Grant Vortex external oil combi boiler, working fine except..... The boiler senses demand and fires up whenever turning off the cold tap. This only happens with the leaver (they are not monobloc) type taps in the house. It doesn't happen when turning off these taps very slowly. It also doesn't happen on the traditional screw type taps. This isn't too much of a problem in the summer, but but it causes problems with the heating in the winter. The boiler quite rightly gives priority to hot water, which means the heating temporarily stops every time we turn off a tap. Rather a pain in the evenings when using the taps a lot for cooking etc. and the heating hardly runs. I'm guessing that the fix might be a hammer arrestor to reduce the shock caused by turning off the tap quickly, which in turn triggers the flow switch in the boiler. Would I need one hammer arrester for each tap, or would just one by the boiler be sufficient? Or am I looking at completely the wrong thing?
As you say a sharp surge in pressure sounds like it is fooling the boiler, a water hammer arrestor near the tap on the cold should cure it. Some boilers have one fitted underneath, have a look at the boiler installation instructions if it does it's worth getting your service engineer to check the one that's fitted is working.