vokera linea

[AntoR]

Hi i have a vokera linea standard efficiency combi boiler, central heating is working fine but when i change to hot water mode and run a tap the water keeps going hot and cold hot and cold and so on. Any help what might be going wrong with my boiler? Thanks

 

[dcawkwell]

Thermistor is first thing to try.

 

[AntoR]

But if the thermistor was fecked or out of range should the boiler not fire at all on sensor check?

 

[dcawkwell]

Most unlikely thermistor would cause boiler not to fire.
DHW temperature will just be irratic.

 

[AntoR]

I will check resistance with multi meter if this is not the problem any other likely causes that i can check while im at it. Thanks

 

[petit_pablo]

Plate heat exchanger is blocked. Very common on the linea. The waterways are quite narrow compared to some.

A fault with the HW sensor generates a fault code.

 

[YELLERBELLY]

Dirty hw heat exchanger most likely.

 

[nickso]

A fault with the HW sensor generates a fault code.

not always, the primary gets coated in the same **** as the h/e does and doesn't read temps right. the dhw can be faulty without flagging a code.

as a rule if an h/e is blocked i change the thermistor. saves coming back later.