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Help needed electric kill switch for air compressor

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  • Help needed electric kill switch for air compressor

    I want to buy or build a switch for my air compressor to shut it off if a hose breaks in the middle of the night.
    I want it to shut off the switch if the compressor runs for say 10 minutes. If it runs more than 10 minutes at a time it will shut down and require a reset to function again.
    i have no idea what I need to get this done.

  • #2
    Seems like just turning it off at night would be a good solution. You'd probably get used to doing that pretty quickly, eh? For me, a 10min limit would interfere with some things I use it for, but mine can run for an hour without issues.
    Southwest Utah

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    • #3
      My wife has been awakened occasionally by my shop compressor kicking on in the middle of the night. A water heater timer is the perfect cure. It powers on after we are awake, and power is off from eight through until morning. Very convenient.
      HVAC companies make timer controlled relays that can do what you’re looking for, but the water heater timer may be cheaper and easier to implement.

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      • #4
        A relay actuated by your lights would work well.
        Location: Saskatoon, Saskatchewan, Canada

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        • #5
          Thermal fuse strapped to the compressor head, run to a NO relay the compressor is plugged into? Pump runs for a long time, heats up, trips the fuse, kills the power

          Other way i can think of involves a bit more work. Get a microcontroller, current sensor of some breed and a relay. Program the controller so if it reads whatever the operating amp load for your compressor is for longer than 10 minutes, it kills the relay, but the timer can be reset by pressing a button

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          • #6
            How about an under-pressure shut off switch, something that will cut off if the compressor if for any reason it is unable to maintain air pressure.

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            • #7
              Assuming you're running the compressor on 220v I'm thinking that in the same situation I'd look at running a 110v controlled contactor off the shop lights that then switches the 220v circuit for the compressor. Wired like this it runs when you're in the shop and using stuff and just can't run when the lights are out because it's either night or you're away doing other stuff.

              That's the thing. If you're away on a trip for a few days you don't want it running all day either. Seems like if it can only run when the lights are on then it will only be running when you're in the shop. And if you're in the shop you'll know if there's a failure pretty quickly...

              110v contactors to control 220v are pretty common. You'd need to buy the contactor, a box, a few box connectors and wire it in.
              Last edited by BCRider; 04-02-2021, 05:39 AM.
              Chilliwack BC, Canada

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              • #8
                Originally posted by Arcane View Post
                A relay actuated by your lights would work well.
                Originally posted by BCRider View Post
                Assuming you're running the compressor on 220v I'm thinking that in the same situation I'd look at running a 110v controlled contactor off the shop lights that then switches the 220v circuit for the compressor. Wired like this it runs when you're in the shop and using stuff and just can't run when the lights are out because it's either night or you're away doing other stuff. ...
                Yep - that's the way I have mine set up. The only downside is that when I'm in the garage & want to use air, the cellar lights might not be on.

                A solid state relay is an alternative to a contactor - might be cheaper. For 240v, you'd need 2 - one for each leg.

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                • #9
                  Originally posted by chipmaker4130 View Post
                  Seems like just turning it off at night would be a good solution. You'd probably get used to doing that pretty quickly, eh? For me, a 10min limit would interfere with some things I use it for, but mine can run for an hour without issues.
                  That's the best idea, turn it off. If it's coming on during the night you have some slow leaks somewhere and the compressor is needlessly running. That's all excess wear and tear on the pressure switch.
                  I have the same problem. I still can't find the leak and I've checked all the fitting and couplings, regulators etc. I've replaced the switch twice already due to arched contacts. The last time I had to swap the guts of the switch because the housing was different. It was a PIA to try and drop a spring loaded switch into a small box.
                  Since then the compressor is off until I need it.

                  JL...............

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                  • #10
                    Originally posted by Jerrythepilot View Post
                    My wife has been awakened occasionally by my shop compressor kicking on in the middle of the night.
                    Funny how I don't hear it.

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                    • #11
                      I forget to shut mine off all the time and hear it kick on at night ---- I do hate that just because I hate to waste electricity like that,,, iv tried to take care of all leaks and have helped it but still must have a small one somewhere,,,

                      as far as you blowing a hose and it running all night when your not there it would be a waste of power but it's really not going to hurt your compressor or motor, they are designed to run up against extreme resistance and will actually be running free and cool with no real heat build up in either component...

                      I guess the worst case scenario is that it's a mild leak - enough to where there's still lots of pressure but the compressor can't catch up and holds it at a steady high pressure...
                      Last edited by A.K. Boomer; 04-02-2021, 10:55 AM.

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                      • #12
                        We shut down and drain the receiver every day when we leave the museum. Also the computer, and any battery charger except the scissor lift one which is designed to be left on 24/7.

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                        • #13
                          I have been working on a relay that will shut off the power to the pressure switch on mine. It will be tied into the shop lights and have a bypass switch so that I can have the compressor on when I need air in the outside shop that is fed underground from the compressor. It is all built except mounting it and hooking it up. The pressure switch only controls the mag starter so, there is low current on this relay.

                          Peter
                          Grantham, New Hampshire

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                          • #14
                            Originally posted by epicfail48 View Post
                            Thermal fuse strapped to the compressor head, run to a NO relay the compressor is plugged into? Pump runs for a long time, heats up, trips the fuse, kills the power

                            Other way i can think of involves a bit more work. Get a microcontroller, current sensor of some breed and a relay. Program the controller so if it reads whatever the operating amp load for your compressor is for longer than 10 minutes, it kills the relay, but the timer can be reset by pressing a button
                            This is what I want to figure out I am going to put the compressor in my second shop a 100’ away. There is a lot of days I don’t even go over there.

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                            • #15
                              Bob E mentioned solid state relays instead of a contactor. For this new information that your compressor is off away at a more remote shed I like the idea of the SSR's because they can be driven by a low voltage DC which requires very little current. Like so little that a bit of old telephone or Cat 5 cable could be set up to control the compressor from the main shop area.

                              However you drive them after that is up to you. It could be just a low voltage DC supply off the lights or it could be some fancy Arduino logic thing related to what you've mentioned. Or it could be simply a set of switches local to your work areas. Or any other sort of logic setup.

                              I'd be a little concerned over the idea of the 10 minutes and shut off until reset. As mentioned the right sort of leak could see it struggling and heating up a lot but never hit the trip point. Or perhaps a bit of a sand blasting job needing lots of air for real WOULD make it trip. I'm still thinking that basing it off something you switch on while you are actually in the shop would be a nice way to go. And that would seem to be the shop lights for each shop where air is installed.
                              Chilliwack BC, Canada

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