I have an open-vented, S-plan system with two 2-port zone valves, 28mm to hot water cylinder and 22 mm, dropping to 15mm, to radiators. There is an automatic bypass valve fitted in a loop-back circuit.
Last winter I started to get a banging noise from the central heating system. The noise was a load bang in the pipework that occured intermittently shortly after the heating cut out.
I think this is described as water-hammer?
As it happened, I was in need of a new boiler anyway, and arranged for British Gas to come and install a new boiler, pump and zone valves. (Pause to wait for traditional BG insults). The idea here was to change everything that could cause the water hammer.
The radiators in the system (13 mixed sizes) were newly fitted about 3 years ago.
So, BG went ahead gave the system a chemical clean, and installed a 300+ HE boiler, new pump and new bypass valve but, due to some admin cock-up, new zone valves were not fitted, so I'm left with the old ones.
When I complained about this, BG told me that there is nothing wrong with my existing zone valves and that the replacement bypass valve should fix the loud-bang-as-zone-valve-closes problem.
Sadly, this turned out not to be the case, and I am still getting the load bangs with the (mostly) all-new system.
Would any CH guru out there care to suggest what is causing the water hammer and what I need to get BG to do to fix it? Is it possible/likely that the zone valves are to blame or am I fixating on them unnecessarily?
I'm currently waiting a call-back from BG and would like to prepare myself with what options there are to diagnose and fix this problem.