Pressure switch not providing true short

[matt_s]

Hello,
A little background:
I inherited a situation here in NC in which the above-ground portion of pipe will freeze at the well head. With the goal of installing some heat cable and pipe insulation, I want to provide a constant source of power for the heat cable. Unfortunately, there's no simple way to get an extra set of wires out to the well head. The existing pump wires are not in conduit (direct burial), and there's a paved driveway between the building and the well head.
So yesterday I installed a power line carrier (PLC) transmitter and receiver.
In this new setup, the wires to the well head are now always energized, wired to both the heat cable and the small receiver in the well head. The receiver is basically just a remote-controlled relay, wired to kick on the pump when energized. The transmitter is mounted in the building next to the pressure switch. I have two wires going from the pressure switch to the transmitter's "trigger" terminals. The transmitter just needs to see a close across those two terminals and it will send a signal across the existing wires to energize the relay at the well head. Once the pressure switch is satisfied, it creates an open across the "trigger" terminals, and the transmitter kills the signal, de-energizing the receiver relay, and shutting off the pump.
Fairly simple. And it all works like a champ, except...
The "trigger" terminals are not seeing the pressure switch close. And this is the same pressure switch that worked fine when connected to 240V! I read zero ohms with the meter, but it's like something with the internal workings of those contacts isn't compatible with the transmitter's input circuitry. When I touch a jumper wire across the pressure switch terminals (which are still wired to the transmitter input), the transmitter's "transmit" light immediately turns on.
So it seems the solution is to either install an add'l relay (which adds more complication), OR, has anyone heard of a pressure switch with contacts better suited for this application? Any other thoughts?
Thank you!

 

[Valveman]

The "except" part means it is not working like a champ. A closed switch should give the same continuity as a jumper wire. I guess you could just try a new pressure switch. But my guess is the problem is in the electronic device as it almost always is. It is a good thing it is not seeing the switch close instead of not seeing the switch open. But I would make sure my pressure relief valve is working just in case the opposite happens.

I have used telemetry like this to radio a signal to shut off a pump from a water tower. But a hard wire is always more dependable for controlling a pump. Telemetry just means sometimes your pump may not come on or go off as it should, and that is not a good thing.

I feel your problem, but I am not sure that is a dependable way to solve it.

 

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[Reach4]

Any other thoughts?

I did not find a pressure switch with "dry contacts" as you are seeking. Your thoughts on the relay are good including the complication aspect, which reduces reliability.

You could bring the water pipes below the frost line by getting a pitless adapter installed . Pitless adapters today are the norm in areas that freeze.