@ksheston - This can be accomplished by pairing a SPST NO 24VAC (Single Pole Single Throw Normally Open) relay with each zone (e.g. http://www.ebay.com/itm/MAGNECRAFT-9AS1A52-24-Enclosed-Power-Relay-30A-24VAC-SPST-/331304146239). The parts list would be 14 SPST NO 24 VAC relays and three pump start relays along with some wire and female tab spade connectors. As the SPST NO relay is just under $6.00 US that puts the cost at ~$84.00 US for the relays, which is less than an additional Rachio unit (and two additional units would be needed).
To wire it up do the following:
- Connect the M/P (Master Valve/Pump Start Relay) terminal to one side of the pole terminal in all 14 SPST NO relays.
2a. Connect the other side of the pole terminal for the relays associated with zones 1 through 5 to one of the pump start relay input wires for pump 1.
2b. Connect the other side of the pole terminal for the relays associated with zones 7 through 12 to one of the pump start relay input wires for pump 2.
2c. Connect the other side of the pole terminal for the relays associated with zones 14 through 16 to one of the pump start relay input wires for pump 3.
- Connect the other pump start relay input wire, or common, for all three pumps to a C(ommon) port on the Rachio. I would wire nut all three pump start relays together or daisy chain from one to the other so that there is just one wire in the Rachio C(ommon) port.
- Then for each Rachio zone run an additional wire from the zone terminal to one side of the coil for the SPST NO relay paired with that zone.
- Daisy chain a wire from the other side of the coil terminal to each SPST NO relay and connect it to a Rachio C(ommon) port.
How this will work is the Rachio will put current on the M/P port when the Rachio is irrigating. The M/P current won't go anywhere because it is blocked at each one of the relays. As there will be one zone energized when the Rachio is irrigating, the current from that zone will travel to the sprinkler solenoid to open it up and it will also energize the coil in the SPST NO relay associated with that zone to allow the M/P current to flow to the associated pump start relay which will then close and provide 120 (or 220) VAC current to the associated pump.
Let me know if you have any questions.
@Gene - any thoughts? Did I over engineer it?