Pump/Fan Overrun question

[jackecole]

Hi

Most, if not all boilers nowadays have a pump or fan overrun built in to remove the residual heat after a demand has ended - but mine has no pump or fan overrun stat, so wondered how it work/was controlled?

Is it done by the board? ....

 

[45yearsagasman]

Are you going to say what boiler you have or do we have to keep guessing?

 

[jackecole]

worcester junior 28i - but was just enquiring in general too

 

[45yearsagasman]

Some Baxi's have no o/run either.I guess the makers deem it not needed and that the heat exch can take it.

 

[jackecole]

mine has a fan overrun but no overrun stat!!

 

[ChrisR]

Yes it's done by the board, in something like a modernish combi. Sometimes timed, usually by temperature.
On old boilers you could add a pipe stat to hold the pump running until it got down to 50 or whatever, not an option in a combi tho!

 

[MJN]

mine has a fan overrun but no overrun stat!!

It doesn't need one - it uses the flow temperature sensor.

Mathew