Moved in during the summer, now the CH is getting used have found that 2 rads out of 10 are cold.
System - is fully pumped single pipe (3/4" or 22mm) in older part of house, or twin pipe 15mm in new part. All rads have TRVs apart from the towel rails. Combi boiler ca 8 years old therefore no header tank. Some previous twit has fully opened all the lockshield valves so it will need rebalancing once I can get two of the rads working again.
Problem - Two rads, both on the older single-pipe part of the system are cold. I have tried turning all other lockshield valves off to direct maximum hot water just at these 2 cold rads but that doesn't help either.
Cold rad #1 just gets luke-warm along the top, rest is cold. It has the LSV on the flow, and Danfoss TRV on the return. The flow pipe gets hot up to the LSV. The return with TRV on it is cold. The Danfoss TRV is the type with the grey plastic screw collar, it's bi-directional, and the arrows indicate that it has been correctly set to be on the return side. I've had the head off, the pin moves in and out ok. I've turned the LSV fully in and out several times, so without taking it off, I assume that is unrestricted.
Cold rad #2 just gets very luke-warm along the top, rest is cold. It has an older Danfoss TRV on the flow, and the LSV on the return. The flow pipe is cool up to the TRV. The return with LSV on it is cold, but the short return between the LSV and the main single-pipe return is hot presumably because it's being heated from the main return. The Danfoss TRV is the type with the black plastic push-on collar, secured by an Allen Key, it's directional, it's been put on the correct way (flow). I've had the head off, the pin moves in and out ok. Again I've turned the LSV fully in and out several times so without taking it off, I assume that is unrestricted.
I have bled all rads including these two - no air appeared, only water. No tell-tale blackish water, only pure and clear.
Questions:
1. Could it be that the pins in the TRVs move freely but the valve inside is stuck? If so can that valve be freed without a drain-down, or does it mean new TRVs?
2. Is it more likely to be sludge? If so I'll take the rads off in the Spring. Any suggestions for a desludge product that works, and the best way to use it?
3. Or is it more likely to be an airlock?
Thanks!
System - is fully pumped single pipe (3/4" or 22mm) in older part of house, or twin pipe 15mm in new part. All rads have TRVs apart from the towel rails. Combi boiler ca 8 years old therefore no header tank. Some previous twit has fully opened all the lockshield valves so it will need rebalancing once I can get two of the rads working again.
Problem - Two rads, both on the older single-pipe part of the system are cold. I have tried turning all other lockshield valves off to direct maximum hot water just at these 2 cold rads but that doesn't help either.
Cold rad #1 just gets luke-warm along the top, rest is cold. It has the LSV on the flow, and Danfoss TRV on the return. The flow pipe gets hot up to the LSV. The return with TRV on it is cold. The Danfoss TRV is the type with the grey plastic screw collar, it's bi-directional, and the arrows indicate that it has been correctly set to be on the return side. I've had the head off, the pin moves in and out ok. I've turned the LSV fully in and out several times, so without taking it off, I assume that is unrestricted.
Cold rad #2 just gets very luke-warm along the top, rest is cold. It has an older Danfoss TRV on the flow, and the LSV on the return. The flow pipe is cool up to the TRV. The return with LSV on it is cold, but the short return between the LSV and the main single-pipe return is hot presumably because it's being heated from the main return. The Danfoss TRV is the type with the black plastic push-on collar, secured by an Allen Key, it's directional, it's been put on the correct way (flow). I've had the head off, the pin moves in and out ok. Again I've turned the LSV fully in and out several times so without taking it off, I assume that is unrestricted.
I have bled all rads including these two - no air appeared, only water. No tell-tale blackish water, only pure and clear.
Questions:
1. Could it be that the pins in the TRVs move freely but the valve inside is stuck? If so can that valve be freed without a drain-down, or does it mean new TRVs?
2. Is it more likely to be sludge? If so I'll take the rads off in the Spring. Any suggestions for a desludge product that works, and the best way to use it?
3. Or is it more likely to be an airlock?
Thanks!