Baxi HE28 noisy only on one hot tap

[1animal1]

Hi. I've had a Baxi HE28 condensing B fitted for almost 6-7 years now, recently flushed the system several times and given it its first dose of inhibitor X100 after a few weeks running the system with X400(didn't know about the stuff previously). The radiators all work fine, as does the shower which is mains fed (not electric). The problem I'm experiencing is when I use the hot water tap on the downstairs sink which is about 3 meters from the boiler (mounted in the kitchen), i get a loud grinding noise from the boiler - I've reduced the temp on the dial and this alleviates the noise, but obviously the preference is to run the boiler at max water temp.

It's weird that the noise only appears on the kitchen hot tap whilst on max water temp - Checking, I can't see that it makes the noise any other time.

Any help would be appreciated

Tim

 

[1animal1]

bump - is anyone able to help or offer suggestions?

 

[1animal1]

Update if this makes any difference - The unit is now making the noise sporadically when using the shower. It sounds to me like bearings going perhaps.