Weird one this. Some radiators sometimes get warm sometimes they remain cold. (but not because of the TRV's or room stat, or boiler stat or boiler overheat stat - all those are normal and set appropriately).
We have tried every combination of CH and HW. Both zone valves move and work correctly when their respective thermostats demand heat.
The pump runs and has been bled of air, and I can hear that it is full of water internally.
The boiler feed pipe to the pump gets hot as normal, and after the pump, the pipes after the respective zone valves for CH or HW also get hot when their service is selected on. So far, so normal.
However, individual radiators sometimes get hot, sometimes they don't. Nothing to do with their TRV or having the HW on or not - even with only CH selected and its feed pipe getting hot; sometimes some radiators will get hot, other times they won't, (TRV's set to max and house is freezing cold). Tonight, four radiators got hot but later went cold, (not because of the TRV's - the feed pipe to the rads went cold too, but still hot water from the boiler going to the main CH pipe via its zone valve).
There seems to be no rhyme or reason.
So, does this sound like a sludge blockage or an air lock? Why does the problem seem to move around the system? No air at the bleed screws of any radiator - just water flows out.
PS, there is some magnetite around where the FE feed joins the boiler feed pipe, and it is blocked - no water from the FE tank can get through. This will be addressed, but for now I put mains water into a drain cock until it came out of the FE overflow to make sure the system was full of water. But no magnetite in the individual radiator feeds.
The system I inherited when we bought the house is old, but I need to keep it going until the warmer weather, and cannot afford to break it open or decommission it just now if I can possibly help it.
Many thanks if you can help - I am running out of ideas and things to check.
We have tried every combination of CH and HW. Both zone valves move and work correctly when their respective thermostats demand heat.
The pump runs and has been bled of air, and I can hear that it is full of water internally.
The boiler feed pipe to the pump gets hot as normal, and after the pump, the pipes after the respective zone valves for CH or HW also get hot when their service is selected on. So far, so normal.
However, individual radiators sometimes get hot, sometimes they don't. Nothing to do with their TRV or having the HW on or not - even with only CH selected and its feed pipe getting hot; sometimes some radiators will get hot, other times they won't, (TRV's set to max and house is freezing cold). Tonight, four radiators got hot but later went cold, (not because of the TRV's - the feed pipe to the rads went cold too, but still hot water from the boiler going to the main CH pipe via its zone valve).
There seems to be no rhyme or reason.
So, does this sound like a sludge blockage or an air lock? Why does the problem seem to move around the system? No air at the bleed screws of any radiator - just water flows out.
PS, there is some magnetite around where the FE feed joins the boiler feed pipe, and it is blocked - no water from the FE tank can get through. This will be addressed, but for now I put mains water into a drain cock until it came out of the FE overflow to make sure the system was full of water. But no magnetite in the individual radiator feeds.
The system I inherited when we bought the house is old, but I need to keep it going until the warmer weather, and cannot afford to break it open or decommission it just now if I can possibly help it.
Many thanks if you can help - I am running out of ideas and things to check.
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