central heating

[Tony Savate]

Hi all,
I have an open vented central heating system with 2 2-port motorised valves.
When I turn on the hot water the radiators also get warm.
I am unsure one of the valves is jamed as when I turn the hot water on both sides of the water valve get hot but not the heating valve. The exit of that valve dosent get hot untill I turn the heating on. So I presume both valve are working as they should be and not letting by?
What would cause the rads to get warm when the hot water is on? Could the system need power flushing as a blockage could be causing circulation problems or is it down to the valves?
Advice from plumbers/heating engineers would be much appriciated

Many thanks :coffee:

 

[AWheating]

how old is the system and has it been working correctly in the past?

 

[Simon F]

as already asked, is this a change to how it was previously working or has it always been like this?
is it all or just some radiators affected?

possibly reverse circulation,
to check, when the heating is on make a note of which pipes get hottest to each radiator, these will be the flow.
then the next day or when the rads have cooled, with the water on check with pipe gets hottest to the rads, if it is the opposite to before then you have reverse circulation taking place due to bad pipe positioning

 

[Best]

If always has been heating the rads when hot water only is on, then would suspect it is piped incorrectly with the return from rads linked in more than once.

 

[Tony Savate]

Thanks for the replies, it is quite an old system and the problem has only just started. Otherwise I would have looked into the problem a long time ago...
Tto my knowledge the system has neve been flushed which is why I thought mabe bad circulation is causing the rads to get warm? Or maybe I'm wrong and it is down to the zone valve??

 

[GasmanxxxR1]

It could be reverse circulation BECAUSE the zone valve is passing, id change that first and see how you get on

 

[Tony Savate]

It could be reverse circulation BECAUSE the zone valve is passing, id change that first and see how you get on

Thanks, would I need to replace the hot water zone valve or the heating one or both?
Many thanks

 

[jtsplumbing]

probley find that pipe work from cylinder is wrong and somewere on system is a check valve that needs replaceing

 

[GasmanxxxR1]

If its the problem we think it is then only ch valve needs replacing.

If its a check valve, it shouldnt need one in the first place, the check valve is just treating the symptom and not curing the problem

 

[jtsplumbing]

If its the problem we think it is then only ch valve needs replacing.

If its a check valve, it shouldnt need one in the first place, the check valve is just treating the symptom and not curing the problem

Yes we know it should not need one ! but they do get fitted, usely caused by return from cylinder not being last back to boiler, then to much trouble (Or cost) to re-run pipework

 

[AWheating]

as your system most likely needs a flush out you could bang some cleaner in and after a few days drain down/flush out (if alot of sludge is present then take each rad outside and flush with hose pipe or get it powerflushed) if possible drop a gate valve in either side of each zone valve. you can then isolate each zone valve to test if they pass and avoid drain down to change any faulty valves. If your valves are working then you may have a some sludge building up causing the hot water return to go around the heating system? this commonly can be at the point your feed and vent pipes connect to the system.