What a waste!

The residual heat in the exhaust is there to carry away the normal products of combustion. Take more heat out and you will end up with acids of both carbon and sulphur rotting any form of steel or aluminium heat exchanger. This is the big problem with modern condensing central heating boilers running on oil. The price of your eber will be astronomic if you have to make all the burner, heat exchanger and exhaust out of corrosion resistant stainless steel or even ceramics.
 
TSB240 said:
The residual heat in the exhaust is there to carry away the normal products of combustion. Take more heat out and you will end up with acids of both carbon and sulphur rotting any form of steel or aluminium heat exchanger. This is the big problem with modern condensing central heating boilers running on oil. The price of your eber will be astronomic if you have to make all the burner, heat exchanger and exhaust out of corrosion resistant stainless steel or even ceramics.
Click to expand...

Even if you take the heat out of the exhaust after it has left the burner?

I have seen some Heath Robinson efforts at heating water using the exhaust pipe, some, apparently, working to good effect.
 
TSB240 said:
The residual heat in the exhaust is there to carry away the normal products of combustion. Take more heat out and you will end up with acids of both carbon and sulphur rotting any form of steel or aluminium heat exchanger. This is the big problem with modern condensing central heating boilers running on oil. The price of your eber will be astronomic if you have to make all the burner, heat exchanger and exhaust out of corrosion resistant stainless steel or even ceramics.
Click to expand...

Even if you take the heat out of the exhaust after it has left the burner?

I have seen some Heath Robinson efforts at heating water using the exhaust pipe, some, apparently, working to good effect.
 
TSB240 said:
The residual heat in the exhaust is there to carry away the normal products of combustion. Take more heat out and you will end up with acids of both carbon and sulphur rotting any form of steel or aluminium heat exchanger. This is the big problem with modern condensing central heating boilers running on oil. The price of your eber will be astronomic if you have to make all the burner, heat exchanger and exhaust out of corrosion resistant stainless steel or even ceramics.
Click to expand...
Where and when does the condensation take place? If the heat is extracted after a condensation trap, e.g. a tee with a drip catcher below, that should protect the Eber.
 
Graham_Wright said:
Where and when does the condensation take place? If the heat is extracted after a condensation trap, e.g. a tee with a drip catcher below, that should protect the Eber.
Click to expand...

I believe the condensation occurs throughout the exhaust pipe. The purpose of lagging the exhaust pipe is to try to keep the pipe hot so that condensation doesn't occur.
 
Suspect that you would have to run it for more time that you would expect to get useable heat as the temp difference may not be as good as you think, that’s always the problem with heat recovery systems especially on small scale
 
Daverw said:
Suspect that you would have to run it for more time that you would expect to get useable heat as the temp difference may not be as good as you think, that’s always the problem with heat recovery systems especially on small scale
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Not really. It is too hot to touch very soon after ignition.
You should see what it did to a couple of pipes it touched during trials! I would guess the temperate at around 90°C but it is not about temperature, it is about heat.
 
The Wallas heaters use a double skin exhaust, the exhaust gasses go out the centre pipe and combustion air comes in the outer pipe, cooling the pipe in the process and heating the combustion air. You can keep your hand on the exhaust except for a foot length from the heater even when turned to full power. Haven't had any condensation issues yet, although it does run on paraffin.
 
Sorry not about heat but temp difference, 90 is not that hot if you want 60 water in a sensible time period, you cannot fit much of a heat exchanger without introducing a large back pressure to the exhaust.
 
A brief discussion of heater efficiency.
Heater efficiency

IIRC, this heater is forced draft. If the efficiency is around 80%, and you "might" recover half of that, we're talking about <1000 BTU or less than 300 W. Given the heater does not run nearly full time... that's not much.

The double-wall flue is probably the simplest way to improve efficiency.
 
I think that there should be a turbine in the exhaust driving the combustion air inlet compressor via a common shaft to save electricity. If the shaft was connected to a larger fan at the input compressor and the compressed air was split between some going through the core for combustion but the majority bypassing the core to go to the heat exchanger for cabin heating purposes even more electricity could be saved requiring an electric motor only at start up.

Hang on, have I just invented the turbofan engine? Could be useful on planes. Where's Rolls Royce's telephone number...
 
I ran my Chinese diesel heater in the garden before I installed it.
24mm exhaust temp on straight runs was around 180, on the curves it was around 320c
Hot Air outlet 3m from heater (insulated pipe) is 95c
You can buy heat exchangers on ebay to heat water from the exhaust.
 
Graham wright - im sorry but unable to find anything on ebay atm and don't know what they are called.
It's a stainless box with in/out for exhaust and in/out for water.
But now some of the chinese hot air heaters also have a water heat exchanger built in !
This guy chops open and tests everything to do with Chinese heaters..
Ever wondered what they look like inside whilst running ?
 
Last edited:
Rappey said:
Graham wright - im sorry but unable to find anything on ebay atm and don't know what they are called.
It's a stainless box with in/out for exhaust and in/out for water....
Click to expand...

Graham: search "heater core" to find the heat exchanger part (get the smallest one). Then build you own air-tight, metal, insulated box. Combined with a small pump it will heat water. BUT I don't think the amount of heat will be material (about 1-2 gph from 70F to 120F). You may not need the pump; concention may be enough, depending on the geometry. The water will probably cool off before it gets to the tank!

I've built industrial versions 1000 times this rating. They are call "economizers" when installed on big boilers and are used to preheat feed water or superheat steam.
 
I would have thought that if you can arrange a constant fall all the way from the heater to the exhaust outlet, you could rob as much heat as you want from the exhaust, because the combustion products are still going to escape, including any condensation. But on most marine installations you're likely to have a rise to the exhaust outlet.
 
Kelpie said:
I would have thought that if you can arrange a constant fall all the way from the heater to the exhaust outlet, you could rob as much heat as you want from the exhaust, because the combustion products are still going to escape, including any condensation. But on most marine installations you're likely to have a rise to the exhaust outlet.
Click to expand...
What happens to the acidic outflow? In fact, what happens in a "proper" installation. Eber recommend drilling a Ø5 hole to allow the residue to drain. What is the effect of sulphuric acid on fibreglass?
 
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