dwh comes on on high burn then reverts to normal
and repeats every 20 seconds
going from hot to just over luke warm

bob leeson, January 2012

Replace water heat exchanger,it's blocked,or clean with acid,you have do drain system open rad vent,shut water supply to boiler,turn power off to boiler,undo heat exchanger with star screw driver or long l n key ,fit as per you removed. Fill system to 1 bar air vent rads

ltd, January 2012