diesel heater - ? maximum length of exhaust

sarabande

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In another thread

http://www.ybw.com/forums/showthread.php?514146-Bought-a-Chinese-diesel-heater-now-tested

there is a poster looking for a 2.5m exhaust hose.


ISTR some discussion a long time ago about adding extension exhaust pipe to a petrol HOnda generator, and Honda were quoted as saying that back-pressure could adversely affect exhaust gas flow with increased back-pressure.

If that is a problem with a four-stroke motor, should one be concerned that a diesel heater (with uncompressed gas flow) might also be affected by frictional restrictions in the exhaust pipe ?

Do any makers quote a maximum length for any particular orientation, e.g. horizontal or vertical ?
 

Steve_N

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Eberspacher quote 2 metres (actually 6'5") maximum exhaust length in the Airtronic installation instructions. Orientation isn't mentioned.
 

lw395

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If 2m is the limit for the standard exhaust, then making it bigger bore will allow a longer run.
But the big problem on Eberbasto exhausts can be condensation, a long exhaust might need careful lagging or some careful drainage. Burning a litre of diesel gives 2 litres of water or something?
2litres of a greasy acid solution might be more accurate....
 

0711

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Can I please ask, how do you make a drain hole in the bottom of bends to allow condensation to drain out? Surely exhaust gasses will also come out the same hole into the cabin/locker space?
 

wingcommander

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Can I please ask, how do you make a drain hole in the bottom of bends to allow condensation to drain out? Surely exhaust gasses will also come out the same hole into the cabin/locker space?
Normally you would include a water trap , the curley pipe seems popular ,though this could be interesting on a healing yacht . Best practice would be to keep exhaust legnth to a minimum and well insulated. Careful planning of installation position to account for short exhaust runwas a main concern when I did mine
 
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wingcommander

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If it’s just water may be ok, but anything corrosive would need careful draining
Yes I install , maintain gas condensing boilers . The products of combustion are quite acidic to the point that all condensate runs must be non metallic . Back in the dark ages when they first became popular manufacturers recommended 22mm copper. This was discovered to be eaten away by the acid within months of install. Hence the reason I didn't want a loop on my installation.
 

Momac

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I checked my heater at the weekend. The heater has been run only a few times but when run it is only on full power for at least half an hour and it looks like there is no significant condensate escaping the drain . Its more than three years since I cleaned the area when I replaced the ECU on the heater in May 2019.
Perhaps the full power running helps.
1670527430309.png
 

wingcommander

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I checked my heater at the weekend. The heater has been run only a few times but when run it is only on full power for at least half an hour and it looks like there is no significant condensate escaping the drain . Its more than three years since I cleaned the area when I replaced the ECU on the heater in May 2019.
Perhaps the full power running helps.
View attachment 147410
A quality insulated exhaust kept as short as possible will result in the majority of condensate evaporating and being blown out
 

0711

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A quality insulated exhaust kept as short as possible will result in the majority of condensate evaporating and being blown out
Thanks Martyn. But sadly, the positioning of the heater, won’t allow a short run of exhaust pipe.
I’m reconning having a larger diameter of pipe to reduce frictional losses.
 

0711

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I’ve just got back to my boat, and measured the distance from the heater, to the skin fitting and it’s 2.5 metres.
I’ve looked into bigger diameter exhausts and from the standard 24mm, it goes up to 30mm and 38mm.
Can anyone give advice on whether 30 or 38mm would be enough for the 2.5 metre distance it has to run.

I have the facility to manufacture reducers from either size down to the supplied 24mm.

The only bends is the 90’ coming out from under the heater a slow 90’ going up to the swan neck then the final 90’ going into the skin fitting.


Thanks again for everyone’s advice and tips.
 
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