The Heat Is On

A while back we visited the Annapolis Boat Show with the mission of finding a heater for the boat that would get us through the winter.  We talked to Bryan Marshall from Annapolis Cruisair (Cruisair website) and settled on an Espar Airtronic D5 kit.  The D5 is a diesel burning forced air heater the size of a shoebox.  It consumes about 1/10th gallon per hour and produces up to 18,000 BTU.  This little baby will be hooked up to our 150 gallon fuel tank, which should be more than enough to get us through the winter.

So, we bit the bullet, laid down the big bucks and ordered a kit.  With the Boat Show discount we paid $2900 which is a good deal but still a major outlay for us.  Bryan was really helpful and let us split the payment over two paydays.  Annapolis Cruisair runs out of a small shop, boxes stacked up everywhere, everyone's friendly and laid back.  They called me the following week when my parts came in and, being anxious to get started on it, I jumped in the car and raced over.  Because this thing is so small I didn't really give any thought to the weeks worth of laundry, five bags of groceries, two suitcases and Bella's travel crate already in the back of the car.  Silly boy.  When I got there the office manager and her dog walked me around to their receiving dock, rolled up the door and pointed to this humongous box.  She helped me wedge it in through the back hatch of our Ford Escape, wished me luck on the install and ran off to find her dog.  I would later need a crowbar to get the box out of the car.

Back at the marina I unloaded the contents of the box into a cart and hauled it out to the boat.  The kit has just about everything you would need for an "average" installation.  Two sizes of flexible duct (90mm + 75mm), vents, reducers, clamps and other hardware, fuel line and pump, exhaust hose and more.

Before you do anything else you're supposed to sit down and plan out the system.  Because of the amount of heat generated the unit must have free flowing air.  Each restriction in the air duct accumulates and causes heat buildup at the heater which will automatically shut off at a predetermined temperature to prevent "component meltdown". To help with planning the system and reduce restrictions, Espar has assigned a numerical value to every component.  Ducts are specified by diameter and length and also by if they're in the primary or secondary system.  Primary is the main run and secondary would the part that goes out from a "Y" to a vent.  There's a rating for 90 degree bends and for different types of outlets or vent plates.  The heater itself is rated as a 10 and the combination of everything else must be less than that.  So, the first thing I did was to ignore the installation manual, skip the pre-planning-by-numbers and begin installing the ducts.  I got the main run of 90 mm ducts installed with a "Y" for each of my planned outlets, four in all with reducers and smaller ducts for each.  Then I sat down and calculated the number total for what I had.  Came out to 14.75.  Hmmm says I, could be a problem.  I read through the book, went on-line and read all of the Espar info there and discovered that the two sources didn't totally agree on the ratings.  I decided to go with the book because it favored my design by about a point.  I was still over 10 though.  I hadn't cut through anywhere for the vents yet so I modified my original plan a bit.  The vent locations I chose are in the aft cabin, Main Salon, forward cabin and the forward head.  If I use closeable vents and 75mm ducts on three of the lines then the ratings for everything from the "Y" to the vent can be ignored because most of the time these lines will probably be closed.  It says that right in the book.  The line in the Main Salon will be 90mm duct with an open grid vent that will always be open and provide enough flow to prevent the heater from overheating.  I plan to run a return line from the galley back to the heater to provide even circulation throughout the living area.  This'll also be 90mm duct with an open grid vent.  OK, so now when I calculate it all out I come up with 8.0.  Perfect!

So, here it is, first week of December and I still don't have the installation finished.  November didn't provide much free time to work on it because of holiday travel and family obligations.  At least that's my excuse.  Next weekend I hope to complete the air duct installation and maybe run the fuel line.  I still have to make a mount for the heater itself which will be located portside aft under the cockpit.  The mount will be made from plywood and glassed in to the inside of the hull.  Never done fiberglass before so that should be fun.  Also have to run lines for combustion air and exhaust and power control and thermostat from the Nav Station.  Let's see......about three more weeks 'till Christmas, still gotta do some shopping for that.  My four day work week just got canned for the next month so I'm down to a two day weekend.  The night's are now getting down into the 20's and the water temperature is in the 40's.  Our reverse cycle heater is still keeping us toasty but probably not for too much longer.  I'm startin' to feel the heat but it's not coming from the D5.