CANARM - Replacement Thermostat for Heated Drinker, H0502

The thermostat (H0502) controls when the heating element activates. A failed thermostat is the second most common cause of waterer problems after element failure. Diagnosis:

• Element runs constantly: If the indicator light is always on and the water is noticeably warm even in mild weather, the thermostat may have failed in the closed (always-calling) position. This wastes electricity and can shorten element life.
• Element never runs: If the indicator light is off and the water is freezing, but the element tests good (correct resistance on a multimeter), the thermostat has failed in the open (never-calling) position.
• Inconsistent behaviour: Intermittent freeze events that come and go suggest the thermostat is at the end of its service life and losing calibration.

To confirm thermostat failure: with the unit at operating temperature, use a multimeter to measure continuity across the thermostat terminals. A functioning thermostat in cold conditions should show continuity (closed circuit). No continuity in cold conditions = failed thermostat.

The Canarm H0502 thermostat is factory-calibrated to activate (close the circuit and energize the heating element) at approximately 2°C (35°F). This is the temperature at which water is at immediate risk of beginning to freeze, making this the optimal activation point for energy efficiency — the element only runs when actually needed.

The thermostat deactivates when the water temperature rises above approximately 8–10°C. The differential between on and off temperatures prevents rapid cycling that would shorten element life.

Note that air temperature around the waterer is not the same as the water temperature inside the bowl. In a well-insulated barn at -10°C, the water inside the bowl may remain above 2°C for extended periods without the element running — this is normal and by design.

Yes — the Canarm H0502 replacement thermostat is compatible with both the H series and HL series steel heated waterers. These include the H50, H100, and their HL variants.

It is not designed for use in the polypropylene P-series waterers (P25, P50, P100), which use a different thermostat specification. If you have a P-series waterer, refer to your installation manual or the data plate on your unit to identify the correct thermostat.