Vaillant Boiler - Pump starts for COLD water! why?

[gollancz]

Ok. Just had a Vaillant 837 installed and all seems well, except that when I run a cold tap, the boiler pump starts up. Not the burner, just the pump. Can't understand this as surely a cold tap should have no effect on the boiler?
Any ideas whether this is normal. seems pretty inefficient to me. I am nervous that the installer scr*wed something up.
Thanks
G

 

[ChrisR]

Air in the pipes. Usually sorts itself. Search on "dead legs".

 

[Agile]

I wonder what the installer has to say?

He should have noticed that and advised you accordingly.

Tony

 

[gollancz]

Installer said nowt. will check with him this morning
what's a 'dead leg' and how do I check it?

 

[gas4you]

Definitely a dead leg. This is a pipe that has been cut and capped instead of being removed. If you used to have a hw cylinder I would check in airing cupboard for the old hot water pipe. Could be as simple as getting installer back to remove cap and put on an air bleed point to remove air.

Have you had a problem with yor installer? If not why do you post on here before giving him a call and a chance to rectify?

 

[bluenosedave]

i know it sounds stuped is cold and hot rev

 

[5TIMES]

These boilers have an aqua sensor (they detect flow) have you a water meter? you may need a mini expansion vessel fitted to the cold main to take up any expansion in the pipes. which is causing your boiler to start up

 

[fazedup71]

my money on a deadleg too, very common problem, the old cylinder cupboard the place to start, if installer argues I belive it is in the regs somewhere about not leaving dead legs in, but dont take that as 100 percent, been a while since i had a good read!

 

[nicknox]

I'd hope the OP had it sorted after 3 YEARS!

 

[fazedup71]

just noticed that your right, this is 3 years old!!!