ferrolli optima 701

[metalmick]

Probably not the best boler in the world but it worked ok till last night,
C/H no problems, DHW turn a tap on and the boiler fires up and the water starts to run hot then the temp decreases and ends up cold, boiler still lit and sounds ok, turn tap off a bit to reduce flow and heat gradually returns,
This came about last night and not a gradual decline over several days.

checked the led's and with dhw on call, g,y,-,g,-,y and with ch on call
g,-,y,g,-,y so that looks to be in order?

Help please..
thanks Mike

 

[payney1974]

First thing is replace thermistors.

 

[Puddle]

well hot runs through and is heated by main heat exchanger on this boiler
So if main burner comes on and stays on when you turn tap on, should have hot water,unless you are not going to high flame and staying on low flame,as said could be a faulty termistor,if staying on low flame ,going to have to get multi meter out,to carry out checks on,thermistor, pcb and gas valve
Or if you are on high flame,could just be flow rate has been increased at boiler,try closing cold inlet valve slightly

 

[metalmick]

got a pair of themistors today, did replace 1 the other year, so will check the outcome later this evening
mike

All working ok, so will keep the new ones for when it packs up permanently,Are these thermisters known for having an intermittant fault/
ta for help
mike