Hot Water Works but Heating Doesn't
The cylinder heats normally, but the radiators stay cold whatever the controls say..
The cylinder heats normally, but the radiators stay cold whatever the controls say.
What is actually going on
The cylinder heats normally, but the radiators stay cold whatever the controls say.
The realistic causes, in order
A heating zone valve that has failed or lost its micro-switch signal A programmer or wiring centre fault on the heating channel only A room thermostat that isn't calling, including flat batteries on a wireless unit
What we test on site
Heating demand traced from thermostat to wiring centre to boiler Zone valve movement and switch continuity Pump operation on heating demand
Questions we get asked
What causes heating that won't run but hot water does on a gas boiler?
A heating zone valve that has failed or lost its micro-switch signal
What normally puts heating that won't run but hot water does right?
Zone valve heads and thermostats are inexpensive parts, and the diagnosis is quick with the right test equipment.
Is it safe to keep using the system with heating that won't run but hot water does?
On an S-plan or Y-plan system the fault is usually in the controls, not the boiler. Diagnosing it properly avoids paying for boiler work you don't need.