Baxi combi 105e

[Johnt96]

My boiler has developed a fault, The hot water supply through the tap is only coming through luke warm, the central heating works fine and all lights look ok, no warning lights on.
The dial that controls the water temperture seems to have a lot of play, moves too freely ?
any one help ?
John

 

[ianmcd]

switch your heating off and then run a hot tap , does it run cold ? then come back and let us know

 

[Johnt96]

Turned heating off and it still just runs warm, however when I turn the tap down to stem the flow it does run hot.

 

[ianmcd]

Do your CH pipes heat up when you are running HW only with the CH switched off ? another thing to look at is how fast your HW is running if you have a vessel that you know the volume of say its 10 Litres time how long it takes to fill from the hot tap i.e if it takes 1 minute then the flow rate is 10Litres a minute

 

[Johnt96]

10 litres in 52 seconds.
I have the heating on, so will switch off, wait to cool down and try the other task.

 

[ianmcd]

your flow rate seems fine either your diverter valve is passing or you have a thermistor problem if your diverter valve is passing your heating pipes will heat when you are running HW only another thing that may be the problem is a mixer valve i.e. shower or thermostatic tap blending way to test is run HW and feel the HW outlet at the boiler and see if it is hot and the water coming out of the tap is cooler then its not the boiler its blending somewhere

 

[Johnt96]

We have a shower with thermomastic tap that has been sticking and running at different tempretures, we have a lot of limescale here.

 

[Johnt96]

also when I run the hot water and try moving the temp dial up or down , it doesn't alter the temp lights on the boiler, they stay with the first two lights on upto 40*, its only when I restrict the flow by turning the tap to a slower flow, then the temp lights go up and the water gets hot.

The temp of the pipe exiting the boiler is the same as the water.

 

[ianmcd]

with the information you have given me I would say that your DHW heat exchanger has a partial blockage or is scaled up but cant guarentee without being in front of the boiler, there are loads of threads on here about how to clear the blockage and how to test if that is indeed the fault

 

[Johnt96]

Ok Will have a look at that, thanks for advice and help.