Vaillant Ecomax pro 28E: fault f5

[winchy]

I drained my system [gravity fed] to get rid of rubbish in the water and re-dosed with protector chemicals. But ... when re-starting the boiler, I got an error F5 - which I now know means it overheated (because I didn't read the instructions in the manual properly ... yes, I know ...).

Pressing the red button on the temperature limiter made the system start up again, but it now switches off immediately when it's reached temperature, and the pump doesn't switch off. Is this because the temperature limiter has become stewed and needs to be replaced - or is more than that wrong?

Thanks!

 

[adlplumbing]

have you vented all air out of the system?

 

[winchy]

Thanks for the lightning fast reply! I can still hear a bit of air in the system - not much though.

 

[adlplumbing]

well it that what might be helping it over heat

 

[winchy]

Sorry, should have been clearer. I got the F5 overheat immediately after I re-filled the system, and now the error has cleared.
I'm now operating the boiler at low temperatures (40'C) until I'm certain it works correctly. The boiler now goes to temperature, and then switches off (with no fault code), while the pump runs indefinitely.
The air which is left in the system is little bubbles - I've got air out of the pump and top of coil in HW cylinder.

 

[Agile]

Running a boiler dry as we call it sometimes changes the characteristics of the temperature sensors permanently.

It would need a very careful measurement of resistance @ temperature to check.

Tony

 

[Bunnyman]

Agile you an your bloody measuring thermistors!! do you have much experience as heating engineer ? or r u a rogue sparky i wonder?

Untitled

• Bunnyman
• 26 Mar 2010
• 499

 

[catfal01]

have you opened the aav on the boiler

 

[winchy]

Thanks to all - turned out to simply be the air in system ...