open vented fully pumped double feed indirect heating system

[desrob]

ikon 60-80 ci,fanned flue boiler,this system is 10 rads and you are lucky if three rads are working to there potential,the cold feed from f&e is tee'd into return at cylinder coil and the heating vent is also on the coil hw feed,the system was pumping over all the time,so i changed the piping arrangement to vent and cold feed behind pump on flow from boiler to mid position valve.i filled the system up vented rads and hoped for the best,the rads were no change,didn't expect there to be,but it stoped pumping over all the time,it did how ever when in hw and central heating mode start to make a loud noise and pumpover ,whats going on,is the pump no good 25/60 grunfos (rads),or have i got some blocked pipe work ,or is some thing else going on.

 

[Anton]

Get yourself one of those telescopic magnetic retrievers for getting back lost tools. I think they sell them in the likes of B&Q
They have a powerful magnet on the end. Copper pipe is non magnetic, so if you run it against the pipework near to where the cold feed entered the system and it sticks like sh*t to the pipework it's a good indicator of cr@p/blockage in that area.
I've located plenty of blockages using this.