Relative lives in an inner, three story town house and needs a new
boiler. The current ~20 year old boiler is located on the ground floor
with the flue running up through the other two (concrete) floors.
There's a garage to the front and a kitchen to the rear and the boiler
is in a walk-in cupboard between the two.

She's been told that the boiler must go on an outside wall with the flue
through the wall, or on the top floor with the flue through the flat
roof. Question is, why can't it go where the existing boiler is? Is
there a limit on the length of flues for modern boilers?

--
F

(Beware of spam trap - remove the negative)

In article , F
writes
Relative lives in an inner, three story town house and needs a new
boiler. The current ~20 year old boiler is located on the ground floor
with the flue running up through the other two (concrete) floors.
There's a garage to the front and a kitchen to the rear and the boiler
is in a walk-in cupboard between the two.

She's been told that the boiler must go on an outside wall with the flue
through the wall, or on the top floor with the flue through the flat
roof. Question is, why can't it go where the existing boiler is? Is
there a limit on the length of flues for modern boilers?

It t' old days this was not a problem as a conventionally flued boiler
could draw air from the room in which it was sited and the exhaust gas
was so hot that it could easily find its way up a long large bore flue
to the top of house.

Nowadays it is not considered safe for new installations to draw air
from the room in the appliance is sited and the regulated requirement
for condensing boilers having low exhaust temperatures means that the
flue gasses no longer have the oomf to make it up a long flue on their
own.

The solution is fan assisted balanced flues which are frequently
concentric (exhaust inside and inlet outside) and although extension
pieces are available they are expensive and there is a limit on the
length that the fan can suck and push the gasses.

Boilers do exist that are capable of driving long flues but this is a
specialist requirement so there aren't that many around and some of them
are expensive. Almost universally they split the flue into 2 pipes to
drive long distances. I know of:

Keston - Reasonably priced boilers, and flues are formed from low cost
(but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25 boiler
but I'm not sure I would give it an unqualified recommendation

Mann Micromat - A top quality German boiler but pricey, extension flue
is flexible corrugated plastic tube which is cheaper than metal
extension but still expensive for long runs. Formerly distributed by Eco
Hometec but I've lost track of who are doing them now.

Ariston - Saw these in a block of flats a while back and noticed they
were using long flues via adaptors, no detailed info.

To cut a long story short, if you chose to go the long flue route then
you will be making life more difficult for yourself, you will be paying
more and tying yourself to a number of specialist suppliers whose
support network may not be as extensive as the mainstream market and as
a result you may have difficulty with spares in the future.

More mainstream boilers are most easily fitted to outside walls but many
can drive concentric flues of 3 or 4m which may mean that you can fit
them in a cupboard and route the flue to the outside.

See also the group boiler choice faq from Ed Sirett:
http://www.makewrite.demon.co.uk/BoilerChoice.html
--
fred
Plusnet - I hope you like vanilla

On 23/12/2007 13:39 fred wrote:

More mainstream boilers are most easily fitted to outside walls but many
can drive concentric flues of 3 or 4m which may mean that you can fit
them in a cupboard and route the flue to the outside.

Thanks for that. The alternative horizontal flue through the wall into
the garage and then out above the garage door was one that I had thought
of but, for some unfathomable reason didn't go down too well with her.

--
F

(Beware of spam trap - remove the negative)

F wrote:
Relative lives in an inner, three story town house and needs a new
boiler. The current ~20 year old boiler is located on the ground floor
with the flue running up through the other two (concrete) floors.
There's a garage to the front and a kitchen to the rear and the boiler
is in a walk-in cupboard between the two.

She's been told that the boiler must go on an outside wall with the flue
through the wall, or on the top floor with the flue through the flat
roof.

That sounds like ******** to me.

Question is, why can't it go where the existing boiler is? Is
there a limit on the length of flues for modern boilers?


May be an issue with condensing types. Dunno.

My guess is that otherwise water drips down the flue pipe or summat.

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low cost
(but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25 boiler
but I'm not sure I would give it an unqualified recommendation

I ordered a set of servicing spares for mine a few weeks ago
thinking they might arrive by end of March when its service
is due, and unlike my previous experiences, every part was in
stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although
I have seen stock still for sale quite recently.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sun, 23 Dec 2007 16:14:31 +0000, Andrew Gabriel wrote:

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low cost
(but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25
boiler but I'm not sure I would give it an unqualified recommendation

I ordered a set of servicing spares for mine a few weeks ago thinking
they might arrive by end of March when its service is due, and unlike my
previous experiences, every part was in stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although I have seen
stock still for sale quite recently.

Presumably they will be bringing out a replacement model in their range?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Sun, 23 Dec 2007 13:55:42 +0000, The Natural Philosopher wrote:

F wrote:
Relative lives in an inner, three story town house and needs a new
boiler. The current ~20 year old boiler is located on the ground floor
with the flue running up through the other two (concrete) floors.
There's a garage to the front and a kitchen to the rear and the boiler
is in a walk-in cupboard between the two.

She's been told that the boiler must go on an outside wall with the
flue through the wall, or on the top floor with the flue through the
flat roof.

That sounds like ******** to me.

Agreed, except for cost issues about the length of flue components etc.


Question is, why can't it go where the existing boiler is? Is there a
limit on the length of flues for modern boilers?

Varies from maker to make but invariably they are all competing with each
other to make things as long and as versatile as possible.



May be an issue with condensing types. Dunno.

One of the make requires a drain+trap at the base of vertical sections of
above a certain height.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 16:14:31 +0000, Andrew Gabriel wrote:

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low cost
(but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25
boiler but I'm not sure I would give it an unqualified recommendation

I ordered a set of servicing spares for mine a few weeks ago thinking
they might arrive by end of March when its service is due, and unlike my
previous experiences, every part was in stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although I have seen
stock still for sale quite recently.

Presumably they will be bringing out a replacement model in their range?

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.
--
fred
Plusnet - I hope you like vanilla

"F" wrote in message
...
On 23/12/2007 13:39 fred wrote:

More mainstream boilers are most easily fitted to outside walls but many
can drive concentric flues of 3 or 4m which may mean that you can fit
them in a cupboard and route the flue to the outside.

Using twin pipes (plastic drain around 2" pipe) 30 foot and more.

Thanks for that. The alternative horizontal flue through the wall into the
garage and then out above the garage door was one that I had thought of
but, for some unfathomable reason didn't go down too well with her.

"F" wrote in message
...
Relative lives in an inner, three story town house and needs a new boiler.
The current ~20 year old boiler is located on the ground floor with the
flue running up through the other two (concrete) floors. There's a garage
to the front and a kitchen to the rear and the boiler is in a walk-in
cupboard between the two.

She's been told that the boiler must go on an outside wall with the flue
through the wall, or on the top floor with the flue through the flat roof.
Question is, why can't it go where the existing boiler is? Is there a
limit on the length of flues for modern boilers?

A boiler can go in the loft, flued through the roof.

"fred" wrote in message ...
In article , Ed Sirett
writes
On Sun, 23 Dec 2007 16:14:31 +0000, Andrew Gabriel wrote:

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low cost
(but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25
boiler but I'm not sure I would give it an unqualified recommendation

I ordered a set of servicing spares for mine a few weeks ago thinking
they might arrive by end of March when its service is due, and unlike my
previous experiences, every part was in stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although I have seen
stock still for sale quite recently.

Presumably they will be bringing out a replacement model in their range?

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are separate
control temperatures depending on the demand source with thermistor sensor
modulated control of DHW temp and they promise compatibility with low
grade heat from solar panels in the future. Full list is: Room
Compensation, Weather Compensation, Solar Control, Modulating DHW Reheat,
Solar Thermal, Analog Demand (0-10VDC), External Lockout Signal, Remote
Fascia Panel plus LCD control panel and display of system params (flue
temp, flow/return temp, other temp densors) in installer mode. They've
retained the 20m/50mm maximum flue length and even extended it to 60m when
increased to 65mm. Suffix H is heat only without pump or expansion vessel,
suffix S is a system unit with those parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

The Qudos 28 has a spiral tube stainless steel heat exchanger top mounted
burner design. They went back to their original designs. The Celsius by the
time they dropped it had all it problems ironed out. A late model Celsius
is good buy.

The Qudos is well priced for what it is.

"F" wrote in message
...
Relative lives in an inner, three story town house and needs a new boiler.
The current ~20 year old boiler is located on the ground floor with the
flue running up through the other two (concrete) floors. There's a garage
to the front and a kitchen to the rear and the boiler is in a walk-in
cupboard between the two.

She's been told that the boiler must go on an outside wall with the flue
through the wall, or on the top floor with the flue through the flat roof.
Question is, why can't it go where the existing boiler is? Is there a
limit on the length of flues for modern boilers?

Look at:
http://www.keston.co.uk/downloads/ma...tions-Q28S.pdf

Long flue lengths using plastic drain pipe.

On 23/12/2007 19:21 Doctor Drivel wrote:

A boiler can go in the loft, flued through the roof.

She doesn't have a loft, just a top floor.

However, my neighbour has had a boiler installed in her loft. It went
AWOL after a few months, BG came out to fix it (the original fitter
couldn't get out to it and there were young children in a very cold
house) and the guy refused to go up into the loft. Elf and safety! He
was persuaded to change his mind when said neighbour asked him what his
supervisor would say when he smelled the alcohol on his breath!

--
F

(Beware of spam trap - remove the negative)

"F" wrote in message
...
On 23/12/2007 19:21 Doctor Drivel wrote:

A boiler can go in the loft, flued through the roof.

She doesn't have a loft, just a top floor.

However, my neighbour has had a boiler installed in her loft. It went AWOL
after a few months, BG came out to fix it (the original fitter couldn't
get out to it and there were young children in a very cold house) and the
guy refused to go up into the loft. Elf and safety! He was persuaded to
change his mind when said neighbour asked him what his supervisor would
say when he smelled the alcohol on his breath!

Must be boarded from hatch to boiler. A permanent light, and a shoot down
ladder. Then he can't refuse.

On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 16:14:31 +0000, Andrew Gabriel wrote:

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low
cost (but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius
25 boiler but I'm not sure I would give it an unqualified
recommendation

I ordered a set of servicing spares for mine a few weeks ago thinking
they might arrive by end of March when its service is due, and unlike
my previous experiences, every part was in stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although I have
seen stock still for sale quite recently.

Presumably they will be bringing out a replacement model in their range?

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

"Ed Sirett" wrote in message
...
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 16:14:31 +0000, Andrew Gabriel wrote:

In article ,
fred writes:
Keston - Reasonably priced boilers, and flues are formed from low
cost (but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius
25 boiler but I'm not sure I would give it an unqualified
recommendation

I ordered a set of servicing spares for mine a few weeks ago thinking
they might arrive by end of March when its service is due, and unlike
my previous experiences, every part was in stock and arrived next day.

BTW, Keston stopped making the C25 over a year ago, although I have
seen stock still for sale quite recently.

Presumably they will be bringing out a replacement model in their range?

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

....at a price that commands attention for what it offers in design and
function. Reliability? Not been around long enough. however they appear to
be using proven parts from other boilers.

In article ews.net,
"Doctor Drivel" writes:

"Ed Sirett" wrote in message
...

This boiler would have the most sophosticated controls of any in that
price bracket.

...at a price that commands attention for what it offers in design and
function. Reliability? Not been around long enough. however they appear to
be using proven parts from other boilers.

My biggest gripe -- lack of availability of spares in a timely
fashion -- looks like it might have got sorted too, but that's on
a sample of only one order. Might be as a result of Keston having
been bought out a while back.

I might consider them when a 17 year old Profile pops its cloggs
(although it's currently running faultlessly and has had no breakdowns
that I know of, certainly none in the last 7 years). When I looked about
6 months back, I don't recall them having a low powered non-combi in the
range.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

The sophistication and the solar hook makes it attractive to the
specialist market and the techies here but I do wonder whether it will
make it in the mainstream market, it's just too clever. I hope that they
and it make it, at last a company who listen.
--
fred
Plusnet - I hope you like vanilla

On 2007-12-24 20:00:40 +0000, fred said:

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

The sophistication and the solar hook makes it attractive to the
specialist market and the techies here but I do wonder whether it will
make it in the mainstream market, it's just too clever. I hope that
they and it make it, at last a company who listen.

You don't have to use the clever bits.

It will work with just a simple switched live for the followers of Ned Ludd.

I doubt whether many people would use it domestically with more than a
thermostat and the weather compensator. The smart move would be to
include the sensor for that in the package because it's a very low cost
item (basically a two wire semiconductor in a weatherproof box).

It may be interesting for small commercial installations involving
multiple boilers controlled by an analogue or Opentherm controller.

Whether it makes it in the market will depend on the number of puffy
anoraks for Plumbcenter counter staff and lunches for their managers.

"Andy Hall" wrote in message news:47701fb5@qaanaaq...
On 2007-12-24 20:00:40 +0000, fred said:

In article , Ed Sirett
writes
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

The sophistication and the solar hook makes it attractive to the
specialist market and the techies here but I do wonder whether it will
make it in the mainstream market, it's just too clever. I hope that they
and it make it, at last a company who listen.

You don't have to use the clever bits.

It will work with just a simple switched live for the followers of Ned
Ludd.

I doubt whether many people would use it domestically with more than a
thermostat and the weather compensator.

Matt, I fo fear that.

The smart move would be to include the sensor for that in the package
because it's a very low cost item (basically a two wire semiconductor in a
weatherproof box).

It may be interesting for small commercial installations involving
multiple boilers controlled by an analogue or Opentherm controller.

Whether it makes it in the market will depend on the number of puffy
anoraks for Plumbcenter counter staff and lunches for their managers.

The ideal setup for this boiler (the Keston C36 combi is the same boiler
with a water section added) is to have the outside weather compensator
fitted (cost about £22). The DHW cylinder sensor (not sure of price) and
the Opentherm standard room temp controller/programmer/optimiser fitted
(Keston use the Honeywell Chronotherm, which can be bought a lot cheaper
elsewhere rather than the £133 Keston ask for it). Then this is a
substantial setup and at a price people can afford. Anyone can do that,
just as simple as rigging up crap stats.

The C38 combi can have the outside temp sensor fitted and the Chronotherm
optimiser programmer too. DHW is not an issue as it is a combi. Then for
what you get and pay this is also well priced. Keston have to offer
advanced control interfaces to five the boiler a hedge. Broag also sell a
well priced boiler offering similar specs using tried and tested parts too.

I have heard no bad reports on the Qudos range....yet. The Celsius turned
me away from Keston after making some super simple and reliable boilers
previously. It should be fine using parts from other boilers in the range.

"fred" wrote in message ...
In article , Ed Sirett
writes
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

The sophistication and the solar hook makes it attractive to the
specialist market and the techies here but I do wonder whether it will
make it in the mainstream market, it's just too clever.

It isn't too clever once people understand that all you do is hook up simple
sensors back to the boiler. The thinking is done for you. DHW sensor has it
own terminals as does the room influence and outside weather sensors
too......and also the zone valves as well. Super simple to wire up.

I hope that they and it make it, at last a company who listen.

"fred" wrote in message ...

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are separate
control temperatures depending on the demand source with thermistor sensor
modulated control of DHW temp and they promise compatibility with low
grade heat from solar panels in the future. Full list is: Room
Compensation, Weather Compensation, Solar Control, Modulating DHW Reheat,
Solar Thermal, Analog Demand (0-10VDC), External Lockout Signal, Remote
Fascia Panel plus LCD control panel and display of system params (flue
temp, flow/return temp, other temp densors) in installer mode. They've
retained the 20m/50mm maximum flue length and even extended it to 60m when
increased to 65mm. Suffix H is heat only without pump or expansion vessel,
suffix S is a system unit with those parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

The C55 (55 kW) is £1821. Two Qudos 28 kW boilers is £1576. ...and a back
up boiler in case. With the right boioper sequence controller this will
modulate from about 6kW to £56 kW.

In article ,
Ed Sirett wrote:
£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

Is that a good thing? ;-)

--
*Starfishes have no brains *

Dave Plowman London SW
To e-mail, change noise into sound.

"Doctor Drivel" wrote in
reenews.net:

... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the Honeywell
Chronotherm, which can be bought a lot cheaper elsewhere rather
than the £133 Keston ask for it)...

Err... The programmer badged by Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/d...ES%20850%20OT%
20neutral_2007_01_309%20872_GB.pdf

The reference to OpenTherm has nothing to do with the Honeywell
Chronotherm, but to the OpenTherm protocol used for data communication
between the boiler and the controller. See:
http://www.opentherm.org/

Kind regards

--
Richard Perkin
To email me, change the AT in the address below
richard.perkinATmyrealbox.com

It's is not, it isn't ain't, and it's it's, not its, if you mean it
is. If you don't, it's its. Then too, it's hers. It isn't her's.
It isn't our's either. It's ours, and likewise yours and theirs.
-- Oxford University Press, Edpress News

"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the Honeywell
Chronotherm, which can be bought a lot cheaper elsewhere rather
than the £133 Keston ask for it)...

Err... The programmer badged by
Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/downloads/BA_RAMSES%20850%20OT%20neutral_2007_01_309%20872_G B.pdf

Here is the Chrontherm on the Keston site:
http://www.keston.co.uk/downloads/userguides/CX51-u.pdf

In the manuals they specifically state Chronotherm.

The reference to OpenTherm has nothing to do with the Honeywell
Chronotherm, but to the OpenTherm protocol used for data communication
between the boiler and the controller. See:
http://www.opentherm.org/

I said, "Opentherm standard", which is a "open" standard used by those who
sign up to it, as the opentherm link you gave explains. Currently is only a
protocol between boiler and room temperature sensor. Two microprocessor
based devices connected via a common "open" protocol so all makers equipment
using the protocol can talk to each other. The boiler and an intelligent
room temp sensor (this may have a sophisticated clock in it as in a clock
stat, like the Chronotherm). There was talk of it 5 years ago, but only
recently have a number of makers started to incorporate it into their pcbs
(Maxie will have to get to know it as he fixes pcb's).

A number of boiler makers use it, mainly German and Dutch, I believe an
Ideal boiler can use the Opentherm protocol. Honeywell, Danfoss, Siemens,
Landis, etc make room temperature sensors which will connect onto these
boilers and modulate the burner or switch the boiler off/on, optimise the
start stop of the boiler, etc (the Honeywell Chronotherm optimises switching
on). Then no rip-off proprietary room sensors to buy, as any makers sensor
will do.

I am sure a Chronotherm using the Opentherm protocol can be bought for under
£133 if you look around. If the Opentherm protocol is implemented further it
will fully simplify boiler wiring and give commercial levels of modulated
burner/pump, etc, control.

Few people in the heating industry have heard of "Opentherm", so many
opentherm compatible boilers will not be used to their maximum efficiency
and I see this boiler being one of them. If pushed properly, even dumb
plumbers could even understand it, it is that simple, with all the control
done on the pcb, not in crude electrical devices external to the boiler, as
is now. The contol is thought out for them, all they have to do is connect
up the devices with wires directly back to the boiler using two core wires
which don't care what way around the wires go in the terminals.

"Doctor Drivel" wrote in
reenews.net:

"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the Honeywell
Chronotherm, which can be bought a lot cheaper elsewhere rather
than the £133 Keston ask for it)...

Err... The programmer badged by
Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/d...SES%20850%20OT
%20neutral_2007_01_309%20872_GB.pdf

Here is the Chrontherm on the Keston site:
http://www.keston.co.uk/downloads/userguides/CX51-u.pdf

In the manuals they specifically state Chronotherm
Indeed. The description and part number a
Keston Chronotherm Room Controller C.17.4.21.00.0

The device supplied to me approx 18 months ago under this description
and part number is the Theben Ramses 850 OT and its details can be
found at the link I gave.

The name confused me when I was speccing the system, and I spoke to
the Keston Technical Department who confirmed that it was not a
Honeywell product. Unsurprisingly, they did not offer any more info
on where I could get a lower cost alternative but did confirm that
any OpenTherm (OT) device would do.

The reference to OpenTherm has nothing to do with the Honeywell
Chronotherm, but to the OpenTherm protocol used for data
communication between the boiler and the controller. See:
http://www.opentherm.org/

I said, "Opentherm standard", which is a "open" standard used by
those who sign up to it, as the opentherm link you gave explains.
Currently is only a protocol between boiler and room temperature
sensor. Two microprocessor based devices connected via a common
"open" protocol so all makers equipment using the protocol can
talk to each other. The boiler and an intelligent room temp
sensor (this may have a sophisticated clock in it as in a clock
stat, like the Chronotherm). There was talk of it 5 years ago,
but only recently have a number of makers started to incorporate
it into their pcbs (Maxie will have to get to know it as he fixes
pcb's).

A number of boiler makers use it, mainly German and Dutch, I
believe an Ideal boiler can use the Opentherm protocol.
Honeywell, Danfoss, Siemens, Landis, etc make room temperature
sensors which will connect onto these boilers and modulate the
burner or switch the boiler off/on, optimise the start stop of the
boiler, etc (the Honeywell Chronotherm optimises switching on).
Then no rip-off proprietary room sensors to buy, as any makers
sensor will do.

I am sure a Chronotherm using the Opentherm protocol can be bought
for under £133 if you look around...

The fact that Keston calls it a Chronotherm does not imply that it is
a Honeywell device. The manual that you linked to on the Keston site
is indeed for a Honeywell product (the CX51), but the PDF is dated
2002 and there is no reference to it that I can find on the Honeywell
UK site. Perhaps it's out there somewhere, but the Keston-badged
device that I have is certainly a Theben product.

As you say, OT devices are uncommon - I couldn't readily find a cheap
one, and opted for the Keston-badged device.

Few people in the heating industry have heard of "Opentherm", so
many opentherm compatible boilers will not be used to their
maximum efficiency and I see this boiler being one of them. If
pushed properly, even dumb plumbers could even understand it, it
is that simple, with all the control done on the pcb, not in crude
electrical devices external to the boiler, as is now. The contol
is thought out for them, all they have to do is connect up the
devices with wires directly back to the boiler using two core
wires which don't care what way around the wires go in the
terminals.

I have the Keston C36. I confess that I was hoping for more from the
OT controller, but perhaps I was over optimistic. Given that OT is a
two-way protocol, it offers:
- display of boiler and pump info, including burner and pump status,
flow temp etc
- display of outside temp
- reasonably comprehensive time programming
- optimised temp control (rather than directly programmed room temp)
via the external temp sensor and return flow temp [but this is poorly
explained in the manual]

However, whether this is much better than an external temp sensor +
normal switched live controller I'm not sure, since with just the
external temp sensor the boiler implements weather compensation
directly...

I'm pleased with the running costs - my gas bill is currently running
at £30 per month for a 12-rad system.

Kind regards

--
Richard Perkin
To email me, change the AT in the address below
richard.perkinATmyrealbox.com

It's is not, it isn't ain't, and it's it's, not its, if you mean it
is. If you don't, it's its. Then too, it's hers. It isn't her's.
It isn't our's either. It's ours, and likewise yours and theirs.
-- Oxford University Press, Edpress News

In article , Richard Perkin
writes

The name confused me when I was speccing the system, and I spoke to
the Keston Technical Department who confirmed that it was not a
Honeywell product. Unsurprisingly, they did not offer any more info
on where I could get a lower cost alternative but did confirm that
any OpenTherm (OT) device would do.


I have the Keston C36. I confess that I was hoping for more from the
OT controller, but perhaps I was over optimistic. Given that OT is a
two-way protocol, it offers:
- display of boiler and pump info, including burner and pump status,
flow temp etc
- display of outside temp
- reasonably comprehensive time programming
- optimised temp control (rather than directly programmed room temp)
via the external temp sensor and return flow temp [but this is poorly
explained in the manual]

However, whether this is much better than an external temp sensor +
normal switched live controller I'm not sure, since with just the
external temp sensor the boiler implements weather compensation
directly...

Thanks for the information Richard which was mostly new to me.
--
fred
Plusnet - I hope you like vanilla

fred wrote:
Thanks for the information Richard which was mostly new to me.

Seconded. Interesting stuff.

--
Andy

"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the Honeywell
Chronotherm, which can be bought a lot cheaper elsewhere rather
than the £133 Keston ask for it)...

Err... The programmer badged by
Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/downloads/BA_RAMSES%20850%20OT%20neutral_2007_01_309%20872_G B.pdf

Here is the Chrontherm on the Keston site:
http://www.keston.co.uk/downloads/userguides/CX51-u.pdf

In the manuals they specifically state Chronotherm
Indeed. The description and part number a
Keston Chronotherm Room Controller C.17.4.21.00.0

The device supplied to me approx 18 months ago under this description
and part number is the Theben Ramses 850 OT and its details can be
found at the link I gave.

It appears, Keston are using the Honeywell Chronotherm for the current unit.

The name confused me when I was speccing the system, and I spoke to
the Keston Technical Department who confirmed that it was not a
Honeywell product. Unsurprisingly, they did not offer any more info
on where I could get a lower cost alternative but did confirm that
any OpenTherm (OT) device would do.

"Any" OpenTherm device will do, that is the beauty of the OT protocol, you
may not have realised that at the time. The temperature sensing device can
have far much more funtionality and sets the boiler temperature from 0C to
82C, as you found out.

The reference to OpenTherm has nothing to do with the Honeywell
Chronotherm, but to the OpenTherm protocol used for data
communication between the boiler and the controller. See:
http://www.opentherm.org/

I said, "Opentherm standard", which is a "open" standard used by
those who sign up to it, as the opentherm link you gave explains.
Currently is only a protocol between boiler and room temperature
sensor. Two microprocessor based devices connected via a common
"open" protocol so all makers equipment using the protocol can
talk to each other. The boiler and an intelligent room temp
sensor (this may have a sophisticated clock in it as in a clock
stat, like the Chronotherm). There was talk of it 5 years ago,
but only recently have a number of makers started to incorporate
it into their pcbs (Maxie will have to get to know it as he fixes
pcb's).

A number of boiler makers use it, mainly German and Dutch, I
believe an Ideal boiler can use the Opentherm protocol.
Honeywell, Danfoss, Siemens, Landis, etc make room temperature
sensors which will connect onto these boilers and modulate the
burner or switch the boiler off/on, optimise the start stop of the
boiler, etc (the Honeywell Chronotherm optimises switching on).
Then no rip-off proprietary room sensors to buy, as any makers
sensor will do.

I am sure a Chronotherm using the Opentherm protocol can be bought
for under £133 if you look around...

The fact that Keston calls it a Chronotherm does not imply that it is
a Honeywell device.

You will find the name "Chrontherm is heavily trademarked and legally
protected. The Keston link is to the Honeywell product. It will be the
Honeywell.

The manual that you linked to on the Keston site
is indeed for a Honeywell product (the CX51), but the PDF is dated
2002 and there is no reference to it that I can find on the Honeywell
UK site. Perhaps it's out there somewhere, but the Keston-badged
device that I have is certainly a Theben product.

The Chronotherm modulation controller is sold openly on the Continent for
less than £133. The Opentherm protocol was a Dutch/German initiative. I
heard the Atmos Multi is supposed to use OpenTherm to its controller, but it
does not state in the manual that it is. I assume if you sign up to
OpenTherm you make it clear it is OpenTherm.

As you say, OT devices are uncommon - I couldn't readily find a cheap
one, and opted for the Keston-badged device.

Few people in the heating industry have heard of "Opentherm", so
many opentherm compatible boilers will not be used to their
maximum efficiency and I see this boiler being one of them. If
pushed properly, even dumb plumbers could even understand it, it
is that simple, with all the control done on the pcb, not in crude
electrical devices external to the boiler, as is now. The contol
is thought out for them, all they have to do is connect up the
devices with wires directly back to the boiler using two core
wires which don't care what way around the wires go in the
terminals.

I have the Keston C36. I confess that I was hoping for more from the
OT controller, but perhaps I was over optimistic. Given that OT is a
two-way protocol, it offers:
- display of boiler and pump info, including burner and pump status,
flow temp etc
- display of outside temp
- reasonably comprehensive time programming
- optimised temp control (rather than directly programmed room temp)
via the external temp sensor and return flow temp [but this is poorly
explained in the manual]

How is the DHW flowrate from the C36?

The problem with current OpenTherm controllers is that they are too complex
for the average user. Simple to use, connect and fire up devices should be
made, then the nerd aspect of the OpenTherm protocol will disappear and the
dumb plumber will use them as the electronic control settings can be
pre-set.

Some Danfoss, and others, OpenTherm room sensors look like normal room stats
with normal knobs. And yes using these when you turn up the knob the burner
will modulate up as most people think happens with normal on-off room stat.
The time clock aspect is usually done via a switched live at the pcb and
separate clock usually on the boiler.. Yet how many of these boiler will
have normal crap on-off stat fitted instead of an OpenTherm room sensor
(looks like a stat), because of ignorance and the OpenTherm device will be
more expensive - yet it delivers full burner modulation of boiler giving
superior economy and comfort conditions.

However, whether this is much better than an external temp sensor +
normal switched live controller I'm not sure, since with just the
external temp sensor the boiler implements weather compensation
directly...

It will be, as the room temperature is supposed to influence the burner too.
First stage is outside weather temperature then the room temp influence to
control the burner - cascade.

I'm pleased with the running costs - my gas bill is currently running
at £30 per month for a 12-rad system.

Appears the electronic controls are doing their job. Does it maintain a
constant room temperature?

"fred" wrote in message ...
In article , Ed Sirett
writes
On Sun, 23 Dec 2007 19:10:40 +0000, fred wrote:

Andy had me worried there for a minute but it looks like they have
introduced the Qudos 28 as a mid level domestic replacement that fixes
some of the original issues I had with the Celsius 25. There are
separate control temperatures depending on the demand source with
thermistor sensor modulated control of DHW temp and they promise
compatibility with low grade heat from solar panels in the future. Full
list is: Room Compensation, Weather Compensation, Solar Control,
Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External
Lockout Signal, Remote Fascia Panel plus LCD control panel and display
of system params (flue temp, flow/return temp, other temp densors) in
installer mode. They've retained the 20m/50mm maximum flue length and
even extended it to 60m when increased to 65mm. Suffix H is heat only
without pump or expansion vessel, suffix S is a system unit with those
parts incorporated.

£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at
discountedheating.

I'm quietly impressed.

This boiler would have the most sophosticated controls of any in that
price bracket.

The sophistication and the solar hook makes it attractive to the
specialist market and the techies here but I do wonder whether it will
make it in the mainstream market, it's just too clever. I hope that they
and it make it, at last a company who listen.

Keston are only doing what the Germans and Dutch have been doing for a
number of years in a limited manner. Vaillant do OpenTherm, yet only on
selected models and not across the range, and up until recently nothing sold
in the UK that I was aware of. The OpenTherm protocol appeared only to be
for Continental models.

Here are the makers who implement OpenTherm. The boilers and the peripheral
devices. It may be slightly out of date:
http://tinyurl.com/2bycs7

The more small third party companies make OpenTherm devices the cheaper they
will become. The hope was that third party pcb makers would make a range of
"standard" OpenTherm pcb's and many boiler makers would use them for their
models. This would also drive down pcb costs too. Then pcb's could be
bought anywhere and fit many boiler models. Just like when you buy parts
for your car and there is a long list of models the part fits. Then a pcb
may be a user replaceable slide in part.

Brilliant thread, it will help me choose a new boiler/ controller in the
spring.

I had a Camray 70/90 Oil boiler in my previous house controlled by a
Honeywell AQ6000, a brilliant controller unfortunately no longer made. I
installed and commissioned it in August 1996, never had any problems with
the boiler or controller and AFAIAA the new owners (4Yrs) have had good
service from it.
However, new technology, we must move on, am looking forward to getting to
grips with it.

Regards
Don

"Doctor Drivel" wrote in
reenews.net:


"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:

... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the
Honeywell Chronotherm, which can be bought a lot cheaper
elsewhere rather than the £133 Keston ask for it)...

Err... The programmer badged by
Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/d...AMSES%20850%20
OT%20neutral_2007_01_309%20872_GB.pdf

Here is the Chrontherm on the Keston site:
http://www.keston.co.uk/downloads/userguides/CX51-u.pdf

In the manuals they specifically state Chronotherm
Indeed. The description and part number a
Keston Chronotherm Room Controller C.17.4.21.00.0

The device supplied to me approx 18 months ago under this
description and part number is the Theben Ramses 850 OT and its
details can be found at the link I gave.

It appears, Keston are using the Honeywell Chronotherm for the
current unit.

The name confused me when I was speccing the system, and I spoke
to the Keston Technical Department who confirmed that it was not
a Honeywell product. Unsurprisingly, they did not offer any more
info on where I could get a lower cost alternative but did
confirm that any OpenTherm (OT) device would do.

"Any" OpenTherm device will do, that is the beauty of the OT
protocol, you may not have realised that at the time.
Of course I realised it - that's one of the reasons why I spoke to
Keston. I (like you) also realised that the asking price for the
'Keston' controller was high - but the company couldn't/wouldn't
suggest an alternative, and I struggled to find one. Perhaps you know
of others readily available in the UK? Or (for the rcord) where the
Honeywell OT device can be purchased?

You will find the name "Chrontherm is heavily trademarked and
legally protected. The Keston link is to the Honeywell product.
It will be the Honeywell.
The same name and part numer are in the C36 manual. The same product
info was also on the Keston site 18 months ago. When I ordered the
controller, what was delivered was the Theben device *not* a
Honeywell.

Perhaps things have changed - you could try ringing them up...

How is the DHW flowrate from the C36?
It's best described as 'adequate'. I was hoping for better - indeed,
a major reason for selecting the C36 was its high output (CH output
OTT for my house, although of course it's fully modulating so no
problem there) and consequent high DHW flow rate. The spec is: 14.5
l/min @ 35deg C rise, 17 l/min @ 30 deg C rise.

However, despite this it is still slower than I would like to fill a
bath with 'properly hot' water. However, the flow rate for a drencher
shower is truly excellent, as you would expect.

The bolier is sited some distance from the bathroom, and the length
of pipework has a significant impact as there is a considerable
'slug' of cold water to come from the tap before the hot water flows
well.

But these are well known consequences of using a combi, so I'm not
surprised.

However, whether this is much better than an external temp sensor
+ normal switched live controller I'm not sure, since with just
the external temp sensor the boiler implements weather
compensation directly...

It will be, as the room temperature is supposed to influence the
burner too. First stage is outside weather temperature then the
room temp influence to control the burner - cascade.

I'm pleased with the running costs - my gas bill is currently
running at £30 per month for a 12-rad system.

Appears the electronic controls are doing their job. Does it
maintain a constant room temperature?
No, it doesn't quite work like that. The Theben controller has two
modes of operation: you can set a target room temperature, or (if the
external temp sensor is present) use weather compensated control.

Weather compensated control is the default when the sensor is fitted,
or more accurately, since the snsor is connected to the boiler
system, when the boiler tells the controller via OT that it is
present. When it is used, the controller uses a predefined heating
curve, but it is possible to set the start and end points. This is
very poorly explained in the manual (read it at the link above) and I
am using the default settings.

This seems to work OK. All rads but the usual suspects (hall,
bathroom) are fitted with TRVs and the controller is in the hall. If
it were set for a fixed target temp I would use 21 deg C - in
practice it works automagically with a displayed temp of around 21 -
22 deg. Room temp is controlled by the TRVs, but the controller +
weather compensation ensure that the CH flow rarely rises above 65
deg (although the max would be 82 deg).

As I write this the controller says the (hall) room temp is 22.6 deg
and the flow temp is 43 deg against an outside temp of 8 deg.

The house is always comfortably warm. In fact many visitors find it
hot, but having spent a very cold Derbyshire childhood I vowed never
to be cold again, so we like it like that

Quite how the device implements the control I'm unclear (which is
unlike me - I like to know the nitty gritty) and I'd prefer to
'play', but the default setting works well and the running costs are
low.

Kind regards

--
Richard Perkin
To email me, change the AT in the address below
richard.perkinATmyrealbox.com

It's is not, it isn't ain't, and it's it's, not its, if you mean it
is. If you don't, it's its. Then too, it's hers. It isn't her's.
It isn't our's either. It's ours, and likewise yours and theirs.
-- Oxford University Press, Edpress News

"Richard Perkin" wrote in message
...

The name confused me when I was speccing the system, and I spoke
to the Keston Technical Department who confirmed that it was not
a Honeywell product. Unsurprisingly, they did not offer any more
info on where I could get a lower cost alternative but did
confirm that any OpenTherm (OT) device would do.

"Any" OpenTherm device will do,
that is the beauty of the OT
protocol, you may not have
realised that at the time.

Of course I realised it - that's one of
the reasons why I spoke to Keston. I
(like you) also realised that the asking
price for the 'Keston' controller was high
- but the company couldn't/wouldn't
suggest an alternative, and I struggled to
find one. Perhaps you know
of others readily available in the UK?
Or (for the rcord) where the
Honeywell OT device can be purchased?

Try Honeywel first. :-)

How is the DHW flowrate from the C36?

It's best described as 'adequate'. I was
hoping for better - indeed, a major reason
for selecting the C36 was its high output

14.5 litres/min is not starting.

However, despite this it is still
slower than I would like to fill a
bath with 'properly hot' water.
However, the flow rate for a drencher
shower is truly excellent, as you would expect.

The bolier is sited some distance from
the bathroom, and the length
of pipework has a significant impact
as there is a considerable
'slug' of cold water to come from the
tap before the hot water flows well.

But these are well known consequences
of using a combi, so I'm not surprised.

Dead leg pipe is well ...dead-leg pipe and will be the same whether from a
combi or a cylinder.

Appears the electronic controls are doing their job. Does it
maintain a constant room temperature?

No, it doesn't quite work like that. The Theben controller has two
modes of operation: you can set a target room temperature, or (if the
external temp sensor is present) use weather compensated control.

That is probably the function of the pcb. It appears it can't do weather
compensation "and" room temperature influence on the compensation.

Quite how the device implements the
control I'm unclear (which is
unlike me - I like to know the nitty gritty)

It "appears" it is either or. Weather compensation or room temperature
control depending what sensor is connected.