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 ?
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 ?
Can I re-use the existing pipework or will I have to run new pipes
throughout the house ? Do I still need a separate pump or will this
be built into the new boiler ? Should I consider doing this in two
phases, i.e Central Heating first and Domestic Hot Water second ?
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) ?
You need what is termed a boiler interlock. This means that once no heating
is required, the boiler must be turned off. This can be done in two ways.
Firstly, you can have a room thermostat in one room with no TRVs. Secondly,
you can have an automatic bypass valve with a flow switch. When the
radiators are all off, the automatic bypass opens, the switch trips and the
boiler turns off. Some logic must be incorporated into the system to notice
that the valves have opened again, though.
You can. Finding the CORGI can be problematic.
Modern condensing and combi boilers frequently have internal pumps. It is by
no means universal, though.
You could do this. You could also use the combi section for the kitchen and
shower and maintain stored water for the bath for higher flow rates.
On 22 Oct 2003 02:18:38 -0700, firstname.lastname@example.org (Kevin) wrote:
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
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.
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.
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.
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
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
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.
To email, substitute .nospam with .gl
email@example.com (Kevin) wrote in message
I'm about to do exactly the same thing. I'm replacing an old
conventional boiler in the basement with a Condensing Combi in the
loft (with suprising little extra pipework required!)
The boiler I'm going to install has a built in by-pass so I'm going to
fit a TRV in every room, then when there's no demand the boiler will
turn off until there is. Since this is part of the biler all the logic
to turn on again etc. is built in. I've chosen a Vaillant EcoMax828
which is pretty pricey, but good quality and has everything built in.
Again, this is my plan. Although I already know a CORGI registered
plumber who is happy to just pop round to check my pipework and
connect to the meter.
I'm planning on reusing the existing, including reusing the current
boiler's 22mm pressure release pipe to take the gas up to the loft.
I'm taking a few days off work to do this and will get all the
pipework in place so that once the old system is disconnected I hope
to get the new one up and running in a day. I'll leave the old system
physically in place though, just in case I need to reconnect for any
Good luck. Let us know how you get on.
For me this is not an issue, my boiler is located in the utility room
and the pipework is surface mounted close to the ceiling hence easy to
get at. When I have finished all of the work I need to do in this
room, I might consider boxing the pipes in but in this particular room
the fact that the pipes are surface mounted isn't really an issue.
everything is done by the combi ...connect heating flow and return, domestic
hot and mains in and gas connection. Combi will contain all controls required
to deal with systems. However it is not recommended that you get corgi person
in to do final connections I am a plumber myself and would not do this as
requirements by law dictate otherwise ....advice only.....
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