immersion heater versus boiler

[The Natural Philosopher]

Not for much longer.

There are inefficiencies but not that

Or if gas exceeds nuclear energy costs by a factor of three, which it looks set to do.

[meow2222]

I've yet to meet a simple passive exchanger that would do that, but I'll accept I've not seen them all.

[dennis]

Never seen a Thorn Apollo in your life? They are more efficient if you set them to max than to min, not that they modulate as it isn't needed.

[David Hansen]

On Thu, 22 May 2008 01:34:52 +0100 someone who may be The Natural Philosopher wrote this:-

Most unlikely.

Gas is an increasingly rare material which has a small amount of processing before it is sent by pipe direct to houses.

Nuclear fuel is an increasingly rare material which has an enormous amount of processing before it is taken to a large power station. The electricity is then taken by cable to houses. We'll leave aside what happens after the fuel leaves the power station.

[Doctor Drivel]

Your knowledge on thermal transfer is sadly lacking.

[Doctor Drivel]

You made that up.

[Doctor Drivel]

You need the bending valve to ensure the non-condensing boiler does not condense and ruin the boier. On commercial boiler it is called "back end protection". In this case it is to improve thermal expansion.

If the system is designed properly and the return runs at 58C, and the condensing system is poorly designed and commissioned that can be the case. However in your case I doubt it as you only have half a clue at most.

[Doctor Drivel]

What do you know we do not?

Even then with an old cast iron boiler gas is still cheaper.

You made that up. The government is giving grants to people who change over from electric to gas CH.

[Doctor Drivel]

Or more likely setting with a "range".

Isn't it?

If the burner is designed to modulate this is not an issue.

Through the heat exchanger? That is a point.

In a non-condensing boiler with set rate burner, having the return at 58C and the flow through the heat exchanger to give the highest temperature rise (highest delta T) will give maximum efficiency. The heat exchanger has to cope with the delta T. Finned copper tube heat exchangers are generally suitable as they are all one piece.

The system can be engineered to give this by sizing the rads to suit 58C return and 82C flow. 24C delta T. Ensuring the rad circuit pumps around on itself to give a return of 58C is the way to do it. The blending valve only opens to allow heat into the rad loop and at the same time ensuring a return back to the boiler of 58C.

It is easy once you know what you are doing.

[Stewart]

Thanks again, my brother is a plumber and he tells me that my cylinder is a non standard size, quite narrow; if and when I have to replace it he tells me I shall not get another to fit in the cupboard. Hopefully that will not be for several years yet. I know that I do not have the best insulation but the cupboard is quite small and with the 2 covers on the cylinder (as well as spare sleeping bags on top) I think it is reasonably well insulated.

[David Hansen]

On Thu, 22 May 2008 14:50:47 +0100 someone who may be "Stewart" wrote this:-

McDonald say they make them down to 200mm in diameter and Newark say they make them down to 300mm in diameter or even less, so that shouldn't be too much of a difficulty.

Standard sprayed on insulation is 25mm thick, but a new cylinder should be at least twice this, which adds 100mm+ to the diameter.

[dennis]

Of course its an issue.. modulating the boiler means compromising somewhere.

[Mary Fisher]

That's VERY important.

I'm off for a bath in a few minutes, water temperature 57C, it's been cloudy today so not so hot but far warmer than I need for a tub full :-)

Mary

[Mary Fisher]

For interest, David, is the spray on a DIY possibility?

PU foam perhaps?

Mary

[David Hansen]

On Thu, 22 May 2008 20:20:13 +0100 someone who may be "Mary Fisher" wrote this:-

If one had the equipment I'm sure it would. Presumably the cylinders are spun and the foam sprayed on. I wouldn't want to do it though.

[Mary Fisher]

I'm in no rush, off for a bath then to Traquair (Peebleshire) tomorrow for a historical event. Back Monday.

Mary

[Doctor Drivel]

You really just don't know. The most common is pneumatic ratio-control burners. This compensates for weather conditions such temperature and barometric pressure. The speed of the fan acts on a venturi. Based on this pressure difference the gas valve opening is adjusted to match the air. They are highly efficient pre-mix burners and can modulate efficiently over a wide range.

There is a slow transition from the metallic pre-mix burner to flameless ceramic burners, which give out far more radiant heat, 35% to 5% to 15%, and much cooler flue gassess, under 1,000C to 1,300C. If the flameless burners are advanced more condensing technology will be reversed. Only when the condensing plumes become a full nuisance and emissions are tightened will this happen, like eliminating all SEDBUK band B boilers. Then a plumeless boiler will be needed for flats - flameless burner boilers can do this and still give high efficiencies..

[meow2222]

Electricity has always cost more than raw fuels, as it has the added costs of power stations plus considerable conversion inefficiency. Short term variations only change that short term.

If it climbed that high people would already have quit using it for nearly all apps. And again I dont see it happening.

NT