Advice for converting Sears Craftsman 220V compressor plug to washing machine plug

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I just want advice for the conversion I just did before I plug it all in.
Details: 1. I have a two-phase 220V Sears Craftsman compressor which uses a 220 volt plug with one blade sideways (otherwise it looks like a normal 120V grounded plug).
2. I have no sockets in the house which fit that 220 volt plug.
3. I have a three-pronged dryer socket in the garage with 220 volts (two hots and a neutral).
4. I just attached a new 3-pronged male dryer cord to a female 220 volt plug with the one blade sideways.
Before I plug in the compressor to the recepticle to the dryer cord to the recepticle, would you have any concerns about safety or other?
I assumed the neutral in the compressor plug was the center wire (looks like a ground pin) while I assumed the neutral on the 3-pronged dryer cord is the L-shaped center pin. Is that the correct assumption for the shared neutral?
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On Jul 25, 2:06 am, Elmo <dcdraftwo...@Use-Author-Supplied- Address.invalid> wrote:

Ummm yeah... Why would you want to plug a 20 amp 240 volt appliance which uses a NEMA 6-20 cord configuration into a 30 amp outlet made for a NEMA 10-30 cord configuration by means of using a cord adapter which you have created yourself...
There is a reason why the outlets for vastly different amperage ratings do not fit into each other... SAFETY...
Why not have a correct 20 amp 240 volt NEMA 6-20 outlet installed in your home so you can use your compressor safely on a circuit which is not capable of supplying more power than your appliance is rated for which could damage it or cause an accident of some kind...
~~ Evan
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Evan wrote:

Nonsense. I have a lamp here which states not to use more than a 100 watt bulb, and uses an 18 gauge cord.
It plugs into a 15A receptacle, fed by a 14 gauge wire.
All of this is perfectly to code.
Jon
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On 7/25/2010 8:41 AM, Jon Danniken wrote:

I don't believe you will find a code reference that allows what the OP described since your example doesn't scale.
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On Sun, 25 Jul 2010 09:11:57 -0400, George wrote:

I wondered about that. Does the "code" cover temperary adapters?
Doesn't the code only apply to the wiring in the walls?
This is an adapter, which is not permanently connected.
And, the wiring is the same, either way, as far as I can tell. The only ground/neutral difference I see is the NEMA 6-20P ground for the compressor is connected to the NEMA 10-30R ground/neutral for the dryer. But isn't that dryer neutral connected directly to ground anyway at the panel on the other side of the wall?
And, the 20-amp rating for the compressor is connected to a 30-amp breaker instead of a 20-amp breaker. But, that will still protect the wiring in the wall from 30 amp surges (it just won't protect the compressor).
Right?
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snipped-for-privacy@Use-Author-Supplied-Address.invalid (Elmo) writes:
| I wondered about that. Does the "code" cover temperary adapters?
That's an interesting question. I've noticed that marine stores sell a lot of twist-lock adapters and the "odd" configurations (like 30A male with 15A female) are not UL listed (or say something like "made with UL-listed parts) while the matched amperage ones have the UL hologram. So maybe the answer is that UL covers this, but nothing stops people from selling, buying, and using adapters that UL won't list.
                Dan Lanciani                 ddl@danlan.*com
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On 25 Jul 2010 21:11:18 GMT, ddl@danlan.*com (Dan Lanciani) wrote:

Why would the lack of a UL rating stop people from selling something? UL isn't the government.
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On 7/25/2010 15:00, snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

UL isn't a government agency, but some jurisdictions may require electrical products to be listed by UL or similar organization in order to be sold there.
The UL listing only means that the product is deemed safe *for its intended purpose.* A listed 18-gauge extension code is safe when run along a wall for a table lamp, while it can be a fire hazard if run under a carpet to power an air conditioner and microwave oven.
--


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Citation please.

Sure, but it is nothing more.
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On Sun, 25 Jul 2010 00:36:55 -0700 (PDT), Evan wrote: On Sun, 25 Jul 2010 00:36:55 -0700 (PDT), Evan wrote:

I agree with Evan, the right way to power the compressor with the NEMA 6-20P plug (20amp rating), is to hire an electrician to add a dedicated 220V NEMA 6-20R receptacle with a 30 amp dedicated circuit breaker.
Or to have that electrician swap out the existing NEMA 6-20R with a NEMA 6-20R and to swap out the 30 amp breaker with one with only a 20 amp rating.
However, the cost of hiring the electrician to change the circuit is more than that of buying a new compressor with, say, standard 110 volt power.
I use the compressor maybe once every six months. Unknowns in the adapter setup are what I'm asking about here.
The unknowns to overcome by asking this post are: a) How do I test if the NEMA10-30R is on a sub panel or not? b) Did I select the right pin ground in the NEMA 6-20R receptacle as the L-shaped neutral in the NEMA10-30P plug?
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On Sun, 25 Jul 2010 00:36:55 -0700 (PDT), Evan

Evan - sorry but your ignorance is showing. Virtually every item you plug into a 15 or 20 amp 115 volt receptacle in your home is rated MUCH below the 15 or 20 amps the receptacle is rated at, and the breaker is designed for. It is NOT a safety issue. Your computer draws something like 2 amps, the monitor 1/2 amp, a 100 watt light bult less than an amp, your fancy little transistor table radio about 250 milliamps.
The "right" way to do it would be a "fused adapter" with a 30 amp plug that fits the dryier receptacle, and a 20 amp receptacle to fit the compressor plug, with a 20 amp fuse or breaker between the two. This would protect the wiring to the compressor motor - which, in all likelihood, already has a thermal shutdown protection device built into it - making the fused adapter redundant anyways.
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On Jul 25, 1:12 pm, snipped-for-privacy@snyder.on.ca wrote:

Umm... No... It is not ignorance... The CONVENIENCE outlets in your home are designed for that purpose...
When you are talking about dedicated circuits for non-convenience loads your logic about that is faulty...
If it isn't designed to fit into that outlet it shouldn't be used with it...
~~ Evan
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On Sun, 25 Jul 2010 06:06:44 +0000 (UTC), Elmo

Huh?
Instead of assuming such things, why not get a meter that measures resistance and figure out whicih wire goes to which prong in each cord? Hint: There is no neutral in a 220 volt appliance or its cord. Two wires will be hot relative to ground and the ground wire should not be connected to the other two.
Also get a meter that goes up to 250 VAC and measure the voltage at all three slots of the receptacle, relative to ground. Then you'll know which 2 slos are hot, and which two prongs of the cord will be hot, when connected to the appliance, and which need to be connected to each other electrically (in the appliance).
This is not to say I think the project is a good idea. No comment on that.
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On Sun, 25 Jul 2010 03:51:43 -0400, mm wrote:

I did use the Fluke DMM to measure the connections; I was just double checking which was the ground/neutral because I didn't wire the house in the first place.
The ground in the two-phase 220v compressor NEMA 6-20P plug should be the center pin and the ground/neutral in the NEMA10-30R dryer receptacle should be the L-shaped center prong.
The two questions I would like to ask here are: a) How do I know if the NEMA10-30R is on a sub panel (it's inches from the main panel on the other side of the wall outside the garage)? b) Are my tests correct that the ground on the 20-amp NEMA 6-20P plug is "equivalent" to the ground/neutral on the 30-amp NEMA10-30R receptacle?
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On Sun, 25 Jul 2010 13:27:42 +0000 (UTC), Elmo

You are right and safe. Use it.
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On Sun, 25 Jul 2010 13:27:42 +0000 (UTC), Elmo

Okay. Good. I jumped to the conclusion that you hadn't.

You keep using "ground/neutral" wrt the receptacle. I think you mean ground. The neutral is one of the two main slots in a *110* volt receptacle. It carries full current when something is using the recept. But it's voltage wrt ground is zero. But that's not the same as being a ground. It's a neutral.
OTOH, in *220*, two of the wires are hot though at different potentials wrt ground. Only the ground is without voltage, but if you call it neutral, I'm pretty sure you will confuse some people, or their reply to you will confuse you, and that could lead to a mistake.
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On Tue, 27 Jul 2010 15:03:51 -0400, mm wrote:

You are correct sir!
I only belatedly, half way through this thread, realized that the green ground wire on the 240 volt compressor was connecting to the white ground wire of the 240 volt dryer receptacle.
If a DRYER were hooked up, then that white third wire in the dryer receptacle would be doing double duty as a ground (for the 240 volt circuitry of the dryer) and neutral (for the 120 volt circuitry of the dryer).
But, I learned in this thread, that the dryer receptacle in the wall has its white ground/neutral wire hooked to ground in the panel. So, even though that white wire does double duty (when a dryer is hooked up), for the compressor, I'm hooking ground to ground so there is no additional danger because current is not being carried in this ground wire.
Thanks for all your help. The compressor worked flawlessly when I hooked it up. I only got one comment on the pictures of the adapter so I'd appreciate if anyone could tell me how to improve it.
A picture of the adapter cord and compressor is here:
http://img534.imageshack.us/i/006ary.jpg/
http://img153.imageshack.us/i/005tqn.jpg/
http://img714.imageshack.us/i/004wtt.jpg/
http://img525.imageshack.us/i/003zpn.jpg/
http://img809.imageshack.us/i/007pet.jpg/
http://img828.imageshack.us/i/002nd.jpg/
http://img265.imageshack.us/i/001aaz.jpg/
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"Elmo" wrote in message

I've seen thousands of dollars of damage done from people replacing plugs and not realizing what they are doing....
Have the proper outlet, wiring, and circuit breaker installed!
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On Sun, 25 Jul 2010 05:33:00 -0700, Bill wrote:

Let's look at this from a "safety" standpoint, which is your point.
The "proper" way to do this, all will agree, is to spend more than the compressor is worth to install a 20-amp dedicated NEMA 6-20R receptacle.
However, from a safety standpoint, if anyone can show me how plugging the 20-amp NEMA 6-20P through an adapter to the 30-amp NEMA10-30P receptacle is inherently more dangerous, then I'll listen.
Of course, I do realize that the "equipment" won't be protected to 20 amps (it will be protected to 30 amps); but I'm not at all worried about the 30-year old compressor burning up.
The "house" wiring is still protected to 30 amps, which is what matters.
And "safety" is the same (as far as I can tell) since we're using exactly the same two hots and the same ground/neutral.
Or did I miss something critical in that analysis? Advice always welcome.
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Elmo wrote: ...

Assuming the adapter is compliant it isn't...

The compressor motor will have it's own overload protection.

That's all the circuit breakers protect against for anything plugged into them; there's no difference in the case of the dryer being plugged into the outlet as the compressor; the internal dryer motor isn't a 30A device by any stretch, either.

Correct, and in fact w/ the compressor being a 240V load only, there is no need for and no neutral current. The shared conductor is serving only the ground function at that time, just as would the third conductor in a 20A plug connection.

No...the others are simply incorrect in understanding of Code and perhaps even function of three-wire dryer circuit...
--
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