Your setup will work as you describe. The Nec prohibits using a 20 amp
receptacle on a 30 amp circuit.
Provided that the motor has built in overcurrent protection, I would install
a 30 amp dryer cord set directly on the compressor
I'm suspecting that out of all these replies, NONE are correct. What i
suspect is that you have a 20a plug on a 120V compressor and you just
don't have any 20a 120v outlets in your house. Better look a little
closer at everything before you feed that unit 240v.
remove the "not" from my address to email
When you're dealing with amateurs, there are many ifs. With the similarities
between nema 20 amp 120 and 240 devices, it's difficult to determine what he
bought, or thought he bought, however as the string progressed, it became
clear that he does indeed have a 240 volt machine. Had you followed the
progression, you may have noticed this as well.
blare is crosswise, not 2 - right? That COULD BE a NEMA 5-20 plug. oR
IT COULD BE A 6-20.
BOTH crosswise would be a 6-15.
WHEN YOU HOLD THE PLUG WITH THE PINS FACING YOU AND THE "U" GROUND
DOWN, WHICH SIDE HAS THE "ROTATED" BLADE??
Rotated blade on the right os a 5-20 - 115 volt 20 amp. (nominal)
Rotated blade on the left is a 6-20 - 230 volt 20 amp (nominal).
If it is a Nema 6-20, go ahead you are OK (and I think you DID say it
was a 6-20R that you were using - which would not let a 5-20P fit)
On Sun, 25 Jul 2010 01:04:05 -0700, Smitty Two wrote:
You know, I bought it that damn Sears Craftsman compressor on a whim in a
sale in the 80's. It was (on sale), about 350 or 400 bucks.
Then, when I brought the huge thing home, I realized I didn't have an
outlet for it, so I just let it sit for a year or so. Then I moved, and
didn't have an outlet for it, so I let it sit for a few years. Finally I
moved to a place that had the outlet, and I used it every six months or so
to blow up the kids toys. I moved again, and guess what, no outlet.
Funny thing is that I've seen Sears compressors on sale over and over and
over and over again for, guess what, just about 350 or 400 bucks. They
never changed prices in decades. Amazing.
In hind sight, I never should have bought it as I barely used it due to the
cord and the lack of needs.
However, I still have it. And I actually want to blow up a kids toy and
then figured I'd plug the NEMA 6-20P into an adaptor consisting of a NEMA
6-20R and a NEMA10-30P and then connect to the NEMA10-30R fused by a 30-amp
circuit for my 20-amp compressor.
I was just asking advice, specifically:
a) How do I know that I'm NOT on a sub panel?
b) Did I pick the correct ground/neutral?
Is there anything else I didn't think of (before I plug it in)?
On Sun, 25 Jul 2010 10:08:51 -0400, Ed Pawlowski wrote:
I just googled my 30-year-old Sears Craftsman model 919.176940 and, as
expected, couldn't find it for sale new anymore to check the prices.
But, used, it's 60 bucks!
Because of this NEMA 6-20P plug, I've almost never used the 350 or 400
dollar compressor that I bought "because it was on sale" thirty years ago
when I was just a kid.
It looks like I can still get parts for it at
But no manual for the 20-gallon 125psi air compressor seems to exist on the
On Sun, 25 Jul 2010 08:35:44 -0500, Steve Barker wrote:
I do appreciate the double check (as that's what this thread is all
Check twice, plug in once! :)
You show what appears to be a NEMA 5-20P; I have the NEMA 6-20P. The
difference is (looking at the plug head on with the ground up), my sidewise
blade is on the right whereas that plug's sidewise blade is on the left.
I've had the compressor for 30 years and barely used it because of this
damn plug. If I can give any advice to a young 30 year old kid buying his
first compressor, it would be to get a 110V smaller one!
BTW, the plate on the wheeled tank says:
Sears Craftsman model 919.176940 240 volts 15 amps
Here's a better comparison, scroll down to the 20a section. It seems it
could be a 120v OR a 240v depending on which side the sideways blade is on.
remove the "not" from my address to email
On Sun, 25 Jul 2010 08:38:16 -0500, Steve Barker wrote:
I like YOUR reference better than mine:
Because yours answers one of my questions, which is to doublecheck which is
the green ground wire in the NEMA 6-20P (g) to mate with the white
ground/neutral in the NEMA 10-30R (w) via the NEMA 6-20R-to-NEMA 10-30P
Your chart has little W's and G's and "X" and "Y" for the hot black wires.
I presume the "w" stands for white, does it not?
Jesus Christ, with all this advice you will be lucky if you don't burn
the house down and put the lights out in the whole neighborhood. Just
go to Home Depot and get a receptacle that fits the plug. Turn off the
breakers and remove the old 30 amp receptacle and install the new 20 amp
one. The "hot" wires go on the outside screws they should be colored
and the ground/neutral on the middle one white if it was done correctly,
might be bare if someone took a short cut. Flip the breakers back on
and there should be 115 volts between each of the outside holes to
neutral/ground holes and 220 volts from outside hole to outside hole.
Plug the thing in and turn it on and get that basket ball aired up.
Working air compressors are just real handy to have around, I use
mine for lots of things, great for blowing out a dusty old computer,
adjusting the pressure in the car tires, gobs of uses.
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