An HDS burner that lights and then stops has passed at least part of its start sequence. The important question is whether it stops because the machine has reached temperature, loses a safety input, loses flame, or fails when the trigger is closed and reopened.
Normal cycling versus a fault
The burner should stop when the selected temperature is reached and restart as water temperature falls. That is normal. It is a fault when the outlet becomes cold, the burner will not restart on demand, smoke appears, or the machine needs to be switched off and on each time.
What can interrupt the burner
- Unstable water flow or a flow-switch signal dropping out.
- Fuel starvation, air entering a fuel line or a restricted filter.
- Weak ignition or poor flame caused by nozzle and electrode condition.
- Thermostat, temperature sensor or overheat protection operation.
- Electrical control, contactor or supply-voltage problems.
Why trigger cycling matters
Some faults appear only after the trigger closes. The machine must unload safely, recognise the next demand for water and repeat the burner sequence. A workshop test should therefore include several hot restarts instead of one successful ignition from cold.
Send the model and symptoms, or ask us to help match a machine to the work.