Sorry about this guys and gals. I know there is a lot of boiler talk
going on here at the moment and I'm trying to keep up with the diverse
and sometimes opposing points of view.

My question is regarding combi versus condensing combi. Is it worth
trying to beat the April deadline for having a normal combi fitted or
are the benefits of the condensing combi worth the extra cost? Is there
a difference on longevity between the two types in general?

Thanks,


--
Paul Giverin

British Jet Engine Website http://www.britjet.co.uk

"Paul Giverin" wrote in message
...
Sorry about this guys and gals. I know there is a lot of boiler talk
going on here at the moment and I'm trying to keep up with the diverse
and sometimes opposing points of view.

My question is regarding combi versus condensing combi. Is it worth
trying to beat the April deadline for having a normal combi fitted or
are the benefits of the condensing combi worth the extra cost? Is there
a difference on longevity between the two types in general?

Wait until after April to see if prices drop, as 90% plus of all boilers
will be condensers then, so makers costs will drop. If you need to replace
a boiler then go condenser. The myths abouth them being unreliable are well
....just myths. Replacing an old cast iron job, you may save up to 40% of
your gas bill.

The message
from "IMM" contains these words:

....just myths. Replacing an old cast iron job, you may save up to 40% of
your gas bill.

Almost a myth.

If the CI boiler has an efficiency of 54% then the condensing
replacement would need to operate at 90% efficiency. To do that it would
have to be an efficient boiler to start with and operate in condensing
mode almost constantly. Not totally impossible but not in the real world
either.

Some relatively efficient fan flue boilers have CI heat exchangers and
over them a more typical saving would be 10-15%.

I wonder if dIMM has a job in the procurement dept of the Ministry of
Defence. :-)

--
Roger

"Roger" wrote in message
k...
The message
from "IMM" contains these words:

....just myths. Replacing an old cast iron job, you may save up to 40%
of
your gas bill.

Almost a myth.

If the CI boiler has an efficiency of 54%

snip ill-informed drivel

[Paul Barker]

Originally Posted by Paul Giverin

Sorry about this guys and gals. I know there is a lot of boiler talk
going on here at the moment and I'm trying to keep up with the diverse
and sometimes opposing points of view.

My question is regarding combi versus condensing combi. Is it worth
trying to beat the April deadline for having a normal combi fitted or
are the benefits of the condensing combi worth the extra cost? Is there
a difference on longevity between the two types in general?

Thanks,


--
Paul Giverin

British Jet Engine Website http://www.britjet.co.uk

If I were changing my boiler at home right now I would definately fit a condensing boiler without question. I would fit one of the better purpose built versions like those which use the Vaillant system (Vaillant, Hastead, other people may use it) the Buderus, Worcesters all of wich have the necessary protection against the acidic water that is hanging around in the exhaust gases.

The grafted on extra heat exchanger style is OK, but they are best operated in Sedbuk band B. Baxi for instance told me during a training day that they don't want their 105he condensing too much, that's why they've limited it to band B. This and others like it have an excellent Class D boiler as their basis, but they pass return water through a preheat extra heat exchanger which sucks the last heat out of the exhauset on it's way outside. They do not want the primary heat exchanger to start condensing as the burner which is in the older position beneath, would quickly corode.

Therefore fit a good one.

I certainly wouldn't fit a Band D boiler for myself.

Roger wrote:

The message
from "IMM" contains these words:


....just myths. Replacing an old cast iron job, you may save up to 40% of
your gas bill.


Almost a myth.

He did say "may" and "up to" ;-)

If the CI boiler has an efficiency of 54% then the condensing
replacement would need to operate at 90% efficiency. To do that it would
have to be an efficient boiler to start with and operate in condensing
mode almost constantly. Not totally impossible but not in the real world
either.

Given the modulating burner and the more sophisticated control system,
you will probably get it operating in condensing mode for the vast
majority of the time.

Some relatively efficient fan flue boilers have CI heat exchangers and
over them a more typical saving would be 10-15%.

As you say 40% is pretty unlikely, but 25% is not unreasonable.

--
Cheers,

John.

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You need to check that this is completely accurate, but, I believe a
lot of the cheaper models of condensing combi's only operate in
condensing mode for heating and not hot water. I know Worcester-Bosch
Greenstar models operate in condensing mode for both heating and hot
water but I don't know which others do/don't.

It should be said that our new condensing combi boiler over our old
model makes a huge difference in gas comsumption (this winters compared
to last winters gas readings). I'm unsure how much of this is down to
the fact that the new boiler doesn't have a pilot light running 24x7
and how much is due to increased efficiency.

I know this doesn't directly answer the original question but hopefully
it's of some use.

Seri

"Seri" wrote in message
oups.com...
You need to check that this is completely accurate, but, I believe a
lot of the cheaper models of condensing combi's only operate in
condensing mode for heating and not hot water. I know Worcester-Bosch
Greenstar models operate in condensing mode for both heating and hot
water but I don't know which others do/don't.

That is true, but only for combi's

It should be said that our new condensing
combi boiler over our old
model makes a huge difference in gas
comsumption (this winters compared
to last winters gas readings). I'm unsure
how much of this is down to
the fact that the new boiler doesn't have
a pilot light running 24x7
and how much is due to increased efficiency.

I know this doesn't directly answer the original
question but hopefully
it's of some use.

The message
from John Rumm contains these words:

Some relatively efficient fan flue boilers have CI heat exchangers and
over them a more typical saving would be 10-15%.

As you say 40% is pretty unlikely, but 25% is not unreasonable.

25% is about as bad as it is likely to get. 23% was the example quoted
in another thread for an upgrade from a back boiler and back boilers are
not exactly renowned for their efficiency.


Assuming a replacement efficiency of about 85% a 15% upgrade is from
about 74%, 25% from 64%.Where would you place a 'relatively efficient
fan flue boiler with CI heat exchanger"?
--
Roger

In article ,
IMM wrote:
Replacing an old cast iron job, you may save up to 40% of
your gas bill.

Note the 'may'. That's the important word. The other important word that
should come after it is 'not'.

Hope for 20%. That's far more likely.

--
*I'm planning to be spontaneous tomorrow *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
John Rumm wrote:
....just myths. Replacing an old cast iron job, you may save up to
40% of your gas bill.


Almost a myth.

He did say "may" and "up to" ;-)

Trouble is many who ask for advice may actually believe this and budget
for the replacement accordingly. However, actual savings of 40% in cash
terms on gas use are most unlikely. Half that would be nearer a norm.

--
*Rehab is for quitters

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
John Rumm wrote:
....just myths. Replacing an old cast iron job, you may save up to
40% of your gas bill.


Almost a myth.

He did say "may" and "up to" ;-)

Trouble

snip drivel

"Dave Plowman (News)" wrote in message
...
In article ,
IMM wrote:
Replacing an old cast iron job, you may save up to 40% of
your gas bill.

Note the 'may'.

snip drivel

Paul Barker typed:

snip.
Baxi for instance told me during a training
day that they don't want their 105he condensing too much, that's why
They do not want the primary heat
exchanger to start condensing as the burner which is in the older
position beneath, would quickly corode.


I thought (but could be mistaken) that the burner on these are ceramic.

Seri wrote:

You need to check that this is completely accurate, but, I believe a
lot of the cheaper models of condensing combi's only operate in
condensing mode for heating and not hot water. I know Worcester-Bosch
Greenstar models operate in condensing mode for both heating and hot
water but I don't know which others do/don't.

That may well be the case, although as has been mentioned before in
other threads, there is no massive gain in efficiency when a condenser
starts condensing. Its extra efficiency is down to a who package of
design features.

--
Cheers,

John.

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