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Old 05-12-2009, 11:20 PM   #1
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220V Splitter...


Hello folks, new here on the forum, and relatively new to the world of AC power and the rules associated with it. I have a good background with rewiring cars from the ground up, but thats DC, hard to really hurt yourself with a car electrical system.

I just picked up an old craftsman 220V air compressor off craigslist, very nice piece, however, i also use a 220V dryer. THere is only one 220v plug in the garage. Obviously it would be foolish to drag the dryer out every time i need compressed air, and i wouldnt be stupid enough to try and run a compressor and the dryer at the same time. So, I need to build a splitter somehow.

I need a male 3 prong dryer cable on one end, and both a female 4 prong dryer end AND a female NEMA 6-20R connector.

I have a problem, I am renting my house, a nice little place, but I find it hard to believe the landlady would be down for adding additional outlets around the garage.

Here is a diagram of what I would LIKE to do, please critique me in any way possible as I want this to be SAFE above all else!


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Old 05-12-2009, 11:41 PM   #2
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220V Splitter...


I don't see a way to do it safely. The grounding is what gets you.

DO NOT use a drain pipe as a ground--unsafe! Copper cold water supply lines are theoretically grounded, but are not a substitute for a ground conductor that runs to the panel, so although it's "safer" than a drain pipe, don't that either.

If
there was a 4-prong dryer receptacle, I would have some suggestions which would yield the safest temporary setup possible (it would NOT meet code, but could conceivably function safely), but unless you can do something about the 3-prong receptacle in the wall, there's no way it can be safe "above all else."


Last edited by thegonagle; 05-14-2009 at 07:06 AM.
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Old 05-13-2009, 12:12 AM   #3
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220V Splitter...


Ok, so, hypothetically if it were a 3 wire dryer, no ground wire issues, then...??? ANd for the compressor, I assume the ground wire would go to the 90 degree kinked pin on the 3 wire dryer cord? Neutral? I believe?

Last edited by 68Datsun510; 05-13-2009 at 12:29 AM.
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Old 05-13-2009, 12:13 AM   #4
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220V Splitter...


BTW thank you for your input!!!
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Old 05-13-2009, 12:37 AM   #5
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220V Splitter...


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Originally Posted by 68Datsun510 View Post
Ok, so, hypothetically if it were a 3 wire dryer, no ground wire issues, then...??? ANd for the compressor, I assume the ground wire would go to the 90 degree kinked pin on the 3 wire dryer cord? Neutral? I believe?
That 3-wire dryer connection has a Neutral connection, not a Ground connection. You would still theoretically have issues with your grounding. Creating the splitter and connecting the ground prong of the 6-20R to the dryer circuit would potentially put return current on the ground of that compressor. So in the event your body happens to make a better path to ground than that neutral wire in the wall, that dryer could be using your body as that return path. This is why neutral and ground are only tied together at the service equipment (usually main circuit panel).

Your best bet is to see about replacing the 3 wire receptacle to a 4 wire. Then you could make a splitter that has a ground connection to your compressor, and a neutral and ground connection to the dryer (of course with a 4 wire plug, and cord on the dryer).
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Old 05-13-2009, 03:28 AM   #6
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220V Splitter...


This is NOT a good idea, especially in a rental property.

This is fodder for starting fires.....
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Old 05-13-2009, 03:38 AM   #7
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220V Splitter...


The harsh reality is that what you propose, while it will work, is some jackleg doo doo.

One issue is grounding. There is no ground, and grounding to a pipe is also bunk. Another issue is the 6-20R and #12 wire on the 30 A dryer circuit. The grounding issue isn't so bad because the circuit is likely dedicated. And if it runs back to a main breaker panel where the main bond is, then effectively the neutral is only a neutral when the dryer is running, and when unplugged is the same as any ground wire.

The only way to leave the circuit intact and still do this in a non-jackleg manner would be to have the capability to un-plug the dryer and plug in a fused adapter. Having both plugged in at the same time is the no-no, due to neutral current and the potential to energize the frame of your other equipment. Maybe make two adapters. One that extends the dryer receptacle to an accesible location, and another that converts the 30 A circuit into a 20 A circuit for the other equipment.
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Old 05-13-2009, 06:03 AM   #8
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220V Splitter...


Some of our more qualified members have already covered this from a 'will it work/is it safe' point of view. From a regulatory point of view, if any of our inspectors saw this, they'd make you take it out on the spot or have the power company disconnect the power to the house until you did. (We had a child killed here a few years ago in a garage with a cluster f*** wiring job, and we've had a zero tolerance policy ever since.)

Last edited by Bigplanz; 05-13-2009 at 06:20 AM.
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Old 05-13-2009, 06:17 AM   #9
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As the others have stated, this is wrong on many levels.

a) No ground exists, only a neutral.

b) You CANNOT have a 20A receptacle on a 30A circuit. Period.

c) Rental. DO NOT touch anything electrical there.
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Old 05-13-2009, 06:38 AM   #10
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220V Splitter...


This is exactly why I came here. Thanks folks for the education!
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Old 05-13-2009, 06:21 PM   #11
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So, how much do you guys think it would be to have an electrician install a 6-20 outlet in the wall right next to a 120v plug with the dryer plug directly below?

Do they install a new line from the fusebox, or do they tap off the dryer power and connect to the 110's ground?
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Old 05-13-2009, 06:44 PM   #12
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Do they install a new line from the fusebox, or do they tap off the dryer power and connect to the 110's ground?
A separate line is needed. A 20A socket and a 30A socket cannot both be connected to the same 10 gauge wire, as the possible load is 50A.

If they are on the same circuit, you have to assume they will be used at the same time.
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Old 05-13-2009, 08:37 PM   #13
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220V Splitter...


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A separate line is needed. A 20A socket and a 30A socket cannot both be connected to the same 10 gauge wire, as the possible load is 50A.

If they are on the same circuit, you have to assume they will be used at the same time.

This logic is all wrong. I mean your heart is in the right place, but the logic is wrong.

If you take that logic to its conclusion, then you can't even use duplex 15A outlets because they could put 30A of load on the 15 amp circuit.
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Old 05-13-2009, 09:09 PM   #14
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Originally Posted by Gigs View Post
This logic is all wrong. I mean your heart is in the right place, but the logic is wrong.

If you take that logic to its conclusion, then you can't even use duplex 15A outlets because they could put 30A of load on the 15 amp circuit.
I was going to post something similar, but it just easier to say I completely agree.
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Old 05-14-2009, 12:20 AM   #15
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220V Splitter...


Yeah, would NEVER attempt to run a dryer and compressor at the same time, my parents have an old sears oilless compressor and i cant even have a flood light on when its running or the breaker goes.

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