Baxi 105e hot water only 50 degrees???

[Rodreguez]

Hi all,

Got a customer with a baxi 105e.

CH is fine.

DHW the temperature is only luke warm. Thermistor just changed.

Tried cleaning the heat exchanger with a lime scale remover overnight.

Flow rate seems ok. Diagphram 1yr old.

Any suggestions as to what it is? The DHW heat excahnger is hot to the top left but only warm on the other side.

I think it is most likely the exchanger but have been told it could be the PCB.

Could anybody help me to narrow it down?

Thanks

 

[petit_pablo]

What's the flow rate and temp rise?

 

[45yearsagasman]

What about checking burner pressure and gas rate?

 

[onlyfitidealboilers]

did you test the thermister before spending your money on a part that wasn't needed??

 

[Boilerman2]

My money is on an incorrectly set mosureg gas valve!!

 

[Rodreguez]

no I didnt check the thermistor because visually it was covered in thick white powdery residue and rust all over the thermistor (looked like it had been leaking from there).

I felt sure it was this, but realise it would have been better to check its resistance when heat is applied to it.

I am going to check flow rate/temp rise, gas rate and burner pressure (again).

Will post findings soon.

 

[Gasman77]

Why check them again? If you have checked them already and they are good?

 

[Rodreguez]

Because im still learning and didnt write them down.

New I should have kept my mouth shut till later

 

[Rodreguez]

incoming cold temp 17 deg !

Temperature rose to no more than 51/52 degrees with a flow rate of more than 12ltr/min.

Lady now thinks her hot water is fine.

burner pressure is at 12.5, g4 meter gas rate 3.23

I noticed at one point the boiler temp guage read 80deg plus and the pump was very hot... too hot to touch.

 

[holty]

when you say temp rose no more than.50/52 degrees i take it your on about the temp of the water at the tap.rule of thumb is that a 24kw boiler would give about 9-10 lpm.at 35 degrees temp rise.the figures your giving would suggest the dhw is working rather well.

 

[newbuildinstaller]

sounds silly but have you tried running the water through the taps more slowly, a lot of people who have combi swaps complain there hot isnt hot but it is because the hot pipework is 22mm (the existing) thus drawing the water through the boiler too fast to heat it.

 

[ServiceNumpty]

That sounds bang on, without checking I think the 105e has 11 or 12lpm @ 35deg rise, which would equate to 52deg if cold mains is 17deg.

 

[holty]

9.8lpm @ 35 degrees. 13.7 @ 30 degrees. as per MIs. dont mean to have a go but you should understand a very basic issue with combis.

 

[Rodreguez]

sorry my previous post not too clear.

even after 30 mins the hot water would still be 51/52 degrees

 

[petit_pablo]

sorry my previous post not too clear.

even after 30 mins the hot water would still be 51/52 degrees

Right, why would it change? Incoming mains temp doesn't change in 30 mins