I have a Vaillant vuw 282 e, when i draw hot water from bath tap, then at same time draw cold from cold tap my boiler cuts out and then get cold water coming out of my hot, I had enginner out, incoming water pressure was 2.5 bar, flow rate from cold was he said 18 lts/min and hot was 11.5 lts/min. Even when i have a shower and toilet is flushed cold comes through shower. can anyone help please. I have recently had a new diaphram and differential pressure switch placed but still have problem.
Many thanks

Trev Scott, June 2012

have you ALWAYS had this problem
or has it just occured RECENTLY
IF ALWAYS:-
a balancing valve fitted on your cold mains & DHW pipes would equalise the pressure from hot & cold taps
this should hopefully stop boiler cutting out
but it depends on layout of your pipework
would have to have someone on site to survey exact layout & recommend appropriate valve
IF RECENTLY:-
have you had any plumbing work done prior to DHW problems?
cause & effect

AWOL, June 2012

Quite a drop inlet to outlet, on water, I would check for an inline filter, clean it. With the pressure readings, Very difficult. I would of said low water pressure. With all your problems, points to low water supply pressure. IS it fed from a tank, or mains. IT should be fed from mains. The parts that you have had replaced, would eliminate any boiler problems, Down to your water supply. But good pressure one side, Low other, something is blocking it. again filter. But some units do have a restricter in line

SD, June 2012