Wallas stove/heater back draft

N

nwboater

New member
Is the Wallas DT stove/heater designed to operate while underway? Earlier this summer we left the Wallas running on low for warmth while cruising. But when our speed increased to around 25 mph, we saw smoke and could smell unburnt fuel. I assumed it was a "back draft" from the exhaust port, so we turned if off immediately. Otherwise, it works great when we're not moving. Is there a solution for this problem? It would be nice to use the heater when underway --
 
With the 4 boats which had the Wallas stove, I never ran them when underway. I did have a couple of back draft instances when we had a strong breeze from the Starboard side. I think if you put a cowl vent (SS--not plastic!) over the exhaust port, that would go a long ways to preventing back draft when running fast. That would have to be one of the larger cowl vents--3 to 4 inches wide. Although the Wallas is a forced draft--it is not a high pressure or high volume fan driven draft. I had a "Pro Heat" which was originally designed for on the road trucking fire box/boiler, circulating water heater, with a strong forced draft blower--and it never had a problem, even in 60 knot winds.
 
Hi Bob, I'm familiar with marine diesel heaters, such as Kabola (hydronic) and the larger Wallas forced air units, but new to the Wallas stove/heater combo. I think you're suggestion to add a cowling over the exhaust vent makes good sense. I'll do that and see if it works underway.
 
I had the same issue. Talked to a technician who works on them last year at the boat show. He said C-Dory really cheaped out on the installation. He said the stove requires a loop in the exhaust pipe and C-Dory was known to have not done that. I installed the proper pipe last year but sadly can't tell you if it worked. I've been turning off the stove after breakfast on the way to the fishing grounds.
 
Thanks for that tip Rob. I called Scan Marine today but no one answering… sounds like I need to add some extra pipe for a “loop”…that plus cowl over the exhaust port should resolve back draft from occurring.
 
It seems sort of dumb, but when I had mine opening a window just a touch solved some of the fume issue for the most part. But with that said, if the conditions were choppy and you had a bumpy ride, the burner in these will not produce a consistent enough flame resulting in the flame sensor sending a signal to shut things down leaving a bunch of unburned fuel in the combustion box. And then in shut down mode, it turns on the glow plug to burn whatever fuel is in there....they can make a lot of smoke! Anyway, that is another possibility of what is going on. I have found that if it is choppy and there is hull slapping, then running the stove wasn't worth the trouble.
 
Scan Marine, yes, the guy I talked to that night at the boat show works there. I happened to meet him when there were very few people at the show so we nerded out on Wallace maintenance for a solid hour. He also said the biggest mistake people make is to run kerosene in their stoves. Not only does diesel have about 3% more BTU's that kerosene, diesel has the proper lube in it to keep the tiny little fuel pump lubed, and also diesel doesn't go bad nearly as fast as kerosene. He was pretty intense about running diesel. He also mentioned the manufacture specifies diesel.

He got me pretty tuned up on how to disassemble and clean the burner and "jet" as well as troubleshooting and how to reset the computer. Mine's been running tops ever since.

Oh, and in the off season, I go out and run my stove as hot as it will go for about 15 minutes at least once a month.

Don't forget the pipe insulation for the exhaust pipe. It's special designed for high temp, probably fiberglass.

Rob
 
While Captain Bob recommends a 3-4” cowl vent, I used a much smaller one, 1 1/2 - 2”; I can’t recall which. But with a little cutting, filing, and reshaping, a smaller one will adapt nicely, allowing you to use two of the existing exhaust port screws for attachment. I’ve had mine on for years and it works well.
 
I made a new cover for mine. I most likely won't post results for on the water testing for a few months but will keep you all posted on how it works. The cover is stainless. The standoffs are 3/8" stainless tubing cut to 1/4" so the gap between the factory outlet and the new cover is 1/4".

Before:
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After:
Cover_plate_1.sized.jpg

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This is kind of a strange thread for me to read, as I’ve had more than my share of Wallas issues with the old Wallas model 95, but I’ve never experienced, the Wallas having operational problems, caused by cruising fast on plane & didn’t realize it could happen. I think possibly this was due to our rarely exceeding 17 mph, while the Wallas was running. On the other hand, I do know, we have been in winds of up to 50 mph at anchor & many times at 20 to 30 mph at anchor or a dock & operated it in very rough seas with again not a problem, other than years ago, when I still had the old 95 model & the rough water, caused the control board, which was poorly secured to short out. I don’t have a deflector over the exhaust outlet.

After replacing the Wallas model 95, during a 2012 SE Alaska three month cruise with the Wallas model 85, like Gary, it’s been virtually trouble free & that’s 12 years now.

Jay
 
MOOSE":2yzmst0q said:
While Captain Bob recommends a 3-4” cowl vent, I used a much smaller one, 1 1/2 - 2”; I can’t recall which. But with a little cutting, filing, and reshaping, a smaller one will adapt nicely, allowing you to use two of the existing exhaust port screws for attachment. I’ve had mine on for years and it works well.
Click to expand...

Did you have the backdraft issue before you installed and do you run diesel?

I’m going to switch from kerosene to diesel. Kerosene I’ve used for years, due to “advice” from the local wallas dealer. Getting a backdraft/ chocking fuel smell way to often.

Keep the updates coming
 
kaelc":1h3pkeqn said:
MOOSE":1h3pkeqn said:
While Captain Bob recommends a 3-4” cowl vent, I used a much smaller one, 1 1/2 - 2”; I can’t recall which. But with a little cutting, filing, and reshaping, a smaller one will adapt nicely, allowing you to use two of the existing exhaust port screws for attachment. I’ve had mine on for years and it works well.
Click to expand...

Did you have the backdraft issue before you installed and do you run diesel?

I’m going to switch from kerosene to diesel. Kerosene I’ve used for years, due to “advice” from the local wallas dealer. Getting a backdraft/ chocking fuel smell way to often.

Keep the updates coming
Click to expand...

Check with Scan Marine before you switch. Some models are made for diesel, some for Kerosene. If you have backdrafting issues on kerosene, they may be even worse on #2 diesel, if you have a kerosene stove/heater.
 
Quick non scientific update. I took my boat out a week ago for its spring commissioning and tested out the heater underweigh. The heater with my new deflector worked just fine with the windows all closed and the back door open traveling in the mid 20s. The second I opened the captain window the heater started smoking.
 
Opening the front window (side?) changes the pressure dynamics in the cabin. However, I don't think of many times you would have the heater on, running in 20's with window and back door open.
 
Agreed Bob. The pressure delta is just a bit more than the exhaust pressure that the little heater makes is what I'm thinking. We were coming back to port, I opened the captain window to snap the fender onto the quick disconnect (another mod I highly recommend. Makes installing the front fenders take seconds and you can do it from the inside, and on the starboard side, do it even while sitting!).
 
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