Change the Temperature Setpoint of Your SPA With a Smart Outlet

I had been looking for a long time for a way to lower the temperature of my spa when it is not in use and the solution turned out to be very simple.

Most spa temperature sensors have a 10,000 ohm thermal resistance, I put a resistor in parallel with the thermal resistor to modify the value that the controller will read. A relay activated by a smart outlet, a 10,000 ohm resistor installed on the normally closed contact of relay with a 120 volts AC coil.

I cut the sensor wire, determine which wires were connected to the thermistor. I connected the resistor so that it is in parallel when the contact is normally closed, when I activate the relay connected to the smart outlet, the resistor is disconnected from the thermistor.

As the resistor is on a normally closed contact when the SPA is deactivated, the relay connects the resistor in parallel is false the reading of the temperature controller as can be seen in the photo, in my case it indicates 119 degrees, when I ask Alexa to activate the spa it activates the relay which will open the contact and remove the resistance of 10,000 ohms which is in parallel with the thermal sensor.