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I have a small 1HP air compressor - Rolair JC10 Plus 2.5 Gal.

It would be very convenient to leave it plugged into AC power at all times so that any time I use it, if I bleed it down it will kick in and re-compress itself, etc.

However, this worries me - what if there is a break in the (copper) air lines or a failure of the socket or ... a serious leak. If that were the case, the compressor could just run forever, or cycle very frequently.

At the very least this is bad for the compressor - at worst, a fire hazard.

Right now, I leave it plugged in but turned off. This means that if I run out of air I have to walk around the building and turn it back on to re-compress.

An easy solution would be to wire in a high voltage switch at the point of use and make the outlet a switched outlet ... and then leave the compressor power set to on. HOWEVER, there are TWO points of use (air outlets) so that gets weird and hard to wire.

So my hope is that there is a plug-in relay with a remote control that I can plug between the compressor and the outlet. So, no wiring involved - just a device between the compressor and the 20amp outlet - and I have two or three remotes that I can place anywhere I like and turn the power on.

Does that device exist ? Can I size a device purely on the 20amp power outlet or do I need to compute the horsepower of the compressor ?

Is there a simple way to do this that I am unaware of ?

Thank you.

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  • Does it have a pressure switch that cuts the compressor motor when the pressure is achieved? If so, let it run like that. Does your heating run on a thermostat? What is the difference - except pressure v temperature... – Solar Mike Jan 1 at 7:41
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    Put a timer on the plug set to supply power only during the hours you are likely to use it. – Kris Jan 1 at 13:29
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    Every time I forget to turn off my compressor, the very slow leakage means that it fires up at the least ideal time. You can theoretically eliminate those slow leaks, but for me, the cost/benefit would tilt in favor of not having it on all the time. Don't forget to drain the moisture from your tank periodically. – Aloysius Defenestrate Jan 1 at 17:29
  • Most plug and play automatic devices won't be rated for 1 HP, you would likely need a relay rated for 30A. Remote controls are still less than passive, you might want to consider using an occupancy sensor. If a significant distance to where a sensor would work using 24v controls and cabling might be more economical than line voltage. – NoSparksPlease Jan 1 at 17:36
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    Posting as a comment, not answer but this is what I was getting at. Obviously the exact outlet (socket), plug will depend upon what country your are in. But they are available. I have to disagree with @NoSparksPlease because they are plug/play available. My dust collector is a 3 HP unit and the remote has worked flawlessly for 20+ years. EDIT: forgot the link: amazon.com/DUST-COLLECTOR-REMOTE-CONTROL-SWITCH/product-reviews/… – George Anderson Jan 1 at 18:35
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I think you are over engineering your solution. It is a small 1HP 4.1 CFM compressor with a small 2.5 G receiver and 90 PSI max operating pressure. The copper pipes will not burst in your lifetime. You may have a very unlikely leak at the receiver valve or a more likely leak in your hoses and connections. I leave my compressors on all the time and have copper pipe to all the outlets avoid pressurising lengthy rubber hoses. I also have a pressure gauge at each outlet. Bursting of pipes and fire hazards resulting from that, are so low I would not consider them. If there is a leak, the motor will run more than it should and you will find out from running noise or moving gauges. Your motor has overload protection in the very unlikely case it runs all day and you do not notice. Establish if it has leaks by monitoring if you lose pressure overnight. Use soap water to find the leaks and eliminate them. My tanks retain pressure for several months without any leaks or the need for the motor to run when not used.

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  • OK, these points are well taken and I appreciate it. I was not aware of the overload protection on the motor - I assume this makes it basically impossible to produce an overheat or a fire hazard ? – user227963 Jan 1 at 19:16
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You are over thinking this. I have a large compressor (about 50 gal) in my shop that never cycles unless I left an air tool connected to a hose that's leaking. I leave it powered up 24/7. It's EXTREMELY unlikely for a copper pipe to fail. All of my air plumbing in my shop is copper and it's been fine for 15 years. Even if it were to "fail", it wouldn't fail catastrophically. Millions of homes have copper plumbing that's pretty darn reliable.

Also, sockets (you must be in the UK) don't just randomly fail either.

If you still want to go down the path of turning it off when not in use, there are remote controlled switches like the one I use for my dust collector in my shop. Just google for the appropriate one for your needs. Product recommendations are frowned upon here, so I'm not going to recommend anything other than to say they are out there.

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Small compressors tend to be under-engineered for a prolonged run.

Some big, custom-built ones are not really "engineered", but built from what's at hand instead.

Both of these types usually lack the protection features that may make them acceptable for unattended operation.

All of them have a nasty failure mode when they don't start because of an undervoltage (brownout) in the power grid, failing capacitor, lost phase (for 3-phase devices), pressure regulator malfunction, etc... and the motor quickly builds up heat.

Yes, running an unattended compressor has its risks.

I personally know at least two cases where the compressor was damaged way more than it would be, should someone noticed that it tries to start and no one noticed because the compressor was left powered on out of hours. I also know a case when the fire brigade saved the workshop from burning down.

And yes, most people still prefer the compressor to be installed at a distance and behind walls (it's noisy).

What can be done:

  1. Absolutely make sure that the compressor is turned off when there are no people at site. Wiring a relay to power it on with lights may be a good idea.

  2. Fit the compressor with :

  • a resettable thermal protection
  • a thermal fuse (it is not resettable, but is more reliable)
  • some sort of overpressure protection (pressure regulators do fail sometimes)
  • a timer preventing it from running more than the minutes stated in the manual
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    The compressor in question has integrated thermal protection, as well as a protective safety valve on its tank, but your suggestion of having it switched on/off alongside the lights is a good one – ThreePhaseEel Jan 1 at 21:46
  • And, of course, if the OP is worried about safety, they should definitely get a licensed tradesman to do the work rather than trying to DIY it. – nick012000 Jan 1 at 21:53
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As a mechanical contractor, I agree with the other contributors here that you are over thinking this. You can leave your system on for this small of a compressor and there is little concern that you would have an issue with bursting pipes. If you check the following. If you have a copper piped system, lets say it it is 1/2" copper type "L" it's working pressure is over 600 psi (soft bendable copper tube or 1200psi hard annealed Copper). (Bursting pressure is even higher at 3,800 / 7,000 PSI See Chart below courtesy of the engineering toolbox.co enter image description here Never put plastic piping for example PVC. in your system because a rupture could project shards that could be lethal. Just be clear most industrial general service compressed air systems are based on 150 PSI rated hose, fittings, and pipe and it is not uncommon to see them operating well over 200 psi. If you are there or over this in ratings you will be fine.

Make sure there are no hoses in the system left under pressure make sure they are not exposed to UV light deterioration and ensure your piping system is free of excessive mechanical vibrations and potential damage caused by other mechanical equipment. You can use hose but make sure it is rated for your system pressure and use Ball valves prior to the hose connection. A common practice is to put a ball valve at each service point then a regulator, then a quick connect for you to attach your hose. Check all threaded connections by spraying with soap water solution and looking for air bubbles. Use Teflon Tape and pipe thread sealant combination and redo the connection if needed. A premium leak free solution is to use bare threads cleaned with no tape and a few drops of blue Loctite 242 thread sealant. This makes for a clean installation and is removable for future repairs or modifications.

In the event your compressor could overcharge there is a required and built in mechanical safety relief on your compressors tank. This will discharge air and then reset once it has relieved pressure. You will need to check and drain your receiver tank periodically as this will collect water/oil condensation and could potentially rust out your receiver tank over time from the inside out. A common practice here is to install a pressurized no loss drain unit (PNLD). This will expel water oil without wasting air in your receiver tank. A lower cost option is to install a condensate timer this will blow off condensate at timed intervals but can cause your compressor to run more frequently if not set correctly.
Finally there is an environmental concern with the condensate oil water mixture safe disposal. Condensate should be separated with an oil/water separation unit or a lower cost alternative would be to setup up a container that can be monitored and the oily water mix skimmed off and then safely disposed of.

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  • My understanding is that some plastics are OK for air lines - nylon, polypropylene, polyethylene are quite commonly and safely used on smaller diameter lines. PVC is a bad idea mainly due to being so brittle and rigid. – SomeoneSomewhereSupportsMonica Jan 2 at 5:25
  • That is Correct thank-you for pointing this out. It is an old habit for me to think of "plastic" piping as PVC. One should really investigate the properties of any material proposed and make sure it is suitable for compressed air. The main concern is that a piping system can be compressive or hydrostatic. Water is hydrostatic, if you had a 100 psi system and it burst, your pressure will drop almost instanly to zero. If the same system is air (Gaseous Form) it will take a period of time for the pressure to relieve. So A brittle plastic system could be quite lethal. – Son of Fire Jan 2 at 16:47

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