Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw, I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

From other posts I see that Worcester Bosch is well regarded, but the boiler
that comes up on a 4-5 bedroom house from their site is 28Kw HE unit! Is
this just their nearest suitable animal?

So the questions a

Is this massive overkill?
Will it modulate anyway so the only money lost is the initial outlay?
Is there a more appropriate smaller system unit from other supplier? (I was
advised to go system in previous thread Worcester Boilers - slight
confusion).
Should I go for the larger unit to give headroom/flexibility?


Any other comments welcome
TIA

Phil

On Wed, 29 Jun 2005 15:32:51 +0100, "TheScullster"
wrote:

Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw, I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

I had one of those. In its day it was OK, but is not well made and
very inefficient by today's standards.


From other posts I see that Worcester Bosch is well regarded, but the boiler
that comes up on a 4-5 bedroom house from their site is 28Kw HE unit! Is
this just their nearest suitable animal?

Yes. Keep in mind that the term "4-5 bedroom house" has little
meaning in this context. The heat requirement can vary enormously
based on size of rooms, construction and location.



So the questions a

Is this massive overkill?

I don't think so.


Will it modulate anyway so the only money lost is the initial outlay?

Yes, and with a higher rating, it will heat the radiators and hence
the house more quickly in the winter mornings.

Is there a more appropriate smaller system unit from other supplier? (I was
advised to go system in previous thread Worcester Boilers - slight
confusion).
Should I go for the larger unit to give headroom/flexibility?

I would (did) but from a different manufacturer (MAN Heiztechnik).

You could perhaps look at 24kW products, but I don't think that 28kW
is unreasonable in the context of a 20kW requirement.




Any other comments welcome
TIA

Phil



--

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The information contained in this post is copyright the
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"Andy Hall" wrote in message
...
On Wed, 29 Jun 2005 15:32:51 +0100, "TheScullster"
wrote:

Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw,
I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

I had one of those. In its day it was OK, but is not well made and
very inefficient by today's standards.

You said you had a Fuel saver. The Spacesaver was very well made.

From other posts I see that Worcester Bosch is well regarded, but the
boiler
that comes up on a 4-5 bedroom house from their site is 28Kw HE unit! Is
this just their nearest suitable animal?

Yes. Keep in mind that the term "4-5 bedroom house" has little
meaning in this context. The heat requirement can vary enormously
based on size of rooms, construction and location.



So the questions a

Is this massive overkill?

I don't think so.


Will it modulate anyway so the only money lost is the initial outlay?

Yes, and with a higher rating, it will heat the radiators and hence
the house more quickly in the winter mornings.

Is there a more appropriate smaller system unit from other supplier? (I
was
advised to go system in previous thread Worcester Boilers - slight
confusion).
Should I go for the larger unit to give headroom/flexibility?

I would (did) but from a different manufacturer (MAN Heiztechnik).

You could perhaps look at 24kW products, but I don't think that 28kW
is unreasonable in the context of a 20kW requirement.




Any other comments welcome
TIA

Phil



--

.andy

To email, substitute .nospam with .gl

The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

On Wed, 29 Jun 2005 16:05:04 +0100, "Doctor Evil"
wrote:


"Andy Hall" wrote in message
.. .
On Wed, 29 Jun 2005 15:32:51 +0100, "TheScullster"
wrote:

Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw,
I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

I had one of those. In its day it was OK, but is not well made and
very inefficient by today's standards.

You said you had a Fuel saver. The Spacesaver was very well made.

I've had both in different houses. Both were crap.




--

..andy

To email, substitute .nospam with .gl

The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

On Wed, 29 Jun 2005 15:40:58 +0100, Andy Hall wrote:

On Wed, 29 Jun 2005 15:32:51 +0100, "TheScullster"
wrote:

Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw, I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

I had one of those. In its day it was OK, but is not well made and
very inefficient by today's standards.


From other posts I see that Worcester Bosch is well regarded, but the boiler
that comes up on a 4-5 bedroom house from their site is 28Kw HE unit! Is
this just their nearest suitable animal?

Yes. Keep in mind that the term "4-5 bedroom house" has little
meaning in this context. The heat requirement can vary enormously
based on size of rooms, construction and location.



So the questions a

Is this massive overkill?

I don't think so.


Will it modulate anyway so the only money lost is the initial outlay?

Yes, and with a higher rating, it will heat the radiators and hence
the house more quickly in the winter mornings.

Is there a more appropriate smaller system unit from other supplier? (I was
advised to go system in previous thread Worcester Boilers - slight
confusion).
Should I go for the larger unit to give headroom/flexibility?

I would (did) but from a different manufacturer (MAN Heiztechnik).

You could perhaps look at 24kW products, but I don't think that 28kW
is unreasonable in the context of a 20kW requirement.

I'm unfamiliar with the current WB range but if there is a comparable 24kW
I'd certainly go for it. Modern boilers are much more
tolerant of being incorrectly over sized but not entirely so.

The existing unit which is 15kW is clearly struggling to meet the 20kW
load. This confirms that 20kW is about right.


--
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

"TheScullster" wrote in message
...

Thanks to Ed Sirett who questioned my boiler sizing!
Somehow, despite having done detailed spreadsheet totalling approx 20Kw, I
had drifted into 28/29Kw boiler territory!
The house is 1970s originally 3 bed detached, having 3 single room
extensions: 1 kitchen, 1 back room and 1 bedroom over garage.
Original boiler is Glow Worm Space saver 50.
Both for age and capacity this is struggling.

From other posts I see that Worcester Bosch is well regarded, but the
boiler
that comes up on a 4-5 bedroom house from their site is 28Kw HE unit! Is
this just their nearest suitable animal?

That is ballpark.

So the questions a

Is this massive overkill?
Will it modulate anyway
so the only money lost is the initial outlay?

Yep. You say 20kW minimum. If it is above and modulates then no problem.
It will heat the rads very quickly though, a bonus. If the cheapest boilers
are around 25kW then go for that, as long as it modulates. .

Is there a more appropriate smaller system unit from other supplier? (I
was
advised to go system in previous thread Worcester Boilers - slight
confusion).
Should I go for the larger unit to give headroom/flexibility?

Go for the best value 20kW or above, modulating system boiler.

Will it modulate anyway so the only money lost is the initial outlay?

It will modulate.

If 28kW isn't enough for you, you should be considering fixing your
insulation, not increasing your boiler capacity. Indeed, if any 3 bedroom
house is coming out at 20kW, some serious look at some Kingspan catalogues
is long overdue.

Christian.

Christian said

Indeed, if any 3 bedroom
house is coming out at 20kW, some serious look at some Kingspan catalogues
is long overdue.

As stated in the original post, the house started as 3 bed detached but has
had 3 significant extensions.
I take the point though Christian, additional insulation generally wouldn't
go amiss.
Not sure with these modulating boilers that it would affect the final choice
greatly though.

Phil

Not sure with these modulating boilers that it would affect the final
choice
greatly though.

You are correct. The boiler choice is unaffected.

Christian.

On Wed, 29 Jun 2005 17:06:17 +0100, TheScullster wrote:

Christian said

Indeed, if any 3 bedroom
house is coming out at 20kW, some serious look at some Kingspan catalogues
is long overdue.

As stated in the original post, the house started as 3 bed detached but has
had 3 significant extensions.
I take the point though Christian, additional insulation generally wouldn't
go amiss.
Not sure with these modulating boilers that it would affect the final choice
greatly though.

I would expect any (condensing) boiler to be fully modulating over at
least a 3:1 range if not better.

--
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

I would expect any (condensing) boiler to be fully modulating over at
least a 3:1 range if not better.

Can you explain this statement please Ed?
In the context of the load I am considering ie 20Kw from cold in the depths
of winter down to 3.5 Kw hot water heating only in the summer. What is my
range?

Also, somewhat away from the initial story line, is there a "standard"
install height such that a boiler can be fitted into a wall cupboard. I
would like to replace the boiler before deciding on final kitchen layout -
is this a recipe for disaster?

Phil

On Thu, 30 Jun 2005 08:34:17 +0100, "TheScullster"
wrote:

I would expect any (condensing) boiler to be fully modulating over at
least a 3:1 range if not better.

Can you explain this statement please Ed?
In the context of the load I am considering ie 20Kw from cold in the depths
of winter down to 3.5 Kw hot water heating only in the summer. What is my
range?

I'll throw something in on this one, although I'm sure Ed will add to
it later.

Modulation range is simply the ratio of max to min output, so a 20kW
boiler with 3:1 range would have a minimum of just over 6kW.

If you had a minimum load of 3.5kW as you suggest, the boiler will run
at minimum output, and cycle on and off to keep average heat output at
3.5kW. Above the minimum modulation output, it runs continuously.

Did you get the 3.5kW output from one of the heatloss programs? This
is the typical figure for an old basic cylinder connected by gravity
circulation. You might be able to get a bit more heat into it than
that when the contents are cold, and thus be above the minimum
modulation point sometimes. However, it's not that satisfactory.

If you can, it's best to use a fast recovery cylinder, replacing the
old one. These have larger coil area through one means or another and
can take a much higher rate of heat from the boiler - 20kW+ is
typical. The advantages of this are that you can reheat the cylinder
faster and either have more hot water available over a given amount of
time or possibly install a smaller cylinder. Moreover, the boiler
will run continuously for most of the reheat cycle and hence more
efficiently. Since the typical control system is HW priority, the
boiler is normally switched to drive the cylinder only when there is
HW demand. This means no heat to the radiators during that time.
Therefore, ideally, you don't want HW cycles to last too long.


Also, somewhat away from the initial story line, is there a "standard"
install height such that a boiler can be fitted into a wall cupboard. I
would like to replace the boiler before deciding on final kitchen layout -
is this a recipe for disaster?

If you look on the manufacturer's web site and download the install
manual for the boiler it will tell you. Normally for the inside there
are clearance dimensions around the boiler mainly for maintenance.
These may not include additional clearance to fit in the flue so that
has to be allowed for.

You then have the exterior location rules for the flue, which are
mainly dictated by British Standard etc. Obviously with flue
types/components you can position the flue terminal some way from the
boiler. I am not sure if your proposed supplier has them, but some
manufacturers do a flue system and adaptors where high temperature
plastic waste pipe can be used for the flue and run over many metres.

Many boilers are designed to fit into a line of kitchen wall
cupboards, but do look out for possible compartment ventilation
requirements (install instructions will say this if there are any) and
overall height. It would be tearful if you mounted the boiler
unnecessarily high or low, for example.

It makes sense if you can to fit the boiler before doing the kitchen
refit because you have more space to work, but I would plan the two
together because you may find that you can so something you want with
the kitchen layout or cupboard choice by having the boiler a few cm to
the right or left of nominal position.





--

..andy

To email, substitute .nospam with .gl

The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

In the context of the load I am considering ie 20Kw from cold in the
depths
of winter down to 3.5 Kw hot water heating only in the summer. What is my
range?

You should note that your cylinder probably has a bigger coil than 3.5kW,
but the heatloss programme just put on 3.5kW to ensure there was always some
capacity to heat it, even in cold weather. When it's just the boiler and the
cylinder, it probably sinks a lot more power.

Christian.

On Thu, 30 Jun 2005 08:34:17 +0100, TheScullster wrote:

I would expect any (condensing) boiler to be fully modulating over at
least a 3:1 range if not better.

Can you explain this statement please Ed?
In the context of the load I am considering ie 20Kw from cold in the depths
of winter down to 3.5 Kw hot water heating only in the summer. What is my
range?

Older (frankly, obselete) designs of boiler used to operate and a fixed
heating power or gas rate as it called. If you wanted less than full
power as was often the case the boiler had to switch off/on/off to adjust
to the requirement. It turns out that less gas is used if the boiler can
be made to adjust its gas rate to suit the load.

Modern non-condensing designs can adjust their gas rates this is known as
modulation and typically they can adjust down to about 40% of maximum.

Non-condensing boilers which use forced premix burners can modulate down
to around 30% or even less of full power.

Your figure of 3.5kW for the HW in summer is rather low. A HW cylinder
which is Part L compliant will take 10kW or more when it is operation and
then the demand will cut out.

So a 20kW (or a little more) boiler will be satisfactory. A lot of the
time in Autumn & Spring the heating load may only be a few kW so a
boiler which can go that low maybe helpful. However so long as a suitable
sized boiler is chosen you should be OK.


Also, somewhat away from the initial story line, is there a "standard"
install height such that a boiler can be fitted into a wall cupboard. I
would like to replace the boiler before deciding on final kitchen layout -
is this a recipe for disaster?

You will need to select a model which fits your requirements. Most
manufacturers will let you either down load the full instructions from the
web site or will let you download a technical spec containing casing
sizes, cupboard requirements, and flue positions.


--
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