I have a problem with the heating system in a three floor house. The radiators on the top floor are only at best luke warm with each radiator progressive colder. I assume the coldest ones are nearest the end of the circuit, although I have not checked this yet. The radiators on the first two floors are hot and feel roughly the same temperature.
Therefore, I think that the system simply needs balancing.
However, the system is slightly unusual in that each floor is on its own separate circuit. They are all connected to the boiler via the same flow and return pipe. Each floor is simply a branch from these pipes with a flow valve and a lockshield valve on each branch.
Therefore my question is before I try balancing individual radiators (there are 25) can I just try balancing the three floor circuits first to see whether that makes a difference?
Would the procedure be similar in that you balance the circuit nearest the boiler first and then do the next two and just make sure that the radiator at the end of each circuit is hot?
Before trying anything I'd check the system is full of water, as it could be the ball valve stuck in the header tank. If water comes out if you bleed the higher radiators it is unlikely to be so. If wate fails to appear from the bleed valves, check in the loft for water in tge header tank.
Well, you could try - but it's a bit crude and wouldn't do anything for the relative balance of the rads in each section. I suspect that the valves are provided more for isolating sections for maintenance than for balancing.
Incidentally, I wouldn't *necessarily* start with the radiators nearest to to boiler, but rather with those which are *hottest* regardless of position - throttling them a bit to give a bit more urge to the others.
Before mucking about with the system, have you checked the obvious things - like that the rads on the top floor are full of water? If it's a vented system, is there water in the F&E tank? If it's a pressurised system, does it have adequate pressure?
When we purchased the house the seller did say that the heating for each floor could be isolated separately. However, I did try closing the locking valves by about a full turn on the lower two floors, but it seemed to make no difference.
Yes, I wasn't sure how to go about this with three separate circuits, but I did turn the locking valves on each of the lower floor rads by at least half a turn. Its made no difference to the temperature of these rads. However,it might have increased the temp of the top floor rads a little, although its difficult to tell. Should I just carry on closing the locking valves on all the lower floor rads a little at a time (a quarter turn) and see whether this does eventually make a noticeable difference?
If its of any relevance the radiators on the first two floors heat up reasonably quickly and they're all of a uniform temperature (too hot to touch) once they have warmed up. Two of the rads on the top floor are hot (albeit they take longer to reach a high temperature compared to the other two floors) and if you feel the flow pipe for the other top floor rads they are all reasonably warm its just that the rads themselves aren't.
You'll have to bear with me as I am very much a layman! I have bled them all and two did have air in them but all the others leaked water so assume they are all full of water. I assume its a vented system as its an old (early1980s) boiler (not a condensing/combi).
Radiator valves - and probably these isolation valves too - are highly non-linear in their response. You only get a significant difference in flow resistance when they are nearly closed. So count how many turns there are between open and closed, and try setting them somewhere in the region of 1/4 to 1/3 open. Turning them down a bit when the are almost fully open will make little difference.
It sounds as if the whole floor is getting less than its fair share of flow, and the cool radiators are getting even less. Check that both valves are fully open on each of the coolest rads.
It's probably vented, but pressurised systems have been around for a long time - although they were not very common in the 1980's. Assuming that it's a vented system, there will be a small fill & expansion tank (not to be confused with the large cold header tank for the HW system) in the attic. You need to find it and make sure that it's got some water in and that the ballvalve isn't stuck shut. There doesn't need to be *much* water - as long as the outlet is covered by 2 or 3 inches, that's fine - and leaves room for expansion when the system is hot without danger of over-flowing.
Assuming you haven't fixed by now, and you checked what the others said about the header tank having water in it, and the ball valve functioning, and the radiators are bled...
... and the radiators are not simply clogged (unlikely)...
You need to read the Balancing FAQ
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and looked at the thread above titled "Balancing radiators - time taken for temperature change"?
Are these lockshield valves (LSVs) or just gate valves? i.e. do they have a cap to prevent inadvertent adjustment. If they are gate valves they are for maintenance and should be wide open. Gate valves a big hand wheel on the end of the spindle, and are often seized up!! Actually you could balance with the gate valves, but they can't be locked so its a bit of a bodge.
With that many radiators over 3 floors it would cripple you running around adjusting, then checking temperatures repeatedly, so it makes sense to do it one circuit at a time. Also trying to do all at once would probably result in some of the LSVs being very nearly fully closed, which makes them very difficult to adjust and probably noisy (hissing/swishing sound) too.
Here's what you do....
Note the settings (see FAQ) off all three circuit LSVs, then close all fully except for the floor you are going to working. Open that one fully.
You may be lucky and find that all radiators on that floor now heat up OK, but if not you need to balance the radiators on that floor with respect to each other. Follow the FAQ procedure to do that. In any case I would check that there is at least on LSV fully open in order to get the best out of the system. If there is not one fully open, it means that the balance is not correct even though the radiators may be hot enough, and the pump pressure is greater than it need be.
Repeat for all three floors, each with the other two floors isolated.
When each floor individually has all its radiators heating fully (or as best you can achieve bearing possible pipework inadequacies in mind - see other thread), you can set about balancing the floors with respect to each other. You do this by treating a whole floor as if it was a single radiator, and treating it's circuit LSV as if it was the radiator LSV, as follows...
With all 3 valves fully open, check the common return pipe temperature for each floor just before it joins the main flow and return trunks that feeds all floors. Also check that all flows are about the same temperature.
Find the floor with the hottest return and throttle back its LSV to drop it's return temperature till it is about the same (or a little hotter) than the coolest floor's return. It will take some time for the temperature to fall due to the mass of all the radiators.
Do this repeatedly on each floor until all returns are about the same temperature. In other words, follow the FAQ but treat the already balanced floors as you would a simple 3 radiator system.
If all goes well , and the boiler/pipes/pump are up to the job, you should have 25 piping hot radiators.
As for a single circuit, as Roger commented, the hottest one is usually nearest the boiler but that is not necessarily the case.
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