I finally got around to adding a safety shutoff to my Nitrox stick/compressor, and figured I'd share how I did it here in case it's useful to anyone else.
First, I'm using an electric (220v 1ph currently) compressor, where the motor is controlled by a big contactor+starter/overload that is in turn controlled by the Bauer control circuitry. Inside the control panel is a transformer that provides 120v control voltage to run the Securus and other safeties.
On the O2 Regulator side of things, I added a 120v NC gas solenoid to the output of the 2nd adjustable regulator:
The solenoid is rated to run up to 8 hours continuous, which is longer than I will ever need to flow O2 for continuously.
I put a 2-pin plug onto the leads from the coil - basically a lamp repair plug. Per the solenoid data, polarity doesn't matter.
On the compressor side of things, I chopped the end off of an extension cord and fitted it thru a hole in the control cabinet with strain relief gland. (This was simpler and actually cheaper than trying to buy 2 feet of SO cord and a socket, and making my own... )
Inside the cabinet, neutral and ground went to their respective connections.
For the "hot" side, I added a current sensing switch, rated for enough current and volts to meet the needs to the solenoid, running one of the motor leads from the load side of the overload/contactor thru the big hole in the middle:
The hot lead from the external plug goes to one side of the switched terminals, and the other goes to the fused 120v control voltage feed from the transformer.
I had debated using a lower voltage external power supply to drive the solenoid, but this was cleaner, and if I ever need to flow gas thru the O2 reg without the compressor running I can just plug it into a standard 120v outlet. In normal use, I'll use a short extension cord to connect the solenoid to the dedicated outlet on the compressor.
I already found a reason I might need to plug into a constant source, when after I tested to make sure it stops flowing when the compressor shuts down, I realized that I needed a way to de-pressurize the reg set. In normal use, I'm pretty sure I'll be turning off the O2 bottle while the compressor continues to run. I don't keep this set up permanently since I only occasionally need to bank Nitrox, so by not permanently attaching a longer cord to the solenoid I have less mess to store.
Hope this helps someone else!
First, I'm using an electric (220v 1ph currently) compressor, where the motor is controlled by a big contactor+starter/overload that is in turn controlled by the Bauer control circuitry. Inside the control panel is a transformer that provides 120v control voltage to run the Securus and other safeties.
On the O2 Regulator side of things, I added a 120v NC gas solenoid to the output of the 2nd adjustable regulator:
The solenoid is rated to run up to 8 hours continuous, which is longer than I will ever need to flow O2 for continuously.
I put a 2-pin plug onto the leads from the coil - basically a lamp repair plug. Per the solenoid data, polarity doesn't matter.
On the compressor side of things, I chopped the end off of an extension cord and fitted it thru a hole in the control cabinet with strain relief gland. (This was simpler and actually cheaper than trying to buy 2 feet of SO cord and a socket, and making my own... )
Inside the cabinet, neutral and ground went to their respective connections.
For the "hot" side, I added a current sensing switch, rated for enough current and volts to meet the needs to the solenoid, running one of the motor leads from the load side of the overload/contactor thru the big hole in the middle:
The hot lead from the external plug goes to one side of the switched terminals, and the other goes to the fused 120v control voltage feed from the transformer.
I had debated using a lower voltage external power supply to drive the solenoid, but this was cleaner, and if I ever need to flow gas thru the O2 reg without the compressor running I can just plug it into a standard 120v outlet. In normal use, I'll use a short extension cord to connect the solenoid to the dedicated outlet on the compressor.
I already found a reason I might need to plug into a constant source, when after I tested to make sure it stops flowing when the compressor shuts down, I realized that I needed a way to de-pressurize the reg set. In normal use, I'm pretty sure I'll be turning off the O2 bottle while the compressor continues to run. I don't keep this set up permanently since I only occasionally need to bank Nitrox, so by not permanently attaching a longer cord to the solenoid I have less mess to store.
Hope this helps someone else!
