calydra comfort 100 hot water problem

[smokey67]

hi all

when the boiler is running central heating it runs fine but when hot tap is opened it starts to make a loud whining noise, any ideas what could be causing this. the diverter valve was replaced recently as well.

thanks

 

[Gary71]

Could be Kettleing as the boiler runs at a high temperture for hot water, I would have the boiler checked for contamination.