Glow-worm DHW priority / flow detection fault

Furnace runs but no domestic hot water, radiators heat normally (combi-style Glow-worm furnace/boiler)

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Faulty DHW flow switch or turbine, Stuck diverter valve, Blocked plate heat exchanger, DHW NTC sensor fault on Glow-worm unit

Safety: Hot water can scald. Allow taps to run cool before working on the system.

User checks:

Ensure hot taps are fully opened; some flow sensors require a minimum flow rate.
Check that cold water supply to the appliance is on.

Technician steps:

Test the DHW flow sensor or turbine for correct operation and replace if not detecting flow.
Inspect and exercise the diverter valve; replace the cartridge or valve body if stuck.
Check the plate heat exchanger for blockage and descale or replace as needed.
Verify DHW NTC readings and replace if faulty.

Hard 4/5

DHW Flow Sensor / Diverter Valve

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