I have a an open vented system which is split into two with one part serving the original house (heating plus hot water via a 3 port valve) and the other part with it's own pump serving the extension. A single boiler feeds both old and new pumps and the feed/return pipework is common to both pumps except for the final 4m or so.
I changed a radiator (old house) and modified the pipework by creating a vacuum which appeared to go ok. New rad was heating up but I wasn't happy with the heat output from the downstairs rads (on drops) but this was actually an issue before I installed the new rad. To try to force the "issue", I turned off all upstairs rads and just left the downstairs ones on which heated up initially. However, after a while I noticed that they were cooling and the boiler had tripped and was "kettling" when turned back on so I realised I had lost circulation to the boiler. All rads were bled but no joy. I thought I had a blockage somewhere so drained the system down and flushed the boiler through to prove there was no blockage there.
I have several drain points and have drained down several times using different points to try to clear any air locks but with no joy.
Now after the last drain down, when I turn the system on, I hear an inrush of water and when I turn it off, I can hear water flowing back into the expansion tank. I also just tested and found that when started, the system draws air through the expansion pipe. I know that the 15mm feed from the expansion tank is not blocked as it re-fills the system through this pipe but I am convinced there is a physical blockage (or perhaps and air lock) somewhere as the system just doesn't feel right when I re-fill (pressure doesn't seem the be there when I bleed the rads). The new pump also does not circulate to the boiler. I had someone (supposed to be reliable on a well known "checking"trade site) come out to take a look 3 days ago and he said that the return from the extension system was in the wrong place and that was the cause of the problem (drawing in air) so I modified the pipework as he suggested (it now T's into the original heating return which then T's into the hot water return). I wasn't entirely convinced by what he suggested so whilst doing the mod I actually capped off the extension return and filled/ran the system but with the same result so this at least proved that the extension return was not the cause of the problem. When he returned after my mod, he did initially get the hot water primary to heat up (just by regulating the pump) but when he introduced the heating, circulation was lost and did not return to the primary circuit. He thought it was an air lock and promised to return 2 days later with his power flush but he let me down today and I don't particulary trust his judgement (I won't go into details here) so have told him I will find someone else.
I have drained the system down many times and modified the pipework without issue before and am convinced there is a physical blockage somewhere rather than an air lock.
Does anyone have any ideas on what may be causing the problem and is there anything else I can check/do without using a power flush etc. (if I need to power flush then I will get someone in to do this.
I changed a radiator (old house) and modified the pipework by creating a vacuum which appeared to go ok. New rad was heating up but I wasn't happy with the heat output from the downstairs rads (on drops) but this was actually an issue before I installed the new rad. To try to force the "issue", I turned off all upstairs rads and just left the downstairs ones on which heated up initially. However, after a while I noticed that they were cooling and the boiler had tripped and was "kettling" when turned back on so I realised I had lost circulation to the boiler. All rads were bled but no joy. I thought I had a blockage somewhere so drained the system down and flushed the boiler through to prove there was no blockage there.
I have several drain points and have drained down several times using different points to try to clear any air locks but with no joy.
Now after the last drain down, when I turn the system on, I hear an inrush of water and when I turn it off, I can hear water flowing back into the expansion tank. I also just tested and found that when started, the system draws air through the expansion pipe. I know that the 15mm feed from the expansion tank is not blocked as it re-fills the system through this pipe but I am convinced there is a physical blockage (or perhaps and air lock) somewhere as the system just doesn't feel right when I re-fill (pressure doesn't seem the be there when I bleed the rads). The new pump also does not circulate to the boiler. I had someone (supposed to be reliable on a well known "checking"trade site) come out to take a look 3 days ago and he said that the return from the extension system was in the wrong place and that was the cause of the problem (drawing in air) so I modified the pipework as he suggested (it now T's into the original heating return which then T's into the hot water return). I wasn't entirely convinced by what he suggested so whilst doing the mod I actually capped off the extension return and filled/ran the system but with the same result so this at least proved that the extension return was not the cause of the problem. When he returned after my mod, he did initially get the hot water primary to heat up (just by regulating the pump) but when he introduced the heating, circulation was lost and did not return to the primary circuit. He thought it was an air lock and promised to return 2 days later with his power flush but he let me down today and I don't particulary trust his judgement (I won't go into details here) so have told him I will find someone else.
I have drained the system down many times and modified the pipework without issue before and am convinced there is a physical blockage somewhere rather than an air lock.
Does anyone have any ideas on what may be causing the problem and is there anything else I can check/do without using a power flush etc. (if I need to power flush then I will get someone in to do this.
