how can i get the downstairs radiators to come hot as two of them stay cold?

I agree with Malcolm. It sounds like your system is out of balance. The difficulty with balancing is that getting one to work can stop others. The approach I take is:

Open all the control valves fully (that is the one that you normally control the flow with. Close all the lockshield valves on HOT radiators (the ones at the other end, you need a small adjustable spanner for this). You should then find that at least one of the cold ones warms up - assuming it has water in it (follow Malcolm's instructions to bleed them). Close the lockshield valve on that one and repeat this until you have just one left. Close that one by about 45 degrees short of fully open.

This is the radiator that the system finds it most difficult to get to so ordinarily it doesn't bother! What you can now do is use the lockshield valves on the other radiators to restrict the flow to them so that it goes through all of them equally. Open each by about 90 degrees. Allow 10 minutes or so and see which (if any) have warmed up. Those that have not can be opened by another 90 degrees and so on until all are warm.

Finally close all your control valves to the temperature you want. If they are not thermostatic, close them by a minimum of 45 degrees. (By "degrees", I mean angles not temperature!)

The reason for closing valves a little is that leaving them fully open increases the risk of them seizing so that you cannot open them when you need to.

Carrying out this procedure may force out airlocks so check the radiators a day or two later to see if they have air in (if so they will be cold at the top and hot at the bottom).

Also, make sure you have inhibitor in to reduce sludge buildup.

Peter
October 2007

I agree with Malcolm. It sounds like your system is out of balance. The difficulty with balancing is that getting one to work can stop others. The approach I take is:

Open all the control valves fully (that is the one that you normally control the flow with. Close all the lockshield valves on HOT radiators (the ones at the other end, you need a small adjustable spanner for this). You should then find that at least one of the cold ones warms up - assuming it has water in it (follow Malcolm's instructions to bleed them). Close the lockshield valve on that one and repeat this until you have just one left. Close that one by about 45 degrees short of fully open.

This is the radiator that the system finds it most difficult to get to so ordinarily it doesn't bother! What you can now do is use the lockshield valves on the other radiators to restrict the flow to them so that it goes through all of them equally. Open each by about 90 degrees. Allow 10 minutes or so and see which (if any) have warmed up. Those that have not can be opened by another 90 degrees and so on until all are warm.

Finally close all your control valves to the temperature you want. If they are not thermostatic, close them by a minimum of 45 degrees. (By "degrees", I mean angles not temperature!)

The reason for closing valves a little is that leaving them fully open increases the risk of them seizing so that you cannot open them when you need to.

Carrying out this procedure may force out airlocks so check the radiators a day or two later to see if they have air in (if so they will be cold at the top and hot at the bottom).

Also, make sure you have inhibitor in to reduce sludge buildup.

Peter
October 2007

Hi, Linda,
It's a question of balance. The hot water naturally wants to rise to the upper radiators, as hot water is lighter and 'floats' to the top of the system. By closing the valves upstairs the flow is only to the downstairs radiators as they are now the top. You will notice however that the pipe to the valves upstairs should be hot below the valves.
What you have to do is go to the valve on the other side of the upstairs radiators and reduce the flow, close them down a bit but not completely. There is usually a plastic cap to pull off and there is a screw inside, turn this clockwise to close and anticlockwise to open. In addition you can 'open' these valves a little more on the downstairs one to increase the flow, but they should be almost fully open anyway.
You may have to do a bit of running around, but keep checking on it and adjust if necessary. You can even do it over a few days to get the balance just right. It is also worthwhile getting a radiator 'key' from your local DIY and bleeding out the air on the topside of each radiator. You just open slightly until the water comes out, then close. Hope that is clear.

Malcolm X
October 2007