Wasted heat on diesel heater exhausts - Eberspacher etc

Scotty_Tradewind

Scotty_Tradewind

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I stuck my head into the lazarette this week and realised what a huge amount of heat was being wasted.

There must be a simple heat exchanger system that fits around the exhaust pipe and allows the heat to be piped back into the boat....???

Anyone ideas if such a thing is on the market, otherwise I'll have to get my man to knock something up?

I reckon if I can collect that heat my Eberspacher Hydronic would be 100% more effective.
As it is, there is far more heat coming from the lazarette than from the matrix heater outlets in the saloon, although the water temp control on the calorifier has to be turned down as that can get too hot..
 
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Scotty_Tradewind said:
How can heat be poison?? The gasses maybe but not the heat surely? :)
S.
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Don't panic - you will find there are a lot of simple minded folk on here from time to time.
To get back to your question, I can see several problems with your idea:
1) making or finding a suitable heat exchanger with a high enough thermal transfer capacity and 100% gas tight
2) Additional blower to feed a seperate, dedicated, outlet.
3) not upsetting the combustion in the heater - balanced flue system?

Better use the waste heat to dry out the aft locker.
 
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Already been tried, you will be upset the settings by effectively cooling the exhaust. I would be interested to see the calculations that lead you to expect a 100% efficiency increase.
 
David2452 said:
Already been tried, you will be upset the settings by effectively cooling the exhaust. I would be interested to see the calculations that lead you to expect a 100% efficiency increase.
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Ah... !00% just my way of saying what a great waste in what at first appears to be a very ineffiient set up.
Losing heat in the exhaust could as you say be a problem with that creating the wrong back pressure etc...

Hav some sympathy for Riviona, it was early hours and he obviously couldn't sleep just like me..:)
 
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cliff said:
Don't panic - you will find there are a lot of simple minded folk on here from time to time.
To get back to your question, I can see several problems with your idea:
1) making or finding a suitable heat exchanger with a high enough thermal transfer capacity and 100% gas tight
2) Additional blower to feed a seperate, dedicated, outlet.
3) not upsetting the combustion in the heater - balanced flue system?

Better use the waste heat to dry out the aft locker.
Click to expand...

Yup I am definatly simple minded. I was always taught that any burnt fuel produces (or can) produce CARBON DIOXIDE or it was CARBON MONOXIDE (I am getting very forgetfull in my dither years).
Thats where I am coming from.

Peter
 
rivonia said:
Yup I am definatly simple minded. I was always taught that any burnt fuel produces (or can) produce CARBON DIOXIDE or it was CARBON MONOXIDE (I am getting very forgetfull in my dither years).
Thats where I am coming from.

Peter
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Yup - 'tis the Carbon Monoxide that does the damage NOT the heat. In any event the exhaust should be gas tight - don't want any nasty poisonous heat - sorry - gas excaping into the boat.

As an aside, it has beeen known for the combustion chamber on the diesel fired heaters to burn through and in effect blow exhaust gas into the hot air circuit - good reason to fit CO detectors. I was in a Eber/Wabasto/Mikuni repair shoppe in East Kilbride a few years looking for bits for my old Eber - was quite suprised when he showed me some of the chamber burn throughs he had in his gallery of failed "ebbers" (and Wabastos)
 
rivonia said:
Yup I am definatly simple minded. I was always taught that any burnt fuel produces (or can) produce CARBON DIOXIDE or it was CARBON MONOXIDE (I am getting very forgetfull in my dither years).
Thats where I am coming from.

Peter
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Hi Peter, were you at the back of the class a bit like me as a kid? :)

I'm on about a
taking heat from the outer exhaust and air ducting it back to the boat.... or at least thats what i think i'm thinking... but I'm not sure now.
Carbon Monoxide etc...
I did rescue a neighbour once when he attempted to gas himself with a tube from his exhaust into the back window of his car.
Didn't help much, poor sole, then went and drove himself straight into an oncoming lorry a month later and it was a wipe-out
 
rivonia said:
Yup I am definatly simple minded. I was always taught that any burnt fuel produces (or can) produce CARBON DIOXIDE or it was CARBON MONOXIDE (I am getting very forgetfull in my dither years).
Thats where I am coming from.
Click to expand...

Sure, but I think we can assume that the exhaust is not being vented into the lazarette. It just has a hot pipe running through it, and Scotty would like to capture some of that heat and use it for something more useful than keeping his spare warps toasty.

Pete
 
As I posted on the noisy exhaust thread, there is an issue with the water produced by combustion. Every litre of diesel you burn produces IIRC over a litre of water. That has to go somewhere, and the eber exhaust generally intends it to leave as steam, not condense in the exhaust. The water will contain dissolved nasties.
As has been stated, the exhaust gas needs to be well isloated from the cabin, at best it smells, at worst it kills.

So if you had a heat exchanger, it would need some carefull design re draining etc.
 
How about you fit a CO monitor in the lazarette and then fan the hot air into the cabin with the alarm as a safety override? Many people make a big issue about avoiding the heater exhaust running through the cabin, but your engine exhaust is in an unsealed box and produces much more exhaust gas.

Rob.
 
This thread will have a lot fewer confused responses if contributors make it clear that they are talking about the Exhaust pipe (sealed) or the Exhaust gasses (potentially poisonous).

I don't think any knowledgeable person would install an eber exhaust gas outllet to discharge into a locker - too geat a risk of it finding its way (possibly via the bilges) into the living area. But there may well be some such dangerous practices happening out there on self-installed units.

Also, heat exchangers do not usually need to access the raw gasses, it would simply require to draw heat from the outside of the sealed pipe. However this could clearly affect the temperature of the exhaust gasses as explained earlier if it was effective, and a waste of effort if it wasn't! Most people just lag the exhaust pipe very well so the heat escapes out side the boat & melts your neighbour's fenders.
 
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cliff said:
Yup - 'tis the Carbon Monoxide that does the damage NOT the heat. In any event the exhaust should be gas tight - don't want any nasty poisonous heat - sorry - gas excaping into the boat.

As an aside, it has beeen known for the combustion chamber on the diesel fired heaters to burn through and in effect blow exhaust gas into the hot air circuit - good reason to fit CO detectors. I was in a Eber/Wabasto/Mikuni repair shoppe in East Kilbride a few years looking for bits for my old Eber - was quite suprised when he showed me some of the chamber burn throughs he had in his gallery of failed "ebbers" (and Wabastos)
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It is interesting that most Webo / Mikuni / Ebers produce very little CO, not the petrol ones obviously, I aim for <160ppm (in the full exhaust flow) when setting them up and consistantly get well below that. Also the heat exchanger is a service replacemebt part and should be replaced at intervals no greater than 10 years, as you say they distort and become porus or burned through, they are surprisingly cheap when compared to most other parts.
 
Scotty_Tradewind said:
HOOray!! :D
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So what you want is an Eber exhaust silencer mounted inside another medal tank filled with an antifreeze solution and a radiator cap for expansion / topping up mounted on top. A pipe leads off to a 12v pump which feeds the calorfier (or a radiator) before returning to the tank.

Back in the real world, how much do you use the heating? might be more beneficial to insulate the hot air tubing to gain efficiency and just leave the exhaust pipe to turn the cockpit locker into a drying room.

Pete
 
prv said:
Sure, but I think we can assume that the exhaust is not being vented into the lazarette. It just has a hot pipe running through it, and Scotty would like to capture some of that heat and use it for something more useful than keeping his spare warps toasty.

Pete
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Ah...Now I understand. Simple me did not get the gist of the message. oops.

Peter
 
Going back to the original question, is it really worth it? Unless you are full-time liveaboard, I doubt that you spend more than £100 per year on heating fuel - seems to me that you are likely to put in a lot of effort and get back ten or twenty quid per annum - if you are lucky!
 
David2452 said:
Also the heat exchanger is a service replacemebt part and should be replaced at intervals no greater than 10 years, as you say they distort and become porus or burned through, they are surprisingly cheap when compared to most other parts.
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The going rate seems to be about £550 for a D3LC, for example. Hardly "surprisingly cheap" is it?
 
maby said:
Going back to the original question, is it really worth it? Unless you are full-time liveaboard, I doubt that you spend more than £100 per year on heating fuel - seems to me that you are likely to put in a lot of effort and get back ten or twenty quid per annum - if you are lucky!
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Ah but I've been doing a refit much of the winter and even with hatches opened I've been nice and toasty inside. Just pretty amazed at all that apparently wasted heat.

I'm going to have to rearrange things from the previous owners habits of storing his petrol and diesel in the same lazarette locker as the Eber'. He did have her well insured though and perhaps he should have 'tried harder' as I bought her for a song.
 
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