I had a new Ideal icos he 18 boiler fitted last october and I have had the above problem since installation. I have delayed the original installer from effecting any modifications until the weather got warmer!
I know a little bit about the system and I know why the problem is happening but I can't work out how. The return connections from the hot water tank and the radiators are both teed directly into the input side of the pump whose output goes directly to the boiler return.
The hot water is pumped (It used to be gravity fed) now via a diverter valve and the hot water is finding a path via the return pipes to all 11 radiators. The installer has changed the new diverter valve for an even newer one and the problem remained. He then altered the original return for the hot water via a new pipe but it is still teed into the pump as before . The radiators do not get as hot now but this is still going to be a problem in the summer months.
My question is this : I am proposing to fit a non return valve in the radiator return feed to the pump since I think that I am getting radiated heat gravitating up the retun pipes to all my radiators -- will this work?
ps the feed pipe from the diverter valve to the radiators does not heat up when asking for hot water only.
I am proposing to fit a non return valve in the radiator return feed to the pump since I think that I am getting radiated heat gravitating up the retun pipes to all my radiators -- will this work? - Yes certainly worth trying.
Also check that hot water is not being fed over the expansion pipe when the system is set on hot water only.
I have the same problem reported, new boiler fitted Aug 08 with pressurised CH tank now. I thought I was going mad when I could not control the new boiler/CH i.e switching it off now that the good weather is here.
I have the company coming out on Monday to take a look. Very useful to read your forum posts before they arrive. Thanks