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

Page 2 of 5  

On Sun, 25 Jul 2010 08:54:47 -0500, dpb wrote:

You seem to understand the situation the best.
The adapter is a standard metal box with the NEMA-6-20R and a three-inch long strain relief for the dryer cord securely attached to the metal box.
The only problem I had was the dryer cord had three brass "circles" as the connection point but the NEMA-6-20R had screws which didn't expect to be taken out to accomodate circular connections. The last few threads removing the screws "broke" something, as the screws are clearly designed to stay in.
When I removed the three screws (two brass for the black wires and one green-painted steel for the ground/neutral wire), it was hard to get them back in.
I wondered if it was the male screw or the female hole that "stripped" when these type of stay-in screws are removed. I guessed it was the female part that stripped, so I cleaned it up with an 8x20 tap and guess what.
The screws went right in.
The DESIGN of these things is amazing. What is the reason for the screws being designed not to come all the way out. And, did I compromise something by cleaning up whatever it was that strips when you do remove the screws?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elmo wrote: ...

a) So they don't get lost???? :)
b) No.
At manufacture the screws are inserted then deformed on the ends to prevent accidentally backing them out fully. The plugs aren't designed for other than wire loop around the screw so there's normally no need to remove them so it's a convenience to have the resistance. Since you had the ring terminals, what you did is fine.
I'd still suggest consideration of the conversion to a 20A circuit for a permanent solution, however, altho I'll agree the solution is safe and electrically compliant w/ Code intention.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I agree. If this is an"extra" dryer outlet in the garage I'd take consider switching it. A 20 amp breaker is only about $10. Another $10 would get you a metal box and proper 20amp outlet. The wire is already there. If it doesn't have a ground you could use the neutral as long as you mark it as ground.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
jamesgangnc wrote: ...

no, No, NO, _NO_!!!
One more time...the third wire in a 3-wire dryer circuit _IS_THE_GROUND_ wire allowed by previous NEC to double as the 120V neutral. It is not, repeat _NOT_ connected to the neutral bus.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It has to original at the service panel, where the neutral/ground conductor of the dryer cable connects to the neutral/ground buss of the panel. It cannot originate in a sub panel where you have separate neutral and ground busses

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

My mistake, it has to originate in the service panel if type SE cable is used. If a cable with an insulated neutral is used, it can originate in a sub panel, in which case the neutral/ground conductor would go to the neutral buss

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jul 25, 2:06am, Elmo <dcdraftwo...@Use-Author-Supplied- Address.invalid> wrote:

Yes, the L shaped prong is the nuetral on a 3 wire dryer. The other two are the hots. Your compressor more likely needs 2 hots and a ground. While what you are doing is not exactly by the book it will run your compressor. The safety issue is that you will be using your nuetral line for a ground and using a 30 amp circuit where a 20 amp one is called for. What you really need to do is install a dedicated 220 outlet in the location of your compressor. Have you looked at the compressor to see if it can be run on 110? Many motors have alternate wiring that allows them to run on 220 or 110.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
jamesgangnc wrote: ..

It is ground serving (per applicable Code of the time) as ground/shared neutral.

It is _exactly_ by current book for 240V service w/ the 240V load there is no need for the neutral; therefore the ground is no longer serving as a shared neutral only as ground.

No, NO, _NO_! There is no safety issue; as above the 3rd conductor in a shared utility (dryer) outlet _IS_ the ground conductor; the NEC formerly allowed it to be shared function of also serving the neutral. It is wired to the ground bus, _NOT_ the neutral.
The second misconception here is that there's some proscription against a higher-rated circuit supply a lesser-rated load--that again is simply nonsense. The 30A circuit breaker/fuse is there to protect the circuit, _NOT_ the load; the load will have its own overload protection for that purpose.
While I'll agree it's certainly a nuisance factor to have a humongous 30A dryer plug on the end of the cord for a small compressor, it is not an issue whatsoever from a safety (or Code, for that matter) standpoint.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 25 Jul 2010 05:41:59 -0700 (PDT), jamesgangnc wrote:

I agree that's the by-the-book method. However, the cost of having an electrician replace the 30-amp NEMA 10-30R with a 20-amp NEMA 6-20R is more than the cost of a compressor that runs off of 110.

I didn't realize the 30-year old Sears Craftsman compressor COULD run on 110. How would I know? (I'll try to dig up a model number and google it after this reply.)

But wouldn't the neutral line ALREADY be used as a ground in the NEMA 10-30R dryer circuit were I to plug in a dryer to that circuit?
Isn't the compressor the same as the dryer from an electrical standpoint with respect to the ground/neutral wire?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elmo wrote:

The motor will marked as dual-voltage if it can...wouldn't be too surprising but I'd stick w/ 240V as you'll need double the amps for 110V and you may well be in worse conundrum of not having a circuit w/ the ampacity to run it on 120V...

There's that turning around of the actual situation on a dryer outlet wiring again for one and the misconception regarding the point of 30A circuit protection having anything to do w/ the load plugged into the outlet. Both are simply wrong.
The third conductor is _NOT_ the neutral serving as ground, it is THE_GROUND_CONDUCTOR_ sharing service as the neutral for the 120V components in the dryer (motor/lights/timer/etc.).
For the other, the 30A breaker is there to protect the circuit wiring; it is the responsibility of the load to have the correct protection for itself internally.

For the 240V components (the heater elements) of the dryer, yes; identically. There is no 120V load on the compressor so the need for the sharing of ground/neutral disappears and is, therefore, fully compliant with current NEC for 240V loads whereas the dryer would require a four-wire connection to be compliant to current NEC. From that standpoint, the compressor is "more correct" than the intended use of the dryer on the circuit (that _was_ compliant w/ NEC of the time, of course).
Again, if the adapter you're using is compliant and well made, ignore the do-gooders' advice here--they mean well but are simply misinformed or overly cautious or just don't understand (or maybe even all of the above :) ).
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 25 Jul 2010 09:14:40 -0500, dpb wrote:

Very well stated!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not true at all. In fact the code required that this 3d wire be insulated and white. That is why it usually got run in 10-3 romex. There was an exception that allowed SE cable with a bare ground.
In part 250.60 (1993 the last cycle this was legal to install) says "except for mobile homes and recreational vehicles, shall be permitted to be grounded to the grounded circuit conductor"
The "grounded" conductor is the neutral.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 25 Jul 2010 13:44:54 +0000 (UTC), Elmo

Actually, the dryer may have an issue with today's code as it is using the "ground" as a neutral for the 110 volt lamp, motor, and timer circuits. Today's code (at least here in Ontario Canada) requires a FOUR wire plug for dryers and other 220 volt devices that use 110 volts as well.
The compressor is a straight 220 device - not requiring a neutral (which is being "faked" on the ground on a 3 wire plug)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 25 Jul 2010 05:41:59 -0700 (PDT), jamesgangnc

If it is a 20 amp 220 plug on the compressor, it would need 40 amps at 110, which is very non-standard. Assuming the 20 amp plug is already over-sized a bit, he might get away with a 30 amp 110 volt circuit - which again is definitely "non-standard" in today's residentiial wiring scheme.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elmo wrote:

Yes. Find out if your compressor expects the third terminal to be a ground; the third wire on your dryer is likely a neutral. If such is the case, you will need to install a properly grounded outlet for your compressor.
As to sharing the receptacle between a dryer and a compressor, I have done that with a welder, and to be honest, it gets old really fast. Eventually, you will want to install a dedicated circuit, and the sooner the better.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The third terminal on a three wire dryer outlet is a neutral/ground, and by code must original in the main service panel and not a sub panel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 25 Jul 2010 05:46:47 -0700, Jon Danniken wrote:

Isn't a ground for the compressor NEMA 6-20P plug the same as the neutral for the dryer NEMA 10-30R receptacle?

Actually, I should have mentioned, there is no sharing. There is no dryer on this spare receptacle in the garage. The dryer is on a separate NEMA 10-30R in the house. I do agree that unplugging a dryer once every six months to use the compressor would be a pain.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If that's the case, why don't you just replace the breaker and receptacle with a 20 amp
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elmo says the name plate says 15 amps. That tickles!
--
Christopher A. Young
Learn more about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elmo wrote:

It's a ground that shares neutral function, not vice versa...

Yes, addressed elsewhere...

In that case, the simple (and relatively inexpensive) solution would be to swap to a 20A breaker to support the proper 20A outlet style to plug the compressor in directly. There's nothing wrong w/ the wiring being _larger_ than required for the ampacity of the circuit; all it does is mean there will be even less voltage drop than otherwise would be.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.