there are 2 possible problems which could cause this, one is the temperature thermistors are faulty. 2 if you live in a hard water area , with lots of scale , your plate heat exchanger could be partially blocked .
brian
July 2007
boiler/system presure may be low require refilling to 1.5 bar when cold stops this boiler from modulation correctly
tony...tsp
July 2007
I can answer this question...
why does my hot water keep going cold then hot every minute or so?
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