how warm will become a Webasto exhaust?

[Erwin Swart]

Hi all,

currently installing a webasto heater.
wondering how warm the exhaust will become. The exhaust will be insulated but will it become so hot you cant touch it?

hope somebody can tell me more

grtz,
erwin

 

[alteredoutlook]

Surely that would depend upon the thickness of your insulation?

Even with reasonable levels of insulation it still becomes hot! Eber recommend insulation and then another metal outer tube - and even this is warm to the touch.

 

[pcatterall]

Warm!!..... no HOT!! hot enough ( without insulation) to ignite wood if it touches it! If the exhaust can come into contact or close proximity to anything vaguely inflammable it needs insulation and then ( as stated ) a cover over that. The answer to your question is entirely dependant on the amount of insulation you fit.

 

[davidwf]

Mines not Webasto but a Mikuni, I can hold onto the exhaust lagging OK so not that bad. I did find on my previous boat with the Ebber that the metal tube added over the outside of the insulation seemed to be much hotter. Suspect it was trapping the heat rather than allowing it to dissipate.

 

[David2452]

I regularly measure the exhaust gas temperatures and they are generally around the upper 200s / early 300s, obviously the tube will try to equalise to that temperature. It is not about thickness of insulation, but the type and quality, the sock provided by Webasto in the kit allows some heat dissipation rather than building it up and then transferring it to another insulated outer metal tube as Davidwf suspects. It is usually possible to touch the so insulated Webo one without discomfort about 4 inches from the heater.

 

[Tony Cross]

Don't know if this helps but the Amel Super Maramu next to me this winter has an Ebberspacher Vorsprung Durch Technik jobbie with an exhaust amidships pointing right at me. I was a tad concerned when he first fired it up about what the hot exhaust would do to my topsides so he invited me to put my hand over the exhaust. What a surprise! It was only just warm as it came out of his boat and within about 6 inches I couldn't feel any heat at all.

 

[lw395]

It needs to be well oer 100 degC to avoid filling with condensation.
for every litre of diesel it burns, it has to lose 2 litres of water as steam.
That's why they are lagged, rather than using the heat of the exhaust.
Vehicle systems just let the water drip out the bottom of the silencer.
Some boats may have a catch tank or be able to let the condensate drain overboard somehow, but that's not the normal way on a sailing yacht.

 

[LadyInBed]

If the exhaust is that hot, is it possible to pass it through some sort of radiator to utilize the heat?

 

[pcatterall]

Blimmy that's a lot!! So overnight running if you fit one of those drain things ( good idea in case water splashes in?) you may have 10 litres of water in the bilge

 

[lw395]

Blimmy that's a lot!! So overnight running if you fit one of those drain things ( good idea in case water splashes in?) you may have 10 litres of water in the bilge

If there is a drain, it risks letting a) carbon monoxide and b) smells into the living space of the yacht, unless it is designed right.
Hence the lagged hot exhaust is the popular easy answer.

10 litres of hot water in the bilge would also negate the wonderful drying effect of the Eberbasto.

 

[David2452]

If there is a drain, it risks letting a) carbon monoxide and b) smells into the living space of the yacht, unless it is designed right.
Hence the lagged hot exhaust is the popular easy answer.

Not so, the drain is simply a condensate drain and will not allow gasses to escape at the pressures present in evaporator heater exhausts, only liquid that replaces the liquid already in its trap and even then it is minimal. On a correctly installed heater there should be no scope for exhaust gasses to enter the living area in the event of a leak anyway. Fact is, even without lagging, unless in a very long exhaust condensation accumulation is minimal and easily coped with by a condensate drain fitted at the lowest point and the heat of the exhaust gasses and tube which are quite high.

 

[David2452]

If the exhaust is that hot, is it possible to pass it through some sort of radiator to utilize the heat?

Possible? yes, that's what the heat exchanger does after all. Desirable or even sensible, probably not, especially using some heath robinson home made effort. Even Webasto, Eberspacher, Mikuni et al stipulate replacement of the heat exchanger at 10 years or after a serious overheat, obviously there is a measure of self preservation in that stipulation but a fabricated effort transferring exhaust heat to recirculated air is frought with danger, now a water heater, maybe.

 

[David2452]

Blimmy that's a lot!! So overnight running if you fit one of those drain things ( good idea in case water splashes in?) you may have 10 litres of water in the bilge

No, the condensate drain hardly ever drips at all on those it is fitted to, you are right that it would let any splash water out though, not that you should get any in with a proper gooseneck.
Condensates only form on the exhaust walls when the heater first starts up, then the exhaust gasses remove it during running, it can form when cooling and the condensate drain will get rid of the few drops, otherwise it will be flashed off during the next run so does not build up. The acids contained in the little bit of residual condensate are possibly the biggest enemy to the integrity of the exhaust but as they are stainless steel (or should be) even that is only a long tem issue, I have seen split exhausts at advanced (and early) age but never one corroded through.