Explain why some boilers have pump over run and others that dont

[Inverness]

Hello guys can someone explain why some boiler have pump over run and others that don't. I'd appreciate it thanks

 

[GasmanxxxR1]

Different materials used for heat exchangers

 

[gassafe]

It's due to the low water content heat exchangers, the overrun takes that excess heat away & prevents kettling noises etc

The ideal icos dosent have one & utilises the fan overrun to cool the hex after switch off...

 

[townfanjon]

Yep the Viessmann compacts are ok without , ( SS heatexchanger )

 

[chris watkins]

Yep the Viessmann compacts are ok without , ( SS heatexchanger )

Unless they have change them in the last couple of years then take care !!! this is not the case, despite what they may tell you I know I have got one & had to alter system controls to stop it from over heating.

 

[townfanjon]

As far as I know they haven't changed them , they come with a wire and plug that connect to the pcb , but have always said they are ok either with or without.
Thanks for that , I know the local engineer so think its worth a call to check

 

[Inverness]

Thank you all