On 18/02/2022 at 21:17, Nickfromwales said:

@graham1

 

Can you upload a diagram of your exact heating layout , as best as you can, please? This may help to get further replies and possible solutions to your ongoing issues.  

 

Sorry for delay. I cannot get to most of the installation and what I can see is rather complicated that I don't think I can make head nor tail of it.

I am expecting the installer to visit within the next 5 days as I have told them I will be making a complaint to MCS  (and any other body that will listen!).

Will  post  any answers that I get from installer

16 minutes ago, graham1 said:

 

Sorry for delay. I cannot get to most of the installation and what I can see is rather complicated that I don't think I can make head nor tail of it.

I am expecting the installer to visit within the next 5 days as I have told them I will be making a complaint to MCS  (and any other body that will listen!).

Will  post  any answers that I get from installer

That should be the straightest route to a resolve. If you could post back here if / when a solution has been found, and what was done to fix things, that would be appreciated.

On 22/02/2022 at 09:16, Nickfromwales said:

That should be the straightest route to a resolve. If you could post back here if / when a solution has been found, and what was done to fix things, that would be appreciated.

The installer BOSS is supposed to be coming bwas ill and now expected next Tuesday  8th. Will let you know wat happens

Not sure of all the details but it appears that  the systems pressure sends it down a larger feeder pipe that goes to a radiator and the returns via the the radiators other pipe so that the radiator is in effect pert of the DHW tank. Hope you can understand that.

The end result is what ReedRichards suggested - they are coming to fit a non return valve which they say will solve the problem.  The technician that fited the plumbing apparently has never come across the problem.

All for now: Thanks for all the suggestions