Vaillant System Boiler With Additional Pump

[Zippymark]

Hi, i've got a job with a Vaillant Ecotec 630 system boiler, and i don't know the full history but the house has definitely been extended significantly since the boiler was installed. There's now 21 radiators/towel rails. It's getting to temperature, but even after balancing, it's not heating everything up great. I've tried tweaking the boiler (setting the pump to always run at speed 2). I've spoke to Vaillant technical and they've suggested i can fit an external pump to help out, wired into either x16 or x40 on the board depending how old the boiler is. Have any of you ever done this, is there anything i should know? And I know this is a bit hard to answer, but any ideas what sort of size pump i should be fitting, would a 15/60 actually improve anything or would it need to be more powerful? I very rarely work on houses this big, so i'm not particularly familiar with this size system.

Thanjks in advance.

 

[Gasmk1]

You could go down the route of a low loss header thus separating the system so second pump isn’t fighting the boiler pump. This way you can get the pump correctly sized for your system

 

[Zippymark]

Hi, thanks for the reply, that did cross my mind but it's a little tight for space where it is, it might squeeze in but I wasn't sure if that was necessary and just an additional pump would do?