On 12 Mar 2006 13:05:19 -0800, "Alister21"
wrote:

I have a recurring problem with the radiators on the upper floor of my
house. From experience I have de-sludged and inhibited them in late
autumn but still the upper system chokes around this time of year and
the radiators go cold. On the ground floor all pipework is 22 mm and 15
mm copper (no problems there). However, on the 1st floor it is 22 mm
copper to and from a manifold and then 10 mm microbore.
My problem is this. Am I right in thinking that the flow and return
lines should serve two seperate manifolds? My system has them both
flowing through one manifold with the 10 mm microbore flowing and
returning from it. Is this right? I would have thought that the water
would follow the easiest route i.e. by-passing the radiators and
flowing straight back to the boiler. I think that as soon as I get any
sort of sludge in the microbore then that is exactly what is happening.
Every radiator in the house has a thermostatic valve, not a lockshield
in sight. No sign of a PRV anywhere else in the system either. I take
it from that, that the single manifold in question is not some sort of
internally divided job and it is 'straight through'. Coming to the
point now....Should I split the line here and install two seperate
manifolds and some sort of pressure relief between flow and return?

I suspect that you will find that this is actually a manifold with two
separate flow and return sections.

Try measuring or feeling the temperature of the pipes feeding it on
the boiler side and those going to the radiators.
If it really were going in and out as you say, there would be little
or no flow through the radiators, even when they are clean.



Does everything work OK immediately after cleaning? If not, then there
is probably a balancing issue and the radiators on the 15mm sections
need to have their flow reduced.

Certainly there should be lockshields on all radiators even if TRVs
are used, or the radiators on 15mm connections will probably receive
most of the flow until those rooms are warm.


If it deteriorates after a while and that is sludge, then there is
something else wrong. If you are using inhibitor, then it should
last for at least a year assuming you are using enough. There should
be little or no sludging. Even 8mm microbore works perfectly well
over long periods of time.

Suspects for early failure of the inhibitor and sludging would be
pumping over or sucking down of air in the feed/expansion tank. Have
you checked this carefully? Pumping over is obvious. Sucking down
will usually cause a sound of air bubbles being pumped around and it
will collect in the radiatrors.



--

..andy