Where to locate furnace exhaust

[pcg]

I’m soliciting more advice. I’m trying to decide where to place a forced air furnace in my 22 Cruiser project boat, and to some extent that depends on the best place for the exhaust gasses to exit. It would be nice to have exhaust gasses exit straight up a pipe through the rear cabin roof, but that will interfere with other items, like a dinghy stored up there and a stove vent.

Some of the furnaces I’ve looked at come with thru-hull fittings for the exhaust gases. I’ve also seen some instructions say that the exhaust gas should not exit underneath a window that can be opened. That starts to narrow things down.

I’m concerned about exhaust fumes getting drawn back into the boat with windows open, either when anchored or underway. I’d like advice or comments regarding the best place to route exhaust gasses, other than the rear of the cabin roof.

Thank you.

 

[hardee]

Most of the exhaust outlets are on the Starboard side, just aft of the sink drain. That stbd window does not open, and generally when anchored the breeze will keep the bow pointing into the wind which would carry the exhaust away to aft.

I would be careful to be sure there is clearance away from directly below the midship cleat to allow for using the furnace when at a dock without cooking your fenders.

Harvey
SleepyC :moon

 

[colbysmith]

What Harvey said. At least that's pretty much where mine is. I have my Webasto mounted underneath the sink. My exhaust port is actually ahead of the sink drain. I've had no problems with exhaust coming back into the cabin with my helm seat window open, although I normally leave that one shut at night because of my exhaust's location. Colby

 

[pcg]

Thank you both. Very helpful!

 

[Sea Wolf]

I know you said you didn't want comments about putting the exhaust stack on the rear of the roof, but, to me, at least, that's the most logical, safest place on the boat.

Would placing it there inside a second tube (double insulated) keep your inflatable (and anything else) protected from the heat?

At the same time, the carbon monoxide would be vented at the best possible point on the boat.

Could be a simple stainless or painted steel tube around the usual vertical self-drawing flue tube with the usual top fitting hidden inside.

e.g., put another tube around something like this:



Joe. :teeth :thup

 

[pcg]

Would placing it there inside a second tube (double insulated) keep your inflatable (and anything else) protected from the heat?

Possibly so. That's a good idea. Another reason I need to make a dinghy decision so I can get one and put it up there and ponder some things.

Thanks Joe.

 

[hardee]

Another advantage of the roof stack is that you get the exhaust heat into the cabin for the length of the stack up to the cabin top.

Harvey
SleepyC :moon

 

[Sea Wolf]

Another advantage of the roof stack is that you get the exhaust heat into the cabin for the length of the stack up to the cabin top.

Harvey
SleepyC :moon

And, you can put a small blower facing the tube and maximize the heat exchange from the flue to the cabin air. I used two computer "muffin" fans.

The blower will not only give you more heat in the cabin, but also reduce your final exhaust temperature.

Joe. :teeth :thup

 

[Discovery]

You don't say what type of forced air furnace? I put an Espar Airtronic D2 in 'Discovery'. It's under the galley cabinet, behind the sink. I also have a Wallas Stove. I exited the Espar exhaust through the starboard side above the walkway and just behind the Wallas exhaust. I don't have to worry about burning fenders as the exhausts are above the walkway and above where fenders are usually placed.

 

[pcg]

You don't say what type of forced air furnace?

I'm planning on using this propane furnace:
https://www.propexheatsource.com/heater ... 0-furnace/

 

[hardee]

Propane has it's own set of conditions, tankage, storage, venting, servos, just seems like too much "stuff" for a C-Dory. you may hear other comments about it, but for me, I would not consider it on my boat.

Harvey
SleepyC :moon

 

[pcg]

Thanks for all the suggestions re. where to locate the exhaust. I'm still holding out for some way to get it on the rear of the cabin roof.

 

[lloyds]

I put a wallas 1300 in the last C Dory 22 I had and went to quite a bit of trouble to make it unobtrusive and route power, fuel and air to best advantage. If I were to do it again I would go the simpler route and just set it on the counter in the starboard rear corner, pointed forward. That way exhaust just goes straight up through the roof, fuel sits on the rear of the shelf under the counter. Really simple, shouldn't take more than an hour so to install. And I think that would have given a better airflow to where you want it, toward the windshield and the v berth.

 

[thataway]

I agree that there are multiple reasons not to use a propane heater on the C Dory. Be use you know and follow the ABYC recommendations for storage and use of propane, the shut off, sniffers, hoses etc. It is far more complicated than a simple, diesel heater, which uses non explosive fuel. One of the biggest issues is to vent the propane locker overboard. It could be done with a fully sealed aft lazaretto, which. vented over the side at the bottom of the locker.

I used propane fuel for the stoves on our larger cruising motor sailors. But even there, there are many precautions to be taken. Once you have witnessed a propane explosion on a boat, it will leave a lasting impression! I have seen too many--and too many people injured or killed.

 

[ssobol]

... Once you have witnessed a propane explosion on a boat, it will leave a lasting impression! ...

I would say that probably applies to any explosion on a boat, not just propane.

 

[hardee]

... Once you have witnessed a propane explosion on a boat, it will leave a lasting impression! ...

I would say that probably applies to any explosion on a boat, not just propane.

I agree, but, (and I am guessing here) that propane is the most frequent cause for on board vessel explosions. I have only seen one, but it took a 34-36 foot pilot house sail boat and turned it into mach sticks down to the water line and spread pars over a football size area in our marina. One fatality, one serious injury, and 2 other folk injured, on of them blown into the water. There were about 6 other boats with major damage.

All from a simple propane tank change, not done quite right.

Harvey
SleepyC :moon

 

[pcg]

Actually, most boat explosions are caused by gasoline…
https://www.boatus.com/seaworthy/magazi ... aboard.asp

As the original poster for this thread I was careful not to mention propane, as the merits of propane vs. diesel was not my question, and I knew the p word wold derail the post. So my bad for responding to someone’s question re. what kind of furnace I was considering, and thus allowing this to happen. In retrospect that’s not so bad, as I think it’s good that any thread that discusses the use of propane also discusses how to use it safely.

There are protocols for using all of these energy sources safely and, if you don’t follow them, you are setting yourself up for a heap of trouble. Carelessness causes accidents, not gasoline or propane or electricity, all of which can be deadly. Personally I am satisfied that I can safely use propane aboard my boat, as I have safely used it on my RV for decades. I believe I understand what is required to do so and am capable of implementing a safe propane installation.

If anyone else comes upon this thread and wants to learn more about how to use it safely here's some information to get you started. The first is an intro, the second two go into more detail, and the fourth is a copy of the ABYC requirements:
https://www.westmarine.com/WestAdvisor/ ... tallations
https://www.passagemaker.com/lifestyle/ ... and-safety
https://www.passagemaker.com/lifestyle/lp-gas-systems
https://archive.org/stream/gov.law.abyc ... 3_djvu.txt

Everyone I personally know who owns a cruising boat (only two as I’m new to this so I don’t have many boat friends yet) uses propane on their boats. One is a Grand Banks and the other is a Tollycraft. I believe propane came standard with these boats, as it does on Ranger Tugs, which many are familiar with. I’m guessing there are millions of RVs on the road in this country that use propane.

There is no question that propane is a dangerous substance, as are gasoline, natural gas, and electricity. Propane is more dangerous than gasoline because propane is heavier than air, and will sink to the bottom of a bilge, cabinet, etc. whereas gasoline fumes will rise and are much more likely to dissipate if conditions are right. Diesel is inherently much safer than either because it is not explosive at room temperatures.

The bottom line in is that there are lots of careless people out there. Every time I go to the Garibaldi marina, I shudder to walk by the commercial fishing vessels and look inside the cabin windows. Besides crap piled everywhere there is often a propane bottle, not in a locker, attached to a catalytic heater and a stove. These are the situations that make the news and give propane a bad name.

Most of us are comfortable being around gasoline, natural gas, diesel, and electricity because we use one or more of these daily and society in general is comfortable with them, despite spectacular failures. Unfortunately, I witnessed a car fire and explosion two days ago, yet I am not afraid to drive my car today. In part because I believe I will not make the mistake that caused that event, but also in part because I’ve become comfortable driving around with 20 gallons of gasoline under me.

Unless you live in a rural area like me, where most people heat and cook with propane, your only exposure to propane is likely the evening news. If you aren’t comfortable with propane, or don’t feel you can use it safely, then DON’T USE IT. It is not to be trifled with!

Thanks again for the suggestions in response to my original post. And thank you to those who took the opportunity to ensure that readers of this post are aware of the requirements for using propane safely.

 

[pcg]

And, if you're wondering why I would go to all the trouble required for a proper propane installation, it was initially because my wife and I like to cook with propane. Then when I started researching diesel heaters I learned about the disadvantages of diesel vs. propane for heating. Specifically:

1) All diesel heaters except the Wallace are relatively much noisier than a propane furnace. I like quiet, both at marinas and at remote anchorages.

2) Diesel heaters use more electricity, primarily because furnaces cycle on and off, and when a diesel heater restarts it draws a lot of current for several minutes.

3) Diesel heaters require periodic (every year?) maintenance. The propane furnace in my camper has been running for just over 20 years with absolutely no maintenance during that time.

 

[hardee]

Paul, Nice write up and good links. Thanks for that and for me to learn some new stuff today. It sounds like you know what you are doing with the propane. I have had a motor home and a trailer, both with Propane fuel devices, (fridge and furnace and water heaters). The difference with abouve ground vehicles and boats is that RV's and trailers are not sealed as tight as boats, and that if propane does leak on board those, it has a place, or can "drain" out to outside air and dissipate. In a boat, it will only collect in the lowest areas and there is where the hazard exists.

My Wallas is going on 14 years and has worked perfectly in all that time. My RV's, went in for an annual check of the propane systems to be sure they were working as designed, no leaks and valves opened and closed. When I used to cook, I liked the gas way better than electric. Still do, but have huge respect for that. I lost a whole family of relatives due to a gas leak years ago. Didn't really endear me to the gas heating and cooking then, but I'm sure it is safer now.

As to propane on a C-Dory, there are a few systems that have been installed on our boats, so you should be able to find threads and pix of those with the "search" box.

Best in your progress, stay safe.

Harvey
SleepyC :moon

 

[pcg]

Thanks Harvey! You and others are making my boat restoration possible. The C-Brats forum is a treasure trove of valuable information and wonderful people!

The difference with above ground vehicles and boats is that RV's and trailers are not sealed as tight as boats, and that if propane does leak on board those, it has a place, or can "drain" out to outside air and dissipate. In a boat, it will only collect in the lowest areas and there is where the hazard exists.

Very good point.