Radiators on when water is heating

[Oggie]

When the hot water is turned on and heating the water (i.e. after a bath) all of the radiators come on too, even though the heating is off. Why?

 

[king.module]

that sounds a bit like our place - we have an old old heating system -around the *antiquated* hot water tank we have a little leaver that diverts water to the central heating - it's well funky.........

 

[sasolshares]

I asked the same question this morning, but no replies, so maybe my question wasnt worded well!
Nevetheless, I would be very interested in responses to Oggie's question as I don't know which part of the CH system to check & would like to understand the cause before deciding if this is a job that needs a callout.

 

[Bahco]

More info needed.
What system do you have
If it is a y plan it points to a faulty 3 port valve

 

[zutman]

If its a gravity feed system the check valve may be shot

 

[sasolshares]

I posted earlier that I had exactly the same problem. From Bahco's reply, thought I would take a look at the motorised valves in the warming cuboard.

Turns out the valve actuator had worked loose from the valve body due to vibration or whatever, retaining screws just about falling out, so not engaging with the valve spindle which was left in the CH -on- position. Tighten 2 screws and all sorted now!