rons, more info please! I did look for one of your posts on this but never figured out the right keywords. What model and what else did you get to make it all work?
$190 is pretty steep for a simple pressure switch. I did check Grainger before buying my last switch but shy away from them because of their prices.
I have done the relay thing on another small coolant pump because the motor kept frying the float switch that I like. That looks like a viable direction at the moment, I just have to figure out how to make it look good with the wires hidden and safe from the elements as it is outside. For $80 that pressure switch that rons has is pretty interesting. A wide open pressure differential but max pressure of 145 psi.
I am using the part number:
ISE30A-NO1-P
I have another one in a SMC box. It is the ISE30-T1-65-L. Somebody wrote down the McMaster part number on the box: 3167K14.
McMaster-Carr
The slightly different numbers for the part are for different connections and internal switching transistor. The important things for me was to
get a 1/8NPT connection on the back and a internal PNP transistor. The McMaster picture shows a push-lock connector for a PVC hose connection.
I wouldn't trust that with my compressor tank pressure going up to 150psi.
The manual has a selection guide. I have to admit that I had to read the manual more than once.
https://www.smcpneumatics.com/pdfs_smc_instructional/PS-OML0003-C.pdf
I have a couple of new old stock Festo's:
SPAB-P10R-N18-2N-K1 (1/8 NPT)
SPAB-P10R-G18-2P-M8 (metric M8 straight thread)
I bought them all from surplus stock at HSC Electronics. They closed operations Jan 2019.
The SMC's cost $15 each and the Festo's were reduced from $25 to $10 each.
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To connect:
The switch has 3 wires, 12-24V, 12-24V return, and switch output.
If I was using a motor starter then I would connect the switch output to something like a octal relay in a socket to control the motor starter coil.
The switch can be programmed to have any hysteresis, I'm using 125-150psi. The display can be programmed for green color when off and red when on, or reversed.
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The original Square-D switch was rated for 3Hp, the starter was rated at 3Hp, and the single phase motor was 5Hp.