Boiler fan question

[lewmar]

I am hoping someone can help with this question. Have a Vailliant combi boiler run by LPG & over the last few months the fan keeps coming on every now & again throughout the day & night. The boiler doesn't fire up when this happens. The fan stays on for exactly two minuts each time & can happen about a dozen or more times each day. We mentioned this when our yearly service was done & the man said it was quite normal. Maybe it is but its only happened in the last few months, never before. Just curious really. Maybe I will get some advice re this on here. thanks

 

[oldplumber]

you proboably have a preheat setting on the hw turned on, vaillant call it "warmstart", but you can normally shut it down if you want, check your instruction manual

 

[lewmar]

hello & thank you for your reply. The "warmstart" is turned off so unfortunately its not that.

 

[oldplumber]

Could be its the aps function whereby the pump spins up regularly to prevent the chances of it seizing up.

 

[Puddle]

which model of vaillant is it,can not think way engineer would think normal for fan to keep coming on

 

[oldplumber]

only thing i can think of is a leaking hw tap that allows enough flow to set ignition sequence to start but then flow is to low to complete the sequence, just an idea, saw something similar once, otherwise you ay have a controls problem with the pcb.

 

[Puddle]

I was thinking hot water flow switch oldplumber maybe to sensitive and reacting to pressure drop and increase in main when used near by or a dead leg with air near by but that depends on model

 

[oldplumber]

good point,leaky tap senario could cause same problem, less profit in changing a washer tho lol

 

[lewmar]

thanks peeps for all your replies. I'm now a little embarrased When the last engineer came, he obviously turned the warmstart on without telling us. Have now turned it off & will see what happens but somehow think it was happening before he came for the service. Re other posts, we do not have any leaking taps. Thanks for all your advice. Probably be back posting about something else in the future!

 

[oldplumber]

As ever, it normally a simple problem that you think of first