Hi all,

I've just done the boiler calculation for my flat, and it came out at
12.25KW, which I think can be handled by any boiler AFAIK. I have two
main requirements. The first is that it runs quietly, as it's going in
a kitchen/lounge. The second is that it is small (it's a flat, so I
would like to save space). I'm open to anything efficency-wise, as
long as it's good value. I'm not sure that in my 900sqft flat, an HE
boiler would make a massive amount of difference to my bills, but I'm
willing to listen.

Any recommendations (I want a combi)? Is it the case that getting a
Potterton, which is what I have now (albeit around 20 years old) will
enable the installer to reuse the flue? It would be a right pain to
get to the outside of the building.

Antony

"antgel" wrote in message
oups.com...
Hi all,

I've just done the boiler calculation for my flat, and it came out at
12.25KW, which I think can be handled by any boiler AFAIK. I have two
main requirements. The first is that it runs quietly, as it's going in
a kitchen/lounge. The second is that it is small (it's a flat, so I
would like to save space). I'm open to anything efficency-wise, as
long as it's good value. I'm not sure that in my 900sqft flat, an HE
boiler would make a massive amount of difference to my bills, but I'm
willing to listen.

Any recommendations (I want a combi)? Is it the case that getting a
Potterton, which is what I have now (albeit around 20 years old) will
enable the installer to reuse the flue? It would be a right pain to
get to the outside of the building.

Antony


I believe you can't use the same flue and since April 1st a new boiler must
be Sedbuk A or B.

In article ,
"RedOnRed" writes:

"antgel" wrote in message
oups.com...
Hi all,

I've just done the boiler calculation for my flat, and it came out at
12.25KW, which I think can be handled by any boiler AFAIK. I have two
main requirements. The first is that it runs quietly, as it's going in
a kitchen/lounge. The second is that it is small (it's a flat, so I
would like to save space). I'm open to anything efficency-wise, as
long as it's good value. I'm not sure that in my 900sqft flat, an HE
boiler would make a massive amount of difference to my bills, but I'm
willing to listen.

Any recommendations (I want a combi)? Is it the case that getting a
Potterton, which is what I have now (albeit around 20 years old) will
enable the installer to reuse the flue? It would be a right pain to
get to the outside of the building.

I believe you can't use the same flue and since April 1st a new boiler must
be Sedbuk A or B.

Some boilers have flues which can be fitted without access to the
outside of the wall (e.g. when you're on the 20th floor), although
this may require some extra optional bits and pieces for the flue
assembly.

--
Andrew Gabriel

Andrew Gabriel wrote:
In article ,
"RedOnRed" writes:

"antgel" wrote in message
groups.com...

Hi all,

I've just done the boiler calculation for my flat, and it came out at
12.25KW, which I think can be handled by any boiler AFAIK. I have two
main requirements. The first is that it runs quietly, as it's going in
a kitchen/lounge. The second is that it is small (it's a flat, so I
would like to save space). I'm open to anything efficency-wise, as
long as it's good value. I'm not sure that in my 900sqft flat, an HE
boiler would make a massive amount of difference to my bills, but I'm
willing to listen.

Any recommendations (I want a combi)? Is it the case that getting a
Potterton, which is what I have now (albeit around 20 years old) will
enable the installer to reuse the flue? It would be a right pain to
get to the outside of the building.

I believe you can't use the same flue and since April 1st a new boiler must
be Sedbuk A or B.


Some boilers have flues which can be fitted without access to the
outside of the wall (e.g. when you're on the 20th floor), although
this may require some extra optional bits and pieces for the flue
assembly.

Both boilers I've fitted recently did not need access to the outside.
Seems to be standard, especially on the smaller models that would tend
to be fitted in flats.
Its unlikely in my experience that a existing hole will be in the right
place for a new boiler. The Potterton is likely to be rear-flued so its
possible the Ariston Micro-genus might fit.
Boilers fitted since 1-Apr-2005 don't have to be Sedbuk A or B if all
the requirements on location can't be met.

On Fri, 06 May 2005 21:18:07 +0000, Andrew Gabriel wrote:

In article ,
"RedOnRed" writes:

"antgel" wrote in message
oups.com...

Some boilers have flues which can be fitted without access to the
outside of the wall (e.g. when you're on the 20th floor), although
this may require some extra optional bits and pieces for the flue
assembly.

The Non-condensing Vaillant boilers let you do this but you have to have a
127mm core drill so you can push the large 'grommet' through the wall from
the inside.

--
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

antgel wrote:

Hi all,

I've just done the boiler calculation for my flat, and it came out at
12.25KW,

How did you do your calculations (and how big's your flat)? I've just done
the calcs for an end-of-terrace 3 bed single glazing medium loft insulation
house and that's 10-12kW (depending on whether I go by my own calcs or
those on http://www.est.org.uk/bestpractice/boiler/ [1]) so you've either
got a very lossy and/or big flat or your calcs are out.

John Stumbles wrote:
antgel wrote:

Hi all,

I've just done the boiler calculation for my flat, and it came out
at
12.25KW,

How did you do your calculations (and how big's your flat)? I've just
done
the calcs for an end-of-terrace 3 bed single glazing medium loft
insulation
house and that's 10-12kW (depending on whether I go by my own calcs
or
those on http://www.est.org.uk/bestpractice/boiler/ [1]) so you've
either
got a very lossy and/or big flat or your calcs are out.

Hmm. I used http://www.idhe.org.uk/calculator.html and my flat's about
900sqft, double glazed, middle floor. Are you able to try this
calculator with your flat? I tried the
http://www.est.org.uk/bestpractice/boiler/ that you refer to, but I
don't know what dimension to type the units in!

Antony

Furthermore, I just used the http://www.est.org.uk/bestpractice/boiler/
calculator (dimensions were metres!), and it gave me the same answer,
pretty much.
Length 8.6m
Width 11.1m
Height 2.3m
1 floor
One external wall along the width = external wall area 25.6sqm
Flat.
Double glazed metal frames.
Unfilled cavity walls. (Was unsure about this, but whatever option I
choose doesn't appear to make a large difference.)
Roof is flat uninsulated.
Location is SE.

Did I miss something?

In article . com,
"antgel" writes:
Furthermore, I just used the http://www.est.org.uk/bestpractice/boiler/
calculator (dimensions were metres!), and it gave me the same answer,
pretty much.
Length 8.6m
Width 11.1m
Height 2.3m
1 floor
One external wall along the width = external wall area 25.6sqm
Flat.
Double glazed metal frames.
Unfilled cavity walls. (Was unsure about this, but whatever option I
choose doesn't appear to make a large difference.)
Roof is flat uninsulated.

That's kind of irrelevant if you're on the middle floor.
If it did somehow feed into the calculations, I suspect
it has calculated for a top floor flat with uninsulated roof.
(I might still assume the flat upstairs wasn't heated though,
so your heating can still cope if the upstairs flat is empty.)

Location is SE.

Did I miss something?


--
--
Andrew Gabriel

antgel wrote:


John Stumbles wrote:
antgel wrote:

Hi all,

I've just done the boiler calculation for my flat, and it came out
at
12.25KW,

How did you do your calculations (and how big's your flat)? I've just
done
the calcs for an end-of-terrace 3 bed single glazing medium loft
insulation
house and that's 10-12kW (depending on whether I go by my own calcs
or
those on http://www.est.org.uk/bestpractice/boiler/ [1]) so you've
either
got a very lossy and/or big flat or your calcs are out.

Hmm. I used http://www.idhe.org.uk/calculator.html and my flat's about
900sqft, double glazed, middle floor. Are you able to try this
calculator with your flat?

Yes, that's better: it agrees exactly with my spreadsheet (which I based on
the manual worksheet method given as part of the C&G6084 training materials
pack).

I tried the
http://www.est.org.uk/bestpractice/boiler/ that you refer to, but I
don't know what dimension to type the units in!

Metres.
It's a bit confusing in that it uses 'length' for what I'd call depth i.e.
front-to-back measurement.

However the idhe calculator is following the same model.

I don't know what figures you put in for your flat but I tried it with 10m x
10m, one external wall on each side, 2.5m height (1 floor, mid-floor flat)
unfilled cavity wall, double glazed plastic/wood frame in SE England/Wales
and got:

The WINDOW heat loss is 1.01 kW
The WALL heat loss is 1.62 kW
The ROOF heat loss is 2.67 kW
The required boiler output is 10.88 kW

However yours is a mid-floor flat so the model should ignore roof losses,
but if you change the roof insulation setting it reports a different
heatloss, so it looks as if their calculator is borked. My spreadsheet
shows 8.95kW for the same values. I've emailed you a copy separately.

Thanks John. Note that you have to replace google with antony for my
email to work. I'm prepared to believe your figures, and there is only
one external wall to boot. My flat attributes are in my reply to my
reply above. Bottom line is that it looks like any boiler will do.

For the sake of progress, let's assume that your 8.95 figure is
correct. I was looking at an Ideal Isar HE as it's nice and compact.
Firstly the 24, but I then realised that the 30 or 35 would give me a
higher flow rate, which I would probably go for.

I have done some research on modulation but don't quite get it yet.
What exactly happens if my need at a given time is lower than 8.8kW?
Does it short-circuit? Does it waste energy?

I'm now thinking about a Glow-worm cxi. The 24 and 30 output as low as
5kW and the 38 outputs as low as 6.6kW - all lower than any of the
Isars. And they appear to be cheaper.

Bearing in mind my situation, is there any reason to pick the Ideal
over the Glow-worm? And bearing in mind what I asked about modulation,
what's better - the 30 with it's min 5kW output, or 38 with it's 6.6kW
min output and 15.5L/min flow rate?

Who knew that boilers were so complicated? I swear that my parents'
plumber just came along and whacked in any old thing...

Antony

"antgel" wrote in message
ups.com...
Thanks John. Note that you have to replace google with antony for my
email to work. I'm prepared to believe your figures, and there is only
one external wall to boot. My flat attributes are in my reply to my
reply above. Bottom line is that it looks like any boiler will do.

For the sake of progress, let's assume that your 8.95 figure is
correct. I was looking at an Ideal Isar HE as it's nice and compact.
Firstly the 24, but I then realised that the 30 or 35 would give me a
higher flow rate, which I would probably go for.

I have done some research on modulation but don't quite get it yet.
What exactly happens if my need at a given time is lower than 8.8kW?
Does it short-circuit? Does it waste energy?

I'm now thinking about a Glow-worm cxi. The 24 and 30 output as low as
5kW and the 38 outputs as low as 6.6kW - all lower than any of the
Isars. And they appear to be cheaper.

AND they have stainless steel heat exchangers not aluminium


Bearing in mind my situation, is there any reason to pick the Ideal
over the Glow-worm? And bearing in mind what I asked about modulation,
what's better - the 30 with it's min 5kW output, or 38 with it's 6.6kW
min output and 15.5L/min flow rate?

Go for the best hot water performance but remember it needs a bigger gas
pipe from the meter.

A tip - make sure you do a "very" good flush of the old pipework and rads.

antgel wrote:

Thanks John. Note that you have to replace google with antony for my
email to work.

OK I've sent it there, but I've just realised you said you want a combi.
D'oh! In that case forget sizing for the heatloss of your flat: the size of
the boiler will be 24kW or so for a decent input into the hot water.

For the sake of progress, let's assume that your 8.95 figure is
correct. I was looking at an Ideal Isar HE as it's nice and compact.
Firstly the 24, but I then realised that the 30 or 35 would give me a
higher flow rate, which I would probably go for.

I have done some research on modulation but don't quite get it yet.
What exactly happens if my need at a given time is lower than 8.8kW?
Does it short-circuit? Does it waste energy?

If you need less heat into your rads the boiler switches on and off. This
wastes energy compared to firing continuously but if the boiler can
modulate down to a low output it's more efficient than if it has to give a
short blast at full output and then switch off again.

Modulation is particularly important for the hot water so that if you need
less than full output the boiler can match the demand rather than switching
off and on: this makes for uncomfortable showering!

I'm now thinking about a Glow-worm cxi. The 24 and 30 output as low as
5kW and the 38 outputs as low as 6.6kW - all lower than any of the
Isars. And they appear to be cheaper.

Bearing in mind my situation, is there any reason to pick the Ideal
over the Glow-worm? And bearing in mind what I asked about modulation,
what's better - the 30 with it's min 5kW output, or 38 with it's 6.6kW
min output and 15.5L/min flow rate?

I'd go for the lower output since I guess you only have 1 bathroom and won't
need the higher output to hot water of the 38.
I'm not mad keen on the Ideals. I don't know about the Glow-worms. I'd also
consider the new Bosch Worcester Greenstar i Junior, although these are new
models so I'd be relying on B-W's reputation rather than an established
track record for these new designs.


Who knew that boilers were so complicated? I swear that my parents'
plumber just came along and whacked in any old thing...

Prolly not much to choose between Ye Olde Heatynge-only Boylers.