Compressor wiring

My guess, based on my limited experience, is that your compressor wires to black, red (to black and red) ground to the third screw. The white neutral is not used.

Dryer plug and socket should work fine. Old style, three conductor. Of course, you can wire in a disconnect switch if you wish.

The reason they went with four wires, is to provide a neutral for 120 volt timer and drum motors, used in some dryers.

. Christ> I have a new 5 horse 80 gallon upright ingersol

rand compressor. I need to wire it up. My outlet I wired years ago in hopes of having a new compressor I ran 4 conductor cable. red,black,white, and ground. My compressor has connections inside the pressure switch but only three. Red and black I understand, however do I put the white neutral on the third spot in the switch or do I put the ground there? This is in my detached garage with a 100 amp sub panel.

Just want to make sure it is right.

Idea and I need a disconnect with the wire from it to the compressor in armor shield?

o wire it up. My outlet I wired years ago in hopes of having a new compress or I ran 4 conductor cable. red,black,white, and ground. My compressor has connections inside the pressure switch but only three. Red and black I unde rstand, however do I put the white neutral on the third spot in the switch or do I put the ground there? This is in my detached garage with a 100 amp sub panel. Just want to make sure it is right.

ct with the wire from it to the compressor in armor shield?

On Wed, 4 Sep 2013 08:07:54 -0700 (PDT), stryped wrote (with a distinct lack of Line Wrap...):

For starters, check the spec sheet and make sure a 30A 240V circuit is what the new compressor wants, it should be. And that you have 10-3 Romex and a 30A breaker.

Do NOT go any larger on the breaker than the compressor nameplate says, if the motor stalls or fails to start (which happens when the check valve leaks) you want the breaker to pop before the motor releases it's Magic Smoke.

A dryer cord is fine - You don't have to use any armor or conduit if it isn't a commercial shop install, or exposed to unusual hazards. And if you do choose to use conduit, the plastic Non Metallic Liquidtight is plenty - run a separate ground wire.

An industrial shop has a whole different set of rules. You'd need a lockable fused safety switch for openers, lockable safety valves with vents on all the shop air lines going out so you can turn off the air to the shop, and a wall full of warning signs for ear protection, eye protection, crushing hazards, "Equipment may start at any time"... Fuhgeddaboudit.

You should put up the newer 4-pin dryer outlet if you have the 4 wires there - all new installs you have to keep the Ground and Neutral separate, since the dryer timers and interior light are 120V and you can't hook that load to the Safety Ground anymore. (You can't use the "Grandfathered" excuse for a 3-pin receptacle on a house built after the rules change.) Hook up all four pins now, and cover it up forever.

Get a factory made 3' 4-pin dryer cord, or a 6' cord if the outlet isn't right where it needs to be. And you do need some sort of a strain relief at the compressor pressure switch, if it doesn't come with one you need to put a knockout style cord clamp on the box.

If the cord has spade lugs, they should slide right into the pressure switch Line Lugs. And you just cap off or tape off the Neutral wire inside the pressure switch enclosure.

Be careful with wire routing, there isn't a lot of room in those switches so fold neatly - If you cram the wires where they cross over each other and smoosh the cover on top, eventually you'll have a short circuit.

(Do NOT cut off the lug if you don't absolutely have to, you might reuse the cord on a real dryer and need it. Tape and tuck away.)

Bonus: The cord is also a Safety Switch - Unplug it before you start changing the oil in the compressor or tensioning the belt, and there's no way it can start on you.

(Unless a Total Moron is in the vicinity, but that applies to all safety steps you can take...)

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I wired years ago in hopes of having a new compressor I ran 4 conductor cable. red,black,white, and ground. My compressor has connections inside the pressure switch but only three. Red and black I understand, however do I put the white neutral on the third spot in the switch or do I put the ground there? This is in my detached garage with a 100 amp sub panel. Just want to make sure it is right.

Is your motor single phase or 3 phase? Is your electrical service single phase or 3 phase? The web shows compressors in both 1 and 3 phase and several voltages.

(experience has shown that mixing requirements and service is usually not effective :-)

5hp is generally 240 single phase. Anything bigger is GENERALLY 3 phase.

And since the switch has only a red and a black connection it is almost CERTAINLY single phase 240.

Well, I looked on the web and that model seems to be sold with a

230VAC, 1 phase or 200VAC 3 phase or 230VAC 3 phase or 460VAC 3 phase motor - see

I once connected 440 VAC three phase to a two wire and neutral wiring system which rather convinced me that it was probably a good idea to be sure of what I was doing before I switched on next time :-)

He should hire an "electrician".

i

Yes, but....