Do It Yourself: 240v from two 120v sources

[fooljoe]

The 120V adapter is so small and easy to use, why bother having a large box to use for this and risking someone taking it, etc.? Keep it simple.

This is just a hypothetical question in the case that I need an exceptionally long run to get to a 240v outlet at someone's house (a dryer outlet upstairs, e.g.) Since I already carry around the easy240 with a long cord, and it can double as a 12 awg 120v extension cord if I don't plug in the short cord, the question is could it also work as a 240v extension cord, provided I have an adapter for the male end? Of course the wire is suitable, but would passing 240v through the relay coil fry it?

I already have a 25' L6-20 extension cord, but I'm talking about the rare case where I'd need that plus another 25' or more.

[tps]

The 120V adapter is so small and easy to use, why bother having a large box to use for this and risking someone taking it, etc.? Keep it simple.

This is just a hypothetical question in the case that I need an exceptionally long run to get to a 240v outlet at someone's house (a dryer outlet upstairs, e.g.) Since I already carry around the easy240 with a long cord, and it can double as a 12 awg 120v extension cord if I don't plug in the short cord, the question is could it also work as a 240v extension cord, provided I have an adapter for the male end? Of course the wire is suitable, but would passing 240v through the relay coil fry it?

I already have a 25' L6-20 extension cord, but I'm talking about the rare case where I'd need that plus another 25' or more.

I thought about using extension cords with 120V plugs for 240V and decided against it. Even though the chance is small, someone might play with the plugs and connect a 120V device to 240V and "let the smoke out". You'd likely "let the smoke out" if you connected 240V to a 120V relay coil, especially for any length of time. I have much less problem with the 120V to 240V adapter, which allows 120V on 240V extension cords for the modified EVSE for 2 reasons: (1) 120V is less likely to fry a 240V device, if someone inadvertantly uses the extension with another device. (2) Devices with L6-20P are not so common around most homes. Other than the modified EVSE and the cords you use with it, how many devices do you have at your house which use this plug?

My recommendation: get another L6-20 extension if you think you'll need more length. I made 2 40ft 10AWG L6-20 extensions; I've only needed 1 so far, but I've got another just in case.

[Volusiano]

My recommendation: get another L6-20 extension if you think you'll need more length. I made 2 40ft 10AWG L6-20 extensions; I've only needed 1 so far, but I've got another just in case.

I agree with this. By the time you're done making an adapter to turn your Easy240 wiring into a 240V extension cord, you'll probably end up spending enough money that maybe with just a little bit more would have bought you another straight and simple 240V extension cord; instead of having to risk frying out your Easy240 relays just to save a few bucks, let alone risk safety and equipment hazard in case somebody (or yourself) do something dumb without thinking or remembering and plug in the other end of the Easy240.

I bought two 15ft and one 25ft 240 L6-20 extension cords so I have various length combinations at my disposal: 15, 25, 30, 40, or 55 ft so I can minimize unnecessary voltage drop by being able to run the shortest length combination that will reach the outlet.

[fooljoe]

Here's my finished product:

Sorry about the iphone pics. The voltmeter shows 236, I promise.

Here are its innards:


The relay on the left (relay 1) is the SPST, on the right SPDT (relay 2). The black cord on top is the L6-20 pigtail, the yellow on the left is the long cord that can double as a 120v extension cord. The indicator lamp is poking out of the lid.

The wiring:
Relay 1:
c1: small gauge (I used black 16 awg from an old extension cord) wire connected to long cord black
c2: 16awg white connected to long cord white (c1 and c2 are red QCs on top)
NO: long cord black with other end of 16awg black from c1 crimped in (yellow QC on left)
COM: L6-20 black with indicator black lead crimped in (yellow QC barely visible under red QCs)

Relay 2:
c1: 16awg black from short cord black (red QC)
c2: short cord white (blue QC)
NO: short cord black and 16awg black crimped together (clearly visible yellow QC on left)
NC: long cord white crimped with 16awg white going to relay 1 c2 (yellow QC you can't see under the NO terminal)
COM: L6-20 white with indicator red lead crimped in (yellow QC under red and blue QCs)

All three green ground wires are twisted together as well, of course.

If you don't want the 120v extension cord / long adapter option relay 2 would be the same except without NC and relay 1 would be the same except c2 would be the long cord white directly, as with relay 2 c2.)

[fooljoe]

My recommendation: get another L6-20 extension if you think you'll need more length.

Well I'm already carrying around a 25' L6-20 extension cord and a 20' 5-15 extension cord (what was left from the "short cord" on my easy240), and the easy 240 itself is effectively a 25' L6-20r to 5-15p extension cord. With all of that plus the upgraded EVSE, my trunk is getting pretty crowded, not to mention those L6-20 extension cords are fairly expensive. All these cords are the same 12/3 wire, so it's just the ends that matter. And I don't see any safety risk at all, since the female end of the easy240 is the L6-20 outlet.

I'm think I'll probably give this a try at some point. After making the easy240 I have a leftover 5-15r with a stub of cord that got chopped off one of my yellow extension cords, so all I need is an L6-20p. Plus I happen to have a relative that lives 65 miles away and has an upstairs dryer outlet. I also have an extra SPST relay after the last minute design change to use an SPDT, so if I fry a relay it's no big deal. But I'd probably take a small piece of 12awg wire with male QCs crimped on both ends to bypass the relay and connect the long cord hot to the L6-20 black wire directly if I ever did this.

[johnr]

Here's my finished product

Very good!

[tps]

I also have an extra SPST relay after the last minute design change to use an SPDT, so if I fry a relay it's no big deal. But I'd probably take a small piece of 12awg wire with male QCs crimped on both ends to bypass the relay and connect the long cord hot to the L6-20 black wire directly if I ever did this.

I could be wrong for your particular relay, but my guess is that a 120VAC relay coil will fry when connected to 240VAC. Seems like the maximum coil voltage at which many nominal 120VAC relays are designed to operate is 110% of nominal, or 132VAC. Maybe you could test it at home, first. Please let us know what happens!

[drmanny3]

Thanks to fooljoe I was able to put one of these together. I choose to go with the two extensions coming in and connecting to the relays then to the recepticle. I used the larger or double gang plastic box, but with the lamp that fooljoe proposed it was a tight fit. I tried it out and it does work. I am not sure what purpose the relays provide? Could I have just connected directly to the recepticle via the two incoming extensions? I would have mated the commons and grounds and just connected the two hots to x and y. Adding the light lets you know you have 200 + volts.
Manny

[mwalsh]

I am not sure what purpose the relays provide? Could I have just connected directly to the recepticle via the two incoming extensions? I would have mated the commons and grounds and just connected the two hots to x and y. Adding the light lets you know you have 200 + volts.
Manny

Yes, it would work the way you describe it, but you would have to be quite careful with the unit yourself and very vigilant in keeping others from messing with it - the relays stop the backfeed of 120v across the second incoming plug while the first one is plugged in.

[fooljoe]

Thanks to fooljoe I was able to put one of these together. I choose to go with the two extensions coming in and connecting to the relays then to the recepticle. I used the larger or double gang plastic box, but with the lamp that fooljoe proposed it was a tight fit. I tried it out and it does work. I am not sure what purpose the relays provide? Could I have just connected directly to the recepticle via the two incoming extensions? I would have mated the commons and grounds and just connected the two hots to x and y. Adding the light lets you know you have 200 + volts.
Manny

I'm not sure what you mean by "commons", but if you mean the neutral (white) wires from the extension cords you would not connect them like you do the grounds. You would just terminate them. But again doing it without the relays is not advised: If any device is connected to the L6-20 which bridges X and Y, then the hot prong on a detached cord would be connected to the hot on the plugged in cord. So if someone happened to unplug one of your two cords and touch the hot prong they could get shocked. The relay prevents this scenario by keeping the connection from either extension cord to the L6-20 open unless the cord is plugged in.