GCH some rads hot when water only on

Hi All,

Sometimes when our gas boilder is heating water some of the rads also get hot.

We have a three zone control system. When the boiler is running to heat the water only the water value is open and the valves and pipes, coming from the boilder, for the upstairs and downstairs zones are cold.

My thinking is that the thermostsat on the tank is not working correctly and the boiler is not cutting off so excess hot water from the hwt is overflowing into the rads

Does this sound like the problem?
Thanks
RB

By the way the thermostat is wirless and attached about half way down the tank

Nothing to do with thermostat, etc. The hw within your cylinder is not the same water that is within your heating system.

It is caused by reversed circulation and caused by the radiator circuit flow pipe being split before the hw flow and re-joining after the hw return. Basically, when the hw only is on, the heat is re-circulating through the return pipework to the radiators. Having the motorized valves on the return pipework can also help to prevent this.

It is easily avoided by connecting the flow to the radiators after the flow to the hw cylinder and the return before the hw cylinder return connection.

If this is not the problem, then another possible cause is that the radiators that are heating are plumbed into the same circuit that heats your cylinder and should be re-plumbed into the radiator circuit that serves that particular zone.

Thanks Shane I will check it out

Shane is bang on there.

You will certainly need to adjust some pipework. Hopefully your floors can come up without too much pain. It also may take a bit of investigating to find where the adjustments need to take place.