20 Amp E-leck-trissssss-i-T

[Barry Digman]

A bum tenant left a nice air compressor behind when he stiffed me for the rent. It has a 2hp motor rated at 18.8 amps. The plug is one of those three prongers, but if you look at it head on with the "U" shaped prong at the top, then the right blade (at the 3:00 o'clock position) is horizontal, and the left blade (at the 9:00 o'clock position) is vertical. I have a receptacle at home that is the same horizontal/vertical configuration except the right and left are oriented to the reverse.

Why the different configurations, and how to plug this shiny compressor in to test it out?

An associate told me to just take a pair of vice grips and twist the horizontal blade into the vertical position. Uh, can you say "Darwin Award Winner..."

[ September 01, 2006, 04:17 PM: Message edited by: coyote ]

[xC0000005]

Without seeing it it's hard to say for sure but I can answer some of your question -
There are a number of different plug configurations, most with a few simple goals. The oldest plugs have a single round hole the size and shape of the ground prong on most appliances. One prong? That doesn't work. Well, yes, it does. These plugs are almost always located near a window and a quick glance outside will fill in how they work.

Next up we have two pole sockets (the ancient predecessor to )dual blade sockets. These have one hot wire in 110. So far, so good, right?

Move along to ground blade recepticals, which look just like a two blad receptical but with an odd slot at the top of the electrical fixture. I've only seen one of these ever. I replaced it. Functionally it is no different than a two blade and prong grounded plug (except that it was for grounds that ran separate).

Moving on from there you have a variety of plugs intended to imply heavier amps are available - these have a normal blade on one side and a right angle or flat blade on the other side. That's usually for higher amp sockets (like 20 amp, but don't quote me, it's been a while since I re-wired the house).

Moving into the 220 range you have a whole host of 220 configurations where the blades are at an angle. The designs for these are intended to prevent them from fitting into each other (there may be an amp based guide to which one you should use) and to help hold the prongs in the socket. My guess would be that this is a higher amperage plug, but I'd have to see it. If it's 220 the problem is solved right there.

Maybe some electricians in here?

[Barry]

Sounds like it's wired for 220 Barry.

[iddee]

It is 220 volt, 1 phase. If you want to keep it and use it, buy you a plug. If you just want to test it before you sell it, cut the U off and turn it over. It will run fine. It is not safe to run it all the time like that because it is not grounded.
If you do it that way, cut the plug off after testing so the new owner has to buy a new plug.
Ever hear "do as I say, not as I do?

If I were doing it, I would run two jumper wires from the flats and poke them into the wall to see if it would run. Of course, I'm an electrician and am used to getting shocked. tongue.gif :rolleyes:

[ September 01, 2006, 05:24 PM: Message edited by: iddee ]

[xC0000005]

Good to hear from someone who knows for sure. smile.gif

[Barry Digman]

Ah, 220 volt, 1 phase it is. I'll have the electrician install a receptacle for me in my little worky shop. The wonderful part is that I don't have any tools that need that much volume or pressure, so I'll have to go get some. Right? No sense in wasting all that air. (No, really, dear, I NEED these....)Thanks guys.

[Sundance]

Sounds like 220 but they do make twist
and lock 110V fittings.

[power napper]

If you are fortunate enough to have an old fashioned hardware store nearby stop and visit. These guys can guide you down the proper path.
We just take the plug and shove it into a piece of the insulation board that is covered with foil--the footprint is exact and the hardware will be able to fix you up with the right receptical!

[iddee]

Sundance, the 110 twist locks are half-moons with locking tabs, not straight, flat clubfeet.

[Sundance]

ahhhhhh tanks Iddee

[Jim Fischer]

Wait a sec... what does the compressor NAMEPLATE say
about Volts, Amps, Watts, and Phases?

18 Amps at 220 volts would be a SERIOUS amount of power,
18 * 220 = 3,960 watts. This would be enough energy
with which to weld! For a compressor, I could
understand 18 amps at 120 volts, as the intial
inrush start-up current to overcome starting tourque
for the compressor could drawn down
18 * 120 = 2,160 watts with ease (recall that a mere
blow-dryer can draw from 1000 watts to 1500 watts).

I've seem many kludged configurations, where the "wrong"
plug was spliced onto a power cable simply to allow the
device to be used with an existing socket, or (even worse)
both plug and socket are "wrong", and were purchased
simply because they were "in stock" or "cheaper" at
the hardware store.

PAY NO ATTENTION TO THE PLUG
PAY CAREFUL ATTENTION TO THE NAMEPLATE INFORMATION

I got my EE ticket punched in the 1970s, and had a Master
Electrican's License in the 1980s. As such, I still have to wet
my fingers to be able to detect 120 Vac smile.gif

[iddee]

>>Ah, 220 volt, 1 phase it is. << coyote

Jim,
I think the above was stated from the label.

The new 2 hp. compressers are chinese motors and only start on 220. The capacitor then kicks out and the motor runs on 110. That is why the high amps. It is for starting only. It runs on >9 amps, including heat loss.

[Barry Digman]

"Wait a sec... what does the compressor NAMEPLATE say
about Volts, Amps, Watts, and Phases?"

When I find the keys to get back in my shop I'll take a picture of it and post it. I remember that there were two numbers for the volts and amps. 220/110 and (I belive) 18.something and 9.something. I don't recall which order they were in. I do know it was 2hp and single phase.

Hey, for Jim and iddee and you electrician types....
I had to have another building wired after the meth heads tied onto the conduit and ripped all the copper wire out, along with the water and gas lines. I think the guy who did it was a true craftsman, and just had to take photos of his work. I know, pictures of an electric panel are kinda wierd, but I was impressed by his dedication to getting everything right rather than just stuffing wires in. See what ya think...

http://s29.photobucket.com/albums/c285/barrydigman/Electric%20panel/


Ok, I added shots of the compressor, the nameplate, and the plug. It says 115/230 and 18.8/9.4, not 220/110. Now do you see why they don't let me handle forks around the toaster?

[ September 02, 2006, 06:55 PM: Message edited by: coyote ]

[iddee]

If he did it for a contract price, he did a heckuva beautiful job. If he did it by the hour, WELL!!!!!

The 220/110...18/9 amps means it uses <9 amps when the motor is wired for 220 volts, and it uses <18 amps when it is wired for 110 volts. Now you have to check the wiring in the make-up box on the motor to see if it is wired 110 or 220. The motor is the type that can be ran on either by just switching a few wires.

[crazy hivan]

On the Name plate in lower right corner of motor it shows how internal wiring of motor should be for either 115 or 230 volts. If look at the plug in picture can see rating on face is 20 amps at 250 volt the configuration is NEMA 6-20P. Would guess is wired for 230 v. Would check wiring inside motor. A 230v induction motor plugged into 115v will get fried quick.

Stu