Forced air heat / HVAC routing

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Nimue's picture
Nimue
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Posts: 429
Forced air heat / HVAC routing

Who out there has cabin heat on their boats? I have a Webasto HL32 which I have just resurrected from the dead, care of a poor installation by the previous owner. After some effort, I got it working and it is blowing nice dry heat into the boat. But...

Currently there is 1 duct coming from the heater to a vent under the dinette table to port. The PO has cut a hole and added a vent for the aft cabin, but never got around to actually splitting the duct. This will be easy as the current duct runs right under the aft berth (heater is in lazarette locker to stbd).

Apparently this heater makes enough heat to split the duct one more time, so I would like to get some heat up to the V-berth as well. We use our boat 11.5 months a year so this is a key feature. Has anyone run a 3" duct forward through the head? Is it possible? What mods will I need to make? I was thinking one of you down south must have had this issue with your A/C units before?

Any other anecdotes from your heater installations would be appreciated.

Jason V
Vancouver, BC, Canada

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LCBrandt
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First please clarify...why is the heater mounted in the lazarette to starboard? The starboard lazarette? Or are you facing aft when you think of starboard lazarette, which is really the portside lazarette? The portside lazarette would be the better location for the furnace, for routing hot air...a shorter run and fewer curves. Curves and length of ducting have dramatic effect on hot air flow. And if the hot air flow is insufficient, the lesser airflow through the heater could cause damage to, or reduce the life of, the combustion chamber. An aircraft's jet engine is cooled not by the air flowing over it (ie, as an air-cooled piston engine in an airplane would be), but by the air flowing through it. And a forced air furnace like an Espar can be thought of as a baby jet engine. Well not exactly, but the internal cooling process is certainly analagous.

Your boat has a slightly different layout than my Mk II, including (I think) having a fuel tank where the Mk II holding tank is. On the Mk II, there is a path for heater ducting from the portside lazarette, through the hell hole, forward beneath the stove and galley counter, under the salon settee, to a narrow but still suitable passage just inboard of the holding tank (fuel tank on your boat???), to the head. Once in the head, a flex hose, say 4 " diameter, ought to be route-able [is that a word?] into the V-berth.

During Pacific Northwest cruising months (early June through late October, say), we find that we do not need heat in the V-berth. Our custom is to turn all heat off at night, open the V-berth hatch all the way (if no rain), and stay snug buried in the down comforters. Our small Espar forced air furnace is not routed that far forward, but is still is entirely satisfactory for heating the boat, which generally involves just 'taking the chill off' on Pacific NW mornings. Though on an ocean trip, Neah Bay to Astoria, sometimes I have had the furnace on the entire 31 hour trip. Of course the desire for heat is a personal thing.

One of my dream projects is to spiffy up the heater routing on our boat, including a heat duct that goes all the way to the head. Then, in the head, I would have an outlet that could be shut off, and just before that outlet a small, say 3", duct tee'd in at that point, creating a 'spur' that would go up to the medicine cabinet. There I would block off the small duct with a cap, easily removable. When uncapped, this 'spur' from the heater mainline would act as a hair dryer! Great idea, no???

Larry Brandt
S/V High Flight #2109
Pacific Northwest, PDX-based
2002 C-36 mkII SR/FK M35B
 

Kevin
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Posts: 7

Hello,
I'm in the process of installing a Wallas Dt30 in "Silver Lining", 2000 C36MkII. I'll have complete photos for posting in a couple of weeks. Ports in the main cabin, the head and forward cabin.  Return in aft cabin. Should I create a new post?
Kevin

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Nimue
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Posts: 429

My mk 1 has the full-width lazarette, not two separate ones. The port side contains the vented propane locker, and the stbd. side has the heater. The current duct runs down under the aft berth, to port of the water tank, forward under the floorboards in the galley, outboard (port) of the fuel tank ( which is in the aft leg of the dinette) and vents from the center of the dinette. I have a holding tank under the fwd. leg of the dinette, which I can get outboard of.

My issue is whether there is room for a duct to run through the head below the counter height, outboard of the toilet and below the sink.

Jason V
Vancouver, BC, Canada

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langweer2
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Posts: 25

My 1989 had an Ardic 041D. I replaced it last fall with a new Wallas system (fairly easy to install). I have outlets in the aft berth, in the galley (next to the engine cover), in the salon along the port settee, and another in the head just below the camode. (Keep those toes warm!) I thought about routing a duct to the V-berth, but aside from a bit of difficulty routing a duct forward of the head, I couldn't really find a suitable place in the V-berth to place an outlet. So far I haven't been disappointed in how the system works, but to be truthful, I haven't tested it for an extended period in really cold weather.

Mark Swenson
Everett, WA
Hull #1016, unnamed

Kevin
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Joined: 2/19/12
Posts: 7

Mark,
I just installed the Wallas in my C36MKII with a 3" duct into head and continuing under the sink into the v-berth. I took copious photos showing the complete install. It should be posted on the site in another week.
Kevin

samueladc
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Joined: 1/13/17
Posts: 2

Any luck with photos?

Samuel Cummings
Catalina 36 MKII - El Dorado II
Hull #2236

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LCBrandt
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Posts: 1282

Mark, is your Wallas a forced air furnace or a distributed hot water system?

Larry Brandt
S/V High Flight #2109
Pacific Northwest, PDX-based
2002 C-36 mkII SR/FK M35B
 

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langweer2
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Posts: 25

It is forced air. The model is "40 D Nautic". The installlation was made easier by already having the fuel tube in place from the old Ardic. Plus I was able to follow the old duct routing. From what one of my dock neighbors tell me, mine is quite a bit quieter than most of the other common models out there.

Mark Swenson
Everett, WA
Hull #1016, unnamed

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