install some type of transfer switch so power can’t backfeed into the utility lines and kill the utility personal trying to repair your electricity.
I would install either an automatic or a manual transfer switch with a flanged inlet locking receptacle under or in the transfer switch. Some transfer switches come with this built-in. The manual transfer switch is approximately $200.00 verses an automatic transfer switch at approximately $400.00. Now, you can make an extension cord to feed this receptacle and have a safe and legal installation.
You need to look at the receptacle on your generator to determine what it is. This is probably either a 20 or 30 amp twist-loc receptacle. The receptacle should have a NEMA configuration number on it. If it is a 5,000 watt generator it is probably a 20 amp receptacle and the number will be L14-20R. For this application you need a L14-20P locking plug (Leviton catalog #2411) with #12 AWG SJ cord and L14-20R locking connector (Leviton catalog #2413). The flanged inlet locking receptacle is a Leviton catalog #2415.
If it is a 7,500 watt generator it is probably a 30 amp receptacle and the number will be L14-30R. For this application you need a L14-30P locking plug (Leviton catalog #2711) with #10 AWG SJ cord and L14-30R locking connector (Leviton catalog #2713). The flanged inlet locking receptacle is a Leviton catalog #2715.
Don’t forget to ground your generator’s frame. The first system I set up for myself like this, I installed an 8′ x 5/8″ galvanized ground rod in the ground where my generator was going to sit during an outage. I left the coil of #6 bare copper wire connected to the lug on the generator’s frame and the acorn clamp on the ground rod. When we had an outage, I would roll up the generator, connect the ground wire and start the generator. Then I would connect my cord from the generator to the transfer switch and change the transfer switch from utility power to generator power and I was up and running again.
After doing this a few times, I elected to get one of Generac’s generators with the automatic transfer switch. I really like this because when the power goes out, within 1 minute my generator is running and power has been automatically transfered.
Here is a website where you can get everything that you need. I have never used these guys before, but the have exactly what you need. http://www.nbmc.com/emergen/
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