How to Fix / Troubleshooting

Safety: Isolate power and allow the unit to cool before touching hydraulic components.

Bleed air: Open automatic and manual air vents to remove trapped air from the primary circuit.
Check pump operation: With power restored, call for hot water and listen for the pump. If it hums but does not circulate, the impeller may be stuck.
Free pump shaft (if design allows): Some pumps have a front screw. Remove it (water may drip) and gently turn the shaft with a screwdriver to free it. Refit the screw and test.
Clean primary filter: Remove and clean the return filter/strainer of sludge and debris.

Note: If the pump does not run at all, check its electrical connector and have a technician test voltage output from the control board.

Error 28; unit indicates primary circuit circulation fault or pump problem.

Possible Causes