Follow on: Boiler flow and return temp/balancing

[bhm1712]

in a previous thread which i cannot locate I was being helped with radiators that don't hear up properly upstairs. I was advised to call in a heating pro which I have now done. He came out today and attempted to balance my system. The system is a British Gas 330 boiler, range rated to 24kw. The original commissioning paperwork said a temp differential of 12 degrees was set across flow and return. Today the engineer balanced for a 15 degree differential across all radiators with a flow temp of 70 degrees. After 7 hours of work which was well above the 2 hour estimate he has admitted defeat: he said he can balance all the radiators to a 15 degree differential but at the boiler the flow is 70 and the return remains at 60 degrees no matter what he does.

Do you guys have any comments as to what may be the cause? I asked the engineer if the auto bypass was causing an issue but he said he had taken his measurements from a position upstream of the bypass.

 

[bhm1712]

To further this he said that with the boiler being presented with 60 degrees return, the heat exchanged is working less efficiently and the boiler will not be condensing as it should be and the return is required to be 54-55 degree for condensing mode. He said he could lower the flow temp to achieve a lower return but this would severely affect the rads which are already struggling to get hot