Central heating upgrade

[Doctor Drivel]

Then raise the boiler temperature. Perfect low temperature combustion gasses, and there will be no plume. It is difficult to get that.

[Doctor Drivel]

Thats so you can knock the price down. Its a bargaining point.

Well none of that is instantly NECESSARY.

A 1980s boiler should still be OK, and any efficiency gains need balancing against the actual cost of a new boiler.

You are looking in the 1500-5000 range to upgrade a CH system, depending on how far you go.

I.e. I would ALWAYS unless it was a bachelor flat, ditch a combi and put in a mains pressure hot water tank,

[Dave Plowman (News)]

Never has a truer word been written.

[meow2222]

Watch normal combustion in action on a balanced flue, you see slight movement of the flame as the wind blows. Its much less blow than an unbalanced flue system, but certainly not zero.

NT

[Roger]

The message from "Doctor Drivel" contains these words:

That is no way to treat one of the few subscribers to this ng who has ever espoused any of your ludicrous theories.

[Roger]

The message

from [e-mail] contains these words:

You seem to be as inventive as Dribble when it comes to not understanding science.

You will get a certain amount of turbulence immediately within the end of a balanced flue if the wind blows across it and a bare perceptible pressure change along the flue as the wind varies but I would be very surprised indeed if there was any detectable air movement in the combustion chamber itself, certainly not enough to transfer a measurable amount of heat to the outside world.

[Roger]

The message from "Doctor Drivel" contains these words:

Being as efficient as possible is by no means the same as achieving the impossible.

Just answer 1 simple question:

What is the return temperature required to achieve maximum recovery of the latent heat?

[The Natural Philosopher]

Absolute zero?

:-)

[meow2222]

yes, if. Most old systems dont though.

Where do you think the heat exchanger heat goes each time? Do you imagine the air inside the boiler is all totally still?

yes... but the percentage lost to the room is low. If it wasnt, any room with a boiler in would be intolerably hot. Most goes elewhere.

how significant depends how rapidly the boiler cycles, which depends on the stat. With short runs it can be very significant.

you've offered nothing to invalidate it

incorrect. surface area is a key factor, and unmachined cast iron has far less.

plenty of us pay that much and more

real world efficiency falls over time due to crud in the exchanger

a fair choice

the ROI is compared to cost of capital. For many people such an ROI is above what any savings account or the stockmarket offers.

quite a few of us here have boilers 20 or more years old

many of us dont borrow for a new boiler, so it would not be constructive to include that in the calc.

Its one case, sure. Obviously some of us spend a lot more than that on fuel, less on a new boiler etc.

You keep crying bullshit but have been repeatedly unable to substantiate such a claim.

NT

[meow2222]

only if an overrun timer is fitted.

NT

[meow2222]

I see you now resort to simple bullshit

so entirely consistent with the above then

thats normally true

it can be, but it costs more, hence it usually isnt

yet another failed attempt at bs then.

NT

[Roger]

The message

from [e-mail] contains these words:

snip

Most? You have done a survey then?

Unlike you I don't imagine anything. I asked you earlier to put figures to the amount of residual heat in the heat exchanger when the boiler ceases firing and you couldn't or wouldn't. The vast majority of the lost heat goes out of the flue while the boiler is firing. 10% of the total heat output locked up in the latent heat. Almost all of the rest in flue gases with a temperature of 200C or more. Cut the burner and there are no excess gases to expel and only convection to drive any exchange of air. Convection doesn't work at all well with a horizontal flue and the temperature difference is much lower as well, being limited by the temperature of the water within the heat exchanger.

Old boilers do get hot when they are firing. When not firing their heat output is less as they cool down but the difference between the heat output of the boiler when it is firing and when it is not is far smaller than the difference between the hot flue gases and the air in the combustion chamber when the boiler is not firing.

Words, words and more weasel words but not a single figure. You haven't dared to say how much you think is "very significant".

Don't be silly. You made a point on the basis of " given physical boiler size". An unnecessary constraint.

Stop waffling and provide some figures.

I seriously doubt that anyone with a normal sized house and a condensing boiler would pay anywhere near the figure you started from in your cart before the horse calculation.

Which should get cleaned out every year and even if it doesn't curiously doesn't seem to translate into increased gas usage year on year.

Not typical though.

I don't know what you mean by ROI unless you mean return on investment which doesn't fit the context but what I do know is that your calculation of savings is the most ridiculous one I have seen since Dribble last tried to manipulate figures.

You have a condensing boiler more than 20 years old? I thought all the TriSaves died long ago. My boiler is a mere 18 years old but it has all those extras that you seem to think don't exist on old boilers in addition to its cast iron heat exchanger.

You didn't include any figure for cost of capital and you seem to forget that my opening proposition was that replacing a boiler in good working order was dubious at best and not to be contemplated if the cost had to be borrowed. And I am quite sure that a good many people do borrow to finance such expenditure. Most people don't have any savings to speak of if the press is to believed.

So produce just one disinterested bystander living in a typical detached house heated by a gas fired condensing boiler who pays as much as you alleged in your flawed calculation.

Try and get an unsecured loan of £3000 and let us know the cost.

[meow2222]

go watch a balanced flue boiler burn on a windy day.

NT

[meow2222]

No, have you?

no, I cba. You can if you want

yes

convection plus turbulence

the air path within the boiler is not horizontal, and the oiler combustion chamber is already hot. Some convection will continue. The short horizontal length of the balanced flue won't stop that. Bear in mind that this stored heat has many minutes in which to dissipate.

yes, but the loss to the room is only a small percentage of total output and of heat losses.

hot flue gases rapidly dissipate when not firing - but this is off point anyway

obviously it varies a fair bit

nonsense

again is a matter of design, there is no universal figure

a =EF=BF=BD327 pa

But not worth it

ask ukdiyers and youll actually know.

There are 2 layers of crud, one on the air side, one on the water side. In most cases neither has been cleaned for years.

of course it does, its an insulating layer. It takes many years for a lot to build up, assuming its burning cleanly.

yes, return on investment.

comparing the annual saving to the cost of implementation... that's ROI.

yet are unable to substantiate it.

what I have isnt relevant

?

as was just explained, the cost varies widely hence I decided better to compare ROI to other options than include a very variable figure

no, not forgotten.

some do some dont, or would you have us believe savings accounts and shares are a rarity?

typical? are you changing the goal posts again? If you want to start a thread asking people for their gas bills its all yours.

what makes you think i'd need to?

NT

[Kostas Kavoussanakis]

Point well taken.

But don't similar considerations apply to a condensing boiler? Is there a reason why a condensing boiler will perform closer to its spec on my set of rads and pipes (I don't think we can make a comparison if we go into the "replace X rads" territory; X will vary a lot). And is there a reason why its performance will also not drop out with time?

Thanks,

Kostas

[Roger]

The message from [e-mail] contains these words:

Your point. Your need to justify your claim.

I have already told you the amount is relatively small and the actual difference between that in a cast iron heat exchanger and one of an alternative metal is much smaller still. Both have to contain significant quantities of water and in the case of a cast iron heat exchanger the water may have as much as half the total heat content.

The only significant turbulence is in your mind.

Many minutes to dissipate by conduction into the immediate surroundings. You make it sound as if the combustion chamber will retain the heat of the flames after the firing stops but that is not the case. The temperature within will very rapidly revert to the temperature of the heat exchanger which is basically the temperature of the water within. The convection within the boiler will be weak and not helped by the horizontal flue.

But large compared to heat out of the flue when not firing.

You mean you missed the point.

Funny. You had no such inhibitions when you said "Exchanger heat is not lost to indoors." That is as close as you have come to giving a figure for any heat transfer. You can't quantify it but you just know it is large and all of it goes out the flue.

What you maintain is indeed nonsense. If boiler design requires a bigger heat exchanger because of the materials involved then the boiler will get a bigger heat exchanger but the whole thrust of your argument - that cast iron is a poor material for a heat exchanger - is misconceived and your statements about its nature incorrect.

Make a heat exchanger out of an insulating material (yes I know a totally stupid idea) and you will soon find out that thermal conductivity is a far more important factor than surface area. (Not that I accept your original contention that cast iron is such a poor material).

No one has owned up so far and I don't suppose anyone will but FWIW gas cost me £718 over the last year and that for a detached house with solid stone walls and precious little insulation and fitted with a old cast iron boiler. You would have us believe that a gas bill for a normal house with a condensing boiler would be

Now why would that effect cast iron heat exchangers and not those of other metals?

I haven't noticed any such increase but then I don't live in a hard water area that would generate scale.

That's the snake oil salesman talking. A boiler is a wasting asset and as such you need to take into account the total loss of said investment over a relatively short period. Straight line write-down on £3000 over

10 years is £300 pa. Even your over-the-top calculation only achieved fuel savings of £327 pa.

Substantiate what? Unlike you I used reasonable figures which do stand up to scrutiny. You can whinge all you like but it is you who have used outlandish figures and have ignored the cost of capital. What should have been your starting figure was well over double what SEDBUKs figures suggest was typical for a 65% boiler.

And there was I thinking you were talking from personal experience with condensing boilers. A number of us have admitted to have old or indeed very old boilers. AFAIK no one has admitted to having a very old condensing boiler but several have complained about the problems they have had with relatively recent ones.

Pump overrun, fan flue and electronic ignition.

Except that you did no such thing.

Shares are for the long term. If you have any sense you don't sell shares to fund a wasting asset. That's always assuming you hold shares directly and not locked away and unusable in a pension fund. The nation apparently is up to it's collective ears in debt with the majority of the population having little on no net worth.

Unlike you I haven't moved the goalposts at all. My calculation is just above. I started from SEDBUKs typical figures and even used your installation and maintenance costs.

To find out whether 10% is too little or too much for the unsecured loan some people considering a replacement boiler will need to take out in order to fund the installation.

[Roger]

The message from Kostas Kavoussanakis contains these words:

But not well made in the first place. There may well be some reduction in efficiency over time but Dribble has no evidence to support the figure he has plucked out of thin air to support his long held belief that boilers with cast iron heat exchangers are extremely inefficient.

No reason why not. Indeed it could be argued that a more sophisticated boiler is more likely to fail to live up to expectations that a comparatively simple one.

To get the full benefit from a condensing boiler the system needs to be designed for such a boiler. To get the low return temperatures required for condensing to occur in all situations radiators need to be substantially bigger with a designed temperature drop across the radiators twice that of a conventional system.

This is not as bad as it seems at first glance as systems should be designed to cope for the worst-case scenario so the warmer it is outside the less heat is required from the radiators and the more chance the flow temperature can be reduced so that the return temperature is low enough to achieve at least some condensing.

[Roger]

The message from The Natural Philosopher contains these words:

Wrong! :-)

Dribble has failed to answer but when has he even given a sensible answer to even a simple question.

[Roger]

The message

from [e-mail] contains these words:

I have but conditions are rather different when the boiler is firing. When the boiler isn't firing there is no gas flow out of the combustion chamber, only an essentially static air mass with marginal pressure changes as the outlet is buffeted by the wind.

[Roger]

The message

from [e-mail] contains these words:

You are the one moving the goalposts.

No.

As a statement of fact it is completely bogus. If it were true then the Merkin boiler mentioned above would indeed be either as inefficient as I implied above or so horrendously expensive that it wouldn't sell.

So how do you explain the Merkin boiler?

That's not bullshit, just scorn, pure and simple.