Air compressor safety shut off

[altereddezignz]

Sorry don't want to offend you, but you asked were just trying to help.

Oh no worries man. You didn't and won't lol

 

[altereddezignz]

Without working out the logic, I would use it in one-shot mode. If the compressor runs for more than x amount of time it trips the starter out by opening the control circuit. Use a reset button on both sides of the wall to reset the timer and control circuit.

Well I would only need one reset button. The only time it would run longer than x amount of time is if there was an issue and the tank was not storing the air. I think this is what your stating.

 

[The Cobbler]

what's being suggested is a spring wound timer. you can get them with many different total times from 15 minutes to several hours. So your brother wants air, he cranks the timer to turn on the compressor. it starts to count down manually . Be sure not to get a spring wound timer that can be turned to stay on.
I would think a 2 hour spring wound timer would work quite well in this situation.


Spring wound timer would allow him to come in any time, wind the timer & voila! he has air.

 

[A_Pmech]

Well I would only need one reset button. The only time it would run longer than x amount of time is if there was an issue and the tank was not storing the air. I think this is what your stating.

You would need a reset button on each side of the wall so either party can reset the timer.

It could also trip out if you were sandblasting, so I'd make it a generous time allowance. Maybe 45 minutes or so.

The motion sensor on an OR circuit is also a very slick idea.

 

[altereddezignz]

what's being suggested is a spring wound timer. you can get them with many different total times from 15 minutes to several hours. So your brother wants air, he cranks the timer to turn on the compressor. it starts to count down manually . Be sure not to get a spring wound timer that can be turned to stay on.
I would think a 2 hour spring wound timer would work quite well in this situation.


Spring wound timer would allow him to come in any time, wind the timer & voila! he has air.

What about from my side. Could I make a direct connection to on off so I do not have to use a timer.

 

[altereddezignz]

I think for what I'm needing or wanting to do its going to end up being a headache other than the spring timer. But would rather just leave it on all the time and have something to shut it down or off if the compressor runs for more than a set amount of time in a single event.

 

[altereddezignz]

Just to many variable. Thanks everyone for the help and I am still reading on some of the suggested items. I hope I can make one work.

 

[The Cobbler]

What about from my side. Could I make a direct connection to on off so I do not have to use a timer.

yes.

put a switch in circuit parallel with the timer .

 

[Cougar]

Have you thought about just putting a sign on the door, "Turn the Compressor Off"

That would be the least expensive and should do the trick.

 

[The Cobbler]

Get a coin operated timer switch from a commercial washer or drier...

 

[altereddezignz]

That would be the least expensive and should do the trick.

Hotwire 240 to the door knob and if the power is on to the compressor it shocks them and they can't leave lol....

A sign is a good idea I'll probably do that anyways but like anything else it still leaves room for human error.

I even would rather take myself out of the equation too so that I myself would not be the one to mess up my compressor. Accidents do happen just trying to minimize it.. Maybe a 60 min timer on their side a 2 hour timer on mine ..

 

[altereddezignz]

Wonder if there is something that would read the psi at a low side maybe at the end of the air main mine run and if the psi dropped below a set point it would shut the power or break the power.

 

[altereddezignz]

Get a coin operated timer switch from a commercial washer or drier...

Lol.. I like this

 

[Spareparts]

Put an additional light switch next to your light switch at the door(s) wired into a light contactor coil and wire the compressor into the contacts, any switch would turn the compressor on or off, just make sure that all switches are on one circuit. They make orange switches for the medical field, just to make sure it is for the compressor only, what you are asking is to have something fool (idiot) proof, and that is almost impossible. Some of the suggestions will be quite expensive, and unless you have the electronic experience, challenging at least. Whatever you decide try to make it simple to maintain.

 

[Charles (in GA)]

What you want to do, limiting the time the compressor runs each cycle, I don't think can be done wholly electrically. If you have a countdown timer that shuts off the compressor after say 10 minutes, then it would reset itself when the compressor shut off. The pressure switch, still calling for the motor to run (broke air hose, low air pressure) would simply turn it back on.

I have seen water well pressure switches that had a lever on the side of them. Say a 40/60 system where the pump turns on at 40 psi and off at 60 psi. If the pump turned on at 40 due to falling pressure, and the pressure continued to fall below 40 (due to a broken pipe faucet left on, etc) then the switch would shut off the pump. Restarting one of these involves holding the lever to force the pump on, until the pressure goes above the 40 psi on pressure.

A similar set up could be installed on a air compressor. Normally a two stage compressor has a 145/175 pressure switch, and if you installed a SECOND pressure switch which was NORMALLY CLOSED and only opened when the pressure in the tank passed below the switch's set point of say, 120 psi, then the compressor would stay off. This would involve simply wiring the second switch in series with the first. Wire thru the first switch, then thru the second switch and then back to the magnetic starter.

To restart the compressor, you probably would need a momentary switch wired across the contacts of the NEW pressure switch, which you would have to hold closed until the compressor pressure rose above the 120 psi of the new switch, at which point you could release the momentary switch.

None of this would prevent FREQUENT cycling of a compressor due to hose leaks from something like an air tool left plugged into a pressurized air hose, and the coupling hissing and leaking, but that may be a non issue.

The needed switch would be a single pole, double throw (SPDT) or a Double pole, double throw (DPDT) with an unused/unneeded set of contacts. These switches are NO/NC and allow you to wire from the common contact to the Normally closed at pressure contact (which IS what you need) or from the common to the Normally open at pressure contact (which is NOT what you need).

Charles

 

[altereddezignz]

What you want to do, limiting the time the compressor runs each cycle, I don't think can be done wholly electrically. If you have a countdown timer that shuts off the compressor after say 10 minutes, then it would reset itself when the compressor shut off. The pressure switch, still calling for the motor to run (broke air hose, low air pressure) would simply turn it back on.

I have seen well pressure switches that had a lever on the side of them. Say a 40/60 system where the pump turns on at 40 psi and off at 60 psi. If the pump turned on at 40 due to falling pressure, and the pressure continued to fall below 40 (due to a broken pipe faucet left on, etc) then the switch would shut off the pump. Restarting one of these involves holding the lever to force the pump on, until the pressure goes above the 40 psi on pressure.

A similar set up could be installed on a air compressor. Normally a two stage compressor has a 145/175 pressure switch, and if you installed a SECOND pressure switch which was

I don't want to limit the time it runs each cycle only **** it off if it runs a long cycle

 

[Charles (in GA)]

I don't want to limit the time it runs each cycle only **** it off if it runs a long cycle

Well, what I am suggesting would cure your problems. If say, a hose broke, the compressor would not be able to keep up, it would take a while, but would eventually drop well below the 145psi where the compressor came on at. This is where my second pressure switch comes in. As the pressure continues to drop, the second pressure switch opens the pressure switch circuit (even though the original pressure switch is still closed) and thus the compressor shuts off, and STAYS off, until human intervention holds that momentary switch to make it run.

Charles

 

[coljar]

My compressor is in the back room of the new garage and I've been thinking of putting a red (panel board type) light near the front door to remind me.

 

[altereddezignz]

Very interesting Charles. Ill do some testing tomorow with a open main air line and a simple air hose to see how long it will run before it falls below the lower set point to see how well the second pressure switch would work.. Very simple solution.. I knew there was one but i was over looking it.. Just have to look at it to see the easiest way to get a psi rating to the second switch.

 

[altereddezignz]

Everything we have is on off all on the breaker panel since it is located openly in the shop. We ahve 2 motion lights on each side that come on when you come in.

 

[OccupantRJ]

Divided shop. Wouldn't work when i am on my side. No motion on side with compressor lol

Use two switches. The occupancy switch on his side, a standard switch on your side. Either would allow power to the contactor coil, depending on when either switch is on. Either switch on, compressor runs. Either switch off, compressor runs. Both switches off, no compressor. Each switch would run from and back to the contactor, independent of the other, in a parallel setup. If you don't trust yourself to turn it off either, use two occupancy switches.

 

[altereddezignz]

Use two switches. The occupancy switch on his side, a standard switch on your side. Either would allow power to the contactor coil, depending on when either switch is on. Either switch on, compressor runs. Either switch off, compressor runs. Both switches off, no compressor. Each switch would run from and back to the contactor, independent of the other, in a parallel setup.

Right but i also want to take myself out of the error equation. So i think dual pressure switches would be the best solution. This also keeps me from having to run wiring back and forth for sensors.

 

[Charles (in GA)]

Since you have a motor starter on the compressor, the pressure switches only carry the amperage of the coil that operates the relay in the motor starter. Its not a lot of draw, I'm just guessing three or four amps at 240v max, probably not that.

I found lots of pressure switches, but very pricey. Found one or two on Ebay that looked promising.

Charles

 

[OccupantRJ]

Read the last sentance in post #61.

 

[altereddezignz]

Been looking around now and yes i am seeing the price of it since it is the opposite of the pressure switch that is on it now.

 

[altereddezignz]

Since you have a motor starter on the compressor, the pressure switches only carry the amperage of the coil that operates the relay in the motor starter. Its not a lot of draw, I'm just guessing three or four amps at 240v max, probably not that.

I found lots of pressure switches, but very pricey. Found one or two on Ebay that looked promising.

Charles

Ok so apparently i am looking for this wrong. All i can seam to find is NC switches? Can you shoot me a link of one so i can see why it is i cannot come up with any?

 

[HemiRambler]

Run the contactor off the lights - lights are on - compressor works - lights are off compressor doesn't work. I have my door opener wired that way for security purposes.

You could run the compressor that way thru the contactor or an electric solenoid on the air line - pros and cons either way I suppose.

 

[Bluearmflames]

Not sure i understand. A time off delay Upon application of input voltage, the time delay relay is ready to accept a trigger. When the trigger is applied, the output is energized. Upon removal of the trigger, the time delay (t) begins. At the end of the time delay (t), the output is de-energized. Any application of the trigger during the time delay will reset the time delay (t) and the output remains energized..

So this would only allow it to run for a specific amount of time but it would not auto kick on when the PSI lowers for the compressor to kick back on again?

You could set the time off delay at what ever time you want. They usually go to 99 hrs max. The idea is that you hit the button it starts the compressor. Then after whatever preset time expires the compressor is electrically off. Press the button and it will start back up.

 

[MN4x4]

Just saw this thread. Here is a link to a pressure switch that activates at 15 psi. It also has both NO and NC contacts. It only costs $38.

http://www.digikey.com/product-detail/en/76072-00000150-01/480-2048-ND/1162778

If you wire it in series with your actuator it would shut off the rig when/if pressure in your system dropped below 15 psi.

You would also need to wire a bypass switch around it or you could never get the compressor to run if it were empty, i.e. bled down. The bypass switch could be a button that has to be held in until the system pressure reaches 15 psi, then could be released. This would prevent someone from simply putting the switch in 'bypass' mode and leaving it there.

Is that more like what you wanted? PM me if I can help more.

 

[altereddezignz]

Run the contactor off the lights - lights are on - compressor works - lights are off compressor doesn't work. I have my door opener wired that way for security purposes.

You could run the compressor that way thru the contactor or an electric solenoid on the air line - pros and cons either way I suppose.

Being in Arkansas we may work from early in morning until 7-8 at night and never turn the shop lights on.

 

[altereddezignz]

Just saw this thread. Here is a link to a pressure switch that activates at 15 psi. It also has both NO and NC contacts. It only costs $38.

http://www.digikey.com/product-detail/en/76072-00000150-01/480-2048-ND/1162778

If you wire it in series with your actuator it would shut off the rig when/if pressure in your system dropped below 15 psi.

You would also need to wire a bypass switch around it or you could never get the compressor to run if it were empty, i.e. bled down. The bypass switch could be a button that has to be held in until the system pressure reaches 15 psi, then could be released. This would prevent someone from simply putting the switch in 'bypass' mode and leaving it there.

Is that more like what you wanted? PM me if I can help more.

Thanks this is also what Charles was talking about but 15 psi I think would be a last resort. I think with the valve all the way open on my tank it will build and keep more than 15 psi but I would have to see.

 

[Ohmthis]

I would agree that a low pressure switch inline with the motor starter control. As a bypass I like the idea of the spring wound timer. If something went wrong it would shut down on low pressure. Once fixed you would twist the timer which would let the compressor run and you could walk away instead of haveing to stand there and hold a button. The pressure would build up before the timer timed out and would close that circuit. When the timer timed out it would open that circuit. BTW the timewould be in parallel to the pressure switch.

 

[crewchief888]

If your brother and his friends are too irresponsible to even shut off the compressor when they leave perhaps you should rethink letting them use that space at all.

What is going to happen when one of them screws up and starts a fire?

Sounds like your brother is taking advantage of your good nature, you are very generious to let him use part of your shop and he apparently has no respect for that or you. Time for him to have his own place.

Have you thought about just putting a sign on the door, "Turn the Compressor Off"

just my $0.02

since it's your compressor
move the compressor
rewire the compressor so it puts the shutoff on your side
toss out the brother and his buddies.

 

[WVBrady]

Whice are you concerned about burning up, the motor or the compress pump? You said that if you had not been there, the 5 hp motor would have burned up. Doesn't the 7.5 hp motor have some sort of overload protection, i.e. protection from overheating?