A pool heater or heat pump is only as accurate as the control and sensor telling it what the water temperature is. Temperature controllers, remote heater controls, thermostats and thermistors decide when the heater fires, when it stops and whether it should run at all. A failed sensor can leave a spa cold on a Friday night or let a heater run past the set point. A bad remote connection can keep the heater from responding to automation at all.
This category covers pool and spa temperature controls: remote controls and thermostats for gas heaters and heat pumps, water, air and solar temperature sensors, thermistors, and related wiring and mounting parts from Raypak, Pentair, Hayward, Jandy, AquaCal and others. Service techs buy sensors and thermistors for diagnosis and repair. Owners with older pads buy remote controls to run the heater from inside. Builders use them when tying heaters into automation.
Water temperature is measured by a sensor in the plumbing, compared to a set point, and the controller turns the heater on or off. Where that logic lives depends on the setup.
| Part | Where It Mounts | What to Confirm |
|---|---|---|
| Water temperature sensor | Plumbing before the heater, after the filter | Thermistor value, probe and clamp style, cable length |
| Air temperature sensor | Shaded spot away from equipment heat | Compatible with the automation controller |
| Solar sensor | Near the solar collectors | Cable length, UV-rated housing |
| Heater internal thermistor | Inside the heater at the header or manifold | Exact heater model and part number |
| Remote heater control or thermostat | Indoors or at the spa, wired to the heater | Heater brand, model and control board |
A quick resistance test separates a bad sensor from a bad board. Disconnect the sensor from the controller, measure resistance with a meter, and compare it to the manufacturer's temperature-resistance chart at the water temperature measured with a reliable thermometer. A reading that is open, shorted or far off the chart means replace the sensor. If the sensor checks good, inspect the wire run, splices and terminals before suspecting the controller.
Temperature controls, sensors and thermistors at HVAC365 are brand-new with the full manufacturer warranty. Product pages list compatible heaters and automation systems, the thermistor type where applicable and the cable length. In-stock items ship in 1-2 business days. If you are not sure whether your heater or controller takes a specific sensor, send us the model numbers and we will help you match it.
After the filter and before the heater, solar return and any chlorinator or chemical feeder. That location reads true pool water temperature and avoids false readings from heated or treated water.
Many pool automation platforms use 10K thermistors, but not all, and heater internal sensors can differ. Use the sensor specified by the manufacturer of the equipment that reads it.
Spa temperature is read through the same water sensor when spa mode is on and water is flowing. If the pump is off, the sensor reads the stagnant water in the pipe. Readings are only accurate after the pump has run for a few minutes.
Most heaters have a remote or external control mode. Set the heater to remote mode or set its thermostat high, connect the heater's remote terminals to the automation controller per both manuals, and let the automation manage set points.
Sensor replacement is relatively simple, but it is inside a gas or electric appliance. A qualified service tech should do it and verify the heater operates safely afterward.
Many automation controllers allow a small temperature offset adjustment in the setup menu, which can correct a reading that is a degree or two off. If the error is large, inconsistent or changes with weather, the sensor or its wiring is failing and should be replaced rather than offset.
The air sensor may be failing, mounted in a cold spot or reading wrong due to a damaged wire. Check its resistance against the chart and confirm the freeze protection set point.
Fast Shipping
Easy Returns
Warranty Coverage
Financing Available
