CH comes on when HW Comes on

[03tohare]

Hello! We have a oil fired heating system (new boiler last year) with a HW cylinder. Both the two way valves for the CH and HW have been replaced but when the HW comes on the radiators around the house get hot. The CH 2 way valve is 100% closed when the HW comes on and the copper pipe the other side of the CH 2 way valve remains cool. How is the CH system getting hot with the CH 2 way valve remaining closed?

 

[Mottie]

Did it used to be gravity hot water at some time in its life? I think on gravity hot water, some rads are deliberately connected to the hot water. Maybe it’s something to do with that?

 

[03tohare]

Did it used to be gravity hot water at some time in its life? I think on gravity hot water, some rads are deliberately connected to the hot water. Maybe it’s something to do with that?

hmmmmm im not sure. It could have been. In the loft there is the old cold water tank and a fair bit of redundant copper piping that appears not to be connected to anything.

 

[CBW]

Could have broken 3 tee rule

 

[foxhole]

Do the pipes for hot water and heating run close together for any distance.
Just a few metres 4” apart used to give us hot water from the cold tap before we insulated the pipework.

 

[03tohare]

Could have broken 3 tee rule

ok after a quick google got the jist of that. Would a NRV on the heating return solve this?

 

[03tohare]

Do the pipes for hot water and heating run close together for any distance.
Just a few metres 4” apart used to give us hot water from the cold tap before we insulated the pipework.

no thats not a problem for us

 

[03tohare]

I just did a test where i turned the HW on then with the nearest radiator to the HW cylinder i felt which side of the radiator got hot first with the CH pipes. The heating return pipe got hot first so I suspect we have a reverse circulation issue?

 

[bigun]

Are you sure the valve is ok? I had an instance where a (banico) valve failed. when I removed the valve, the ball thing was missing( never did find it either) so it was open all the time

 

[03tohare]

Are you sure the valve is ok? I had an instance where a (banico) valve failed. when I removed the valve, the ball thing was missing( never did find it either) so it was open all the time

Yep its only 3 months old and the pipe the other side of the valve does not get hot when the HW comes on

 

[terryplumb]

Sounds like Reverse circulation . How long have you lived in the property ? Has this always been a problem ?

 

[03tohare]

Sounds like Reverse circulation . How long have you lived in the property ? Has this always been a problem ?

been here 2 years. Yeah its been a problem since we moved in. Will get a heating engineer booked in to sort out the reverse circulation and not just replace the 2 way valve!