This one is puzzling me

[Blackadder43]

Hi guys, sorry to bother you again.
I did a service on a friends boiler today
Baxi 105e
So everything was good and went ok until i tryed to check the burner pressure at the boiler
Connected mano and turned bath tap on full
Gauge would boost up to 13mb then after 10 seconds drop down to about 5 then boiler would shut down, then start up again....
Checked temp controller was full on max and it was.....
I had the cover down and accidently turned the water temp control knob the wrong way to what should have been minimum temp...
The boiler fired up and the gauge read a steady 13mb.....
so i then turned the knob to what should have been maximum and the pressure dropped and then the boiler cut out again.....

So disconnected everything and checked the knobs were on correctly
They were, no other way for them to have been fitted.

Tryed the same with the heating and found out that when knob was on max then boiler would only fire to 60degree...turned it to what should have been min temp and boiler fired up to max temp...

Took the cover off and noticed that a new pcb board had been fitted (it had the name of a local supplyer on it)

Could the person who fitted the board have put the wrong one in? (maybe the 80e and the controls are round the other way)
Or is there a problem somewhere with the wiring which has reversed the knobs controling?
Or is it blatently obvious and i am missing something..

The house was my friends elderly mothers who has since died and he will be renting it out...

He said that some numpty had done some work on it about 5 years ago and had told his mum he had set the controls up and she was not to touch them.......

So other than that everything works and checks ok....

Its strange that both the heating and the hot water temp controllers are working back to front....
Ive never come across this so am struggling to give an answer..
The only things i can think of are the pcb board is the wrong one or the pcb board has been faulty from day one?

Any help appreciated

 

[Agile]

The knob shaft has been inserted into the PCB at an angle of 180° out of phase.

Because the pot may have been turned past its stops it might have been damaged.

Again I dont understand why you are going to repair a boiler which has just been ( badly ) repaired by someone else?

These matters are better discussed in the Combustion Chamber part of the site.

Tony

 

[Blackadder43]

Again I dont understand why you are going to repair a boiler which has just been ( badly ) repaired by someone else?

The repair was alledgedly done abour 5 years ago.
As far as my friend was concerned it wasnt/hasnt been a problem
It only came to our attention when i tryed doing the boiler pressure and realised through trial and error that min temp was max temp and vice versa....on both the heating knob and the DHW knob...

The guy who did the repair 5 years ago must have known something was up but my friend remembers his mum specifacly saying "the heating man has set the boiler up and told us not to touch the knobs on it)
What he did was set it just a little past the shown minimum mark which infact turns out to be almost max temp.
I can understand the knobs being forced out maybe but on both controls?

Its all running safely, and all is ok except the fact that the temp controls now run back to front....

Sorry if i got the wrong forum, i will try and correct it..

Thanks anyway

 

[Onetap]

Potentiometers usually have 3 connections, one is common. The other two are coonected to opposite ends of the track so that one changes from 0 to 100% as the other changes in the opposite direction, from 100 to 0%. The original manufacturer would usually only connect to one of these two terminals.

Is there any way the repairer could have interchanged the wiring from the potentiometer to the PCB? The connectors are usually designed to stop that being done.