fan on central heating boiler activated by cold water

[capon]

any ideas why the fan on our worcester combi boiler comes on when cold water tap is turned on [but does not ignite[ same happens after flushing toilet ,as soon as cystern has filled up , a plumber thought he might need to fit a return valve , but this didn't happen before ,he hasn't actually changed anything apart from moving the cold pipe closer to the wall ,could it be air in the pipes?

 

[tonybhoy]

Your plumber's correct a non-return valve on the cold supply to the boiler will sort it.

 

[The831Bunny]

Before fitting a NRV go round ALL your hot & cold outlets (taps/shower/wc/outside tap etc etc) and run them making sure all air is out. If still no joy you have a dead leg of pipe with air trapped at the end. A NRV can help, but better to find and remove the dead leg.

 

[The831Bunny]

duplicate

 

[capon]

[quot
tet

="thanks a lot that sounds like it could be the reasonThe831Bunny";p="1998266"]duplicate[/quote]

 

[capon]

Before fitting a NRV go round ALL your hot & cold outlets (taps/shower/wc/outside tap etc etc) and run them making sure all air is out. If still no joy you have a dead leg of pipe with air trapped at the end. A NRV can help, but better to find and remove the de
ad leg.

 

[tonybhoy]

Never easy to find a dead leg mate, the pipe could be anywhere in your house.

Just stick a NVR in and it'll be fine.

Vokera compacts and the Sabre variants were pretty bad for this. I used to fit the NVRs as standard when fitting the boiler as they only cost about a £1 however not all of the boilers I installed suffered from the problem just some of them but Vokera tech's advice was to fit an NVR.