Compressor wiring

I am finally getting around to wiring the garage for 220Vac again. This time I am putting in a switch.

Do I need a fancy ($$$$) motor starting switch for a 5HP two stage compressor,or is it not needed?

Why or why not?

I'm just confused because mine has its own switch, which would seem to be specialized by being part of the pressure-sensing part, having positions "off" and "auto". It seems odd to me that your pressure-sensitive switch wouldn't also have the facility to shut it off, and even odder not to have a pressure-sensitive switch.

I would not be at all surprised to hear I'm missing something...

Ransom wrote: I'm just confused because mine has its own switch, which would seem to be specialized by being part of the pressure-sensing part, having positions "off" and "auto". It seems odd to me that your pressure-sensitive switch wouldn't also have the facility to shut it off, and even odder not to have a pressure-sensitive switch. I would not be at all surprised to hear I'm missing something...

Maybe I am!

I was under the impression that the outlet needed a switch if I couldn't reach the box, but I am basing that on hearsay.

Yes, if you want to switch 20-30 amps, 220V you need a switch that can handle it (as well as 8-10 gauge wire between panel and compressor).

Usually the breaker, and switch/pressure regulator on the compressor is enough - why do you want an additional switch?, is your panel far away from the garage? If so you might consider having a small sub-panel installed in the garage.

mlwebb wrote: Yes, if you want to switch 20-30 amps, 220V you need a switch that can handle it (as well as 8-10 gauge wire between panel and compressor). Usually the breaker, and switch/pressure regulator on the compressor is enough - why do you want an additional switch?, is your panel far away from the garage? If so you might consider having a small sub-panel installed in the garage.

I guess I don't need a switch after all, I'll just stick to the one on the compressor.

I just wired my garage for a 220V 5hp compressor, and it came with an "Off/Auto" switch on the compressor that seems to be part of the pressure cut-off. So I hard-wired that to a junction on the wall with some flexible conduit. The compressor switch was in a housing that had a hole for the strain relief. The circuit is on a dedicated 30 amp breaker. All I did was read the instruction manual

Installed...

There is no "backwards" with 220Vac, right?

No "backwards." There are 2 hot legs and one neutral leg. As long as you have those 3 wired correct, you are good.

DISCLAIMER: I AIN'T AN ELECTRICIAN.

Dr. Hess wrote: No "backwards." There are 2 hot legs and one neutral leg. As long as you have those 3 wired correct, you are good. DISCLAIMER: I AIN'T AN ELECTRICIAN.

No, you're not! In residential 220VAC, there are two hots and a ground. No neutral.

Okay, to be fair, some residential 220VAC offers two hots, a ground, AND a neutral, but that's mostly for devices that make some use of 120VAC internally, so they can use a hot leg and the neutral to create 120VAC. A compressor has no use for 120VAC, so no neutral.

3 wires?

Maybe in a stove or drier that uses 110V controls and a light maybe.

Your compressor will use just the two hots (each side giving you 110V each, together it's 220V).

You ideally should wire (and breaker) the compressor to 3X the Full Load Amperage (FLA). My 5hp IR is rated at 21.5A, so I've wired it to 60A for that start-up spike.

I also plan to use a switch like THIS ONE to remotely shut off the compressor via a wall switch.

Yup, you all got it.

It's a 50A fuse and wire that's way bigger than needed (which makes installation a super pain).

Look for me buying a HVLP someday soon.

The ten buck HVLP gun on super sale at HF is fantastic. I have like 4-5 cheap guns and that one is my favorite. It is almost too cheap to clean, but I do anyway.

Dr. Hess wrote: The ten buck HVLP gun on super sale at HF is fantastic. I have like 4-5 cheap guns and that one is my favorite. It is almost too cheap to clean, but I do anyway.

Since I eventually want to paint the truck very well, I was considering spending more to get this:

https://www.amazon.com/gp/product/B0040Y301S/ref=ox_sc_act_title_1?smid=A2L77EE7U53NWQ&psc=1

Amazon warehouse deals are great.

SkinnyG wrote: 3 wires?

Either you're not considering the ground to be a "wire", or you don't think a compressor needs a ground.

tuna55 wrote:

Dr. Hess wrote: The ten buck HVLP gun on super sale at HF is fantastic. I have like 4-5 cheap guns and that one is my favorite. It is almost too cheap to clean, but I do anyway.

Since I eventually want to paint the truck very well, I was considering spending more to get this: https://www.amazon.com/gp/product/B0040Y301S/ref=ox_sc_act_title_1?smid=A2L77EE7U53NWQ&psc=1 Amazon warehouse deals are great.

And the wife bought this from the Amazon cart.

Here we go.

I'm sure that gun will work out fine. Also keep an eye out for the $10 HF one. Can't have too many, and it's handy to have one for primer.

SkinnyG wrote: 3 wires? Maybe in a stove or drier that uses 110V controls and a light maybe. Your compressor will use just the two hots (each side giving you 110V each, together it's 220V).

It will run on two wires, but it won't be safe without a third wire for grounding.

In reply to BrokenYugo:

I have three wires, the third is ground, it's all good.

In reply to tuna55:

One other option to consider if you really want remote switching, would be to install a relay. That would allow a regular 120 wall switch to control the 220 to the compressor.

To answer the original question, I'm no electrician but I don't see why you'd really need a starter for a single phase compressor motor. It's controlled automatically via the pressure switch, a compressor doesn't need power outage protection (no big hazard if it fires back up when power is restored) they aren't big enough for the inrush current to be a huge problem, and the motors typically have overload protection built in. You're already planning a disconnect switch so a starter won't do you any good there either.

As mentioned, the manual probably has a pretty decent installation guide.

EvanR wrote:

SkinnyG wrote: 3 wires?

Either you're not considering the ground to be a "wire", or you don't think a compressor needs a ground.

The post in question said two hots and a ground, which would not be correct. A range was two hots, a neutral AND a ground.

If I go to the store, I would buy 14/2 or 12/2 or 10/2 or 8/2 wiring. Inside there are two wires..... and a ground.

To me, the ground is a given - you want that. But in the post in question, it's not a neutral in there.

In reply to Melendez :

Canoe. 

I might consider one of those rotary timer switches... at least for me.

I can't tell you how many times I finish a day in the shop, crack open a beer, crawl in my nice warm bed, and the compressor kicks on because I forgot to turn it off.