big maxx vent installation question

[mhm993]

We're finishing up the new 21x28 detached garage. Going to install a 45000 btu big maxx heater from Northern tool, using their horizontal vent kit, for "weekend" heat.

My question: I'm going to mount it at the top of the rear wall. The roof overhangs the back wall about a foot, close to the height of the vent. When the instructions say I must install atleast a 3 foot long vent, with atleast 18 inches outside, does the 18 inches start at the back wall, or at an imaginary line plumb with the edge of the soffit?

Also, are there any issues that the rear wall is sunk down into the hill about 2 feet, so the vent will be maybe 5 or 6 feet above the ground?

Thanks

 

[Chetter]

Call Mr Heaters tech people, they are very helpful. I just finished installing one of the Big Maxx 45000 btu LP heaters with the vertical kit and works beautiful. I set the thermostat at 52 degrees and runs very little to keep it there.