On Sun, 13 Jul 2003 01:42:26 +0100, "Colin Forsyth"
wrote:


I'll look into this, however boiler in question can cope with open vented or
sealed systems.


Don't forget to give the system a thorough flush.



Since you mention imperial pipe sizes etc. presumably the rest of the
system is 30 years or so old as well?

When I refurbished my system a year ago it was 17 years old and the
pipework (22mm feeds and 8mm to radiators) was all in good condition
as were the radiators. I had been quite fastidious about using Fernox
etc. in the system. However, I did take the opportunity while the
system was out of use to do a thorough check through and clean.


I had decided that I was going to replace the DHW cylinder anyway -
the existing one was too small for the current requirement and also
the pipework in the airing cupboard - done by the original
subcontractor was badly laid out.

If the cylinder is 30 years old, it may be worth considering a
pre-emptive replacement while the system is down. You can obtain
rapid recovery cylinders from the major manufacturers such as Albion,
Telford etc. These have a coil with a much higher surface area than
old cylinders either by having more turns or by splitting into
multiple pipes. This, together with switching to a pumped
arrangement anyway will make a large difference to how quickly the
cylinder recovers temperature after a large draw of water. This is
useful anyway but also if you are going to have a control system with
priority to hot water (fairly typical) then the effect is that the
heat is diverted away from the radiators for a shorter time.

Before fitting the new boiler, I removed the old one and modified the
plumbing for sealed operation. To simplify this, I fitted the
expansion vessel/filling loop/pressure gauge in place of the old small
feed/expansion tank and connected on to the feed pipe. The old vent
pipe was disconnected in the airing cupboard where it connected to the
system. It doesn't really matter where this goes as long as there is
access to a mains water supply. I temporarily capped off the boiler
connections to the system and provided hot water with the immersion
heater.

I then organised a simple production line for the radiators. At
each radiator I disconnected and emptied it carefully (remember that
rust, sludge etc. stain indellibly). I then took it off and outside
and flushed through with a pressure washer. The thermostatic
radiator valves had been replaced not that long ago and were fine. If
you don't have them, they are well worth considering with a condensing
boiler because they do help towards better temperature control and
more efficient operation. However, the lockshield valves were
original and one or two had shown signs of seeping even under gravity
pressure, so I replaced them as I went. I then turned on the
water to the system and in turn each valve at the radiator position.
This flushed out quite a lot of original crud such as copper swarf
from the system. Then the radiator went back and I went on to the
next. I think that this is worth doing, even if you aren't going
sealed - you can still just use the tank supply. Since you can get
good quality lockshields for about a fiver, to me it was a no-brainer.
I used Pegler Terrier valves with a built in drain cock. These are
useful in that you can isolate a radiator and drain it a bit more
cleanly than by just undoing the valve unions.

On fitting the new boiler, I added a strainer on the return from the
system before the boiler. This is a small brass fitting with a
removable stainless steel mesh filter which catches any remaining
bits in the system. Most new boilers have quite small waterways so
it's a good practice, even if the makers don't stipulate it.

FInally, on commissioning, I ran some Superfloc system cleaner for a
day to mop up anything else in terms of fluxes etc., did one final
drain and flush and after a few days to check for any leaks added
Fernox.



Will do ! Its actually empty at the mo while I replace a radiator. Had an
experience with a lockshield valve with water flying past the screw. Dare
say the poor little seal hadnt been disturbed for a long long time !!! So
it was hose on and emty the system and then the main drain off seal failed
so I had to drain the lot!!!

Then I think that a replacement exercise is probably worth it rather
than having to mess around with each one later.



Ho hum....



..andy

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