compressor max run timer

[dreasoner]

I'm sure this has been covered before. I want to add a maximum run timer in the control circuit of a 240V compressor that would shut the compressor off in the event of a predetermined run time. If the max run time is not reached the unit will cycle normally on the pressure switch. If the max run time is reached, I want the compressor to shut off and only be allowed to be restarted with a manual reset of the control circuit. I think this would be similar to a pick and hold circuit.

 

[wyliesdiesels]

I'm sure this has been covered before. I want to add a maximum run timer in the control circuit of a 240V compressor that would shut the compressor off in the event of a predetermined run time. If the max run time is not reached the unit will cycle normally on the pressure switch. If the max run time is reached, I want the compressor to shut off and only be allowed to be restarted with a manual reset of the control circuit. I think this would be similar to a pick and hold circuit.

I see no one answered this.

Just wire a timer in series with one side of the contactor coil.

What kind of compressor do u have?

 

[Norcal]

If there is a mag starter with the compressor use a spring wound timer in the control circuit, the timers come in different time intervals, such as 60 min. , 12 hour, & shorter times, if no starter, a contactor could be used, anything else will get to be expensive, Intermatic is one mfg. but their 12 hour units have been a POS.

 

[md21722]

This is some good input, but doesn't account for the case where the contactor itself fails & gets stuck closed. It will account for blown pipe/hoses or failed pressure switches and other common issues though. Caveat emptor. Smart relays or PLC's with timer logic added to their programs can also work, but this is part of the "gets expensive fast" that Norcal referred to. The safest thing to do is have a good ON/OFF disconnect and turn it off every night. Or shut the breaker off. If you have a fully plumbed shop there is always the potential for air leaks for one reason or another. It may be a tool that has a small air leak connected, an air hose failed, your filter/regulator got some debris in the drain valve and got stuck open... The timer will help with all of those except for the failed contactor scenario.

 

[sberry]

Just out of curiosity,,, why?

 

[Know Wosad]

Just out of curiosity,,, why?

I was thinkin' the same. Even if I couldn't hear the dogs run outside and the whole place shakes when they're on charge. They get bled and disconnected at night.

 

[matt_i]

Here is a circuit to throw darts at. Basically it would be a timer-on delay, it could not be a retained time (retentive or motorized timer which keeps counting) and have to reset when the coil signal was removed. Or...that reset feature would have to be wired separately into the NO-contact of the pressure switch.

The "why" makes sense to me, if the compressor dropped a valve, blew out a hose fitting without being disabled, etc. It would run for a very long time (until someone discovered it and shut it off).

 

[rlitman]

Just out of curiosity,,, why?

I had a coil hose burst on me last year. It split open, and was blowing out ferociously. Still, my compressor was cycling on and off every few minutes. This sort of on-timer would not have helped at all.

What saved me, was a cheap pan-tilt network camera that was set to email me when it detects motion. I get an email whenever someone enters the shop, and while I was at work, I kept getting emails. The camera was mounted to something that vibrates when the compressor runs, and every other image was blurry, so when I logged into the camera and looking around the shop I found a plastic blag blowing in the breeze, I figured it out and had someone stop by and shut the power until I could fix it later.

When I'm sandblasting, my compressor still cycles, but I could conceive of times when it might have an extended run time due to heavy air use, where such a timer would be quite an annoyance.

I was thinkin' the same. Even if I couldn't hear the dogs run outside and the whole place shakes when they're on charge. They get bled and disconnected at night.

Ok, and just out of curiosity, why do you bleed your compressors down at night?

 

[jdieter]

Lost a motor from a busted airline and I wired a similar circuit to matt_i's sketch. Included a auto/man switch to bypass protective circuit if needed and a hold/reset feature for a power outage. A cycle counter would be needed to control repetitive on/off cycles. Or the whole sha-bang could be programed into a mini-plc. As for stuck contact the only practical way is an upstream latched contactor. My main protective plan is closing the air valve at the tank and hitting the stop button when I'm done for the day.

 

[jdieter]

oh ya forgot to say I added an hour meter for oil changes at the same time as the protective circuit.

 

[sberry]

Another question. This is for guys with meters. What type of shops and duty do they see to clock 100 hrs on one? Engine drives often have meters on.
Most of the equipment failures I see are from crappy connected additional shate. There are a LOT of guys here, a handful of incidents may make it seem like a lot but have 2 comps on with half a dozen hoses which would be moot with a valve or disconnected even but have never had a failure in this context and cant recall a case I have direct personal knowledge of where this has happened.
Almost all real incidents I have seen with air involve an operator and most of it due to **** on the floor.
There seems to be some endorsement without warning of some ideas and by electricians that worry to tears about a 5 hp on a 10 cable but seems modification to a listed appliance after the fact is fair game. The controls and the wire it came with are all designed to be safe on the max ocpd the machine may be connected to, some by nature of the plug but putting **** on it didn't come with and doesn't need should be done with care and usually causes as many problems at it attempts to solve.

 

[Davefr]

I completely understand what the OP is trying to do and think it's a great idea.

I could have lost my home due to a crappy 5 HP IR compressor. I came home and the compressor was running continuously. It turns out a reed valve broke which created a huge leakage path from intake to exhaust. That triggered the pressure switch to come on and stay on and ran the compressor continuously.

Fortunately I caught it. If not, maybe the motor's overload would have shut the thing down or maybe the motor would have burnt up. (and possibly cause a fire).

From now on I throw the breaker whenever the compressor is not being used but having a better fail safe system would be a great idea.

A countdown timer and 240 V relay would be all that's needed for a home workshop. Or a digital timer for a full shop and program it for when the shop is staffed.

 

[Todd.Brock]

I get what the OP is trying to do. My compressor leaks down and had run all night. When I bought my Champion, it had a typical mag starter. I replaced the pressure switch and used one with an auto/on off knob. This way I switch off the knob to off and when I'm ready to work, switch it to auto so it runs. When I leave for the night , switch it to off. The pressure switch just completes the circuit for a mag starter as needed / even if you didn't have a pressure switch with auto/off, you could wire in a light switch even to serve as an interrupter between the pressure switch and starter. Flip switch on when ready to work, off when done. Or the condor pressure switch I used is 30 bucks from grainger. Serves a similar function as what the OP is trying to prevent. Some folks try to switch the 240v circuit and that would work, as well as flipping the breaker ( not good for the breaker). JUst my .02