I am integrating a Nest Thermostat with an open automation software, and need to make it think its W, Y and G wires are connected to something -- normally a 24VAC relay driving 120V appliances.

How do you fake such a relay? I tried resistors down to 220 Ohm (connected to C wire), with no success, the thermostat still complains that nothing is connected.

Sure I could connect an actual relay, but I want something compact that will fit behind the thermostat panel. Plus I am sure there is a better solution than a resistor wasting power into heat -- near the thermostat temperature sensor what is more!

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    \$\begingroup\$ Can you draw a diagram of how you have it hooked up? Where is the 24VAC coming from? \$\endgroup\$ – evildemonic Jul 10 '18 at 22:03
  • \$\begingroup\$ And add a link to the datasheet for the device. \$\endgroup\$ – Transistor Jul 10 '18 at 22:29

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