I have just bought a 2 bed lower flat into which I am intending to
install a condensing combi system. Based on the on-line radiator
calculators I need about 8.5kW of output in total for the six
radiators and hot water, so my questions to the group are a few:

1) I had though I could use 15mm (plastic) pipe for the feed and
return to the radiators, but it has been suggested to me that this
should be upped to 22mm - is this good advice or would 15mm suffice
for this sort of installation?

2) Being a condensing boiler I understand it will run more efficiently
with a lower circulation temperature - does this mean I have to derate
the radiators below their quoted capacity?

3) Since all the boilers I have seen are substantially more powerful
than I require for this building, I will have to put in an over
powerful model. I am guessing that I should also over spec the
radiators, to an extent, in order to provide a decent load for the
boiler and use a room stat as an additional step to prevent short
cycling (the other rads will all have TRVs on them). Is this
sensible?

4) I have collated a chunk of info / FAQs on this, but if anyone can
point me in the direction of substantial / useful resources, again
this would be greatfully received.

Many thanks in advance for any help,

Mark

1) I had though I could use 15mm (plastic) pipe for the feed and
return to the radiators, but it has been suggested to me that this
should be upped to 22mm - is this good advice or would 15mm suffice
for this sort of installation?

It depends on the configuration. If installing the radiators off a snaking
"main", then I'd use 22mm. If you are running each radiator pipe to a
central manifold, then you'd get away with as low as 10mm (or even 8mm) for
most radiators.

2) Being a condensing boiler I understand it will run more efficiently
with a lower circulation temperature - does this mean I have to derate
the radiators below their quoted capacity?

You don't have to, but it will be more efficient if you do. You'd have to
derate them a little anyway, as they are normally quoted at an unreasonably
high delta T.

I am guessing that I should also over spec the radiators, to an
extent, in order to provide a decent load for the boiler and use
a room stat as an additional step to prevent short cycling (the
other rads will all have TRVs on them). Is this
sensible?

Modern boilers are modulating and simply turn down the heat before switching
off and cycling. Just ensure that your chosen boiler model has a low minimum
burner rate.

There's no need to overspec the radiators for the reason given. However,
oversizing will be more efficient as it would enable ever lower flow
temperatures to be used, as the expense of wall space.

Christian.

Mark Begbie wrote:

I have just bought a 2 bed lower flat into which I am intending to
install a condensing combi system. Based on the on-line radiator
calculators I need about 8.5kW of output in total for the six
radiators and hot water, so my questions to the group are a few:

What is the current heating setup? How is hot water provided at the moment?

1) I had though I could use 15mm (plastic) pipe for the feed and
return to the radiators, but it has been suggested to me that this
should be upped to 22mm - is this good advice or would 15mm suffice
for this sort of installation?

15mm is only good for 6kW or so (or less at lower temperatures), hence I
would use 22mm for the backbone pipework and 15mm runs to the rads.

2) Being a condensing boiler I understand it will run more efficiently
with a lower circulation temperature - does this mean I have to derate
the radiators below their quoted capacity?

Yes.

3) Since all the boilers I have seen are substantially more powerful
than I require for this building, I will have to put in an over
powerful model. I am guessing that I should also over spec the

Most condensors will moduleate down to much lower outputs (say 6 - 8kW,
some will go lower still) so not as much of a problem. Obviously once
the house is warm the heating load will fall to the a low level and the
boiler will cycle to maintain it.

Your most important consideration will be hot water performance. If you
mainly take showers then a smaller combi (24 - 30kW) will be fine. If
you prefer baths you may want faster water delivery than you will get
from a smaller boiler. If you already have a hot water cylinder heated
from a boiler then you could retain that for the bath (heated from the
radiator circuit) and use the direct hot just for the other taps. If
there is no current hot water cylinder then look at a larger combi or
one that includes a storage tank. How much space you have available for
the boiler will also be a consideration.

4) I have collated a chunk of info / FAQs on this, but if anyone can
point me in the direction of substantial / useful resources, again
this would be greatfully received.

http://www.diyfaq.org.uk/
http://www.makewrite.demon.co.uk/SealedCH.html




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Thanks for the info, I'm getting more mentally clear about this by the
day. So to answer some of your questions.

The current setup is a cold tank in the hall cupboard with hot
cylinders in the lounge cupboard heated by an immersion. There is no
boiler at all in the house with the only heating provided by a gas
fire in the lounge (heading for a skip). Space is very tight (I have
a lot of stuff!) so I am keen to go down the combi route and get rid
of all the tanks. Also I can't remember when I last had a bath (yes,
obvious riposte duly noted ;-) )

The system I am planning to put in is a combi running a feed and
return loop to the radiators, so it sounds like I should really be
using 22mm for the loop. Plan is for barrier Hep2O with copper
through the floor. The boiler I was looking at is a Glow-Worm 24cxi
as a) it's a condenser b) it modulates down to only 4.95kW and c) it's
available from energysmart. Everything except (probably) the lounge
will be on TRVs with a roomstat for the final rad.

I am now leaning toward overrating the rads so that the total is
closer to the boiler output (18kW) than the "required" value of 6kW
that the online radiator calculators come out with. Probably put in
about 12kW worth of radiator area.

My master plan is to do all the installation and then get a CORGI
engineer in to pressure test and hook in to the gas supply.

Many thanks again,

Mark

In article ,
(Mark Begbie) writes:
I am now leaning toward overrating the rads so that the total is
closer to the boiler output (18kW) than the "required" value of 6kW
that the online radiator calculators come out with. Probably put in
about 12kW worth of radiator area.

Not clear if this includes downrating the rads for lower temperature
rating. In my case, I had to downrate the rads to 60% of their data
sheet ratings for condensing boiler operation down to -3C outside.
Some manufacturers overrate even worse and their rads will need
downrating by 50%. That gives you your 6kW output from 12kW of rads.
On the other hand, there no necessity to have the boiler still in
the condensing region of operation when outside temperature are
down to -3C.

Something else this enables you to do is to avoid predictive heating
using a timeswitch, where in many cases for me at least, the heating
would end up coming on ages before I arrived home. By being able to
dump far more heat into the house than it needs to compensate for
losses, you can do a damn fast bringing up to temperature. I now
turn my heating on when I get in, and the warmup time is so fast
I just don't notice it. (If it's really cold, I can ring up the
home automation system and have it switch on the heating and/or
hot water before I get home, or I can do it as I leave the office
via the Internet;-)

--
Andrew Gabriel

In article , Andrew Gabriel
wrote:
On the other hand, there no necessity to have the boiler still in
the condensing region of operation when outside temperature are
down to -3C.

I switched to a Glow-worm 24Cxi earlier this year from a Potterton
Envoy (!!!) condensing boiler/cylinder system. A key plus of the
combi arrangement is that for most of the year you can keep the CH
flow temp down at the condensing level with beneficial effects on the
boiler efficiency and heating performance (the rads aren't glowing
and sending the heat straight up), whilst with a boiler/cylinder
setup you need to keep the flow temp up (assuming a single boiler
stat) if you don't want extended cylinder reheat times.

As you imply, on a condensing combi system it's the loss in
efficiency caused by turning the temp up when it's really cold will
probably cost a lot less than oversizing the rads.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm

On 8 Sep 2004 11:32:28 GMT, (Andrew
Gabriel) wrote:

In article ,
(Mark Begbie) writes:
I am now leaning toward overrating the rads so that the total is
closer to the boiler output (18kW) than the "required" value of 6kW
that the online radiator calculators come out with. Probably put in
about 12kW worth of radiator area.

Not clear if this includes downrating the rads for lower temperature
rating. In my case, I had to downrate the rads to 60% of their data
sheet ratings for condensing boiler operation down to -3C outside.
Some manufacturers overrate even worse and their rads will need
downrating by 50%. That gives you your 6kW output from 12kW of rads.
On the other hand, there no necessity to have the boiler still in
the condensing region of operation when outside temperature are
down to -3C.

Something else this enables you to do is to avoid predictive heating
using a timeswitch, where in many cases for me at least, the heating
would end up coming on ages before I arrived home. By being able to
dump far more heat into the house than it needs to compensate for
losses, you can do a damn fast bringing up to temperature. I now
turn my heating on when I get in, and the warmup time is so fast
I just don't notice it. (If it's really cold, I can ring up the
home automation system and have it switch on the heating and/or
hot water before I get home, or I can do it as I leave the office
via the Internet;-)



Of course you could put a temperature sensor outside the office window
and hook it up to a machine in the office. Taking the average
temperature differences over the last century for the differences
between the home and office locations from the Met Office database,
you could control the home system remotely. Of course it might
take several phone calls to control it properly.

I would think that this would be a good application for a SunFire
E25K, and every office worker should want one.


..andy

To email, substitute .nospam with .gl

In article ,
Andy Hall writes:

Of course you could put a temperature sensor outside the office window
and hook it up to a machine in the office.

I have one outside at home and hooked up to the computer which
controls the room temperatures, call for heat, etc. However,
apart from logging the outside temperature, I have not found
it useful for adjusting the behaviour of the heating control
system. This is in an old house which takes many days to cool
down if you switch the heating off -- it might be different in
a new house with almost zero thermal inertia.

Taking the average
temperature differences over the last century for the differences
between the home and office locations from the Met Office database,
you could control the home system remotely. Of course it might
take several phone calls to control it properly.

I would think that this would be a good application for a SunFire
E25K, and every office worker should want one.

Well, an E25K computer system is around 30kW. You can modulate
it down by using dynamic reconfiguration (DR) to switch off
CPUs. I don't know what the lowest setting with just 1 CPU
running would be. An interesting idea though - a heating system
which is just the control computer;-)

I actually control the heating with a 120MHz Pentium I, and it's
way over-powered for the task.

--
Andrew Gabriel

"Andrew Gabriel" wrote
| (If it's really cold, I can ring up the home automation system
| and have it switch on the heating and/or hot water before I get
| home, or I can do it as I leave the office via the Internet;-)

Of course, in the 'good old days' wives did all this without being told :-)

Owain

On Wed, 08 Sep 2004 01:39:33 -0700, Mark Begbie wrote:

Thanks for the info, I'm getting more mentally clear about this by the
day. So to answer some of your questions.

The current setup is a cold tank in the hall cupboard with hot
cylinders in the lounge cupboard heated by an immersion. There is no
boiler at all in the house with the only heating provided by a gas
fire in the lounge (heading for a skip). Space is very tight (I have
a lot of stuff!) so I am keen to go down the combi route and get rid
of all the tanks. Also I can't remember when I last had a bath (yes,
obvious riposte duly noted ;-) )

The system I am planning to put in is a combi running a feed and
return loop to the radiators, so it sounds like I should really be
using 22mm for the loop. Plan is for barrier Hep2O with copper
through the floor. The boiler I was looking at is a Glow-Worm 24cxi
as a) it's a condenser b) it modulates down to only 4.95kW and c) it's
available from energysmart. Everything except (probably) the lounge
will be on TRVs with a roomstat for the final rad.

I am now leaning toward overrating the rads so that the total is
closer to the boiler output (18kW) than the "required" value of 6kW
that the online radiator calculators come out with. Probably put in
about 12kW worth of radiator area.

My master plan is to do all the installation and then get a CORGI
engineer in to pressure test and hook in to the gas supply.

Since you are a shower man a 24kW unit will be quite adequate.
That is the water heating power. A condensing model will try to
modulate down to the few kW you need, it will likely do a much better job
than a non-condensing unit could do.

Make the radiators up to about double what's needed by the heat loss
program. There is no need to be too strict about this, if say, there
are places where you don't wish to have the extra width or depth or rad.

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.

I would be happy to fit Vaillant Ecomax 8xx units but the (trade) price
is really to high ATM.



--
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

On 8 Sep 2004 14:09:09 GMT, (Andrew
Gabriel) wrote:

I have one outside at home and hooked up to the computer which
controls the room temperatures, call for heat, etc. However,
apart from logging the outside temperature, I have not found
it useful for adjusting the behaviour of the heating control
system. This is in an old house which takes many days to cool
down if you switch the heating off -- it might be different in
a new house with almost zero thermal inertia.

Hi,

It could be used to optimise the flow temperature.

cheers,
Pete.

Ed Sirett wrote:

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.

I fitted a Ideal Isar HE35 in March this year. It has performed very
well since then. Boiler is physically very small and neat (hence the
reason for choosing it - it had to fit a pre existing gap left by a
Gloworm Fuelsaver 55F).

Operation is very quiet (better that the one it replaced). Heating
performance seemed fine using a programmable thermostat. It seems to
modulate to match the actual load very well. Seems to run in condensing
mode 90%+ of the time (judging by the pluming) when running the heating.
This may improve later since I have not balanced the radiators yet,
since I knew I would be adding more radiators to it in the near future
anyway.

Not had chance to asses the impact on fuel usage since the time is too
short, and for a good proportion of the first couple of months there
were various holes in the house as I was getting stuck into the
structural bits of a loft conversion. These I presume would not make for
a fair like for like comparison!

Instalation was pretty straight forward, no setting up procedures to
perform as such. Pipework all runs to a mounting tray which the boiler
is lifted onto afterwards (that was the hardest bit!). Standard
concentric flue turret at the top.

DHW performance is OK. It does not attempt to modulate the flow of
water, so if the incoming water is cold enough and the supply is up to
it, then demanding water too fast will result in the temperature
falling. In the winter with ground water at 5 degrees you could open a
bath tap to approx 70% max flow before reducing the temperature to below
bath temp. In the summer our mains feed (about 22 lpm) is not up to
dropping it below bath temp. The thermostat works well at setting a
maximum temperature for the water. It runs a heat exchanger preheat
every few hours to ensure that there is always hot water available
"instantly".

Anything else you want to know?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Pete C writes:
On 8 Sep 2004 14:09:09 GMT, (Andrew
Gabriel) wrote:

I have one outside at home and hooked up to the computer which
controls the room temperatures, call for heat, etc. However,
apart from logging the outside temperature, I have not found
it useful for adjusting the behaviour of the heating control
system. This is in an old house which takes many days to cool
down if you switch the heating off -- it might be different in
a new house with almost zero thermal inertia.

Hi,

It could be used to optimise the flow temperature.

I might do that when I've hacked my Celcius25 so the computer can
set the flow temperature. I finally found some dual linear taper
motorised pots, which was the key part I was missing for the
design I have in mind.

--
Andrew Gabriel

On 8 Sep 2004 23:14:35 GMT, (Andrew
Gabriel) wrote:

In article ,
Pete C writes:
On 8 Sep 2004 14:09:09 GMT, (Andrew
Gabriel) wrote:

I have one outside at home and hooked up to the computer which
controls the room temperatures, call for heat, etc. However,
apart from logging the outside temperature, I have not found
it useful for adjusting the behaviour of the heating control
system. This is in an old house which takes many days to cool
down if you switch the heating off -- it might be different in
a new house with almost zero thermal inertia.

Hi,

It could be used to optimise the flow temperature.

I might do that when I've hacked my Celcius25 so the computer can
set the flow temperature. I finally found some dual linear taper
motorised pots, which was the key part I was missing for the
design I have in mind.


A servo driven by /sbin/twiddled?

Another pretty simple approach would be a suitable optical coupler
with the output side replacing the pot, then drive the input side from
a DAC. Have a lookup table in software to linearise the conversion.
No moving parts.


..andy

To email, substitute .nospam with .gl

"Ed Sirett" wrote in message
news
SNIP

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.


I've fitted a few of the Glow Worm condensing range both Combi and straight
boilers Ed. Generally the response has been highly satisfied customers with
one exception where the water flow detector (turbine type) impellor stuck on
its shaft a couple of times. Glow Worm sent their own guy out as an in
warranty repair. No further problems encountered. One of the straight
boilers had a displaced rubber joint on the condensate trap which showed up
inside an hour and was a trivial job to correct it.

On Wed, 08 Sep 2004 22:46:30 +0100, John Rumm wrote:

Ed Sirett wrote:

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.

I fitted a Ideal Isar HE35 in March this year. It has performed very
well since then. Boiler is physically very small and neat (hence the
reason for choosing it - it had to fit a pre existing gap left by a
Gloworm Fuelsaver 55F).

Operation is very quiet (better that the one it replaced). Heating
performance seemed fine using a programmable thermostat. It seems to
modulate to match the actual load very well. Seems to run in condensing
mode 90%+ of the time (judging by the pluming) when running the heating.
This may improve later since I have not balanced the radiators yet,
since I knew I would be adding more radiators to it in the near future
anyway.

Not had chance to asses the impact on fuel usage since the time is too
short, and for a good proportion of the first couple of months there
were various holes in the house as I was getting stuck into the
structural bits of a loft conversion. These I presume would not make for
a fair like for like comparison!

Instalation was pretty straight forward, no setting up procedures to
perform as such. Pipework all runs to a mounting tray which the boiler
is lifted onto afterwards (that was the hardest bit!). Standard
concentric flue turret at the top.

DHW performance is OK. It does not attempt to modulate the flow of
water, so if the incoming water is cold enough and the supply is up to
it, then demanding water too fast will result in the temperature
falling. In the winter with ground water at 5 degrees you could open a
bath tap to approx 70% max flow before reducing the temperature to below
bath temp. In the summer our mains feed (about 22 lpm) is not up to
dropping it below bath temp. The thermostat works well at setting a
maximum temperature for the water. It runs a heat exchanger preheat
every few hours to ensure that there is always hot water available
"instantly".

Anything else you want to know?

Ta. Price.

--
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

Ed Sirett wrote:

Anything else you want to know?


Ta. Price.

Twas about 900 including standard flue package from the local village
plumbers merchant when I got it (or about 1K at the on-line discount
places!). It seems to have come down in price a little since then. Best
price seems to be about 800 at the mo unless you can get a decent trade
discount. The range of Isars also includes a 30 and 24kW version which
are cheaper.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 8 Sep 2004 23:14:35 GMT, (Andrew
Gabriel) wrote:

Hi,

It could be used to optimise the flow temperature.

I might do that when I've hacked my Celcius25 so the computer can
set the flow temperature. I finally found some dual linear taper
motorised pots, which was the key part I was missing for the
design I have in mind.
Hi,

Is it possible to set the flow temperature to maxium and get the
computer to switch it out to control the flow temperature?

cheers,
Pete.

"John" wrote in message
...

"Ed Sirett" wrote in message
news
SNIP

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.


I've fitted a few of the Glow Worm condensing range both Combi and
straight
boilers Ed. Generally the response has been highly satisfied customers
with
one exception where the water flow detector (turbine type) impellor stuck
on
its shaft a couple of times. Glow Worm sent their own guy out as an in
warranty repair. No further problems encountered. One of the straight
boilers had a displaced rubber joint on the condensate trap which showed
up
inside an hour and was a trivial job to correct it.

Apart from these problems are you happy with the design & build quality? Are
they easy or fiddly to set up?
They seem a hell of a weight - definitely a 2-man lift, then?

On Fri, 10 Sep 2004 10:52:43 +0100, Pete C
wrote:

On 8 Sep 2004 23:14:35 GMT, (Andrew
Gabriel) wrote:

Hi,

It could be used to optimise the flow temperature.

I might do that when I've hacked my Celcius25 so the computer can
set the flow temperature. I finally found some dual linear taper
motorised pots, which was the key part I was missing for the
design I have in mind.
Hi,

Is it possible to set the flow temperature to maxium and get the
computer to switch it out to control the flow temperature?

cheers,
Pete.

One could, but it's a very bad idea because the boiler, pump and fan
will be going on and off.

Having an analogue control is a much better way.




..andy

To email, substitute .nospam with .gl

"John Stumbles" wrote in message
...
"John" wrote in message
...

"Ed Sirett" wrote in message
news
SNIP

I'm interested to hear from anyone who has a condensing combi.
I want to know what your experience of it is.


I've fitted a few of the Glow Worm condensing range both Combi and
straight
boilers Ed. Generally the response has been highly satisfied customers
with
one exception where the water flow detector (turbine type) impellor
stuck
on
its shaft a couple of times. Glow Worm sent their own guy out as an in
warranty repair. No further problems encountered. One of the straight
boilers had a displaced rubber joint on the condensate trap which showed
up
inside an hour and was a trivial job to correct it.

Apart from these problems are you happy with the design & build quality?
Are
they easy or fiddly to set up?
They seem a hell of a weight - definitely a 2-man lift, then?

As far as I'm "happy" with any modern (accountant engineered) product they
are well built, at least they use stainless steel and plastics properly
rather than aluminium in contact with acidic condensate. I'd not classify
them as a two man lift by any stretch of the imagination but I suppose I've
been around long enough to expect bags of cement to weigh a hundredweight
(approx 50kG) not these namby pamby 25kG bags that are the norm nowadays.
I have installed an Isar in the past so by way of comparison I can say it
was much heavier and not as easy to install

On Fri, 10 Sep 2004 22:11:03 +0100, Andy Hall
wrote:

Is it possible to set the flow temperature to maxium and get the
computer to switch it out to control the flow temperature?

One could, but it's a very bad idea because the boiler, pump and fan
will be going on and off.

Oops, meant to say burner/fan, the pump would best be left running.

Having an analogue control is a much better way.

Bit unnecessary for a non modulating boiler I would have thought.

cheers,
Pete.

On Sat, 11 Sep 2004 22:06:39 +0100, Pete C
wrote:

On Fri, 10 Sep 2004 22:11:03 +0100, Andy Hall
wrote:

Is it possible to set the flow temperature to maxium and get the
computer to switch it out to control the flow temperature?

One could, but it's a very bad idea because the boiler, pump and fan
will be going on and off.

Oops, meant to say burner/fan, the pump would best be left running.

Having an analogue control is a much better way.

Bit unnecessary for a non modulating boiler I would have thought.

Except that the Keston Celsius 25 is a modulating boiler........





cheers,
Pete.

..andy

To email, substitute .nospam with .gl

On Sat, 11 Sep 2004 22:14:01 +0100, Andy Hall
wrote:

Having an analogue control is a much better way.

Bit unnecessary for a non modulating boiler I would have thought.

Except that the Keston Celsius 25 is a modulating boiler........

Ooops, I'm not a boiler spotter )) Does the temperature control
affect CH as well as DHW? I'd have thought it only affects DHW, and
the rest of the time the boiler operates in condensing mode where
possible.

For DHW it could be useful to have a lower output temp for bath
filling, this could be done with a preset and changeover relay.

For more control something could be done with the flow and return
thermistors.

cheers,
Pete.

On Sun, 12 Sep 2004 17:00:11 +0100, Pete C
wrote:

On Sat, 11 Sep 2004 22:14:01 +0100, Andy Hall
wrote:

Having an analogue control is a much better way.

Bit unnecessary for a non modulating boiler I would have thought.

Except that the Keston Celsius 25 is a modulating boiler........

Ooops, I'm not a boiler spotter )) Does the temperature control
affect CH as well as DHW? I'd have thought it only affects DHW, and
the rest of the time the boiler operates in condensing mode where
possible.

It isn't a combi either.



For DHW it could be useful to have a lower output temp for bath
filling, this could be done with a preset and changeover relay.

For more control something could be done with the flow and return
thermistors.

I have this functionality on my (MAN Micromat) boiler.

http://www.man-heiztechnik.de/index_e.php

It has an outside temperature sensor as well as an indoor one, and
programmable curves for CH operating temperature vs. environmental
temperatures. It will thus modulate the CH temperature down to
around 40 degrees and 3kW if there is not a great heat demand.

For DHW, there is a temperature sensor in a pocket in the cylinder
which starts a hot water reheat cycle when a rapid drop in temperature
is detected. In this mode, the boiler is run up to full output to
reheat the cylinder rapidly.




cheers,
Pete.

..andy

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