I am just starting to think about replacing my boiler so no doubt this will
be the first of a few question posted here.

I live in a 1990 built 4 bedroom detached house. My existing boiler which
is now getting on for 18 years old is rated at only 50,000 btu/ 14.65kW. I
say only because when I look at websites for boilers I apparently need a
larger output. My existing boiler serves a Flowmax thermal heat store, so
the tank is full of central heating water while the hot water runs through a
copper tube inside the tank which serves all taps at high pressure. The
boiler is only set at 50% with the room and tank thermostats controlling the
temperatures

It works great so I intend to keep it. So the first question is do I really
need a higher output heat only condensing boiler.

In article ,
"PC Plod" writes:
I am just starting to think about replacing my boiler so no doubt this will
be the first of a few question posted here.

I live in a 1990 built 4 bedroom detached house. My existing boiler which
is now getting on for 18 years old is rated at only 50,000 btu/ 14.65kW. I
say only because when I look at websites for boilers I apparently need a
larger output. My existing boiler serves a Flowmax thermal heat store, so
the tank is full of central heating water while the hot water runs through a
copper tube inside the tank which serves all taps at high pressure. The
boiler is only set at 50% with the room and tank thermostats controlling the
temperatures

It works great so I intend to keep it. So the first question is do I really
need a higher output heat only condensing boiler.

The higher outputs you'll see on many modern boilers are because
they are combis, so they have to have enough power to instantly
heat a stream of shower/bath water. For a stored system like you
have, this isn't the case. However, a stored system can take a
more powerful boiler without any negative effects, and it would
give you a faster heat up from cold.

Start by reading Ed's Choosing a Boiler FAQ...
http://www.makewrite.demon.co.uk/BoilerChoice.html

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

PC Plod wrote:
I am just starting to think about replacing my boiler so no doubt this will
be the first of a few question posted here.

I live in a 1990 built 4 bedroom detached house. My existing boiler which
is now getting on for 18 years old is rated at only 50,000 btu/ 14.65kW. I
say only because when I look at websites for boilers I apparently need a
larger output. My existing boiler serves a Flowmax thermal heat store, so
the tank is full of central heating water while the hot water runs through a
copper tube inside the tank which serves all taps at high pressure. The
boiler is only set at 50% with the room and tank thermostats controlling the
temperatures

It works great so I intend to keep it. So the first question is do I really
need a higher output heat only condensing boiler.


If what you have works, of course you don't need a higher output.

The max output of the boiler should equal or exceed the max heat loss
from the house in the coldest weather you are likely to encounter.

After that, its pure cost benefit analysis..if the capital outlay on the
new system will be offset in terms of fuel cost savings over the period
its likely to last, or you are likely to stay living there.

(IME as long as you sell a house with functional systems, whether or not
its the latest and greatest is not usually a thing that affects price
greatly anyway)

Example: if your fuel bill is £500 a year, and your existing boiler is
60% efficient, there is £200 a year being sent 'up the chimney'

And 80% efficient boiler would cut that in half. So £100 a year.

If the boiler itself costs - say - £1300 to buy and install, that's a
payback period of around 13 years. Or a cost of capital at 10% borrowing
of £130 a year..not worth it is it?


Of course that isn't a real world example. YMMV.

"The Natural Philosopher" wrote in message
...
PC Plod wrote:

If the boiler itself costs - say - £1300 to buy and install, that's a
payback period of around 13 years. Or a cost of capital at 10% borrowing
of £130 a year..not worth it is it?



Thanks guys for those great replies.

My old boiler which is 18 years old has cut out twice in the last 2 weeks.
The overheat thermostat trips and the pilot light goes out. If I could get
someone to fix it for under £100 and I got another 5 years out of it I would
get it repaired as it has never gone wrong. But I am thinking that I might
be just throwing money away due to its age.

I pay £30 a month for gas so with a 30% efficiency saving I would save
around £108 a year. This would no doubt be written off with a required
annual service and parts due to the complexity of modern designs. I have to
confess I have only bothered getting the old boiler serviced once so what I
have saved in maintenance visits will cover the cost of the new boiler.

The max output of the boiler should equal or exceed the max heat loss
from the house in the coldest weather you are likely to encounter.

This isn't strictly true. The boiler has also to have sufficient excess
capacity to both achieve the above situation and to also heat up the system
in a reasonable time - say 20% overcapacity.

PC Plod wrote:
"The Natural Philosopher" wrote in message
...
PC Plod wrote:

If the boiler itself costs - say - �1300 to buy and install, that's a
payback period of around 13 years. Or a cost of capital at 10% borrowing
of �130 a year..not worth it is it?



Thanks guys for those great replies.

My old boiler which is 18 years old has cut out twice in the last 2 weeks.
The overheat thermostat trips and the pilot light goes out. If I could get
someone to fix it for under �100 and I got another 5 years out of it I would
get it repaired as it has never gone wrong. But I am thinking that I might
be just throwing money away due to its age.

I pay �30 a month for gas so with a 30% efficiency saving I would save
around �108 a year. This would no doubt be written off with a required
annual service and parts due to the complexity of modern designs. I have to
confess I have only bothered getting the old boiler serviced once so what I
have saved in maintenance visits will cover the cost of the new boiler.


Mmm., Your choice then.

£108 a year probably just covers a decent service.

Unless you want the boiler renewed for other reasons., I'd just get it
serviced...

In article ,
"PC Plod" writes:

"The Natural Philosopher" wrote in message
...
PC Plod wrote:

If the boiler itself costs - say - £1300 to buy and install, that's a
payback period of around 13 years. Or a cost of capital at 10% borrowing
of £130 a year..not worth it is it?

Thanks guys for those great replies.

My old boiler which is 18 years old has cut out twice in the last 2 weeks.
The overheat thermostat trips and the pilot light goes out. If I could get
someone to fix it for under £100 and I got another 5 years out of it I would
get it repaired as it has never gone wrong. But I am thinking that I might
be just throwing money away due to its age.

I doubt that it's anything major wrong. Might be a new pump,
and system might benefit from a drain down and flush.

If it's not a room sealed system, you really should get it
checked to ensure the flue is operating correctly and it
isn't generating any significant Carbon Monoxide. Otherwise
it could kill you. If you can see the burner flames, do they
look a clean fierce blue directed up the heat exchenger (good)
or is there any yellow/white flame, or any flame at all wafting
out from under the heat exchanger (bad)?

I pay £30 a month for gas so with a 30% efficiency saving I would save
around £108 a year. This would no doubt be written off with a required
annual service and parts due to the complexity of modern designs. I have to
confess I have only bothered getting the old boiler serviced once so what I
have saved in maintenance visits will cover the cost of the new boiler.

I wouldn't write the old boiler off soley on the basis of the
reported symptoms just yet.

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

Touchy wrote:
The max output of the boiler should equal or exceed the max heat loss
from the house in the coldest weather you are likely to encounter.

This isn't strictly true. The boiler has also to have sufficient excess
capacity to both achieve the above situation and to also heat up the system
in a reasonable time - say 20% overcapacity.


'or exceed'

Depends on whether you run 24x7 in very cold weather. I do. ;-)

"The Natural Philosopher" wrote

Mmm., Your choice then.

£108 a year probably just covers a decent service.

Unless you want the boiler renewed for other reasons., I'd just get it
serviced...


Thanks everyone for your input. I think I might now well go down the path
of getting it serviced. So what is the life expectancy of a 1990 Potterton
Flamingo boiler? I guess it must be or borrowed time.

On Sun, 16 Dec 2007 11:16:39 +0000, PC Plod wrote:

I am just starting to think about replacing my boiler so no doubt this
will be the first of a few question posted here.

I live in a 1990 built 4 bedroom detached house. My existing boiler
which is now getting on for 18 years old is rated at only 50,000 btu/
14.65kW. I say only because when I look at websites for boilers I
apparently need a larger output. My existing boiler serves a Flowmax
thermal heat store, so the tank is full of central heating water while
the hot water runs through a copper tube inside the tank which serves
all taps at high pressure. The boiler is only set at 50% with the room
and tank thermostats controlling the temperatures

It works great so I intend to keep it. So the first question is do I
really need a higher output heat only condensing boiler.

I'd be interested to know what web sites are suggesting a larger output
unit. This existing unit will be sized for the space heating requirements
which for a modern house will be relative modest.

So it comes down to what 15kW condensing plain heating boiler you need.
Some thermal stores have a coil for indirect primary heating and so a
sealed boiler can be used. Otherwise you are needing a plain heating
boiler.

--
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

On Sun, 16 Dec 2007 16:51:13 +0000, PC Plod wrote:

"The Natural Philosopher" wrote

Mmm., Your choice then.

£108 a year probably just covers a decent service.

Unless you want the boiler renewed for other reasons., I'd just get it
serviced...


Thanks everyone for your input. I think I might now well go down the
path of getting it serviced. So what is the life expectancy of a 1990
Potterton Flamingo boiler? I guess it must be or borrowed time.

There is little to go wrong. If the main heat exchanger is intact and you
keep it cleaned out from time to time. Then the only item of hassle will
be the pump, the themocouple, very very occasionally the gas valve,
ocassionally the overheat stat.

It will send a sizeable chunk of the gas bill up the chimney.


--
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

Andrew Gabriel wrote:

Start by reading Ed's Choosing a Boiler FAQ...
http://www.makewrite.demon.co.uk/BoilerChoice.html


I don't know if Ed reads this group any more, but the boiler calculator
at http://www.idhe.org.uk/calculator.html has gone - with the whole web
site.

Andy

"Ed Sirett" wrote
I'd be interested to know what web sites are suggesting a larger output
unit. This existing unit will be sized for the space heating requirements
which for a modern house will be relative modest.

So it comes down to what 15kW condensing plain heating boiler you need.
Some thermal stores have a coil for indirect primary heating and so a
sealed boiler can be used. Otherwise you are needing a plain heating
boiler.


Try
http://www.vaillant.co.uk/homeowners...e-right-system

They recommend the ecoTEC plus 428 which is a 28.2Kw condensing boiler for
a 3-4 bedroom house. I have seen another website but can't find it now

"Andy Champ" wrote in message
...
Andrew Gabriel wrote:

I don't know if Ed reads this group any more, but the boiler calculator at
http://www.idhe.org.uk/calculator.html has gone - with the whole web site.

Andy

You have an "e" missing

Try this http://www.idhee.org.uk/calculator.html after doing the
calculations I only need a 10KW boiler

On Sun, 16 Dec 2007 21:52:24 +0000, PC Plod wrote:

"Andy Champ" wrote in message
...
Andrew Gabriel wrote:

I don't know if Ed reads this group any more, but the boiler calculator
at http://www.idhe.org.uk/calculator.html has gone - with the whole web
site.

Andy

You have an "e" missing

Thanks for pointing out the broken link. Time for an edit, I think.


Try this http://www.idhee.org.uk/calculator.html after doing the
calculations I only need a 10KW boiler

Which rather illustrates the point I make in the FAQ.

.... This calculator tend to suggest boiler a little less than I would
fell comfortable installing. ...


--
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

On Sun, 16 Dec 2007 21:06:41 +0000, PC Plod wrote:

"Ed Sirett" wrote
I'd be interested to know what web sites are suggesting a larger output
unit. This existing unit will be sized for the space heating
requirements which for a modern house will be relative modest.

So it comes down to what 15kW condensing plain heating boiler you need.
Some thermal stores have a coil for indirect primary heating and so a
sealed boiler can be used. Otherwise you are needing a plain heating
boiler.


Try
http://www.vaillant.co.uk/homeowners...ystem/#choose-
the-right-system

They recommend the ecoTEC plus 428 which is a 28.2Kw condensing boiler
for
a 3-4 bedroom house. I have seen another website but can't find it now


They are playing safe. A large 4 bedroom house with uninsulated
everything, draughty ill-fitting sash windows, old unblocked fire
places,....might just need 28kW


--
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