On 31 Aug, 11:42, (Andrew Gabriel) wrote:
Geoff usually posts a reminder about now to make sure your heating is
working ready for the winter. However, since I did mine yesterday and
it's fresh on my mind, I thought I'd post a reminder.

Mine's a sealed system, installed over 7 years ago, but never yet
flushed or had the inhibitor changed. Should normally do this about
every 5 years for a sealed system, but it depends how often you have
to top up the pressure, and this system has only needed topping up
2 or 3 times in the 7 years, so I stretched it out on that basis.

Firstly, I drained the whole system. This is quite easy because I
designed it with all the pipework sloping down towards the drain
points, so it doesn't get left with any pockets of water left inside
(except possibly a little in the bottom of each radiator).
Also noted position of all the radiator stop valves (how many turns
to close), befaore opening them all fully. *The drained water was
clean although it ponged a bit, but no black sludge so there was
still enough inhibitor remaining to protect the system.

Then I refilled it with cold water and used the filling loop, drain
valves, and radiator and other isolation valves to force the water
through all parts of the system to flush out the remaining old water
(and the pong went).

Next, I closed off the drain cocks, bled everything, and cranked the
pressure up to about 2.2 bar (higher than it normally gets when hot,
but not enough to risk the over pressure valve letting by) and left it
for a couple of hours. Now I can go around and check for any leaks,
and since the system is cold, the evidence doesn't dry up before I
see it. I found two radiator stop valves were weeping on their shaft
seals, but more anoyingly, the two full bore isolation valves for
the upstairs circuit were also leaking at the shaft seals. Drained
down and replaced the radiator stop valves, but didn't have any
spare 22mm full bore valves (and I recall they were a real bugger
to install in the space available in the first place), so I tightened
down the stuffing boxes and hoped for the best -- and fortunately
that worked. One of them doesn't turn anymore anyway, at least, not
with the limited force I'm prepared to try without having a spare
one to hand;-)

Finally, refilled with fresh inhibitor, bled everything and left the
pump running for a while until sounds of bubbles in pipework dimished,
and then bled again. Reset the radiator stop valves to their original
settings, and let boiler fire up and make sure it's working and the
mid position valve operates correctly. At some point, I'll check the
balancing of the radiators (the two new stop valves may have different
flow from the originals), but that's a job for when the heating needs
to be on anyway, and not now.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

I done something similar to our system, although it was cleaned by the
installers when it was installed I wasn't impressed with the way they
cleaned it, so X800 was used to flush the system and a lot of crap was
removed, while the X800 was circulating in each radiator I checked for
leaks etc. Once cleaning, draining and flushing was complete X100 was
added and the system was filled, bleeding was easy because there is a
purging program on my boiler which you run and it helps to bleed the
system. System was re-balanced and tested and everything works fine.
The system is currently working at a 9C-10C differential and the
radiators and pipes are woefully undersized, the boiler needs to be
working at 65C+ most of the year which is a shame as it's a condensing
boiler.