hot water flucuating.

[strawhatfox]

I have a ravenheat csi 85T with the problem that the hot water goes hot then cold and then hot and cold, I have replaced the dhw thermistor and the diverter valve. the boiler lights for about twenty seconds then goes off and then comes on again as the tap is running. it the same on ch or hw setting. even if the ch is running the flame goes off and on when the hot water tap is on. Thanks for any help,

 

[Dotty]

Not a diy repair.

You need a gsr in to fix it.