On the surface it appears that it will work. Here is a picture of the box for that zone. I see power coming in (top), existing two wires from the thermostat (top brown) and wires going to pump (bottom). Is this considered a dry contact switch? It's not clear how I would hook up such a device to this though.

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[![the following is a schematic of your control system. The center item you need to purchase and install. It also needs 110-volts.Good Luck. P.

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That's a switching relay, and it does not expose the C terminal (see the PDF).

You may be able to access the C terminal, but you'd have to disassemble the device. Which almost certainly voids the warranty, and could lead to unrepairable damage.

  • I believe this is correct. At the very least, I think you would have to solder in a lead to the common on the board; not a wise strategy. – Paul Logan Nov 23 '17 at 23:42

It appears to me that it would work. Leave the big wires alone. It's the two small stat wires that you will be working with. Treat those two wires as the first example shows in the instructions, the two wire example. Good Luck. P.

  • The two terminals on this device are for the thermostat. One is R (one transformer terminal), the other is W (internally linked to one of the relay coil terminals). The other transformer terminal (C), is internally linked to the relay coil. – Tester101 Nov 23 '17 at 20:17
  • I believe that Tester is correct. I now remember that on those pump relays, I could never find the common terminal. So Ryan, you will need another transformer/relay pkg that has a common available. Then use the N.O. contacts of that relay to close the thermostat contacts on the pump relay. – Paul Logan Nov 23 '17 at 23:35

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