baxi 105e

[calrob]

hello guys this is my first post on this forum so here goes
boiler in question baxi 105e intermittant hot water' when demand for hot water is needed micro switch on diverter is activated and boiler fires reaches max temp cuts out cools right down and re ignites going through the same process have changed sensors still the same have even tried another pcb still the same. now what ive noticed when the micro switch is activated at the hot water differential should the other micro switch drop out [central heating]
or should it remain closed============regards========bob

 

[ian macca]

hi,sounds like youve got a blocked plate hex

 

[calrob]

do you mean hot water heat exchanger ;there seems to be a good supply
regards==bob

 

[Deleted member 2053]

These things can block on both sides. The fact that you get a good flow rate though the tap is indicative that the secondary is OK but the flow of central heating water through the primary may be low. This would certainly give the symptoms you describe.
Perhaps your system was not flushed adequately when the boiler was installed. 🙁

 

[cwrplumbing]

The way to test a plate heat ex is to take the temperature on the return pipe above the pump and take the temperature of the hot water outlet pipe under boiler, if its not blocked the temperature should be the same. if theres a big difference in temp it means its blocked and boiler shutting off on return tep stat.
replace plate hex hope this helps.

 

[calrob]

thank you will try that before anything else
regards===========bob