HI


I am thinking of changing my Combi boiler as its old and a bit
unreliable.

I have seen some offers in the local plumber merchants and wondering
how one works out what size of boiler is required.  By Size i mean the
capacity in KW

Is there somewhere (website) where you can work this out.  I guess its
based on no of rads and bathrooms etc.

Thanks

Bhupesh

In an earlier contribution to this discussion,
bp   wrote:

> HI
>
>
> I am thinking of changing my Combi boiler as its old and a bit
> unreliable.
>
> I have seen some offers in the local plumber merchants and wondering
> how one works out what size of boiler is required.  By Size i mean the
> capacity in KW
>
> Is there somewhere (website) where you can work this out.  I guess its
> based on no of rads and bathrooms etc.
>
> Thanks
>
> Bhupesh


Not really. The main consideration with a combi is how fast it can heat your 
hot water - so that it doesn't take all day to run a bath.

Get that right, and you'll have more than enough capacity for your 
radiators - unless you live in Buck House! <g>
-- 
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 2008-07-21 16:30:03 +0100, bp  said:

> 
> HI
> 
> 
> I am thinking of changing my Combi boiler as its old and a bit
> unreliable.
> 
> I have seen some offers in the local plumber merchants and wondering
> how one works out what size of boiler is required.  By Size i mean the
> capacity in KW
> 
> Is there somewhere (website) where you can work this out.  I guess its
> based on no of rads and bathrooms etc.
> 
> Thanks
> 
> Bhupesh

In terms of hot water production, the best thing is to go for the 
largest that you can get.   However two caveats:

- Gas supply must be adequate all the way back to the meter.    This 
usually means at least 22mm pipework for the whole length.

- Some of the larger boilers are quite physically large so check the size.

- You can't determine the CH requirement by counting the number of 
radiators.   They vary in size too much.   However, if you go for a 
large combi, it doesn't matter because it will reduce its heat output 
when warming the radiators.   Usually heat requirement for hot water is 
much greater than for room heating.

In article ,
	bp  writes:
> 
> HI
> 
> 
> I am thinking of changing my Combi boiler as its old and a bit
> unreliable.
> 
> I have seen some offers in the local plumber merchants and wondering
> how one works out what size of boiler is required.  By Size i mean the
> capacity in KW

What have you got now?
Other than the unreliability, does it meet your requirements
for hot water provision and heating?

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

On Mon, 21 Jul 2008 08:30:03 -0700, bp wrote:

> HI
> 
> 
> I am thinking of changing my Combi boiler as its old and a bit
> unreliable.
> 
> I have seen some offers in the local plumber merchants and wondering how
> one works out what size of boiler is required.  By Size i mean the
> capacity in KW
> 
> Is there somewhere (website) where you can work this out.  I guess its
> based on no of rads and bathrooms etc.
> 
> Thanks
> 
> Bhupesh

Take a read of the Boiler Choice FAQ. 


-- 
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

Hi

Thanks for the replies

I currently have a Vokera EXcel 80 SP, thats what written on the box,
but I dont know any more about it.  heating is fine but getting DHW is
a real pain.  When you turn the hot tap on the boiler fires and give
hot water for about 5 mins, then the boler shuts down for 5 mins,
giving cold water.  Then it starts up again.

I have had a few engineers look at it, but I dont really want to spend
any more money on it.  Its over 10years old according to the people
that look at it.  It was present when I purchased the house 2 years
ago.

I have seen a 28KW Valiant for 700 (+ VAT), and thought that ir  would
be OK for me.  I live in a 3 bed house, one bath, no shower, 7 rads

Is 28KW OK

Thanks

Bhupesh

On 2008-07-22 10:11:44 +0100, bp  said:

> Hi
> 
> Thanks for the replies
> 
> I currently have a Vokera EXcel 80 SP, thats what written on the box,
> but I dont know any more about it.  heating is fine but getting DHW is
> a real pain.  When you turn the hot tap on the boiler fires and give
> hot water for about 5 mins, then the boler shuts down for 5 mins,
> giving cold water.  Then it starts up again.
> 
> I have had a few engineers look at it, but I dont really want to spend
> any more money on it.  Its over 10years old according to the people
> that look at it.  It was present when I purchased the house 2 years
> ago.
> 
> I have seen a 28KW Valiant for 700 (+ VAT), and thought that ir  would
> be OK for me.  I live in a 3 bed house, one bath, no shower, 7 rads
> 
> Is 28KW OK
> 
> Thanks
> 
> Bhupesh

The Vokera one is 23kW.

Are you happy with its hot water output?   If you are then the Vaillant 
will do more.     If you are not, it needs to be researched more and 
perhaps you need something larger.

As has been said, the radiator count says nothing about the CH 
requirements.  Again though, if it has been OK with the Vokera in the 
past it will be with the Vaillant.

Did you check physical sizing of the box and the gas supply?

HI Andy

THanks forthe info on the Vokera.  23KW sounds quite low as most now
start at 24KW and they are recommended for smaller properties (flats
etc).

The hot water is really poor at the moment as I have described, so I
am hoping that will get better with a new one.  Heating is very good.
I have actually reduced the number of radiators in the house as well.

I have not checked the size of the boiler, but I am moving the
location (from upstairs to downstairs), and I have a blank wall to put
in on so I hope there will not be any problem in that area.  The
vokera is actually quite big.  I am sure the new ones are more
compact.

Not checked the gas supply, but since I am moving location, that will
have to be redone almost certainly.

Bhupesh



Andy Hall wrote:

> On 2008-07-22 10:11:44 +0100, bp  said:
>
> > Hi
> >
> > Thanks for the replies
> >
> > I currently have a Vokera EXcel 80 SP, thats what written on the box,
> > but I dont know any more about it.  heating is fine but getting DHW is
> > a real pain.  When you turn the hot tap on the boiler fires and give
> > hot water for about 5 mins, then the boler shuts down for 5 mins,
> > giving cold water.  Then it starts up again.
> >
> > I have had a few engineers look at it, but I dont really want to spend
> > any more money on it.  Its over 10years old according to the people
> > that look at it.  It was present when I purchased the house 2 years
> > ago.
> >
> > I have seen a 28KW Valiant for 700 (+ VAT), and thought that ir  would
> > be OK for me.  I live in a 3 bed house, one bath, no shower, 7 rads
> >
> > Is 28KW OK
> >
> > Thanks
> >
> > Bhupesh
>
> The Vokera one is 23kW.
>
> Are you happy with its hot water output?   If you are then the Vaillant
> will do more.     If you are not, it needs to be researched more and
> perhaps you need something larger.
>
> As has been said, the radiator count says nothing about the CH
> requirements.  Again though, if it has been OK with the Vokera in the
> past it will be with the Vaillant.
>
> Did you check physical sizing of the box and the gas supply?

bp wrote:
> HI Andy
> 
> THanks forthe info on the Vokera.  23KW sounds quite low as most now
> start at 24KW and they are recommended for smaller properties (flats
> etc).
> 
> The hot water is really poor at the moment as I have described, so I
> am hoping that will get better with a new one.  Heating is very good.
> I have actually reduced the number of radiators in the house as well.
> 
> I have not checked the size of the boiler, but I am moving the
> location (from upstairs to downstairs), and I have a blank wall to put
> in on so I hope there will not be any problem in that area.  The
> vokera is actually quite big.  I am sure the new ones are more
> compact.
> 
> Not checked the gas supply, but since I am moving location, that will
> have to be redone almost certainly.
> 
> Bhupesh
> 

In general the peak demand for hot water easily exceeds the background 
demand for heating in MOST houses.

So, with combis, sizing for hot water s generally good enough.

A very dirty rule of thumb for heating is that you should allow 
50W/square meter TOTAL floor area in a well insulated house, 100W in an 
average one, and 200W in a rather poor one.

This is by no means accurate, but helps get the 'feel' of the requirements.


OT aside...
===========
If you note that the winter average solar energy can be down to as 
little as 40W/sq meter for a surface, you can see why even covering the 
entire roof of a two storey property with solar panels (netting you 
20W/sq meter at enormous cost), makes bugger all difference to heating 
bills..

On 2008-07-22 12:36:44 +0100, The Natural Philosopher <a@b.c> said:
> 
> OT aside...
> ===========
> If you note that the winter average solar energy can be down to as 
> little as 40W/sq meter for a surface, you can see why even covering the 
> entire roof of a two storey property with solar panels (netting you 
> 20W/sq meter at enormous cost), makes bugger all difference to heating 
> bills..

You mean that that salesman with the dripping gold isn't telling me the 
truth again?

On Tue, 22 Jul 2008 03:26:13 -0700, bp wrote:

> HI Andy
> 
> THanks forthe info on the Vokera.  23KW sounds quite low as most now
> start at 24KW and they are recommended for smaller properties (flats
> etc).
> 
> The hot water is really poor at the moment as I have described, so I am
> hoping that will get better with a new one.  Heating is very good. I
> have actually reduced the number of radiators in the house as well.
> 
> I have not checked the size of the boiler, but I am moving the location
> (from upstairs to downstairs), and I have a blank wall to put in on so I
> hope there will not be any problem in that area.  The vokera is actually
> quite big.  I am sure the new ones are more compact.
> 
> Not checked the gas supply, but since I am moving location, that will
> have to be redone almost certainly.
> 
> Bhupesh
> 
> 
> 
> Andy Hall wrote:
> 
>> On 2008-07-22 10:11:44 +0100, bp  said:
>>
>> > Hi
>> >
>> > Thanks for the replies
>> >
>> > I currently have a Vokera EXcel 80 SP, thats what written on the box,
>> > but I dont know any more about it.  heating is fine but getting DHW
>> > is a real pain.  When you turn the hot tap on the boiler fires and
>> > give hot water for about 5 mins, then the boler shuts down for 5
>> > mins, giving cold water.  Then it starts up again.
>> >
>> > I have had a few engineers look at it, but I dont really want to
>> > spend any more money on it.  Its over 10years old according to the
>> > people that look at it.  It was present when I purchased the house 2
>> > years ago.
>> >
>> > I have seen a 28KW Valiant for 700 (+ VAT), and thought that ir 
>> > would be OK for me.  I live in a 3 bed house, one bath, no shower, 7
>> > rads
>> >
>> > Is 28KW OK
>> >
>> > Thanks
>> >
>> > Bhupesh
>>
>> The Vokera one is 23kW.
>>
>> Are you happy with its hot water output?   If you are then the Vaillant
>> will do more.     If you are not, it needs to be researched more and
>> perhaps you need something larger.
>>
>> As has been said, the radiator count says nothing about the CH
>> requirements.  Again though, if it has been OK with the Vokera in the
>> past it will be with the Vaillant.
>>
>> Did you check physical sizing of the box and the gas supply?

I suspect that the current boiler is much below 23kw effective HW heating 
due to. Limescale build up and/or diverter valve let by and/or water flow 
diapragm problems. etc.

The Vaillant 28kW will be a good choice (the 24kw still pretty good). Do 
check that the gas pipes are up to the job fr the 28kW version. 



-- 
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

Andy Hall wrote:
> On 2008-07-22 12:36:44 +0100, The Natural Philosopher <a@b.c> said:
>>
>> OT aside...
>> ===========
>> If you note that the winter average solar energy can be down to as 
>> little as 40W/sq meter for a surface, you can see why even covering 
>> the entire roof of a two storey property with solar panels (netting 
>> you 20W/sq meter at enormous cost), makes bugger all difference to 
>> heating bills..
> 
> You mean that that salesman with the dripping gold isn't telling me the 
> truth again?
> 
> 
Don't get me going. My doddery 88 year old F.I.L. has just signed up to 
spend 30% of all the capital he has left (£4800 I think the bill was) to 
save '50% of all his heating bills, except the aga sir'

I pointed out to him that the combination of panels he had selected 
would produce at the most optimistic using the figures in the brochure 
£200 a year saving, if they were 100% efficient and he could in fact 
make use of *all* the summer sun.

His oil bill is around £2000 a year at current rates..of which perhaps 
30% is the aga at most..


He assures me that all the people they gave as referees assured him that 
the kit was stunningly wonderful, best thing they had ever bought, etc etc.

But he is panicking about his oil bills and reason has gone out of the 
window.

On 2008-07-22 16:50:21 +0100, The Natural Philosopher <a@b.c> said:

> Andy Hall wrote:
>> On 2008-07-22 12:36:44 +0100, The Natural Philosopher <a@b.c> said:
>>> 
>>> OT aside...
>>> ===========
>>> If you note that the winter average solar energy can be down to as 
>>> little as 40W/sq meter for a surface, you can see why even covering the 
>>> entire roof of a two storey property with solar panels (netting you 
>>> 20W/sq meter at enormous cost), makes bugger all difference to heating 
>>> bills..
>> 
>> You mean that that salesman with the dripping gold isn't telling me the 
>> truth again?
>> 
>> 
> Don't get me going. My doddery 88 year old F.I.L. has just signed up to 
> spend 30% of all the capital he has left (£4800 I think the bill was) 
> to save '50% of all his heating bills, except the aga sir'
> 
> I pointed out to him that the combination of panels he had selected 
> would produce at the most optimistic using the figures in the brochure 
> £200 a year saving, if they were 100% efficient and he could in fact 
> make use of *all* the summer sun.
> 
> His oil bill is around £2000 a year at current rates..of which perhaps 
> 30% is the aga at most..
> 
> 
> He assures me that all the people they gave as referees assured him 
> that the kit was stunningly wonderful, best thing they had ever bought, 
> etc etc.
> 
> But he is panicking about his oil bills and reason has gone out of the window.

That's a dirty trick to pull on someone in that position.    Can you 
help him to undo it?

I suppose that there are no other conventional fuels that could be 
accessible to him?

I can see why you would want to hang a greenie. By the bollocks.    The 
massively overoptimistic claims have paved the way for charlatans.

Andy Hall wrote:
> On 2008-07-22 16:50:21 +0100, The Natural Philosopher <a@b.c> said:
> 
>> Andy Hall wrote:
>>> On 2008-07-22 12:36:44 +0100, The Natural Philosopher <a@b.c> said:
>>>>
>>>> OT aside...
>>>> ===========
>>>> If you note that the winter average solar energy can be down to as 
>>>> little as 40W/sq meter for a surface, you can see why even covering 
>>>> the entire roof of a two storey property with solar panels (netting 
>>>> you 20W/sq meter at enormous cost), makes bugger all difference to 
>>>> heating bills..
>>>
>>> You mean that that salesman with the dripping gold isn't telling me 
>>> the truth again?
>>>
>>>
>> Don't get me going. My doddery 88 year old F.I.L. has just signed up 
>> to spend 30% of all the capital he has left (£4800 I think the bill 
>> was) to save '50% of all his heating bills, except the aga sir'
>>
>> I pointed out to him that the combination of panels he had selected 
>> would produce at the most optimistic using the figures in the brochure 
>> £200 a year saving, if they were 100% efficient and he could in fact 
>> make use of *all* the summer sun.
>>
>> His oil bill is around £2000 a year at current rates..of which perhaps 
>> 30% is the aga at most..
>>
>>
>> He assures me that all the people they gave as referees assured him 
>> that the kit was stunningly wonderful, best thing they had ever 
>> bought, etc etc.
>>
>> But he is panicking about his oil bills and reason has gone out of the 
>> window.
> 
> That's a dirty trick to pull on someone in that position.    Can you 
> help him to undo it?
> 

Not if he chooses to believe the salesmen and their shills, instead of 
me ;-(

> I suppose that there are no other conventional fuels that could be 
> accessible to him?

Plenty of wood in the shed..

Actually the whole house needs a complete draught and insulation 
overhaul. That would be more cost effective.


> 
> I can see why you would want to hang a greenie. By the bollocks.    The 
> massively overoptimistic claims have paved the way for charlatans.
> 
> 
This isn't greeny, this is plain climbing on the oil price bandwagon and 
using classic FUD to sell crap.

On 2008-07-22 20:26:37 +0100, The Natural Philosopher <a@b.c> said:
>>>> 
>>> Don't get me going. My doddery 88 year old F.I.L. has just signed up to 
>>> spend 30% of all the capital he has left (£4800 I think the bill was) 
>>> to save '50% of all his heating bills, except the aga sir'
>>> 
>>> I pointed out to him that the combination of panels he had selected 
>>> would produce at the most optimistic using the figures in the brochure 
>>> £200 a year saving, if they were 100% efficient and he could in fact 
>>> make use of *all* the summer sun.
>>> 
>>> His oil bill is around £2000 a year at current rates..of which perhaps 
>>> 30% is the aga at most..
>>> 
>>> 
>>> He assures me that all the people they gave as referees assured him 
>>> that the kit was stunningly wonderful, best thing they had ever bought, 
>>> etc etc.
>>> 
>>> But he is panicking about his oil bills and reason has gone out of the window.
>> 
>> That's a dirty trick to pull on someone in that position.    Can you 
>> help him to undo it?
>> 
> 
> Not if he chooses to believe the salesmen and their shills, instead of me ;-(

Oh dear.   The trouble is that by the time he figures this out, it will 
be way too late to do something to the company.


> 
>> I suppose that there are no other conventional fuels that could be 
>> accessible to him?
> 
> Plenty of wood in the shed..
> 
> Actually the whole house needs a complete draught and insulation 
> overhaul. That would be more cost effective.
> 
> 
>> 
>> I can see why you would want to hang a greenie. By the bollocks.    The 
>> massively overoptimistic claims have paved the way for charlatans.
>> 
>> 
> This isn't greeny, this is plain climbing on the oil price bandwagon 
> and using classic FUD to sell crap.

Unwittingly, or perhaps wittingly, the greenies are providing the 
marketing without cost and ROI factored in.

In article ,
 The Natural Philosopher <a@b.c> wrote:

> Don't get me going. My doddery 88 year old F.I.L. has just signed up to 
> spend 30% of all the capital he has left (£4800 I think the bill was) to 
> save '50% of all his heating bills, except the aga sir'

It's safe to assume, NP, you being the son-in-law in question, that he 
has got all his free-for-the-over-70s insulation installed by now?  
(cavity wall, 1000mm in the loft (whatever the latest "standard" is 
(it's changed four times I think, since I first started putting in loft 
insulation!))

john

In article 
,
 jal  wrote:

> In article ,
>  The Natural Philosopher <a@b.c> wrote:
> 
> > Don't get me going. My doddery 88 year old F.I.L. has just signed up to 
> > spend 30% of all the capital he has left (£4800 I think the bill was) to 
> > save '50% of all his heating bills, except the aga sir'
> 
> It's safe to assume, NP, you being the son-in-law in question, that he 
> has got all his free-for-the-over-70s insulation installed by now?  
> (cavity wall, 1000mm in the loft (whatever the latest "standard" is 
> (it's changed four times I think, since I first started putting in loft 
> insulation!))
> 
> john

p.s I should add also: a friend of mine discovered that his mother was 
entitled to god-knows-what (new CH system?!) free from "the council" as 
long as she was in receipt of *any benefit whatsoever*.  I think they 
discovered she was getting about a fiver a month for some reason or 
other, and the floodgates opened...