Compressor timer switch question

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Greg_Lewis
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Compressor timer switch question

Post by Greg_Lewis »

Hi folks:
I need some help with a timer switch setup for my air compressor. I came out from my post-lunch siesta the other day to find an air hose popped and the compressor on. It could have been on for as much as two hours. I have worried about what would happen if I was away for the day.

While there are many ways to deal with this, and I read the thread here from 2017 where Bill Shields suggested a solution to a similar problem posted by Mauro, what I'm looking for is a bit different. What I want to do is to leave the compressor on at all times. Yes, I do shut off the breaker when I am going to be away for more than a couple of days, but I don't want to be bothered with turning it on and off frequently. I want it to be on and ready for use when I need it, which is often.

So I'm looking for a timer relay of some sort that would kick off if the compressor ran for more than, say, 15 minutes. And I want the whole setup to be automatic. So the compressor comes on when the pressure drops, but if it runs for more than the set time, a timer will shut it off and it will stay off until I reset it.

Now I've found various timer relays on the net, but the terminology is confusing and my brain just can't figure out what to get and how to hook it up. The data plate on the motor says 230 volts, single phase, 5 hp, 15 amps, although the motor doesn't look big enough to be a 5 hp.

What I'd be most appreciative of is if someone could tell me exactly what to get (part numbers), and exactly how to wire it in (as in a drawing). Have any of you been down this road before? THANKS!
Greg Lewis, Prop.
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BadDog
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Re: Compressor timer switch question

Post by BadDog »

It doesn't cover all points of run-on failures, but I have a 3/4" ball valve right off the side of the tank before a short length of 1/2" hose that feeds my routing manifold (itself with various ball valves). I left it on pretty much 24/7/365 for years with no problems. And with the throw of a leaver (or two), I've instantly got pressurized air according to my needs. The only time it ever gets turned off is when I'm working on it, or going to be gone for an extended duration (no different than other things treated similarly).

Oh, and it's not a good idea to use a breaker as a switch, so I would still want to address that with or without the timer or external control circuits.
Russ
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armscor 1
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Re: Compressor timer switch question

Post by armscor 1 »

I had a 10 HP Broomwade and fitted a lockout timer on it so it would not start after 2 hours of use after complaints from neighbour when the thing started in the small hours.
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liveaboard
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Re: Compressor timer switch question

Post by liveaboard »

What you're looking for is a general use programable delay relay / time relay.
Some have many functions you can select with micro-slide switches.
So each time it runs the timer starts, then when the power is interrupted and starts again the time starts from the beginning.
I use a couple of them for similar, but different jobs.
one keeps the furnace on for an hour after impulse from a thermostat or manual button.
Another runs my compressor for an hour after pressing a button [I have 3 buttons in different buildings, all piped to 1 compressor].

The exact switching and wiring will take a while to figure out; you want to set it up as a run limit timer, and you'll need a reset method.
Few of them can switch even a moderate compressor so you'll probably need an extra contactor relay to take the load.
The programable timers can be a bit expensive; $50 +
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GlennW
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Re: Compressor timer switch question

Post by GlennW »

I just use a ball valve like Russ and it gets turned off any time I leave the shop.

The compressor also has a switch for the power as part of the pressure switch that gets turned off if I don't plan on being there for an extended time.
Glenn

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tornitore45
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Re: Compressor timer switch question

Post by tornitore45 »

Separate the control "smart" of the circuit from the "muscle" the power handling of the circuit.
Select the best delay relay for the job, then drive a contactor to control the motor.
Mauro Gaetano
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Greg_Lewis
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Re: Compressor timer switch question

Post by Greg_Lewis »

Thanks for the comments, guys. What I'm looking for is part numbers and a schematic.
Greg Lewis, Prop.
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Bill Shields
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Re: Compressor timer switch question

Post by Bill Shields »

Suggestion

I would make it programmable so that it does not come on at night...unless that is not a problem

And...if it runs for more than a few minutes shuts off until a reset.

You are going to have a couple 100 $ on this before it is over to do it right.

The cheap PLC is probably the smallest part.
Too many things going on to bother listing them.
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Greg_Lewis
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Re: Compressor timer switch question

Post by Greg_Lewis »

Thanks, Bill. No problem for nights. But it would seem to me that there should be a relay available that would do the job. I've found some at Grainger but the timing might not be long enough. Here is the description and a link to the longest interval listed:

______________
INTERVAL DELAY: When power is APPLIED to the coil (the start switch must be jumped in multifunction timers), the INTERVAL timing period begins and the contacts transfer, either connecting (normally open contacts) or disconnecting (normally closed contacts) the load. When the INTERVAL timing period ends, the contacts return to their original position. The unit resets when the power is removed from the coil, making the unit ready for a new cycle.

https://www.grainger.com/product/DAYTON ... lay-24EN79
_____________

So it would seem to me that you could have the compressor's switch operate the relay, which would, in turn, operate the compressor motor. So if the air pressure drops, the compressor switch turns on the relay, which runs the motor for a set time. If there is a leak, the pressure switch will stay on and the timer relay will not reset for another cycle. The relay linked above is just over $40 but the interval is only five minutes. That might be long enough but I'd think there must be one out there with a longer interval in the same price range. The beadblast cabinet and some of the air tools might make the compressor run longer than 5 minutes. I may have to experiment with that.

Your thoughts?
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
John Hasler
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Re: Compressor timer switch question

Post by John Hasler »

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Greg_Lewis
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Re: Compressor timer switch question

Post by Greg_Lewis »

Thanks, John. I'll check that out. I looked at McMaster but didn't see that.
Greg Lewis, Prop.
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Bill Shields
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Re: Compressor timer switch question

Post by Bill Shields »

Gregg's idea will work just fine.

Plug the lot into a Torq time clock to keep it off at night and you could have a winner.
Too many things going on to bother listing them.
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