Espar/Webasto Location

[ak-guy]

I have a small 26' trawler and I want to install a Espar type forced air heater. There is not a lot of choice in location. I have a fairly large hold under the aft deck, it is open to the engine area. My batteries are also located in this area, 235 amp hour house and 100 amp hour start, all open wet cells. I will have very well controlled charging both off the alternator and a small AC charger. I would really like to locate the heater in this area but I am concerned about the batteries off gassing hydrogen. Can I provide enough passive or active ventilation to mitigate the safety concerns or should I just forget about it.

 

[DHeckrotte]

Adequate ventilation is appropriate for combustion air and fresh air distributed by the Espar, and for off-gassing.

I'm under the impression (it was not installed while I had the boat) that the air the Espar is heating, and that you'll be breathing, is pulled directly into the Espar. Mine was in the sailboat lazarette which communicates pretty directly with the engine space and the bilge.

 

[Ka_sea_ta]

You should probably vent the area if for no other reason to provide air for the furnace. If your really concerned replace the the batteries with AGMs Having access to the engine room probably provides enough air to reduce the hydrogen concentration but may not be adequate for the furnace...

 

[Marlinmike]

Right off the top of my head this does not sound like a good idea putting the furnace in the bilge area, but a better source then me would be a call to the manufacturer. All the best.

 

[ksanders]

OK, I've put in lots of heaters in a variety of sized boats.

If your 26' trawler is diesel then you can put it in the engine space. If it is gasoline powered you can't since the espar is not ignition protected.

Any forced air heater is going to have two cabin air ports on it. One is return, one is hot. Make sure you route both into your cabin somewhere. These are sealed from the combustion air system.

The espar is also going to have an exhaust and combustion air port. Exhaust goes through an exhaust fitting in the hull or transom. I've never plumbed the combustion air, just use air from whatever space the unit is in. Make the exhaust air run as short as possible and insulate the pipe with the sleeve you'll get in the installation kit.

Best of luck and enjoy.

 

[Moonfish]

Wallas forced air diesel heaters can be mounted in lockers or spaces inside the cabin. We have the largest Wallas, the 40 Dt, but the 20 or 30 Dt models would fit your boat. Very quiet and efficient, our slip neighbor can't even tell when ours is on. We don't sell them or make any money from them, but made a video of our installation:

Pacific NW Boater - PRODUCTS - Wallas Diesel Heater Install

 

[Roamer Blue]

1) If you want to worry about hydrogen off gassing, why aren't you worried right NOW about the accumulation, or not, of an explosive atmosphere? Lots of other things down there to spark it off, before the furnace arrives?

2) the furnace has 2 separate air flows, the intake and return from/to the living space via the heat exchanger portion, and the intake and exhaust for the combustion process.

Don't be pumping engine room/bilge air through the heat exchanger and into the living space.

So long as the engine room/bilge space is open to the outside, the unit will draw air satisfactorily on its own. A proper exhaust system requires focused attention and design, to get the combustion gases properly out, leak free, and of great importance, away from being sucked back inside the boat.

RB

 

[koliver]

I had an Espar D7L mounted beside the Port diesel engine so close that in order to access the high pressure pump on the engine, the Espar had to be removed.
The thru hull exhaust fitting was at the end of a very short run from the outlet of the Espar to the side of the hull, just below the overhead of the ER.
In some the exhaust fitting doubles as an air intake, one smaller outlet inside the bigger inlet, That way you are not using ER air for combustion, as that air is brought in directly to the Espar from the outside. In others, mine included, combustion air came from the ER.
My batteries are between the stringers, just ahead of the port diesel, as close to the Espar location as possible. That geography existed from the moment a PO installed the Espar until I took it out and gave it away (maintenance was way too expen$ive) without issue.

Both Espar (Eberspacher) and Webasto are Bus heaters, designed to hang under the floor of a German or Scandinavian Bus, so open to the snow covered road below. Thus they may only incidentally be ignition protected. Worth checking, especially if your boat is Gas powered.

 

[Nomad Willy]

Ak-guy,
I put one (Wabasto) in my Albin under the cat walk just to stbd of the helmsman's right leg. Very short exhaust right through the hull. My present boat has a maximum length exhaust (10') to the stern. Either exhaust length works just fine. With the Albin I had one hot air outlet and w the Willard two.

You can burn diesel. We did for 8 years but plugged it up really bad. Sure Marine recomended we burn kerosene. Installed a dedicated 2.5 gal (about 2.5" thick) tank on the outside of the cabin. I used a combination of copper tube and hose fuel supply line. I plumbed in an 8" shunt hose w a "Y" and a drain valve at the end. Ideally one would route the supply line so there are no "dips" where water ect can get trapped and cause trouble later. The doseing pump is small and sensitive to variations like air so make your connections air tight. Sure Marine has excelent hose clamps for that. My i-pad battery is down to 10%. Be back home in several days for more input.

PS even if you plumb for gravity feed you need the dosser pump installed.

 

[CaptTom]

I have a similar unit (Planar) and the exhaust scares the crap out of me. It gets dangerously hot. The run is probably 6-8' in my installation, and it's behind wooden cabinetry. I've insulated it with the heat shield material used for race car exhaust manifolds, and made sure it's well away from any wood, but I'd still never leave it on unattended.

Moral of the story: make the shortest exhaust run humanly possible.

 

[Nomad Willy]

CaptTom,
What does Planar say? Sounds OK to me. We leave our Wabasto on for hours while we are away. I was polishing my Albin one day and the Wabasto started up. I think it had been on for weeks. On Willy the Willard I turn off the master power switch on every shutdown .. and the fuel shutoff valve.

The only problem I've had w the Wabasto is startup fuel delivery issues. I left the filler cap off in the rain on the last cruise so need to finish flushing out the water. But in the past I had issues because I had it plumed into the engine fuel manifold. It needs a dedicated fuel supply.

 

[CaptTom]

CaptTom,
What does Planar say?

The manual says "When installing the exhaust pipe, be mindful of its high operating temperature... To protect some parts of the vehicle (electric wiring and other harness) from high temperatures, there must be heat insulation installed."

and "A vehicle that uses the heater shall be equipped with a fire extinguisher."

When I first ran it, the oils from the manufacturing process burned off the exhaust pipe immediately, which was smoky and a bit scary. I kept a close watch on it and shot some readings with a laser thermometer. 700+ degrees! That's when I bought the extra insulation.

As I said, the exhaust pipe runs below and behind some wooden cabinetry. Even with the insulation, I can't bring myself to leave something like that unattended on a boat.

If I had it to do over again, I'd install it right next to the exhaust outlet, with lots of open space around and especially above the exhaust pipe. I'm seriously thinking about removing and re-installing it for that reason.

 

[sunchaser]

Not sure about forced air units, but the hydronic units I am familiar with have the exhaust pipe enclosed within the air intake pipe. This cools the exhaust run considerably. The pipe system is then wrapped with insulation.

 

[ksanders]

Not sure about forced air units, but the hydronic units I am familiar with have the exhaust pipe enclosed within the air intake pipe. This cools the exhaust run considerably. The pipe system is then wrapped with insulation.

You are correct, certain brands of furnaces have a much safer exhaust system.

Espar forced air and hydronic units uses a single tube exhaust system which results in very high exhaust pipe temperatures.

Wallas is one brand of furnaces that use a tube within a tube system like Sunchaser described.

The inner tube is exhaust and the outer tube is intake air. This system results in a "exhaust" pipe that is not so hot that a person would get burned by touching it, reducing installation challenges.

 

[DavidM]

Does anyone know of a boat exploding due to hydrogen vapors?


This concern is always voiced about ignition sources close to a battery bank but I have never heard of it happening. The only way a battery will generate significant hydrogen is when equalizing them as that is when the electrolyte is being disassociated to hydrogen and oxygen. In that case I would take some precautions, maybe set up a blower if it were a big battery bank and a big charger.


Otherwise fuggitaboutit.


Also taking return air from the engine room for an Espar or similar isn't ideal, but it is done a lot. I had a couple of Espar heaters on a catamaran and only ran them after the engine was shut down overnight to warm the cabin up the next morning. Smelled ok to me.


David


David

 

[sunchaser]

Is there an ABYC recommendation of this topic? I do recall an article in PMM by Steve D that mentioned issues with using inside air for combustion and acceptable exhaust run temperatures..