Baxi 105e problem

[Flashbaztard]

Hi
Just fitted a second hand 105e boiler to replace my knackered one
I only use this for hot water only!
But it runs when you put the tap on but then the temp gauge lights go up to 60 and it stops heating.then after a while it will heat again!
It is like its running the heating system and not the water system
Both micro switches need to be open for it to work where as in my old one only the resr switch needed to be on
I have swapped the pcb but no affect
Any ideas please. As I need a bath!!!

 

[terryplumb]

Bit confused ,are you saying the hot tap water runs hot for a while then cold then hot ,then cold repeatedly ? If so suspect plate hex.

 

[Flashbaztard]

Hot water runs as the water gets hotter it then cuts out the burner. If leave tap running it will cool down and burner will start again for a bit then cut out. And keep going like this!

 

[terryplumb]

Sounds like the dhw heat exchanger is blocked. You stated you only use the boiler for hot water but I assume the central heating side is fully connected .

 

[Flashbaztard]

Connected but only a foot of pipe each side then blanked off (old system ran ok like this)
Pressurized to 1 bar

 

[terryplumb]

I question the wisdom of that set up !! Anyway if the plate hex is blocked the symptoms you describe is what you get.

 

[Flashbaztard]

Thanks
System was all connected to house full of rads but we never used them! Over time some of the rads were moved ect so I capped pipes nr the boiler temporarily . that was many years ago. And never got round to putting it all back may do soon!

 

[AGAS]

now why change the pcb , someone diagnosing and fixing would have saved cash and time for you to have a bath . could either be a couple of reasons

 

[durhamplumber]

fitted second hand 105....FFS!!!!!

 

[Flashbaztard]

Sorry mate but im skint. And with any new boiler. Starting at £500. I had no choice!
I run a animal rescue and never have more than £50 in the bank at any time!
,there are poor people in the world you know !
It was advertised as in good working order!

 

[Flashbaztard]

Changed pcb because some forums put the blame there! And I took it out the old boiler witch im keeping for spares!!

 

[terryplumb]

What was the old boiler doing / not doing that caused you to change ?

 

[AGAS]

its a good boiler with good water flow rate to be honest and luckily good for you cheap parts , which knob jockey told you to change the pcb for first court of call

 

[AGAS]

either plate - hw differential - hw sensor - pressures is the first things to think amongst others things

 

[Flashbaztard]

Thank you for your help
Ill work down the list
Heat exchanger first
Thanks again!