Diesel heater exhaust

[C-Wolfe]

I’ll be installing a forced air diesel heater inside the galley cabinet and debating about where to install the exhaust port. I have a Wallas stove with the exhaust port right below it, just above the waterline, very similar to my previous 22 cruiser. I had in a few rare occasions, in both the current and previous boat, got some back drafting of the exhaust inside the cabin. It happened while underway with some good wave actions, water will be temporarily blocking the exhaust port forcing it to leak where it can, inside the cabin. It doesn't last long but it does get quite stinky inside, I normally just shut it down when this happens.
In an effort to avoid this, I’d like to install it much higher, the best location I can come up with is high between the side windows, that will have the pipe running in the forward corner of the head compartment. I’m also hoping that will radiate a bit of heat inside the head as a bonus. I’m planing to increase the size of the pipe a bit to reduce flow restriction of a smaller pipe. A good portion of it will be going straight up, I’m not sure if the stack effect will be helping it enough to be noticeable. I will also be adding heat shield to any nearby material.
I don’t really see where that approach will create any issues, but if if I’m missing something, please let me know.

[Peter & Judy]

I have the same setup and only rarely have I had problems. I installed my exhaust, which was a Wallas exhaust pipe about a foot away just above the waterline. The only problem that I have had is with water getting into the exhaust ports in heavy seas. So I made up a couple of corks that can close off the pipes.

[C-Wolfe]

Peter & Judy, thanks for your comment. Like you, it is a very rare occurrence but it does happens. right now I feel like I have an opportunity to improve on it with the added bonus of getting a bit of heat inside the head compartment.
I’m running it through this site first to make sure I’m not missing something that will make me regret doing it this way.

[colbysmith]

At least on Webasto's, it calls for the exhaust to be below the heater. I think this is to keep water out of the burner box.

[C-Wolfe]

Thanks Colby, I’ll try to minimize the chance of getting water inside the burner as much as I can.

[T.R. Bauer]

Many larger boats are going to have an install with the exhaust higher than the furnace. It is because of the water as noted and there are work arounds....not really that big of a deal.

[ssobol]

[T.R. Bauer]

[thataway]

My experience in some larger boats, is that they have a forced draft (exhaust pressure increase) to avoid water in the system of the burner, and to resolve issues with the different heights of the furnace fire box and exhaust port.

It may vary from brand to brand.

I have always lagged the exhaust pipe of my heaterx/Wallis Stove, to prevent burns or incendiary accidents. The old lagging used to be Asbestos, now it is fiberglass. Some will even put a plaster finish on the lagging--I have just left mine as knitted fiberglass wrap.

[tsturm]