Baxi 105 overheating

[Koogatubac]

Hi guys, been to customers and the hot water has been getting scalding hot and then once the boiler reaches its temperature the boiler kicks out. And you have to wait for the boiler to cool down before you get any response from it (roughly 5-10mins)

The high limit stat must be working fine as its kicking the boiler out, so surely its the DHW temperature stat?

I turned the thermostat down on the boiler and had 47* at the kitchen tap, however the boiler lit up at 60*

Its getting heat out the boiler too, plenty of 22mm and is a 3 bedroom semi detached house.

What you guys think?

 

[diamondgas]

Does sound like it koogatubac! have you tested the stat's resistance?

Any flashy lights?

 

[Koogatubac]

Tell you the truth, im rubbish on the multimeter parts, which your all probly thinking i dont know what im doing and its impossible to know without testing. However ive got a course booked in to go unfortunately its in september.
I dont want to fob this customer off though and dont want to 'tell her anything'
This is where i need help in the fault finding as i know its the most important part!
Theres 2 DHW Sensors which dont cost that much, so if the customer wants a hit at it it wont be that expensive

However as a professional i like to get things right the first time! Still young guys so go easy

 

[mountainman]

Even professionals don't get it right first time every time.

 

[galaxy_plumbing]

check manual and use multimeter to test resistance, not mega difficult, also check it at right temperature eg.25 deg

 

[Koogatubac]

Manual tells me how to remove sensor which is helpful, just learning my ways how to use the multimeter. I know i got to have it on the right setting (voltage >200) but never gone as far as that lol
I know... Im totally rubbish at this part lol

 

[Koogatubac]

Glad you all think its the same part as me too though will be a massive confidence boost if i fix it first time like! (never touched fixing boilers, just total installation!)

 

[galaxy_plumbing]

set it to ohms(resistance) if its auto setting then its ok, but if not, set it to maybe 10-20k limit, not sure what your multimeter is like..reading is usually 10-11k, but might be different, you need to look in your manual.

 

[diamondgas]

I'm always making mistakes! How else will I continue to learn Don't like the word mistakes actually, more errors of judgement! It's usually when I'm on something unfamiliar or there's no mi's at hand and the educated guess work comes out

 

[Koogatubac]

Thats what others have told, said i should of blagged it and said the boilers nakered lol i have noticed a few crustings inside her boiler mind!

Spoke to her and going ahead fitting the new sensors tomorrow, will let you all know if it works.
Told her that theres a chance it might not solve the problem and will have to go down next route, either way getting paid for fitting the new sensors!!

Thanks guys! Will let you all know, need to learn how to check resistance ASAP! Was hoping to only get small jobs when im starting up however getting broken boilers and big jobs! Lol o well....

 

[galaxy_plumbing]

Good luck mate.. We all learn everyday, so more you do, more you learn and get confidence

 

[Billy Bob Bob]

its unlikely to be the sensors
1,gas pressures could be way out i would have checked these first,2 main heat exchanger is badly scaled up,but there not difficult to change,3,pumps failing4 pcb is failing eventually it will melt the plastic venturi but this is a rare thing to happen on a 105

 

[Koogatubac]

She said this problem only happened when they were doing road works down the road and she had airlocks. I bled the pump straight away which had no air, doubt it could be gas pressures (why would that all of a sudden go crazy?!) heat exchanger, maybe the next port of call. However due to the age and ive seen crusting inside her boiler. Could try to persuade her to get a new boiler instead of throwing parts etc at it when its 12yr old baxi 105. Wont have much life left in it

 

[Billy Bob Bob]

Thats what others have told, said i should of blagged it and said the boilers nakered lol i have noticed a few crustings inside her boiler mind!

Spoke to her and going ahead fitting the new sensors tomorrow, will let you all know if it works.
Told her that theres a chance it might not solve the problem and will have to go down next route, either way getting paid for fitting the new sensors!!

Thanks guys! Will let you all know, need to learn how to check resistance ASAP! Was hoping to only get small jobs when im starting up however getting broken boilers and big jobs! Lol o well....

if your changing the ch thermistor you dont need to drain down its a dry fit pocket but looks like a wet type but i feel this is not your fault check its cold resistance should be 11k decreasing with temp

 

[diamondgas]

its unlikely to be the sensors
1,gas pressures could be way out i would have checked these first,2 main heat exchanger is badly scaled up,but there not difficult to change,3,pumps failing4 pcb is failing eventually it will melt the plastic venturi but this is a rare thing to happen on a 105

Was thinking one step at a time especially in this open arena! Sheeeeeeeeeeesh!! :lol: