Heater Flow Switch
Most pool heaters, gas or heat pump, use a pressure switch to determine if there is water flow and the heater should run. There are conditions when the pressure switch will sense pressure in the heater pipes but there is no flow, such as when:
- the heater is bypassed and pressure is trapped in the pipes
- the heater is installed above the water line
- the heater is installed below the waterline allowing the pressure switch to be closed from static pressure with no flow
The pressure switch has an adjustment range for heater placement. Consult the manufacturers installation manual. If the heater placement is outside the pressure switch adjustment range then the pressure switch needs to be replaced by a flow switch.
