Boiler Cuts Out When a Hot Tap Is Opened
Heating is fine, but opening a hot tap makes the boiler stop rather than fire..
Heating is fine, but opening a hot tap makes the boiler stop rather than fire.
What is actually going on
Heating is fine, but opening a hot tap makes the boiler stop rather than fire.
The realistic causes, in order
Insufficient gas supply, so the extra demand pushes working pressure below the minimum A flow sensor giving a false reading and confusing the appliance's control logic A hot water thermistor fault causing an immediate overheat trip on hot water demand
What we test on site
Gas working pressure at maximum rate with all appliances on, which is the definitive test Meter and supply pipe sizing against the total appliance load Sensor resistance values against the manufacturer's table
Get a boiler that drops out when a tap runs diagnosed properly
Where supply pipework is the cause, upgrading it also improves every other gas appliance in the house.
Questions we get asked
What causes a boiler that drops out when a tap runs on a gas boiler?
Insufficient gas supply, so the extra demand pushes working pressure below the minimum
What normally puts a boiler that drops out when a tap runs right?
Where supply pipework is the cause, upgrading it also improves every other gas appliance in the house.
Is it safe to keep using the system with a boiler that drops out when a tap runs?
Undersized gas supply pipework is a genuine compliance issue, not just a performance one. It must be corrected to the appliance manufacturer's and gas regulations requirements.