Here is my underbed "mechanical room" with the original 7500 BTU Panasonic AC unit behind it's cover. The Trident propane locker that sat to the rear of it is removed in most of the pictures below.
**NOTE WELL**: Some of the pictures--like this one--show an aluminum propane tank that looks dangerously and inappropriately installed. Don't despair; it's not mounted, it was only sitting there for a while. It's not part of the van. I will not be blowing myself up. <g> That said, this picture shows the original AC with the rear cover removed.
A closer shot of the original unit. The white plastic tube protects a propane line.
This is the floor vent that was originally supposed to vent the exhaust to under the truck. Pretty clever, as you could open and close the vent by moving the handle that ran under the propane locker. But it was, in retrospect, a pretty clueless approach. As you can see, not a lot of room for airflow. All that happened was that the vents on the side of the AC sucked in the hot exhaust air and tried to cool it. Within a few minutes, the intake air was up to 140 degrees and the current draw had doubled. "No chance of this working whatsoever," he said with perfect hindsight. <g>
The quick fix was to put a vent fan on the side of the enclosure. The idea was that the fan would exhaust the air to somewhere and the makeup air would come in through the floor vent. That improved things . . . about one percent.
Time for out of the box thinking . . . I am very fond of portable air conditioners and I found out that a Costco 9K BTU Windchaser unit I'd used in my Unimog fit into the mechanical room. "And then what, Mike? Seems to be ready and able to cool the mechanical room." I thought about creating a plenum that ducted to the interior, but since the unit itself took up storage space I really needed. I gave up on the idea.
Here's the plan that actually cools best. Set the portable AC in the cabin. Sadly, it was a little awkward trying to cook, shower, etc. with the unit sitting in the middle of the floor.
Still, it was easy. I had this vent piece from an earlier portable AC. Get to the campsite, put the vent in the window and turn it on. Worked like a charm.
Here's the view from the inside. Sadly, having the unit in the middle of the floor in a vehicle as small as this camper proved intolerable.
Now this is the work of a desperate man. Lay the portable AC on its side with the controls up and out and rig it to exhaust through the floor of the mechanical room.
Here's the view from the rear of the prone portable unit. At this point, a fair amount of work would have been required to go further and, given that the AC wasn't all that likely to work long-tem when installed 90 degrees out of whack, I gave up. I'm sure it was for the best. <g>
So, here's how to do it. First, get a much shorter unit. Unfortunately, that also meant giving up a third of the cooling capacity; a 5500 BTU Sharp unit from Costco was as big as I felt it could be. (The silver lining, though, is that the Sharp draws about five amps, versus about eight on the original Panasonic.)
The original vent was filled to look like this. In the center is an automotive electric radiator fan that sucks exhaust air out. The outside two holes are for intake air taken from the rear of the van.
Here's what it looks like from the underside of the van.
This shows how the intake hose goes back to the rear bumper.
The Sharp case was temporaily removed to get at the wiring for the compressor.
The electirc fan was spliced into the power running to the compressor. When the need to cool starts the compressor, the fan goes on. This approach lets the AC unit act in ventilation mode without running the fan. The fan noise, BTW, is about 90% hidden by the noise from the (pretty quiet) AC.
One-inch foam insulation board was cut in a way that kept the intake air going to the unit's side intake vents and the exhaust air going to the fan at the bottom.
This foam plenum was calibrated so that it would be held against the Sharp unit by the pressure resulting from screwing on the back cover.
A top piece was added and rubber insulating tape used to hold it permanently together. With the rear cover piece from the original install fit in place, this install looks the same from the rear as when the original Panasonic unit was in there.
Not as lucky at the front, but not bad. The new smaller unit was about the same height, but it was narrower, leaving 3/4 inch gaps on the sides that I need to trim out Real Soon Now.
This is how the mechanical room looks with the Trident propane locker back in position to the rear of the air conditioner. To the left is the fresh water tank and the shelf for the tire-inflating CO2 tank; the space at the right gets filled with tools and the Honda EU2000i generator..
