Compressor Wiring Question

[MartyO]

The compressor in my home shop is a 240v single-phase unit.

It is located outside the shop directly behind the service panel which is in the back right corner of the shop.

I currently turn the compressor off and on using the circuit breaker.

I would love to have a switch at the front of the shop near the personnel door, which is in the front left corner of the shop.

The shop is approximately 40 deep and 50 wide.

What is the best way to do this?

 

[930dreamer]

How about a single phase 240V disconnect?

 

[MartyO]

How about a single phase 240V disconnect?

I have that at the back of the shop next to the compressor.

What I want is a switch at the fromt of the shop which woyld be about 95 linear feet from the compressor and the power panel.

 

[Zrexxer]

The best way to do it is to wire it in series with the coil of a magnetic starter, but you haven't given us enough information to figure out if you even use a mag starter.

 

[89GLH]

You mean like a switched relay for that breaker, to save trip all the way to the back of the shop to turn it on/off?

 

[mrb]

id make up a little control panel with a contactor, ice cube relay, and 24vdc supply. Then have on/off buttons and pilot light both at the control panel and at the remote location.

 

[Milton Shaw]

Wire in a relay with your lights. That way one switch turns everything on and you have lights closer than 95 feet that you would have to run wire to put another switch by the door. You would need a two pole relay with 120 volt coil and then wire the coil it to the nearest light. The wattage it pulls would not be enough to make any difference on the light circuit. Make sure you get one rated for continuous use.

 

[71flh]

You could run 14/2 from the pressure switch to wherever you want and switch power on and off to the pressure switch.

The new switch is in series with the pressure switch so in order to turn on the compressor motor (or mag starter), the new switch has to be on, and pressure in the tank has to be low enough to switch the PSW on.

 

[fefarms]

You could run 14/2 from the pressure switch to wherever you want and switch power on and off to the pressure switch.

The new switch is in series with the pressure switch so in order to turn on the compressor motor (or mag starter), the new switch has to be on, and pressure in the tank has to be low enough to switch the PSW on.

This is not a bad idea, but suffers from two potential problems:

Many mid-range and low-range compressors (including name-brand true 5HP models) use a two-pole pressure switch to directly connect power to the motor (no relay, contactor, or starter). You can't put a long run of 14/2 in series with the pressure switch with this configuration -- insufficient ampacity, too much voltage drop, and you leave the compressor in an unsafe state with voltage still applied to one side of the motor.

The other problem is that such a switch isn't idiot proof, even with a contactor. You must supply discipline to not turn the compressor off with the switch while the compressor is running. Doing so will defeat the unloader function of the pressure switch. You must then wait for the head pressure to bleed down before flipping the switch back on, or you risk overloading the motor on the next start.

 

[fefarms]

One interesting option is to put an electrically or pneumatically actuated ball valve in series with the output from the tank. This lets you cut off the shop piping from the compressor tank using a remote switch. You can then leave the compressor powered up and the tank fully charged. The compressor will not run unless it has internal leaks.

This option gets you compressed air immediately when you re-enter the shop and re-open the valve; you don't have to recharge the tank.

 

[71flh]

fefarms, thanks for the reply and pointing those things out. I went out and looked at how my unloader works to make sure there isn't a problem.

You're entirely right on both points. Obviously a long run of wire shouldn't be used unless its just switching the coil of a starter, and if the coil is 240V things could get more complicated.

In my case, I don't see a problem because the unloader isn't run to the pressure switch, and I have an antique setup where the coil of the starter is 120V so I'm not switching half of the 240V. The switch is also right next to the PSW and starter so there are no problems with a long run of wire.

 

[cnc-me]

Use a magnetic starter with momentary pushbuttons, you can have as
many start/stop stations as you want.

 

[MartyO]

Interesting ideas.

Here is what I was thinking.

I was thinking of keeping it simple.

There is a disconnect box outsidde the building in the compressor house.

I was thinking whether that disconnect box (or another) could be relocated to the man door -- basically run in series. Then I leave the breaker on full time and power up the compressor with the disconnect box.

Make sense?

 

[fefarms]

Interesting ideas.

Here is what I was thinking.

I was thinking of keeping it simple.

There is a disconnect box outsidde the building in the compressor house.

I was thinking whether that disconnect box (or another) could be relocated to the man door -- basically run in series. Then I leave the breaker on full time and power up the compressor with the disconnect box.

Make sense?

While simple, (and maybe feasible with heavy enough wire), this is rather sub-optimal. Your panel and the compressor are at the opposite corner of the shop. You'll be lengthening the supply wires by 180 feet. The total amount of copper from L1 at the panel through the disconnects and the motor and back to L2 at the panel will be more than 360 feet. This raises issues of voltage drop and motor starting problems.

 

[mrb]

that and the cost of the wire, when with $50 in contactor, ice cube relay, and 24vdc power supply you can run the control with thermostat wire.

 

[nate379]

Remote control for dust collection. Search on here under my name, I have a thread asking about it.

 

[Wackerjr]

I just kept it easy.... leave the "switch" on the compressor in the on position (on the starter) and wired one of these to then 30a 240v outlet....

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

Thaat way I can turn the outlet on and off.... and my "service disconnect" is the plug, or the Starter switch on the compressor outside....

Done easy...

 

[MartyO]

I just kept it easy.... leave the "switch" on the compressor in the on position (on the starter) and wired one of these to then 30a 240v outlet....

http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

Thaat way I can turn the outlet on and off.... and my "service disconnect" is the plug, or the Starter switch on the compressor outside....

Done easy...

That sort of disconnect was my plan but the issue is running a heavy gauge wire from one end of the shop to this disconnect at the other end of the shop.

 

[MartyO]

that and the cost of the wire, when with $50 in contactor, ice cube relay, and 24vdc power supply you can run the control with thermostat wire.

I sent you a PM.

 

[MartyO]

Well, I decided to go with a contactor.

I will be using a contactor by teh compressor/breaker panel and then will wire a 120 volt circuit to the front of the shop which will serve as the switch circuit for the contactor.

Seems simple enough and should keep me within budget.

Everytime I walk into the shop, i wish I had this set up already, so this is on this weekend's list!

 

[nate379]

The dust collector switch was easy for me. Took a few mins to wire the correct plugs for it and that was it. On/off like a TV remote ~100ft away from my garage.

 

[MartyO]

The dust collector switch was easy for me. Took a few mins to wire the correct plugs for it and that was it. On/off like a TV remote ~100ft away from my garage.

I am not sure I could find your thread on this.

A wall mounted switch prevents those with access from my shop from losing the remote. LOL

 

[Trey T]

I like the idea of using a relay(contactor) w/ 120v coil. the 24v coil is kinda messy.

 

[MartyO]

I like the idea of using a relay(contactor) w/ 120v coil. the 24v coil is kinda messy.

I ended up going the contactor triggered by 120 route.

A 120 volt line was run from the panel at the back of the shop to the switch at the front of the shop. This triggers the contact which was located under the service panel in a separate can.

The contactor was then wired with a breaker to the compressor.

I am not an electrician, but I had the licensed electrician who wired my shop do this for me. I was pleased with his neat work, the fact that he let me watch him work (I helped with the wire pulls and height work), and the outcome is just what I wanted at a reasinable price.

The orange switch (I painted it) now controls the compressor. Now when I come in the shop if I will be using compressed air, I can just flip the switch when I come in and I am good to go.

I am happy.

 

[camarotoolman]

Don't do anything, just think of all the good exersice you are getting!

 

[MartyO]

Don't do anything, just think of all the good exersice you are getting!

I am too fat to exercise.

Besides, I worry about everyone else who uses my shop having to walk past my cars.

 

[dave67fd]

One good idea is to make it a lighted switch or even better add a large pilot light. If the switch is left on (tank full, compressor not running) and you leave with other things on your mind it's a good reminder that it's still on and it doesn't kick on in the middle of the night and needlessly run.

 

[MartyO]

One good idea is to make it a lighted switch or even better add a large pilot light. If the switch is left on (tank full, compressor not running) and you leave with other things on your mind it's a good reminder that it's still on and it doesn't kick on in the middle of the night and needlessly run.

I like that pilot light!