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Project Log:  Monday, July 11, 2011

A 90° day in mid-July seems an odd time to consider boat heating systems, yet that's where I ended up on this day.  I'd been considering various heating options for a time, from simple bulkhead-mount propane or diesel-fired units to the more expensive air and hydronic systems from Webasto and Espar.

Early on, I'd eliminated diesel-fired stand-alone heaters (i.e. Dickinson, Refleks, Sig Marine) from contention as I didn't have the room to spare, and would have difficulty providing the requisite stack heights for these units. 

Similarly, I soon discounted bulkhead-mount propane-fired heaters like the Dickinson Newport from consideration as I felt again that the boat's layout didn't really offer the bulkhead space to spare for one of these units, at least not without compromises I was unwilling to make.

This led me down the road towards the small diesel-fired Webasto and Espar forced air heaters.  In many ways, these solved the problems I faced, but I had to sort through the usual accolades and criticism on the Internet to attempt to gain a clear picture of these units' reliability and utility.  These were still under consideration.

During an offhand conversation with a friend, I learned of a heater I'd never heard of, called a Hurricane Heater.  Searching online, I soon found the information I needed, and felt these units--hydronic, rather than forced air--had some potential.  In particular, I was interested in the Hurricane Combi unit, which combined diesel-fired hydronic (forced hot water) heating with domestic hot water capability, all in one package.  I liked the idea of this since it could mean we could have domestic hot water at anchor without needing to run the engine (typical domestic water heaters are fired by 120VAC--unusable without a shoreside connection--or engine coolant bypass).

The problem with the Hurricane unit was that it was relatively bulky, with specific clearance and access requirements for the rectangular unit. With limited space available for such an installation, the first order of business was to determine whether I could conceivably fit the unit.

From the beginning, I'd planned on installing a traditional water heater in the engine room, in an open space on the aft port side behind the new saddle tanks and outboard of the center fuel tank beneath the cockpit.  There was adequate space here for one of several brands of 120VAC/coolant-bypass water heaters on the market.  The question now was whether this space was large enough for the Hurricane Combi, which had base dimensions of 23" x 16" x 14".


With measuring tape in hand, I measured up the space available, and quickly determined that at best, the clearances were close.  This led me to build a quick cardboard mockup of the unit.

At some point during the mockup construction, I started to wonder whether there were additional space clearances required for this unit (I remembered a requirement for a certain clear access to the front panel), and also whether the dimensions I'd noted on a scrap of paper a couple weeks earlier during my initial research included the various plumbing and exhaust fittings on the top of the unit.  I thought I'd better double check this online; I immediately discovered that an additional 6" space was required in addition to the 14" height of the base unit, which completely eliminated it from consideration since my early engine room measurements had suggested that the unit itself might not even fit (which is why I'd started the mockup).

This was disappointing, as I'd been excited at the possibility of combining my heat and domestic hot water in this way.  However, this forced me to spend more time researching the alternatives, which included both forced air and hydronic units from Espar and Webasto.

Specifically the Air Top 3900 forced air and Thermotop C/E hydronic heaters from Webasto:


Or the Hydronic M10 and Airtronic 4 from Espar:


The advantage of the hydronic units was that it would be possible to heat domestic hot water as well (at least with the Webasto Thermotop).  Otherwise, I'd still require a regular water heater (current units under consideration were the 6-gallon versions by Isotemp and Superstor), which use would be somewhat restricted at anchor since it would require the engine to have been run relatively recently to heat the water.  This would not pose a problem on travel days, but for lay days in port it might.  We didn't anticipate much if any time dockside where we could heat the water with AC power, so needed to take at-anchor usage into consideration.

I found the manufacturers' websites (Espar in particular) to be confusing, contradictory, and difficult to sift through in order to determine the best choices, so as of this writing the research continued as I tried to make the basic choice in the near future, to be sure I accounted for the heating system's requirements, ducting, piping, fuel, exhaust, and other considerations.

Total Time Today:  2 hours

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