Have an ancient gas boiler, currently configured as a gravity fed
system.

Generally, how easy is it to replace the boiler with a combi one? Any
major gotchas?

As there'll be a problem with getting a mains water supply to the
boiler, is it acceptable to 'bridge out' the headre tank?

sPoNiX

Generally, how easy is it to replace the boiler with a combi one? Any
major gotchas?

Not usually, provided the existing radiators are on a modern two pipe
system. Any controls have to be brought up to modern standards, including
thermostats when appropriate and TRVs, when appropriate. Any part of a
gravity system on its last legs may leak when pressurised. This should be
taken as a sign that the component needed replacing anyway, and at least the
plumber is on site when it happens.

As there'll be a problem with getting a mains water supply to the
boiler, is it acceptable to 'bridge out' the headre tank?

What do you mean by this? Most boilers can accept the filling loop being
remote from the boiler. However, a combi boiler needs a mains supply to the
hot water section so it can provide hot mains water out. If you can't supply
a cold mains supply to the boiler, then you can't use a combi (unless you
have a cold tank gravity system through the combi section).

Christian.

On Tue, 1 Feb 2005 14:25:55 -0000, "Christian McArdle"
wrote:

Generally, how easy is it to replace the boiler with a combi one? Any
major gotchas?

Not usually, provided the existing radiators are on a modern two pipe
system. Any controls have to be brought up to modern standards, including
thermostats when appropriate and TRVs, when appropriate. Any part of a
gravity system on its last legs may leak when pressurised. This should be
taken as a sign that the component needed replacing anyway, and at least the
plumber is on site when it happens.

Good. As expected. The exisiting system is 70's vintage so is it
reasonable to expect a twin pipe system?

As there'll be a problem with getting a mains water supply to the
boiler, is it acceptable to 'bridge out' the headre tank?

What I mean is that there's currently a cold feed going to a header
tank in the loft. The output of this tank goes to the existing boiler.

I'm unable to provide a cold feed directly (Due to layout of the
building) but could connect the header tank feed to the header tank
output somewhere in the airing cupboard.

This'd mean the cold feed to the combi would take a bit of a
convoluted route.

sPoNiX

On Tue, 01 Feb 2005 14:59:08 GMT, (s--p--o--n--i--x)
wrote:

On Tue, 1 Feb 2005 14:25:55 -0000, "Christian McArdle"
wrote:

Generally, how easy is it to replace the boiler with a combi one? Any
major gotchas?

Not usually, provided the existing radiators are on a modern two pipe
system. Any controls have to be brought up to modern standards, including
thermostats when appropriate and TRVs, when appropriate. Any part of a
gravity system on its last legs may leak when pressurised. This should be
taken as a sign that the component needed replacing anyway, and at least the
plumber is on site when it happens.

Good. As expected. The exisiting system is 70's vintage so is it
reasonable to expect a twin pipe system?

As there'll be a problem with getting a mains water supply to the
boiler, is it acceptable to 'bridge out' the headre tank?

What I mean is that there's currently a cold feed going to a header
tank in the loft. The output of this tank goes to the existing boiler.

I'm unable to provide a cold feed directly (Due to layout of the
building) but could connect the header tank feed to the header tank
output somewhere in the airing cupboard.

This'd mean the cold feed to the combi would take a bit of a
convoluted route.

sPoNiX


Be careful in that case because the flow rate could be poor,
especially if most of the existing pipework is 15mm.



--

..andy

To email, substitute .nospam with .gl

I'm unable to provide a cold feed directly (Due to layout of the
building) but could connect the header tank feed to the header tank
output somewhere in the airing cupboard.

This'd mean the cold feed to the combi would take a bit of a
convoluted route.

sPoNiX[/quote]

Got yer. Not a problem, but sounds odd someone competent to fit a gas appliance can't route a cold pipe to anywhere in the house.

On Tue, 1 Feb 2005 21:39:59 +0000, Paul Barker
wrote:


I'm unable to provide a cold feed directly (Due to layout of the
building) but could connect the header tank feed to the header tank
output somewhere in the airing cupboard.

This'd mean the cold feed to the combi would take a bit of a
convoluted route.

sPoNiX

Got yer. Not a problem, but sounds odd someone competent to fit a gas
appliance can't route a cold pipe to anywhere in the house.

It's the shortest practical route without doing major structural work
to the house.

Concrete floor in the kitchen so its got to go over the ceiling. The
cold feed would only be about 3' longer if we make a connection in the
airing cupboard thatn if we surface mounted a new cold feed.

There is insufficient space under the upstairs floor to route a new
pipe without taking an even longer route.

sPoNiX