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L

long-pass

Hi guys, i am not too clued up on open vented system layouts and fault findings so any help will be much appreciated.
a friend contacted me to say some of there rads where not heating and they regularly had to bleed the rads on the top floor (3 floor house) i was rushing to another job but dropped in,checked the f and e which looked ok checked the pump (grundfos 15-50) which had stopped working removed it and replaced it like for like. there was red type sludge in the pump. bleed the rads on the top floor got the heating back on and said i would go back for a proper look at the system and the air in the system problem.this was about 2 and a half weeks ago. they called me to say the rads on the top floor were not heating again so i went back yesterday.
the layout is as follows= pumped central heating gravity hot water
ideal mexico boiler. you have to put on central heating and hot water on the controls and the room stat up to fire it up as its both or nothing
the pump is on the return coming out the hw cylinder then the cold feed (i assume its the cold feed as its 15mm and hard to trace) then it must be the tee for the central heating but i cant see it then the boiler
the flow is boiler then tee for central heating (onceagain i cant see it but it must be) then vent pipe (i assume as its 22mm and hard to trace) then a 2port valve (can only find one of these and assume theres only 1 hence the heating and hot water having to go on together?) then hw cylinder

the system has a lot of problems. heres mine, i balanced the system as it had not been done and put the pump speed up to 3 it was on 2. had a problem getting any heat in the highest rad a towel rad. i opened the bleed valve on it with the system running it was again full of air then i heard vent pipe in the loft pumping over into the f and e so closed the valve and turned off the boiler and went to have a look the water did not reach the overflow in the f and e. so re bleed the towel rad fired the system back up but the new pump had packed up! so went home as it was late due back tomorrow. any ideas? on the pump and literally rverything? they plan to have a new system installed in the near future.
cheers in advance
 
sounds like a poorly converted gravity system to pumped system, best advice would be to quote for new system.
 
just replaced the pump like for like as the vent pipe just about reached its 6.33m height over the pump and yes the pump is on the return coming out of the hw cylinder strange as it sounds
 
it turns out the pump turns off when the hw cylinder stat reaches its temp leaving the central heating to be a gravity system. have advised my friend to replace the lot, the system as lame plumber said is a really poor attempt at converting a gravity to a pumped system which is only pumped till the hw stat is satisfied.
 
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