Wall Switch on Mag Starter Compressor

[vwpieces]

I still have a 120V small compressor on a wall switched outlet at the door to conveniently turn off everything in the shop as I leave.

I recently installed a large compressor 230V 5HP with a mag starter. Also wanting to have this compressor switched off at the door when I leave.
Suggestions on how to do this?

My initial thought is to wall switch the pressure switch since this is now low current.
I have been to too many shops that use the breaker to turn off/on the air compressors and not really wanting to use the disconnect box switch to turn it off every time I shut down the shop. Having everything wires on wall switches at the door make it idiot proof and easy to make sure it's all off.

 

[wyliesdiesels]

you will now need a 240v rated switch since you would be switching the contactor coil which is 240v.

Doesnt matter how you connect it, as the pressure switch just cycles the coil in the contactor.

 

[BillK]

I prefer the entire power be turned off to the compressor. I use the breaker myself but I walk past it as I leave so its no problem for me. I guess if you want to have a switch at the door then the prssure switch line would be the way to go.

 

[Citation]

Get a 120v relay. The relay is on when you're wall switch is on. The relay switches the line from the compressor's pressure switch. So when the relay is off the motor starter sees an open circuit, same as compressor full. When you turn the wall switch on the relay turns on and now the pressure switch can control the starter.

 

[BillK]

Get a 120v relay. The relay is on when you're wall switch is on. The relay switches the line from the compressor's pressure switch. So when the relay is off the motor starter sees an open circuit, same as compressor full. When you turn the wall switch on the relay turns on and now the pressure switch can control the starter.

That seems to over complicate things. If you are going to run a line from the compressor to the wall switch why not just run the line from the pressure switch ? One less thing to go wrong.

 

[Terry D]

I agree with wylies, keep it simple. Use a 240 volt rated toggle switch and wire it in series with the pressure switch. Unless the circuit breaker is in sight, you will still need a disconnect for servicing the compressor

 

[exranger06]

I wired a toggle switch in series with the pressure switch. I also ran a neutral wire so I could power a 120V indicator light to remind me the compressor is on. It lights up when the toggle switch is on, and turns off when the toggle switch is off. I made a crude diagram showing how it's all wired. I used a double-pole switch because of the light. If I didn't have the light, I could've (and would've) used a single-pole switch.

 

[nadogail]

I think this is a great idea.

I wired a toggle switch in series with the pressure switch. I also ran a neutral wire so I could power a 120V indicator light to remind me the compressor is on. It lights up when the toggle switch is on, and turns off when the toggle switch is off. I made a crude diagram showing how it's all wired. I used a double-pole switch because of the light. If I didn't have the light, I could've (and would've) used a single-pole switch.

 

[joe_padavano]

you will now need a 240v rated switch since you would be switching the contactor coil which is 240v.

Doesnt matter how you connect it, as the pressure switch just cycles the coil in the contactor.

^^^THIS. That's exactly how I wired mine. It works fine. The mag starter is just a big relay. The pressure switch operates the relay coil (control side).

 

[Wrench97]

The pressure switch on mine only switches one leg of the 240v and the coil is a 120v coil.

 

[Citation]

That seems to over complicate things. If you are going to run a line from the compressor to the wall switch why not just run the line from the pressure switch ? One less thing to go wrong.

I'm assuming the wall switch is a typical switched outlet. If it's a dedicated wire then yes, just put it in series with the pressure switch. However, if it's a typical switched 120v outlet then the relay is a way to keep the rest of the setup stock. Heck with a relay you could connect a standard lamp timer so the compressor would automatically cut off at night.

 

[alfredeneuman]

Toggle switches come in 2 ratings. 120V only, and 120/277V.
Make sure you choose the 120/277V to control the coil. The switch will see 240V.
Because the wall switch is external to the starter, you need to run a #14 (minimum) to the switch

 

[vwpieces]

I wired a toggle switch in series with the pressure switch. I also ran a neutral wire so I could power a 120V indicator light to remind me the compressor is on. It lights up when the toggle switch is on, and turns off when the toggle switch is off. I made a crude diagram showing how it's all wired. I used a double-pole switch because of the light. If I didn't have the light, I could've (and would've) used a single-pole switch.

Thanks @exranger06
You confirmed my thought on what I wanted to do and if it would work.

 

[justsam]

The pressure switch on mine only switches one leg of the 240v and the coil is a 120v coil.

The pressure switch on mine only switches one leg of the 240v and the coil is a 120v coil.

Seems like an odd configuration, certainly doable but would require a neutral to be wired to the compressor, where as most just require 2 hots and ground.

 

[Citation]

OP, are you looking to use the existing wall switch or add new wires and a new switch? The options that put the wall switch in series with the pressure switch, similar to what exranger06 is showing would require taking that switched outlet out of service.

Here is a simple relay that can use a 120V input and handle a 240V switching voltage
https://www.automationdirect.com/ad...,10a_-_75a_(ad-ssr6_series)/ad-ssr640-ac-480a
(note, I just did a web search to find this, no experience with this specific model or seller)

All you need to do it run the line from the pressure switch through the switched side of this relay. You then connect a simply electrical plug lead to the switching side and plug that into your existing switched wall outlet. If you want a "compressor on" indicator plug a lamp into the same switched wall outlet.

I've modified a typical compressor starter diagram showing how the relay is added.

 

[vwpieces]

@Citation
The 120V switched outlet at the exit door is only an example of what I wanted for the 240V mag starter compressor. The 120V small compressor will continue to exist as is where is. The New compressor switch will be located right next to it, on the wall.

And as I am typing this I just remembered that the Big compressor was not turned off last night. If the wall SW was installed I would remember to turn it off.

 

[cabranch47]

I wired my 240V compressor to a relay connected to my light circuit. Lights off, compressor off. Works fine and don't have to remember to turn it off when leaving.

 

[Citation]

@Citation
The 120V switched outlet at the exit door is only an example of what I wanted for the 240V mag starter compressor. The 120V small compressor will continue to exist as is where is. The New compressor switch will be located right next to it, on the wall.

And as I am typing this I just remembered that the Big compressor was not turned off last night. If the wall SW was installed I would remember to turn it off.

OK, that does change things. Based on your original post I read it as you wanted to use the same switch. Yeah, if you want the switch near the compressor then exranger06's option looks good. Any 240V "light switch" in series with the pressure switch wires would work nicely. If you want a "compressor on" light one suggestion was to put either a 240V neon light or a universal LED power supply (typically accept 100-240V input) with a 12V output. Then you connect a simply 12V LED lamp to indicate power.

 

[Milton Shaw]

I went with a motorized ball valve to shut the air off at the compressor instead of turning the power off. This lets you eliminate all leaks while shop is unoccupied and gives full air supply the minute you turn the lights on. My ball valve is wired to turn on with the lights, so only one switch to turn off lights and air. Several other posts on here about air and compressor cut offs.

 

[rlitman]

I went with a motorized ball valve to shut the air off at the compressor instead of turning the power off. This lets you eliminate all leaks while shop is unoccupied and gives full air supply the minute you turn the lights on. My ball valve is wired to turn on with the lights, so only one switch to turn off lights and air. Several other posts on here about air and compressor cut offs.

I went the motorized ball valve route as well (and just replaced my valve, after the first motor failed after 2 years). However, in my case I did not want to tie it to the lights (though it's a really good idea). I have two hose reels outside my garage and there are many times I'll want air when the lights are off, so I'm controlling it using a WiFi controlled relay.

 

[vwpieces]

Motorized ball valve sounds like a good idea but also sounds pricey (haven't looked it up) and if it only lasted 2 years...

And a Wi-Fi relay switch, didn't think of that for the compressor. I don't have cable TV so all the TV's in the house have computers attached. I use those remote controlled outlets to turn on everything at each TV with one click. I can appreciate the suggestion but I am still going wall SW.