My friends need a boiler to replace the conventional floor mounted one
which works the central heating and the hot water system. The HW is
gravity fed and the CH is pumped round a single pipe system of
radiators. It's a fair sized 3 bedroom detached house.

They'd like a wall mounted one but one quote says they can't have a
gravity fed HW system wall mounted. Any idea why he'd say that?

They also thought about getting a combi boiler as the idea of always
having hot water available sounded good but on the minus side they've
learnt that

1) combi boilers don't last very long - maybe 5 years or so.

2) In a hard water area, having mains water run through the heat
exchanger doesn't do them much good either.

3) Some people say you can't have a combi with a single pipe system (for
some reason).

Is that right? They're aware of the other things like only one hot tap
at a time and reduced flow but it's these points that sound worse as
they don't want to have to get a new boiler that often. The
conventional one in there has been there for decades.

Don't know if it matters they have a conservatory so the flue would have
to be angled so it goes out through the wall and up through the
conservatorey roof as it does at present.

--
http://www.beluga.freeserve.co.uk

They'd like a wall mounted one but one quote says they can't have a
gravity fed HW system wall mounted. Any idea why he'd say that?

With gravity circulation and single pipe central heating, you would be
strongly recommended to upgrade to fully pumped twin pipe system. It will be
difficult to install any new boiler into your house whilst not breaking
building regulations, let alone a modern type. Soon it will be absolutely
impossible, as only modern condensing boilers will be allowed. These will
not work with gravity flow.

Your fears of combi boilers are unfounded. The main problem with them is
relatively low flow rates. This won't matter if you only have baths
infrequently. As your storage system is seriously non-compliant anyway, it
may be the cheapest way of getting up and running again.

Whilst I can't see that single pipe heating circuits are specifically banned
at all, you are required to have separate heating controls, such as TRVs in
each room. I don't know if you can get TRVs for this type of system, which
have not been installed in the UK for many years (decades).

Christian.

In article ,
Peter Smithson writes:
My friends need a boiler to replace the conventional floor mounted one
which works the central heating and the hot water system. The HW is
gravity fed and the CH is pumped round a single pipe system of
radiators. It's a fair sized 3 bedroom detached house.

They'd like a wall mounted one but one quote says they can't have a
gravity fed HW system wall mounted. Any idea why he'd say that?

Gravity fed HW system requires that the boiler directly heats
up a tank of water. Boilers don't work that way any more -- they
heat up a water pipe which has to be continuously pumped whilst
being heated, or meltdown follows within a few seconds ;-)

3) Some people say you can't have a combi with a single pipe system (for
some reason).

There's no problem with a single pipe system. It's not what would
be installed now, but the boiler itself will have no clue about it.
(A condensing boiler with a single pipe system would however be
quite a challenge I suspect.) You will likely need to add some
thermostatic radiator valves to conform to building regs when boiler
is changed.

--
Andrew Gabriel

"Peter Smithson" wrote in message
...

My friends need a boiler to replace the conventional floor mounted one
which works the central heating and the hot water system. The HW is
gravity fed and the CH is pumped round a single pipe system of
radiators. It's a fair sized 3 bedroom detached house.

They'd like a wall mounted one but one quote says they can't have a
gravity fed HW system wall mounted. Any idea why he'd say that?

Small tubed heat exchangers require a pumped circuit at all time.

They also thought about getting a combi boiler as the idea of always
having hot water available sounded good but on the minus side they've
learnt that

1) combi boilers don't last very long - maybe 5 years or so.

No so.

2) In a hard water area, having mains water run through the heat
exchanger doesn't do them much good either.

Firstly some combi's have reduction controls. Secondly, on any system in a
hard water area always have a phosphor scale reducer on cold water mains
(the drinking taps can't be off it. Thirdly, most new combi's have plate
heat exchangers which resist scale.

3) Some people say you can't have a combi
with a single pipe system (for
some reason).

A combi is no different to any other boiler in this respect. Single pipe
system are best ripped out, or amended to 2 pipe.

Is that right? They're aware of the other things like only one hot tap
at a time and reduced flow but it's these points that sound worse as
they don't want to have to get a new boiler that often. The
conventional one in there has been there for decades.

There are high flowarte combi's around, so don't go on old wives tales.

Don't know if it matters they have a conservatory so the flue would have
to be angled so it goes out through the wall and up through the
conservatorey roof as it does at present.

Not a problem with modern flexible flues.




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"Peter Smithson" wrote in message
...

Thanks for all the replies.

Some of my misconceptions about combi boilers are from here

http://www.gasman.fsbusiness.co.uk/c...on_boilers.htm

Another question - more than one of the people coming to give a quote
have said that a wall mounted boiler isn't going to work with their
single pipe CH and gravity HW system. They currently have a free
standing one. Any ideas why some quotes are saying that?

The single pipe system will still work, but they inefficient and are best
replaced. They are ca pig to get right after a boiler change. Having rad
valves with them can also upset the performance too. Also the same with
gravity hot water. Modern small capacity boilers require a minimum flow at
a all times, so a pump is required at all times.



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Thanks for all the replies.

Some of my misconceptions about combi boilers are from here

http://www.gasman.fsbusiness.co.uk/c...on_boilers.htm

Another question - more than one of the people coming to give a quote
have said that a wall mounted boiler isn't going to work with their
single pipe CH and gravity HW system. They currently have a free
standing one. Any ideas why some quotes are saying that?

Thanks

Peter

--
http://www.beluga.freeserve.co.uk

In article ,
says...

Another question - more than one of the people coming to give a quote
have said that a wall mounted boiler isn't going to work with their
single pipe CH and gravity HW system. They currently have a free
standing one. Any ideas why some quotes are saying that?

The single pipe system will still work, but they inefficient and are best
replaced. They are ca pig to get right after a boiler change. Having rad
valves with them can also upset the performance too. Also the same with
gravity hot water. Modern small capacity boilers require a minimum flow at
a all times, so a pump is required at all times.

So it's really a matter of having to have a pumped HW system with modern
systems rather than a certain kind of modern boiler. Odd that the chap
said he could do gravity with a floor standing boiler but not a wall
mounted one!!!

--
http://www.beluga.freeserve.co.uk

"Peter Smithson" wrote in message
...
In article ,
says...

Another question - more than one of the people coming to give a quote
have said that a wall mounted boiler isn't going to work with their
single pipe CH and gravity HW system. They currently have a free
standing one. Any ideas why some quotes are saying that?

The single pipe system will still work, but they inefficient and are
best
replaced. They are ca pig to get right after a boiler change. Having
rad
valves with them can also upset the performance too. Also the same with
gravity hot water. Modern small capacity boilers require a minimum
flow at
a all times, so a pump is required at all times.

So it's really a matter of having to have a pumped HW system with modern
systems rather than a certain kind of modern boiler. Odd that the chap
said he could do gravity with a floor standing boiler but not a wall
mounted one!!!

Ideal still do a cast iron floor mounted boiler, which when the new regs
come in will be discontinued as it will be too inefficient. Changing from
gravity to fully pumped is not a big thing an much more efficient too.


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Odd that the chap said he could do gravity with a floor standing
boiler but not a wall mounted one!!!

It's because you need a boiler designed at least 30 years ago to make it
work. They didn't make wall mounted boilers back then.

Quite frankly, you should fix the system properly rather than spend money on
1970s technology that is about to be banned and will cost you dearly in fuel
bills.

Christian.

"Christian McArdle" wrote in message
t...
Odd that the chap said he could do gravity with a floor standing
boiler but not a wall mounted one!!!

It's because you need a boiler designed at least 30 years ago to make it
work. They didn't make wall mounted boilers back then.

They did. On the Continent they have been around for about 40 years. The
first sold en-mass in the UK was the Glow Worm Spacesaver in 1969, but
Continental makes were still available well before that, with forced flues
and all that. Even then installers would not fit the cast iron Spacesaver
(which could do gravity DHW), saying it would burn out. A fitted one for my
cousin over 30 years ago and its still going today, although very
inefficiently to today's boilers.

Quite frankly, you should fix the system
properly rather than spend money on
1970s technology that is about to be
banned and will cost you dearly in fuel
bills.

Very true. Bring it up to date.


---
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In article ,
Andrew Gabriel wrote:
Gravity fed HW system requires that the boiler directly heats
up a tank of water. Boilers don't work that way any more -- they
heat up a water pipe which has to be continuously pumped whilst
being heated, or meltdown follows within a few seconds ;-)

There were/are plenty of gravity systems using an indirect heating coil.
Modern boilers tend to have a much lower water content so need the pump to
shift it faster. As it were. ;-)

--
*He who laughs last has just realised the joke.

Dave Plowman London SW 12
RIP Acorn

In article , cmcardle75
@nospam.yahooxxxx.co.uk says...
Odd that the chap said he could do gravity with a floor standing
boiler but not a wall mounted one!!!

It's because you need a boiler designed at least 30 years ago to make it
work. They didn't make wall mounted boilers back then.

I'm talking about gravity for the HW only - the CH is pumped. I know
they've made boilers that do that 20 years ago as I've got one!

Quite frankly, you should fix the system properly rather than spend money on
1970s technology that is about to be banned and will cost you dearly in fuel
bills.

My friends are just getting quotes from people and getting different
advice - not one of the quotes has suggested putting a pump in for the
HW system which seems really strange to me.

I think I've figured it out - one of the people said they had to have a
free standing boiler for gravity fed and the other people said they'd
stick a wall mounted one in. But they didn't actually say they'd leave
it as a gravity system - now my friends tell me! They assumed it would
be left as gravity but it wasn't specified when the idea of putting a
wall mounted boiler was suggested. So I suspect the wall mounted quotes
would have involved a HW pump but they just didn't mention it verbaly.

Anyway, now they've just got some people saying it's OK to put a flue
through two walls and another person saying its against regulation to
put it through two walls! Might try and find these regs on the
internet.

Thanks for the replies.

Peter
--
http://www.beluga.freeserve.co.uk

In article ,
Dave Plowman writes:
In article ,
Andrew Gabriel wrote:
Gravity fed HW system requires that the boiler directly heats
up a tank of water. Boilers don't work that way any more -- they
heat up a water pipe which has to be continuously pumped whilst
being heated, or meltdown follows within a few seconds ;-)

There were/are plenty of gravity systems using an indirect heating coil.

Oh, I know. The 'tank of water' I was referring to is
the tank forming the boiler, often called the water jacket.
That's what's gone.

--
Andrew Gabriel

On Fri, 3 Oct 2003 10:08:30 +0100, "IMM" wrote:



They did. On the Continent they have been around for about 40 years. The
first sold en-mass in the UK was the Glow Worm Spacesaver in 1969, but
Continental makes were still available well before that, with forced flues
and all that. Even then installers would not fit the cast iron Spacesaver
(which could do gravity DHW), saying it would burn out. A fitted one for my
cousin over 30 years ago and its still going today, although very
inefficiently to today's boilers.


You're admitting to fitting a "cast iron clunker"?? For shame!
You'll be telling us that you have a standing order payable to
Conservative Central Office next....... ;-)



..andy

To email, substitute .nospam with .gl

Peter Smithson wrote:

Anyway, now they've just got some people saying it's OK to put a flue
through two walls and another person saying its against regulation to
put it through two walls! Might try and find these regs on the
internet.

I think it unlikely that any manufacturers will forbid a modern fanned
flue going through two walls.
They do specify maximum equivalent [1] lengths of flue which you will
have to comply with.
In fact given the price structure of the flue extending parts they'll
likely be quite pleased with a flue through two walls.


[1] The length allowing for bends usually 1m per Elbow.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Andrew Gabriel" wrote in message
...

---8---

... You will likely need to add some
thermostatic radiator valves to conform to building regs when boiler
is changed.

AIUI (from the last time I ploughed through Part L looking for this) you
don't have to have TRVs as long as the system is controlled by a room 'stat.



--
John Stumbles
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-+
No Rules, OK

In article ,
"John Stumbles" ] writes:
"Andrew Gabriel" wrote in message
...
... You will likely need to add some
thermostatic radiator valves to conform to building regs when boiler
is changed.

AIUI (from the last time I ploughed through Part L looking for this) you
don't have to have TRVs as long as the system is controlled by a room 'stat.

That's correct, but most people have many more rooms than they
do room stats.

--
Andrew Gabriel

"Andy Hall" wrote in message
...
On Fri, 3 Oct 2003 10:08:30 +0100, "IMM" wrote:



They did. On the Continent they have been around for about 40 years. The
first sold en-mass in the UK was the Glow Worm Spacesaver in 1969, but
Continental makes were still available well before that, with forced
flues
and all that. Even then installers would not fit the cast iron
Spacesaver
(which could do gravity DHW), saying it would burn out. A fitted one for
my
cousin over 30 years ago and its still going today, although very
inefficiently to today's boilers.


You're admitting to fitting a "cast iron clunker"??

Unless you bought a special import they were all cast-iron.

For shame!
You'll be telling us that you have a standing order payable to
Conservative Central Office next....... ;-)

I would rather slit my throat first.


---
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Version: 6.0.520 / Virus Database: 318 - Release Date: 18/09/2003

John Stumbles wrote:

"Andrew Gabriel" wrote in message
...

---8---

... You will likely need to add some
thermostatic radiator valves to conform to building regs when boiler
is changed.

AIUI (from the last time I ploughed through Part L looking for this) you
don't have to have TRVs as long as the system is controlled by a room 'stat.



AIUI there are two ways to comply:

1) All TRV's + smart bypass interlocked to boiler.
2) Room Stat + TRV's on bedrooms, cooler and less often used rooms.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html