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Old 11-23-2015, 12:21 PM   #11
ksanders
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City: SEWARD ALASKA
Country: USA
Vessel Name: LISAS WAY
Vessel Model: BAYLINER 4788
Join Date: Feb 2011
Posts: 4,487
Quote:
Originally Posted by refugio View Post
I've had several Espars (forced air), one Wallas cooktop/stove, one Webasto AirTop 2000ST, and - currently - a Hurricane hydronic. IMHO the Espars and Webastos are very comparable - German (excellent documentation, expensive spares, etc.) truck heaters with little to no marinization. Your success with these will depend largely on your installation - central location, balancing the domestic and combustion air runs (and keeping them short!), adequate voltage, correctly sized fuel supply, and so on. Sure Marine has a guide that you should buy and pay very close attention to.

I know you said you don't want hydronic, but have you carefully considered your domestic hot water situation? You get that essentially free with hydronic - every other approach has "issues".

If you are planning to cruise in winter, or want to stay warm at the dock without supplementing with electric heat, you are not looking at enough capacity. 13,600 BTUs (Wallas) and 17,000 BTUs (Webasto) aren't going to be enough when temperatures get down near freezing. If you don't need to be on the boat near freezing temperatures, then either will help extend your cruising into the fall.

Also, forced air systems are not ideal on their own. Yes, they blow warm air - but you really need thermal mass to absorb the heat and radiate it back when the blowing stops. And the warm air / no warm air cycle is not a premium experience. The folks talking about a Dickinson stove are on the right track. And I strongly suggest that you have a tested backup heating system other than dockside power. It doesn't have to heat the entire boat to 70, but if you have a fireplace - can put a clay pot upside down over your stove - whatever, you will be able to keep any hiccup in the main heater from becoming truly uncomfortable.

Finally, closely related to heating is ventilation. I know nothing about the Pacific but with a couple of living (transpiring!) people on board...cooking...taking showers...perhaps with a wet dog?...you are going want to exchange a ton of air to the outside to get rid of that moisture. You really, really need more heating capacity.

Excellent post above! Many of the issues you posted about are precisely why we picked our Wallas forced air system over a hydronic system, which like you we've had several of.

So, lets take your great points one at a time to explain some of the thought processes I used in furnace selection.

Ventilation.

Hydronic heat exchangers for the most part do not provide any ventilation of the cabins air. Yes they blow it around but they do not exchange fresh air with cabin air. A forced air system allows that easily by using the return air plenum and mixing cabin air with outside air. The Wallas furnaces actually have two separate return air inlets specifically for that.

ON/off cycling

The other systems I've dealt with operated in either on or off mode, both the hydronic and the forced air. The hydronic furnace would cycle on and off to keep up the liquid temperature, and the fans in the individual heat exchangers would cycle on and off based on local thermostats. I've not seen a small boat hydronic installation that involved fluid valves that were operated by a thermostat, but it is a possibility. The Wallas furnace constantly adjusts the BTU output of the unit based on the room temperature, making for a very even heated space temperature under varing outdoor conditions.

Zone control

This is where the hydronic systems shine. Since you have individual heat exchangers in the separate heating spaces it's easy to have the fans for these controlled by a local thermostat. To acomplish this using the forced air furnace I chose to install three total furnaces in our boat. One 10,000 BTU unit is dedicated to the lower cabins. One 10,000 btu unit is dedicated to the salon. One 7,500 BTU unit provides heating and defrost in the pilot house.

The thing I gave up in choosing forced air is hot water heating. For my boat, since it is all electric that is not an issue, we run the generator enough to supply more hot water than we need at anchor. Underway the hot water heater is supplied by one of the engines.

Cost wise I found no price advantage of forced air over hydronic. I'm into the system at $14K installed, which is comparable to a hydronic installation on the same size boat.
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Kevin Sanders
Bayliner 4788
Seward, Alaska
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