In an earlier contribution to this discussion,
Kroma wrote:

Hi,

We had 'a man' round to remove the radiators in our lounge and dining
room prior to decorating as they were 'loose'. It was discovered
that the lounge radiator was cold just before this but a large amount
of sludge came from the pipe upon removal so we guessed that this was
to blame (we are new in the house so have no idea of the previous
history).

When the decorating was finished, the radiators were re-hung but
something broke on the dining room rad. The lounge radiator was now
working fine. A date was made for the dining room radiator to be
sorted out.

Unfortunately 'the man' forgot to come!

In the meantime, a leak appeared from a radiator valve upstairs. This
was fixed promptly (although the white 'knob' broke in the process).

Today, 'the man' returned to finish the job on the dining room
radiator. Apart from managing to empty the system into the fishpond
(sorry fish!) everything seemed to go ok. This evening the dining
room rad was warm and the lounge radiator was stone cold. We phoned
'the man' who suggested that we turn off a couple of upstairs
radiators to release trapped air. This worked for the dining room
radiator which is now hot. We then discovered the top of the
bathroom rad was only warm but this was fixed by bleeding it.

We are now left with the situation that the upstairs radiators are
fine, the kitchen radiator appears to be at about 80% heat, the
lounge radiator is stone cold (it was working yesterday) and the
other downstairs radiators are fine.

Any ideas as to what could be the problem with the lounge radiator?
It's freezing!!!!

Thanks in advance,

Daz

As others have said, you're going to need to balance your system very soon,
and de-sludge it fairly soon (although I would wait until the end of the
winter for de-sludging if possible).

It is distinctly possible that your immediate problem is caused by an
airlock. I would guess that you have solid floors downstairs so that the
pipework cannot go under to floor but has to come down the wall from above
for each radiator. Is this correct? It's very easy to get airlocks in the
pipes to individual radiators with this setup. Before doing any bleeding,
make sure that there is some water in the small fill and expansion tank in
the attic (not to be confused with the large cold water header tank) and
that its ballvalve is working properly. Then bleed all your radiators until
water comes out of each one.

If you've still got a cold radiator, turn off all other radiators - both up
and down - and turn up the pump speed temporarily to try to get water
flowing to this cold radiator. If that doesn't work, you need to bleed each
of the pipes connected to this radiator separately. Turn off one valve, and
bleed a couple of litres of water out of the bleed hole. Then turn the valve
back on and turn off the other one, and repeat the exercise.

When everything is working, turn all rads back on and put the pump back to
its normal speed. Then balance the system.
--
Cheers,
Set Square
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