On 22 Oct 2003 02:18:38 -0700, (Kevin) wrote:

I am considering replacing my conventional boiler with a combi-boiler
and during the replacement I will probably also relocate it. One
option is to move it on the same wall but closer to the origin of the
pipework, i.e. I will only need to cut the existing pipework not
introduce any new joints except where they actually connect to the
boiler. The other option is to move it onto the opposite wall which
will involve new pipework.

I have done plumbing before and am reasonably confident but for
obvious reasons I am a little wary of messing around with Gas. The
controller is also fairly old and will need to be replaced. Also
there are no room thermostats although I have fitted thermostatic
valves to every radiator, so do I actually need one ?

Yes you do. The best solution is to put a room thermostat (ideally
with time controller and night setback) into a location such as the
living room, dining room, hall or landing. Either remove the TRV on
the radiator in said location or fully open it. You don't want to
have the TRV of that radiator and thermostat both in operation, or
the temperature in the rest of the house will tend to wander all over
the place.



If possible I would like to do most of the work myself and get a CORGI
man in to do the final connections into the boiler. Any ideas how
realistic this is ?

It is, but it would be prudent to find one that will agree to do it
first. That may or may not be easy. Some CORGI people are
reasonably relaxed about doing this as long as they feel that you know
what you are doing, others won't because they are taking on a
responsibility or simply for commercial reasons. Getting the flue
right in terms of location and seal is as important as the pipework.

Can I re-use the existing pipework or will I have to run new pipes
throughout the house ?

Generally, if the pipework and radiators are in good condition, they
can be re-used. Normally, you will be converting the system to
pressurised operation. This is not difficult - some components may
be built into the boiler - but you may create seepage at radiator
valves and need to replace or tighten them. Refer to Ed Sirett's FAQ
on sealed systems.




Do I still need a separate pump or will this
be built into the new boiler ?

Typically it is built in. If not, and the pump is not recent, then
replacing is a good plan.

As part of the upgrade, giving the system a very thorough flush is
important (see other posts for a method that I have used) and fitting
a strainer to the return is a good idea too.


Should I consider doing this in two
phases, i.e Central Heating first and Domestic Hot Water second ?

Have you sized the combi to be sure that enough hot water is being
produced for your needs? If you have a separate bath and shower,
then a large model is needed. Before you do anything, check the
mains water flow rate at the kitchen cold tap. Then measure the
flow rate at bath taps and shower. Bear in mind that a combi
boiler is rated for a 30 or 35 degree temperature increase. This
means that in the winter when the water may only be at 8 degrees or
so, the *total* water for a shower will be the spec. figure for the
combi. A small one at 11 litres/min will be disappointing in most
cases.

You could proceed in stages. For example, you could keep the HW
cylinder in place and contine heating it with the boiler or even an
immersion heater. Then fit the new boiler and rejig the hot water
pipework last.


I'd like to minimise the amount of time we are without hot
water/heating. Anybody aware of any web resources which may advise
the best approach (i.e. order of activities) ?

I would tend to do what is needed to keep the hot water in service.
You can always warm rooms with a fan heater or something. Absence of
hot water is a major pain.




..andy

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