Upstairs radiators getting warm when heating is turned off

[PHarley]

The upstairs radiators are getting warm when the heating is off and the hot water is on - the upstairs raditors are getting warm via the return pipe i.e. the return from hot water piping is syphoning back up heating return pipe and vice versa when the hot water is turned off and the heating is turned on, hot water is syphoned up the return pipe on the water system via the return on the heating pipework.


The boiler has recently been installed and is a Vailiant system condensing boiler. The system works from two control valves one for the heating and one for the hot water. The return line to the boiler incoporates a Magniflow filter. Return pipe from hot water and upstairs heating return pipe are approx. 75mm from each other.

Does anyone have any ideas how to overcome this problem?

 

[45yearsagasman]

1, It may be that the heating zone valve is simply not shutting off 100%.
2, Reverse circulation due to incorrect pipework connections, is another possibility. Call your installer back.

 

[PHarley]

Thanks for the reply.

We think we can rule out the heating zone valve not shutting off 100% due to the fact that this does not effect the downstairs heating. Therefore it could be due to your second point - incorrect connections.

The problem can be controlled to a certain extent by opening the return valve of a radiator which is positioned within approx. 700mm of the return pipes from the hot water and upstairs central heating. By opening the valve fully this stops hot water from syphoning back up the upstairs central heating return pipe. [/u]

 

[ianmcd]

The return from the indirect coil from your HW cylinder must be the last connection before the boiler , if it connects to the return pipework and then the radiators return pipework connect to the same pipe than that is your problem