I am thinking of replacing my conventional central heating and hot 
water system with a gas combination boiler, for my four bedroom 
extended semi, with one bathroom.  My present system is 25 years old, 
when I did the heating calculations and ended up with a 10kw boiler, 
which works perfectly well with ample heat output, even in the coldest 
weather.  When I did the heating calcs, the house was *very* well 
insulated, and I have continued adding insulation/double glazing over 
the years, so it is now *extremely* well insulated.   I am therefore 
looking for a combi with less than 10kw output to central heating, 
plus enough say 10l/m to the DHW.   

Objective is to save space.

I have looked in Google Groups for old threads, and tried to answer 
the questions which may be asked. 

Kitchen tap gives 16l/m 
Bath tap hot water gives 9l/min
Soft water.

Googleing for combination boilers  only gives huge 20+kw models does 
anyone here know of anything smaller? 

As I will now be pressurizing the central heating pipes (copper with 
Yorkshire fittings) does anyone expect problems with this? 

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

In message , Dave Fawthrop 
 writes

>
>I am thinking of replacing my conventional central heating and hot
>water system with a gas combination boiler, for my four bedroom
>extended semi, with one bathroom.  My present system is 25 years old,
>when I did the heating calculations and ended up with a 10kw boiler,
>which works perfectly well with ample heat output, even in the coldest
>weather.  When I did the heating calcs, the house was *very* well
>insulated, and I have continued adding insulation/double glazing over
>the years, so it is now *extremely* well insulated.   I am therefore
>looking for a combi with less than 10kw output to central heating,
>plus enough say 10l/m to the DHW.
>
>Objective is to save space.
>
>I have looked in Google Groups for old threads, and tried to answer
>the questions which may be asked.
>
>Kitchen tap gives 16l/m
>Bath tap hot water gives 9l/min
>Soft water.
>
>Googleing for combination boilers  only gives huge 20+kw models does
>anyone here know of anything smaller?
>
>As I will now be pressurizing the central heating pipes (copper with
>Yorkshire fittings) does anyone expect problems with this?
>


Dave,

AFAIK, You have to look at Heating and DHW separately. Whilst 10Kw might 
be enough for Heating, you need much more to get a decent temperature 
rise and flow for DHW. It looks like 24Kw gives a 9l/m flow with a 35C 
rise in temp, and you wouldnt want any less than this. In fact, having 
had 24Kw boilers, I would definitely buy a more powerful one the next 
time - for DHW, not heating.

Hope this helps - Others who are experts may give a better answer.

-- 
Richard Faulkner

Dave Fawthrop wrote:

> I am therefore looking for a combi with less than 10kw output to 

 > central heating, plus enough say 10l/m to the DHW.

You want a boiler with as high a kW rating as possible, to get the best 
hot water flow (you said one bathroom - bath or shower?), but which will 
modulate down to 10kW or lower for the heating.

As IMM isn't here right now, I'll make the obligatory suggestion of 
getting two small boilers, use each on alternate days for the heating 
and run both together for the hot water, replacing all your Yorkshire 
fittings with plastic pipes cut with a hacksaw. A win, win, drip drip 
gurgle situation^Wdisaster.

Owain

"Dave Fawthrop"  wrote in message
news:4o73h1150qicrvkvvs2r497b907cc3jlm9@4ax.com...

>
> I am thinking of replacing my conventional central heating and hot
> water system with a gas combination boiler, for my four bedroom
> extended semi, with one bathroom.  My present system is 25 years old,
> when I did the heating calculations and ended up with a 10kw boiler,
> which works perfectly well with ample heat output, even in the coldest
> weather.  When I did the heating calcs, the house was *very* well
> insulated, and I have continued adding insulation/double glazing over
> the years, so it is now *extremely* well insulated.   I am therefore
> looking for a combi with less than 10kw output to central heating,
> plus enough say 10l/m to the DHW.
>
> Objective is to save space.
>
> I have looked in Google Groups for old threads, and tried to answer
> the questions which may be asked.
>
> Kitchen tap gives 16l/m
> Bath tap hot water gives 9l/min
> Soft water.
>
> Googleing for combination boilers  only gives huge 20+kw models does
> anyone here know of anything smaller?
>
> As I will now be pressurizing the central heating pipes (copper with
> Yorkshire fittings) does anyone expect problems with this?


firstly ignore the heating requirement and concentrate on the hot water
side - 40kW gives 16 litres per min approx - look for one that will modulate
down to your 10kW for the heating
FWIW - I have just had an Alpha CD50 fitted and am well impressed - this
modulates from 6.3 to 29.7 kW on heating and upto 32kW for water, it has a
small store for instant hot water and is wall mounted ( in loft on gable
end )
LMK if you want more info

Regards Jeff

In article ,
   Dave Fawthrop  wrote:

> I am thinking of replacing my conventional central heating and hot 
> water system with a gas combination boiler, for my four bedroom 
> extended semi, with one bathroom.  My present system is 25 years old, 
> when I did the heating calculations and ended up with a 10kw boiler, 
> which works perfectly well with ample heat output, even in the coldest 
> weather.  When I did the heating calcs, the house was *very* well 
> insulated, and I have continued adding insulation/double glazing over 
> the years, so it is now *extremely* well insulated.   I am therefore 
> looking for a combi with less than 10kw output to central heating, 
> plus enough say 10l/m to the DHW.


With a modulating condenser, the maximum heat output isn't so much of an
issue, since unlike older boilers it will actually increase efficiency
when not running at full output.   


> Objective is to save space.


Then it's a good choice.


> I have looked in Google Groups for old threads, and tried to answer 
> the questions which may be asked. 

> Kitchen tap gives 16l/m 
> Bath tap hot water gives 9l/min
> Soft water.


This is the existing storage system? Normally, the bath is fed from larger
bore pipe and should give much better flow - even although if a floor
higher and with less 'head'.


> Googleing for combination boilers  only gives huge 20+kw models does 
> anyone here know of anything smaller? 


With a combi, you need to size it for decent hot water flow - especially
if you like big baths. This is the real problem with them - they generally
can't fill a bath anywhere as fast as a *decent* storage system.


> As I will now be pressurizing the central heating pipes (copper with 
> Yorkshire fittings) does anyone expect problems with this? 


No - they'll be fine.

-- 
*Be more or less specific *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Dave Fawthrop wrote:


> Objective is to save space.


Save space as it "loose the tanks etc" or really save sapace as in the 
boiler needs to be tiny?


> I have looked in Google Groups for old threads, and tried to answer 
> the questions which may be asked. 
> 
> Kitchen tap gives 16l/m 
> Bath tap hot water gives 9l/min
> Soft water.


I would start by downloading the free boiler database program:

http://www.sda.co.uk/qsedbuk.htm

That will give you the stats for most boilers.

As the others said you can pretty much ignore the heating side, however 
it is worth looking for a model that will modulate as low as possible. 
In a well insulated house however even a small boiler will cycle a bit 
since it is not often going to be cold enough to keep above the minimum 
modulation point.

Based on my experiance with my HE35, you may find something like the 
Ideal Isar HE30 about right for your needs. It is physically very 
compact, and will modulate down to 8kW. There is also the ECO Hometec 
EC23s which will modulate right down to 4kW and still gives 28kW to DHW.

(personally I would not install anything smaller than about 35kW for 
water heating though).


> As I will now be pressurizing the central heating pipes (copper with 
> Yorkshire fittings) does anyone expect problems with this? 


With the pipework no. With radiators, only if they are close to 
knackered anyway. With very old lockshield valves - they may weep and 
need replacing - but most won't.

-- 
Cheers,

John.

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

On Sun, 28 Aug 2005 18:12:22 +0100, "Dave Plowman (News)"
 wrote:


| This is the existing storage system? Normally, the bath is fed from larger
| bore pipe and should give much better flow - even although if a floor
| higher and with less 'head'.

Completely conventional two header tanks, and indirect (coil) HW cylinder.
Two circuits, downstairs and upstairs which only gets used in very cold
weather

The only oddity is that it will work by gravity in power cuts, but as we
have had no long power cuts in 25 years, that is going. 
-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

In article ,
   Dave Fawthrop  wrote:

> Completely conventional two header tanks, and indirect (coil) HW
> cylinder. Two circuits, downstairs and upstairs which only gets used in
> very cold weather

> The only oddity is that it will work by gravity in power cuts, but as we
> have had no long power cuts in 25 years, that is going.


Does this refer to the heating? It must be pretty old if there's no
electrics in the boiler. And if it works without the pump running this
will need sorting, as it will waste energy with the new boiler.

If you mean the hot water, no electricity is needed to access stored hot
water.

-- 
*If you're not part of the solution, you're part of the precipitate *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Mon, 29 Aug 2005 09:02:43 +0100, "Dave Plowman (News)"
 wrote:

| In article ,
|    Dave Fawthrop  wrote:
| > Completely conventional two header tanks, and indirect (coil) HW
| > cylinder. Two circuits, downstairs and upstairs which only gets used in
| > very cold weather
| 
| > The only oddity is that it will work by gravity in power cuts, but as we
| > have had no long power cuts in 25 years, that is going.
| 
| Does this refer to the heating? It must be pretty old if there's no
| electrics in the boiler. And if it works without the pump running this
| will need sorting, as it will waste energy with the new boiler.

It uses a conventional controller with pump but could be switched to manual
in the case of another "Winter of Discontent"  All that will be ditched
when a new boiler is installed.

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

In article ,
   Dave Fawthrop  wrote:

> | Does this refer to the heating? It must be pretty old if there's no
> | electrics in the boiler. And if it works without the pump running this
> | will need sorting, as it will waste energy with the new boiler.

> It uses a conventional controller with pump but could be switched to
> manual in the case of another "Winter of Discontent" 


Please explain?

-- 
*How many roads must a man travel down before he admits he is lost? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Mon, 29 Aug 2005 18:18:21 +0100, "Dave Plowman (News)"
 wrote:

| In article ,
|    Dave Fawthrop  wrote:
| > | Does this refer to the heating? It must be pretty old if there's no
| > | electrics in the boiler. And if it works without the pump running this
| > | will need sorting, as it will waste energy with the new boiler.
| 
| > It uses a conventional controller with pump but could be switched to
| > manual in the case of another "Winter of Discontent" 
| 
| Please explain?

Maybe you are too young to remember the "winter of discontent" when we had
long power cuts c1976.
Too much effort to explain as the whole lot is for the bin.

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

Dave Fawthrop wrote:


> | > It uses a conventional controller with pump but could be switched to
> | > manual in the case of another "Winter of Discontent" 
> | 
> | Please explain?
> 
> Maybe you are too young to remember the "winter of discontent" when we had
> long power cuts c1976.
> Too much effort to explain as the whole lot is for the bin.


I think he ment please explain how it worked in "manual mode" rather 
than the winter fo discontent.... then again maybe he is younger than we 
thought ;-)

-- 
Cheers,

John.

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

In article ,
   Dave Fawthrop  wrote:

> | > It uses a conventional controller with pump but could be switched to
> | > manual in the case of another "Winter of Discontent" 
> | 
> | Please explain?

> Maybe you are too young to remember the "winter of discontent" when we
> had long power cuts c1976. Too much effort to explain as the whole lot
> is for the bin.


Heh heh - I can well remember the 'Winter of Discontent' being one of the
very discontented workers - fed up to the back teeth with government
trying to control prices and incomes - but only partially succeeding in
controlling incomes for some - including me. While prices rocketed.

I was interested in how a pumped system could be switched to manual. A
hamster in a wheel to turn the pump?

-- 
*Sometimes I wake up grumpy; Other times I let him sleep.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Wed, 31 Aug 2005 18:35:23 +0100, "Dave Plowman (News)"
 wrote:


| I was interested in how a pumped system could be switched to manual. A
| hamster in a wheel to turn the pump?

OK I give in.   I was an Engineer designing little power stations for
aircraft, so thinking outside the box was normal for me.

I put two loops of one inch pipe, one on each side of the house, which
worked by gravity a treat, when tested.   I shorted out the pump with a
gate valve, and shorted out the motorized valve which cut off the upstairs
with another stop valve.  I also put in an extra pipe to feed the
downstairs radiators when the upstairs motorized valve was shut.  In the
case of a power cut, open the two gate valves. The only problem left was to
feed the gas valve from an invertor from a battery.   Unfortunately, in the
next 25 years, we never had long power cuts, so it was a complete waste of
time and effort :-( 

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

On Sun, 28 Aug 2005 12:26:22 +0100, Dave Fawthrop wrote:


> 
> I am thinking of replacing my conventional central heating and hot 
> water system with a gas combination boiler, for my four bedroom 
> extended semi, with one bathroom.  My present system is 25 years old, 
> when I did the heating calculations and ended up with a 10kw boiler, 
> which works perfectly well with ample heat output, even in the coldest 
> weather.  When I did the heating calcs, the house was *very* well 
> insulated, and I have continued adding insulation/double glazing over 
> the years, so it is now *extremely* well insulated.   I am therefore 
> looking for a combi with less than 10kw output to central heating, 
> plus enough say 10l/m to the DHW.   
> 
> Objective is to save space.
> 
> I have looked in Google Groups for old threads, and tried to answer 
> the questions which may be asked. 
> 
> Kitchen tap gives 16l/m 
> Bath tap hot water gives 9l/min
> Soft water.
> 
> Googleing for combination boilers  only gives huge 20+kw models does 
> anyone here know of anything smaller? 
> 
> As I will now be pressurizing the central heating pipes (copper with 
> Yorkshire fittings) does anyone expect problems with this?



The lowest gas rate I've seen is an 18kW Vaillant unit made around 15
years ago. This will provide an even more limited flow of HW than the
'standard' 24kW units. 

It might work for a small dwelling with no bath.

-- 
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

Dave Fawthrop wrote:

> ... Unfortunately, in the next 25 years, we never had long 

 > power cuts, so it was a complete waste of time and effort :-(

Not at all. Had you not gone to all that trouble you would have had 
power cuts several hours a week, every week, for years.

Owain

In article ,
   Dave Fawthrop  wrote:

> | I was interested in how a pumped system could be switched to manual. A
> | hamster in a wheel to turn the pump?

> OK I give in.   I was an Engineer designing little power stations for
> aircraft, so thinking outside the box was normal for me.

> I put two loops of one inch pipe, one on each side of the house, which
> worked by gravity a treat, when tested.   I shorted out the pump with a
> gate valve, and shorted out the motorized valve which cut off the
> upstairs with another stop valve.  I also put in an extra pipe to feed
> the downstairs radiators when the upstairs motorized valve was shut.  In
> the case of a power cut, open the two gate valves. The only problem left
> was to feed the gas valve from an invertor from a battery.  
> Unfortunately, in the next 25 years, we never had long power cuts, so it
> was a complete waste of time and effort :-( 


Sounds like flawed thinking given I've got a plumbed in invertor that will
run the heating all day off a standard car battery.

But like you it's never been used in anger. ;-)

FWIW, I had a rented flat with an ancient completely non electric central
heating system. All the pipework in iron barrel - and the timeswitch on
the boiler clockwork. It worked very well. Think it dated from the early
'50s.

-- 
*Everybody lies, but it doesn't matter since nobody listens.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In message , "Dave Plowman (News)" 
 writes

>In article ,
>FWIW, I had a rented flat with an ancient completely non electric central
>heating system. All the pipework in iron barrel - and the timeswitch on
>the boiler clockwork. It worked very well. Think it dated from the early
>'50s.
>

Clockwork ?

What's that then

You may wish to ignore the throwaway punchline

-- 
geoff

"Dave Plowman (News)"  wrote:


>Sounds like flawed thinking given I've got a plumbed in invertor that will
>run the heating all day off a standard car battery.
>
>But like you it's never been used in anger. ;-)


The way gas prices are going, and the over dependence on gas for power
generation makes me wish I'd simply plugged the boiler in rather than
use an FCU, the drawbacks of not bodging!    I've an inverter as a
last resort but I'd probably fire up the generator instead and keep
the lights and TV on too.


--