Roof Fan - Maxxair 7500K
I intended to install a Maxxair 6500K fan, but there seemed to be a global shortage of them when I tried to purchase one, and the only ones available in Canada cost more than the 7500K, so I bought this instead. The complaints I've read about the 7500K are the remote failing, and the lid closing when you turn the fan off (though there seems to be some magic moves you can do with the remote to trick it). It appears you can also manually open it by turning the knob by hand, but I haven't hooked the electronics up, so I have yet to play around with it. I also ended up buying the 6 button wired remote to mount in my control panel area on the van. You need a Cat5 cable to use as a wire, and the end that attaches to the fan needs to be low profile to fit. I couldn't find a good source for a wire with low profile connectors, or low profile connectors, so I ended up buying the tool to crimp the connectors, and took a hack saw to a standard connector before crimping it.
I decided to install it at the rear location on our 170, above the bed. I installed rain guards on the front windows, so the air will flow in through the front of the van, and out through the fan at the back. Long term I also plan to put in at least one floor vent when I install a fridge. I will have an induction cook top but it will be right next to the slider door, so I could always open the slider to vent (weather permitting) when cooking. I think direct ventilation is more of an issue for a propane stove as the combustion creates a lot of moisture, we shall see. I have an idea to route a range vent to the rear fan if it seems necessary.
This install involved a surprising number of parts/tools to do properly:
Parts
-Maxxair 7500K Fan
-Maxxair 6 Button wired remote
-Cat5e Cable
-Rear 170 Roof Adapter
-1/8" x 1" Aluminum bar
-3/4" Plywood (to make a frame)
-3M Window-Weld 08609
-Dicor self-leveling lap sealant (2)
-Butyl tape
-10-24 x 2" 18-8 stainless steel screws (16)
-10-24 316 stainless steel tee nut inserts for wood (16)
-Nickel anti-seize paste
-Cold Galvanizing spray paint
-Primer spray paint
Tools
-Plywood and towels for sitting on the roof
-Clamps
-Drill and bits (step drill would be nice)
-Chamfer bit to clean up drill holes
-Jigsaw and fine/ thin metal blade
-deburring tool to clean cut line
-Wide tape to protect roof
-Plastic sheet or large trash bag
-rubber gloves
-vacuum
-ladder
-Foam brushes
-Q-tips
-Cat5e crimp tool
Throughout the process of cutting / deburring the screw holes and main vent hole, I must have vacuumed the roof 10 times. It was a windy day, so it was hard to stop shaving from going everywhere. Also, between the window-weld, anti-seize, and lap sealant, it got fairly messy, so a few pairs of disposable gloves would be nice.
Before getting on the roof and cutting the hole, I made a plywood frame to mount on the inside of the van. I cut the inside of the frame to match the roof adapter, and made the outside of the frame about a 1/2" larger all the way around. I clamped the fan frame, roof adapter, and plywood frame together and drilled holes for the hardware. Instead of using the provided screws, I bought 10-24 machine screws and tee nuts that press into the wooden frame. In an effort to avoid galling, i used dissimilar stainless steel grades for the screws and nuts, and used a nickel anti-seize. From my experience, you really don't want to use a high speed drill when assembling stainless hardware, as this significantly increases the chances of galling. I then drilled the plywood frame holes out to accept the tee nuts, spray painted it, and then pressed the tee nuts into the frame. I also drilled and cut the aluminum strips to put on top of the fan frame, to act as a stress relief for the screw heads.
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I put the towels and plywood on the roof, and taped a large trash bag below to catch metal shavings. I put the adapter in place (checked about 10 times that I had it the right orientation) and marked and drilled the corner holes for the cutout. I used a handful of drill bits to enlarge the pilot hole to be large enough to insert the saw blade. This is where a step drill bit would have been very useful. The roof is so flexible, it would be easy to warp the sheet metal as you drill. The bit pulls once when you punch through the roof, and once again as you pull back on the drill. Using lots of bits to step it up worked well with light pressure and high speed.
I then taped the roof to protect it from the jigsaw, used the adapter to mark the cut lines, and cut the hole. This part was relatively straight forward, but be sure to use a new blade intended for thin metal with fine teeth. High reciprocating speed and slow progress made a very clean cut. Before cutting the last edge, I put some tape under the piece of sheet metal that would be removed so it wouldn't fall or start bending at the end of the cut.
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