On Sun, 13 Jul 2003 00:12:20 +0100, "Colin Forsyth"
Not particularly. You could consider a system boiler where it is
If you are going to have pipes dropping down such that the boiler
becomes a high point, then you will need to make a venting arrangement
consisting of manual or automatic vents at the boiler position.
In the garage, you will also need to insulate the pipes very
thoroughly and fit a frost protection thermostat if the boiler doesn't
have its own arrangements. A pipe contact type is most suitable if
you need to add one.
For all pipework, take care that it does not run where it can suffer
mechanical damage - e.g. from a car.
Unless the run is very long, 22mm should be enough since this size fed
the pumped heating before.
If you wanted to implement this, the usual way is to use an extended
version of Honeywell's S plan. With this, instead of having a three
way valve, you use 2 port valves. You would have one covering the hot
water cylinder and one for each manifold.
Look at S Plan Plus.
Hard to say, unless there is a vent or something missing or the feed
and vent pipes are connected to the wrong places.
A boiler change like this would be a good opportunity to switch the
whole primary system to sealed operation. This is very easy to do
and you may find it a prerequisite for your chosen condensing boiler.
Quite a lot require sealed operation, but there are some that don't
such as the Keston Celsius.
Ed Sirett has a FAQ with info. on sealed systems.
Assuming that the pump is on the boiler flow, the bypass goes from
after the pump but before the motorised valves, via an adjustable
valve and then to the return. Its purpose is to provide a path to
allow water to be circulated through the boiler if the CH or HW
thermostat stops demanding heat while the boiler is in full firing.
Not all boilers need it, but in those that do the purpose is to make
sure there is water running through the heat exchanger to avoid it
You can use a lockshield for this purpose, although a better solution
is to get an automatic bypass valve. These are pressure operated and
open when the pump is running and both or all three motorised valves
Agreed, been thinking of a Gloworm 30Hxi which has built in frost
Only problem area would be the doorway to the utility room, but intend to
enclose the pipework.
I'll look into this, however boiler in question can cope with open vented or
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!!!
On Sun, 13 Jul 2003 01:42:26 +0100, "Colin Forsyth"
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
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
Then I think that a replacement exercise is probably worth it rather
than having to mess around with each one later.
For starters, don't use a 3-way valve - use individual zone valves. In your
circumstances, I would use 3 - one for hot water and one each for upstairs
and downstairs heating.
Each zone valve would be controlled from the programmer and would have its
own room or cylinder stat, as appropriate. Each valve has an independent
pair of contacts which close when the valve is fully open. These are all
connected in parallel to switch the boiler and pump - so that the boiler and
pump only run when one or more zones are calling for heat. It may make sense
to use programmable stats for the two heating zones - so that you can have
them on at different times should you so wish. The main programmer would
then control the hot water on a timed basis, but would have heating switched
to continuous - leaving the actual control to the programmable stats.
As someone else has explained, with this arrangement (zone valves rather
than 3-way valve) you will need a bypass loop in order to ensure that the
water always has somewhere to go when the boiler over-run stat decides to
keep the pump running after the boiler has stopped.
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