Radiator heats ups when hot water only is on

[eltommos]

Searched wiki etc.but couldn't find any related info.

When hot water only is on, one of the upstairs radiator heats up. All other radiators remain cold. Three seperate control valves on heating system, 1 for hot water, 1 for upstairs and 1 for down stairs heating.

Radiator heats up from rad thermostat side when hot water is on. Normally this radiator heats up from the other side when the heating is on.

I can only think that this radiator is getting hot because of backflow through the system. When hot water is on the upstairs and down stairs control valves are both closed.

Any tips or help appreciated.

 

[kevplumb]

I can only think that this radiator is getting hot because of backflow through the system. When hot water is on the upstairs and down stairs control valves are both closed.

sounds as if its been piped up wrongly

 

[eltommos]

System has been working fine for 3 years and this has only just happened.

 

[kevplumb]

ok anything been altered changed

bear in mind i can't see it

 

[eltommos]

Added a new radiator downstairs and replaced the control valve on the hot water system but that was 4 weeks ago and all 3 systems were working independant of each other.

 

[doitall]

Where did you connect the new radiator in.

99% says it's the problem.

Can you do a drawing.

 

[eltommos]

Have added a drawing - hope this helps. Is there a chance that there could be some backflow from the hot water circuit entering the upsatairs radiator?. Only one radiator heats up all others remain cold. Hot water enters this radiator from the thermostat side which is the opposite side when the heating is on.

//www.diynot.com/network/eltommos/albums/

 

[doitall]

I think it needs to be a tad larger.

IS this rad that gets hot in the bathroom by any chance.

 

[kevplumb]

try 3 clicks dia

 

[doitall]

Well it ain't that.

Really need all the layout now.

 

[eltommos]

I don't have details of the complete layout. All I can say is that it's only started happening 2 days ago and it was ok before, even after the changes made.

Any other ideas would be appreciated.

 

[doitall]

Have you tried putting the heating on/off a few times, it may be a stuck MV, and letting by a tad.

Check any auto by-pass valves as well.

Has the pump speed been turned or changed.

 

[eltommos]

OK thanks - I will try switching on and off. Pump speed not turned or changed. Where would the MV be? Is this short for Main Valve?

 

[kevplumb]

motorised valve View media item 11149 View media item 11148