timer solution for 3hp compressor?

[merrill77]

I will soon be running a few air lines in my shop and moving my compressor farther away. I expect I will not be able to eliminate all air leaks and I don't want it running unless I'm actively using it. I already know I won't always remember to turn the switch back off. So I'd like to put a timer on it, so I can turn it on for 4 hours when I go into the shop, confident it won't kick on a 3am. It has a 240v 3hp motor.

I haven't found anything marketed specifically for this, at least not in a reasonable price range. So I started looking for a DIY solution. I found this 50A contactor (which has an option for a 120v coil) and this in-wall 120v timer switch. My plan is to power the timer switch from one leg of the 240v circuit and then put the contactor in-line with the existing pressure switch. Looks like those will set me back $55.

Anyone see a flaw in my plan? Or a better solution?

 

[junquecol]

I understand your plan, just not the part about not getting rid of all the leaks. If using threaded pipe, get some Rector-Seal #5. Forget about the Teflon tape, as it isn't a sealant, but rather a lubricant. For copper use LACO flux. Be sure and include a BALL valve on each drop.

 

[McRabbet]

Here is a very reliable 240VAC/40 Amp contactor with a 120V coil from a good US company. I believe you can buy a suitable time at your local Lowe's or HD.

 

[ScottM]

Here is a very reliable 240VAC/40 Amp contactor with a 120V coil from a good US company. I believe you can buy a suitable time at your local Lowe's or HD.

Rob the link is not working.

 

[scsmith42]

Hi Chris. A couple of random thoughts...

First, instead of a timer, why not simply activate the contactor from the lights in your shop? That way, whenever you turn on your shop lights your compressor is active, whenever you leave the shop and turn off the lights, it isn't.

PEX is a great, "zero leak" solution to a lot of air hose needs too.

Take care.

Scott

 

[McRabbet]

I like Scott's suggestion, too. But you'll also need the contactor -- I fixed the link in my earlier post.

 

[merrill77]

Hi Chris. A couple of random thoughts...

First, instead of a timer, why not simply activate the contactor from the lights in your shop? That way, whenever you turn on your shop lights your compressor is active, whenever you leave the shop and turn off the lights, it isn't.

PEX is a great, "zero leak" solution to a lot of air hose needs too.

Good suggestion, except I'd need to run a line from my shop lights to the compressor, which would need to go 25' and through two walls. I'm already going to need to do that for the air line, so I guess I could do that at the same time, though I suspect the code requirements are different?

That does get me thinking, though. If I bought a low-voltage contactor, then I could run a low-voltage line from the shop to the compressor and activate it in the shop right next to the light switch...with a bright red light on it so I'd remember to turn it off :> I dunno anything about code requirements for a low-voltage line.

I will be using PEX for most/all of the lines, since I got a good bit of it free when I bought my compressor (used). Good to hear that it is not leak prone. That said, I am working on the assumption that auxilliary lines and tools are prone to small amounts of leakage.

Chris

 

[merrill77]

I understand your plan, just not the part about not getting rid of all the leaks. If using threaded pipe, get some Rector-Seal #5. Forget about the Teflon tape, as it isn't a sealant, but rather a lubricant. For copper use LACO flux. Be sure and include a BALL valve on each drop.

I likely won't be using threaded pipe or copper - as I have a good amount of Pex on hand. I have zero confidence that where I want the lines/taps today is where I'll want them 5 years from now :> It will be much easier to change my mind with Pex.

 

[Alan in Little Washington]

My DC control wiring is all low voltage (26V) so I took no special precautions other than where and how I mounted the transformer. If you look at the low voltage door bell/chime wiring in most houses it is just 18 - 22 gauge bell wire than runs from a transformer (mounted to a standard junction box) to the buttons and bell unit with no jacket or other protection.

I have air leaks too- from quick disconnects and the hose reel swivel mechanism. I have manual cut-off valves at each drop but don't always remember to close them. But, I struggled with the idea of turning the compressor off- with the leaks, that would allow the entire system, air lines, regulators, AND my 80 gallon tank to drain down to nothing. It would require a lot of compressor time to refill.

I think a better option might be to put a solenoid air valve on the output of the tank. The air lines and regulators will still bleed down but that is only a fraction of the air volume of the tank so the compressor would not need to run as much.

 

[merrill77]

I think a better option might be to put a solenoid air valve on the output of the tank. The air lines and regulators will still bleed down but that is only a fraction of the air volume of the tank so the compressor would not need to run as much.

That is a great idea! I've been unable to find a reasonably-priced (<$100) option, though :no:

 

[Alan in Little Washington]

That is a great idea! I've been unable to find a reasonably-priced (<$100) option, though :no:

I found this 3/4" normally closed solenoid valve on Ebay for $50. It is rated at 230psi (I have a 175 psi compressor) and has a CV-7, .8" orifice. Can anyone tell me if that opening is large enough to run an HVLP sprayer through my 1/2" copper air lines?

It has a 110V coil, however.

Here is the same valve, same vendor, same price, but with a 12V coil. The vendor has valves rated for 110 PSI for less $.

I would prefer a valve with a low voltage coil- simpler to wire using lightweight bell wire and I have a spare 24V transformer (and diode rectifier), but I can't find a 24V valve rated at 230 PSI! The 12V coil draws only 1.3 Amps so a small 120 VAC to 12 VDC power supply (like this one for $10 on Amazon) shouldn't be too hard to find locally. It would need to be something larger than a typical wall wort power supply though- with a minimum current rating of 2A (power rating of 24 Watts)- the higher the rating, the better.

For some reason door bell transformers are typically 16V and don't put out DC.

 

[junquecol]

Alan, for 12V DC, just get hold of a CHEAP battery charger. Or you could get a thermostat transformer that has primary connections for either 110, or 220. Connect the 220 leads across 110 and you get 12V instead of the normal 24 volts. Most sprinkler systems use a 12 volt transformer, along with low voltage land scaping lights. Remember that when you add a diode to the 12V AC, you will produce about 1.4 times the original voltage, if memory serves me correctly. It may not. Ususally the difference between AC and DC coils is the DC one doesn't retain magnetism. Which means you can use DC coils with AC, but not AC coils with DC.

 

[merrill77]

I found this 3/4" normally closed solenoid valve on Ebay for $50. It is rated at 230psi (I have a 175 psi compressor) and has a CV-7, .8" orifice.

Thanks! I think I may do both: after going through the trouble of running a 12v control line for the air supply valve, adding a solenoid to control power to the motor will be pretty easy.