Boiler shows E18; DHW does not start or stops unexpectedly during use

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

Stuck DHW flow switch, Scaled plate heat exchanger restricting flow, Faulty DHW flow sensor, Clogged inlet filter on cold water supply

Safety: Shut off cold water supply to the boiler and relieve pressure before opening DHW components.

Clean inlet filter: Remove and clean the cold water inlet strainer on the NTI combi boiler.
Check DHW flow switch/sensor: Remove the DHW flow switch and inspect for debris or scale. Ensure the paddle or turbine moves freely. Clean or replace as needed.
Descale plate exchanger: If DHW flow is low and temperatures fluctuate, the plate heat exchanger may be scaled. A technician should chemically descale or replace it.

Medium 3/5

DHW Flow Switch / Flow Sensor

Check Price on Amazon

We may earn a commission from links on this page.