--Have been googling around to find out more info but haven't found any winners yet. I keep finding solenoid valves at the surplus store but some of them are incomprehensible to me. If I could figure out how they work it would be a whole lot cheaper than buying a new one that does exactly what's needed, yes? Any pointers appreciated..
I have been doing the same sort of thing and learning the hard way what the differences are. Look at the ASCO web site and print out some of the PDF files. You will be surprised at the various types of valves!
I have been trying to control the water loss in our printed circuit board washing system by using back flow stoppers and solenoid valves. Each change seems to work for a little while, then more water on the floor. I am looking at a valve on EBAY right now that may solve the final problem. However, I see in the ASCO listing that some valves need at last a 5 PSI differential to work properly. We need them OFF with no power and no PSI. Some others list operation with 0 PSI differential.
The valve we are currently using is so old there is no listing for it, so I can't tell if it needs 5 PSI to function or will work at 0 PSI. When the machine is off, there is no pressure, we just don't want the water to run out and overflow the holding tank.
I also got a normally open valve because I didn't check first. So obviously there are some things that you quickly learn about then valves. 1: normally open or normally closed. 2: the size of the pipe they connect with. 3: the voltage they operate with. 4: number of ports. Then I see some valves are proportional based on the power to the solenoid, some have flow restrictions inside, some are quick acting and some are slower. Yes, it is a real learning experience!
--Not likely to use plastic valves as I'll be running propane! Have been trying to figure out an NP LJ601305 solenoid valve that's currently common at the local junkyard. It's got 3 ports marked "NO" "NC" and "COMM";
2 wires, 24v. Have tried every concievable combination of air in/out and can't make anything pass thru it! Any help appreciated..
NO = Normally open...the position when no power is applied to the solenoid NC = Normally closed...same way COMM = common...the inlet.
Assuming it works properly, fluid enters in the COMM side and exits the NO side when the solenoid is deenergized, and exits the NC side when the solenoid is energized. Essentially what you have is a switching valve, but
*should* not be able to cut off flow. If nothing goes through, it sounds like you might have a gunked up valve body. If you can, discombobulate the body and see if the disc and seats can be restored. Also, take a look at the solenoid...it says 24V, but is it AC or DC...they're not interchangeable. You should be able to hear and feel the click of the solenoid energizing and moving the plunger/stem.
Adding to what Trid said, if you just want it on and off, you can plug the NO port and it will work like an on/off valve. It may be that it requires a few PSI to operate but you should get flow from COM to NO without the solenoid energized.
If you're using it for a fuel gas, you should absolutely be using a solenoid rated for such use. You'll find gas solenoids a common item for things like gas furnaces. Stop in at an HVAC service company and see if you can scrounge a few valves from equipment they have replaced and are scraping. Also note that the valves for gaseous vs. liquid propane aren't the same.
You absolutely MUST tell people your application when asking for advice. The valves for gases significantly differ from those for liquids, and you need to ensure that the seals and diaphragms are compatible with the gas. Propane for instance can dissolve rubber.
Go to a junkyard that has junk forklift trucks. The first valve in the line from the tank is the one you want. It turns the propane on and off with the key. It normally will be 12 vdc. and obviously rated for propane.
Basically, air should flow between the NO and COMM port (either way) with no power to the solenoid, and between the NC and the COMM with
24 VDC applied to the solenoid coil. How *much* will flow will be determined by what kind of aperture it has. (So you may not be able to tell by blowing through it by mouth.) Do you have compressed air available? Connect it (through a needle valve) to the COMM port, and with no power applied, you should get air through the NO port. Apply power and it should switch to the NC port.
There should be a nameplate on the coil part of the solenoid, and that will tell you whether you need to apply 24 VDC or 24 VAC.
24 VDC will probably operate an AC solenoid, but may overheat it if applied for long periods. 24 VAC will probably do nothing applied to a 24 VDC coil.
If you want to use it for an on/off valve, you will want to plug either the NO or the NC depending on which behavior you wish.
This is just a tiny start in the field.
BTW I've used similar valves with a 115 VAC coil with a proportional controller to produce a constant temperature bath for photo processing in the past. One port was connected to the hot water, and the other to the cold, and it would switch back and forth over a 5-second period, with the percentage of time the hot was open vs the cold being determined by the temperature of the bath. Luckily, I don't need to do that now with digital photos. :-) The clacking of the solenoid was a royal pain. :-)
Could also have a reverse flow check valve built in - which would require feeding pressure to the NC, and having flow from the COMM when energized--------. Remember, most of these are VACUUM control solenoids. Plug the outlet you don't need with epoxy, then cap with a rubber cap for good measure.