Can anyone shed some light on my heating noise problem? My system is fully pumped with 3 port valve, header tank, 8 radiators all with TRV's. I understand one radiator should not have a TRV in-case all the valves shut down, therefore one is set fully on. When the system is heating hot water only or HW and radiators it's fine, no noise. If it's only pumping water to the radiators there is a loud whooshing sound from the pipe work around the pump, this noise gets worse as radiator TRV's close down. I assume this is something to do with flow rate being too high, I've reduced the pump to it's lowest speed and I'm sure there's no air trapped in the system, also all lock shield valves are fully open, but to no avail. It's confusing because a friends heating system (very similar setup) is silent even with only one radiator on.
Shouldn't the system be almost silent even if only one radiator is on? Would an automatic bypass valve solve my problem?
Dan