My wife keeps complaining about it being to cold during many of our camping excursions and wanting something with hard sides to play cards in, namely a FWC, so instead I purchased the Rec Vee Panels to go with my 2.5M awning (by the way I have a like new 2M Eezi Awn Awning for sale if anyone is interested) and installed a Espar D4 diesel heater on my AT Horizon. I remember from and old Overland Journal that Scott Brady was going to do a write up on the install of one of these, but with his new rig, possibly this fell through the cracks (or at least I missed it), in any case I started researching it and bought a heater.
The install that my feeble mind came up with required that I remove the AT fuel can holders (I have plenty of room in the bed of my Tundra for spare fuel), and mounted the Espar unit (inside a 20mm Rocket Box) and a 10L Scepter can to hold the diesel in there place. I used the 10L Scepter, as the pulse fuel pump mounted more readily on top of the can than a 20L Scepter, and the thing is so efficient that a 10L is about all I would need. The fuel burn at high is .4/L Hr or about 20 hrs, and at medium .25/L hr or about 32 hours (and this assumes only 8L usable), and I can always refill the little 10L from a larger can if need be.
I used a hole saw cutter to cut a return air and heater holes in opposite sides of a 20mm Rocket box and ran the exhaust and combustion air intake out the bottom of the box and routed the lines opposite from where the RTT folds out. The D4 fit perfectly inside the Rocket box and is bolted in. I installed marine deck plates to close up the return air and heat holes, and the hole unit seals up real good for transport and I can place the lid on while it is running if say it is raining or snowing out to protect the unit.
The thermostat has a temperature sensor integrated in it, so I just take it up to the Eezi Awn 1800 tent on top of the Horizon or inside the awning with the three walls. Heating the tent up is way fast and you need to put it on low. Bringing up a fresh air return duct into the tent is most efficient, as then already warmed air is returned to the heater. You can also set the thermostat to fan mode only, and it blows in a surprising amount of air to help cool things down.
I wish Eezi Awn made a 4th panel for the Rec Vee Panel set up that would attach to a welt on their awning & zip to the other walls - they would have a killer app if they did. As it stands now you get a fair amount of cold air coming from under the vehicle, but the little heater with my attached ducting placed inside the "hootch" keeps it fairly warm inside, down to just below freezing. I'm going to try to come up with my own canvas for a 4th wall, but it is a bit of a problem.
The vast majority of folks couldn't justify one of these, as I have over $1,500 invested in it, along with the high altitude kit, but I can move it quite easily to a FWC shell model which I might purchase someday, or it would be fairly straight forward to order a new fuel pick up stick and plumb into a diesel tank if Toyota or some one ever comes out with a small diesel for a Taco, or something like that. In any case the build quality of the Espar unit is incredible and should last a long time.
Scott MacButch
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2006 Tundra Access Cab, Donahoe Coil Overs, ARB Sahara & HID, Warn M8000