diesel air heater (100.--), who installed?

[JeffJuneau]

This is exactly what my Wallas 1300 looks like mounted on the front bulkhead.

[rsvpasap]

If you decide to use a sound muffler with a "Chinese diesel heater," strongly suggest you use a marine quality stainless steel exhaust muffler rather than the item provided the heater unit.

[NiceAft]

Thanks for the detailed info Jeff.

Third time: how warm does it get in the cabin during those cool nights? Inquiring minds want to know.

[LordElsinore]

The combination Wallas heater+stove was mentioned earlier. I thought this combination heater+water heater looked clever too...

https://wallas.fi/product/viking-combi/

[Jimmyt]

Thanks for the detailed info Jeff.

Third time: how warm does it get in the cabin during those cool nights? Inquiring minds want to know.

Ray,

Depends on the thermostat setting. Most of those units will have enough capacity to easily heat a Mac to comfortable temps.

The Wallas, and the Chinese diesel heaters have a combustion air intake pipe and an exhaust pipe. The flame is fully enclosed in a sealed combustion chamber/heat exchanger so that combustion products don’t wind up in the occupied space served by the heater. Then cabin air is drawn (or blown) across the heat exchanger to warm the air; in-turn warming the cabin. Basically, air blowing across a can with a fire sealed inside.

Since cabin air is recirculated while being warmed, you’ll want to make sure there are some small openings for ventilation air (my washboard/companionway hatch has a gap you could sling a cat through).

Also, the heater doesn’t remove moisture from the air. Heating the air INCREASES the amount of moisture that the air can absorb (lowers the relative humidity). Heating the air and warming the interior surfaces, to get them above the dew point of the interior air, will prevent condensation - by allowing the moisture in the air to stay in the air. But, make no mistake, any moisture that’s actually leaving is going out due to ventilation - not heating.

As humans, we off-gas water vapor constantly. So, if you have the cabin sealed leak-tight, the water vapor will accumulate until you have saturated air (or until you suffocate - whichever comes first). Also, cooking, bathing, dishwashing, etc, release water vapor into the occupied space. So, even if your cabin was dry while you were sailing, when you hunker down for the night in cold weather, you’re likely to see a lot of condensation after awhile as you trap the vapors and build moisture content in the space.

In winter, the moisture content of the outside air is virtually always lower than the moisture content of the indoor air. So, some ventilation will limit moisture content of the occupied space (as well as keeping the occupants alive).

Unfortunately, some climates (and waters) are so cold that, condensation on an uninsulated boat like our Macs is unavoidable - while maintaining an indoor humidity that I can find comfortable. You folks in cold, and/or dry country can probably stand 10-15% RH. My gills dry out, and I turn into a cracking bleeding pile of skin flakes. All that to say, finding comfort and keeping the boat bone-dry in winter can be a challenge.

The small portable propane and butane heaters use space air for combustion and release combustion products to the space. Ideally, these are CO2 and H2O. So, if you use one of these in your cabin, you’ll want to make sure you have adequate ventilation. You will be adding a good bit of moisture WHILE heating. This is one big difference between the Wallas and other heaters that use sealed combustion and heat exchangers.
Probably missed your question, but thought I’d take a shot.

Jim

[NiceAft]

Jim, I understand all of that. Without rereading, I think it was stated the air is dried by the unit.. I just want to know how warm it gets.

The unit is being used in an Alaskan environment. We know that it gets cool in the evenings. So, how well does the unit work? That answer is explained with a temperature. Maybe the temperature was never checked? I know on our recent Chesapeake trip, the air conditioner cooled the boat down quite well. I never checked to see how cool it got. That maybe the case here; never checked a thermometer.

[Jimmyt]

Jim, I understand all of that. Without rereading, I think it was stated the air is dried by the unit..

Psychrometrics is a field that is often misunderstood. Stating that a heater is “drying” air has always made my blood run cold.

But, it probably only matters to me, so sure…

[JeffJuneau]

I am having fun trying to remember my 50 year old lessons on Boyles Law and gas partial pressures from this discussion thread. I believe I understand your point, Jimmy. Of course, in an enclosed system, the number of total moles of H2O (H2O gas phase +H2O liquid phase -lets say at sea level & 20 degrees C) stay the same if you increase or decrease temperature. The moles of H2O that are in the gas phase as water vapor as opposed to moles in a liquid phase will shift when temperature goes up or down in that closed system. But the Mac example I described was absolutely not a closed system. You are drenched with rain from sailing on a typical 100% humidity day in SE Alaska at 10 degrees C and go into the cabin of your mac and close the hatch, to dry off. Now the total number of moles of H2O in the cabin is all the rain water on your clothes +h2o sweat,+ water vapor in the air+ condensation on other interior surfaces. You can either turn on your Buddy heater and vent the mac or turn on your heat exchanger heater and vent the mac exactly the same amount. If you turn on your buddy heater to 25 degrees C, good luck… come morning (if your able to keep it on all night) you will still have almost all that moisture in the boat on your clothes even with venting. With the heat exchanger at 25 degrees C, your clothes and rain gear are dry long before morning though it is still 100% humidity outside at 10 degrees C. The total moles of H2O in the cabin, vapor + liquid phase are decreased…a lot... and relative humidity has dropped to less than 50% inside. Okay, so your not actually “drying” the air in the context of a closed system with the heat exchanger, but your reducing the total moles of H2O vapor+ liquid phase in the cabin in the context of a real world vented system. That is my understanding, but I love being corrected.

Oh, NiceAft, to your question. The heating performance W 1300 in my boat depends on a lot of factors, especially including how much moisture there is in the cabin air, how long the heater is running, how close I am to the blower outlet, if I am in the rear birth or sitting at the table. I can just say, that for me, in spring, summer, and early fall it works well. I think I read that it is similar to a 1,000 watt space heater. I bet that Todd at BWY can give you a more quantitative description of heating performance, since he as installed a lot of these. Jeff

[kurz]

A question

When I install the diesel air heater outside, on the back. I want to take the air from inside the cabin. So the nearest is to take it from the compartment in the back where the flotation foam is inside.
Is it a problem taking bad air from there? Becouse it stays humid and with no ventilation there?
Or is this no problem becouse the air circulates in the whole boat anyway.

Thanks

[Jimmyt]

I am having fun trying to remember my 50 year old lessons on Boyles Law and gas partial pressures from this discussion thread. I believe I understand your point, Jimmy. Of course, in an enclosed system, the number of total moles of H2O (H2O gas phase +H2O liquid phase -lets say at sea level & 20 degrees C) stay the same if you increase or decrease temperature. The moles of H2O that are in the gas phase as water vapor as opposed to moles in a liquid phase will shift when temperature goes up or down in that closed system….

You nailed it.

You are correct by noticing the difference between what you are calling “open” and “closed” noting that there is more to the real problem.

At 10 deg C (50 deg F), saturated, air has about 51 grains per of moisture per pound of dry air [gr/lb].

If we warm that “outside” air to 25 deg C (77 deg F), the resulting relative humidity will be about 37%. But, we have additional moisture coming from wet clothing, people breathing, etc, so the steady state relative humidity settles out to something like 50% (your number here, not possible to accurately calculate without some idea of vent rate and amount of wet clothing, number of people etc). At 77deg F and (assumed) 50% RH, the moisture content of the “inside” air is 69.5 gr/lb. So, the “drying” is coming from the ventilation air, because it has a lower moisture content than the cabin air (69.5 gr/lb inside vs 51 gr/lb outside). By warming the air, we cause it to be able to absorb more moisture, and carry that additional moisture outside as the ventilation leaves - thus providing the drying effect.

If we do this with a buddy heater, we are constantly adding moisture from the combustion process, whereas the closed combustion heaters vent the combustion water vapor to the outside. This can make a big difference.

[JeffJuneau]

Hi Kurz, I don't think any of the diesel/kerosene heat exchanger type heaters we are discussing in this thread are designed to mount "outside" of the cabin. They simply are not capable of handling the weather. They mount inside the cabin, and have the outside intake and exhaust for combustion gasses accessed through the hull or deck. I might not have correctly understood what you were proposing to install, or am not familiar with the products you are describing.

[rsvpasap]

I have a Wallas 800D Diesel stove/heater with the blower lid. I've had it for about 5 years and it has 9,740 hours of use. I'm in the Pacific Northwest and I cruise year-round, actually, I prefer the winter. My 2002 26X is partially insulated with EVA foam and cork. The heater is rated at 950-1450 watts. It will raise and hold the cabin temperature approximately 35 degrees Fahrenheit. When it's really cold, below 25 degrees Fahrenheit, I sometimes supplement in the evenings with a Olympian Wave 3. Were i doing it all over again, I would probably purchase the two burner model which is rated up to about 1900 Watts. The only other heater I personally would seriously consider for cold weather cruising on a small boat is a Refleks 66MK. Unfortunately, that requires a hole in your cabin roof. Appealing things about the Refleks include the fact that it can be set up to be gravity fed, thus requiring no electricity, and that it also has an integrated cooking surface. In the winter, I really like slow cooking on the diesel stove with an omnia stove top oven.

[JeffJuneau]

I've heard great reports about the Wallas stove/heater. I just couldn't come up with a way of allowing the galley to continue to slide in my 26M with that system, or I might have ended up with one like yours.

[LordElsinore]

From what I can tell, the Wallas heater pulls combustion air in and pushes exhaust out of the same sleeved through-hull. Am I right? That's pretty cool. I wish the chinese heaters did that - one less hole to put in a boat that way. But they really aren't made with boats in mind I think, since they primarily seem to be marketed for vans/cars/trucks

[JeffJuneau]

Yes, that is the way my intake/exhaust is configured. It is the same approach used on a residential Toyostove Lazer or Monitor kerosene heaters.