Furnace Install - Part 1

alpinista · **Posted:** 10 Feb 2013 15:03

I have been researching heating systems for a couple of years now, and finally bought a Webasto 3900 Air Top Evo forced air system. The decision to go with forced air over hydronic was primarily due to the high cost, electrical budget and additional complexity for the hydronic systems vs forced air. The decision to go with the Webasto system was forced on me by finding a new in-box system at the extremely low price of $450.00 from a truck/RV supplier getting out of the heating system business. This system retails on line for over $2,000.

The main downside of a forced air system is in the size of the ducting. I wanted to end up with a 90mm vent at the forward end of the salon, and a 60mm vent in both the v-berth and below the galley stove. This would mean a continuous run of 90mm duct with two 90mm x 60mm Ys, and two short runs of 60mm duct.

FInding space for a run of 90mm ducting is tough in our Tartan's. I elected to mount the furnace in the starboard lazarette, and run the ducting forward through the under-sink area, then behind the stove and refer just below the cabinets, through the storage compartments below the pilot berth and finally into the salon and vberth hanging lockers. Really, this is the only feasible route, and was really pretty easy except for the one tight pinch point at the forward corner of the refer, where there is only about 6" of space, where I already had refrigeration lines and propane line for the Cozy Cabin heater I have mounted in the salon (and will keep as redundant heat source).

I had to remove the fiberglass liner behind the galley range, which meant removing the fiddles from the refer and sink countertops, then drill 4.25" holes through all the bulkheads and dividers for the 90mm ducting, and 3" holes for the 60mm ducting for the v-berth and galley ducts. The extra diameter is to accommodate the closed-cell foam insulation. I also had to buy 20' of additional ducting ($100.0) that didn't come with the install kit.

I've included a few pictures of the install of the ducting. Next steps are the mounting of the furnace, installing the exhaust system, fuel line and electrical. I'll add to this post when I've completed that phase of the installation.

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File comment: Insulated duct run behind stove and refer

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File comment: Ducting running below the pilot berth awaiting insulation wrap

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File comment: 60mm vent under the galley stove

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File comment: Ducting in the salon's hanging locker

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File comment: Ducting in the v-berth hanging locker

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File comment: 60mm vent under the galley stove

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File comment: 60mm vent in the v-berth, 90mm vent in the salon

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File comment: Range liner back in place

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Jay

Velera · **Joined:** 29 Dec 2006 09:38 **Posts:** 656

Beautiful job. I have had a Wallas 40D (made in Finland and sold by Scan Marine here in US) forced air heater in my T37 for about 15 years. Really makes a difference in the sailing season both when I was in California and in Velera's new home in Maine. I installed the ducting the same as you did, except that I did not think to run the little extra run to the forward cabin. This turned out to not be a big issue as it seems to heat OK any way by directing the grate that direction, but I might follow your lead. Really important that you insulated the duct work. I did not the first time around and went back and did it and it increased the heat delivery incredibly. Except on the coldest days, we cannot run the unit much over half speed. I would be interested to see the actual furnace installation. I put mine under the starboard dishpan with the exhaust out the stern. Make sure you have a good filter in the fuel line, these units do not like dirt. Again you do beautiful work. You are really going to like having a forced air heater. I even used mine down in the tropics when I was in Central America to dry out the boat during the rainy season. But it will really extend your sailing season and your comfort. One of the best additions I ever made. Well worth the $2K, but I do not think there is really anything special about the units, they all seem to work largely on the same principles. The Wallas unit is very quiet.

Tartan37.com

Furnace Install - Part 1

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