hi. just wondered if you guys could help me. i have just installed a vaillant 637 on a one pipe system. the problem is that only half the rads are getting hot. i have tried balancing them all and even resorted to fitting an extra pump so it now has 2 running (one flow and 1 return) the pipes in the premesis are roughly 54 mm steel with 40mm branches so the extra pump was to help boost the water as the top floor is around 8-9 metres above the boiler in the basement. i know the best solution would have been to run a seperate return to the rads but the customer desperately needed some heating as the old boiler was condemned. the old boiler was the same set-up apart from being open vented? now with a fully pumped system i would have expected a better performance than the old system.
the only changes to this system we have made is put 1 additional rad on which is downstairs and gets hot.
asll the rads downstairs apart from one get hot and most of the ones upstairs range between luke-warm, hot and cold.
i have come across this problem before but that was due to an non-return valve and me changing flow and return to a combi but with this one i am 100 percent sure that the pipes are correct and if it worked before why wont it now? im thinking its either an air lock or sludge but i think its unlikely that a 40mm pipe would become blocked. anyone?????
the only changes to this system we have made is put 1 additional rad on which is downstairs and gets hot.
asll the rads downstairs apart from one get hot and most of the ones upstairs range between luke-warm, hot and cold.
i have come across this problem before but that was due to an non-return valve and me changing flow and return to a combi but with this one i am 100 percent sure that the pipes are correct and if it worked before why wont it now? im thinking its either an air lock or sludge but i think its unlikely that a 40mm pipe would become blocked. anyone?????
