I was originally going to make one thread with my roof projects, but I decided it would be too unwieldy to combine so many projects into one post... and I might never get around to it. So here is the part that deals with the fridge vent.
Replacing the the fridge vent, reflashing the opening, provisioning for Solar cable
PPL Fridge Vents (http://www.pplmotorhomes.com/parts/rv-refrigerators/rv-refrigerator-roof-vents.htm)
5" x 24"opening.
Vent Cap #31-8295
Base # 31-1622
I bought the universal base and metal cape from PPL and did some modifications to it to suit my needs. I took off the aluminum loose weave wire mesh which was just held in place by being crimped over the edge of the lip on the base. I wanted to be able to easily remove the cap and the screen in case I want to work on the wiring for the solar, or for whatever reason need to access the top of the fridge compartment. I found some aluminum flat screen at Lowes that seemed like it would do the trick. I cut it to size and then riveted it to two pieces of ¾" angle aluminum space to just fit inside the fridge vent base. Then I drilled some holes through the base and angle aluminum, and after adding a flat piece of ⅛" X ¾" flat stock aluminum to the inside of the angle pieces to make it thick enough for cutting tapping machine screw threads, I tapped 10-32 machine screw threads. Hard to explain in words, but the end result is that I can remove the screen by taking out 6 stainless screws and easily put it back on afterwards. I also riveted on more of the flat stock aluminum to the short sides of the fridge vent base so I could tap two holes, one on either end, with 10-32 machine screw threads to hold on the cap. Originally, the cap was to be held on by bending metal tabs over the lip of the cap. I figured that this method would only be could for one or two removals before they tabs broke off.
To seal around the solar cable entry, I found some flat cable weather seal fittings that perfectly fit three of the ten gauge solar cables and will seal nicely by just tightening the nut which expands the rubber plug and compresses on the cable. Since the solar cable enters under the protection of the lid, maybe just a dab of silicone will be all that is needed to keep the water out. While I had the fridge vent removed and the gooey stuff all cleaned off, I filled the old holes with some fiberglass reinforced marine bondo. While the vent was off, I flashed the opening in layers with some aluminum vent tape, some window flashing tape (thick plastic polymer based stuff that I used when I put new windows in my house), and finally some "eternabond" tape over the edge. Man, is that stuff tenaciously sticky. I used it for some temporary patches on the roof when removed the curbside Hadely and before I put the new plumbing vents on, and it kept the water out, but boy, was it a PITA to remove and clean off the residue later. Now I feel that that vulnerable part of the roof where the fridge vent opening had some bare wood with a some not very well adhered caulking is now well protected even if some wind blown torrential rain should enter the area.
Don
Edit: I want to add that, between the vent base and the opening, I used some stuff called "Tacky Tape" recommended by a tech at a trailer supply place in town. He called the best thing since sliced bread... Though we don't eat any wheat, I knew what he meant :D Tacky Tape (http://tacky-tape.com/products/butyl-sealants/sm5227/)
After timing off the squeeze out and waiting a day for more to squeeze out, I added a bead of 3M 4000 UV resistant caulking around the perimeter and screw heads. This last step was probably not necessary and wasn't done when Foretravel built the coach. They used putty tape alone on the Skylight, Kool-O-Matic, and fantastic fan.
Don,
My only concern is the reduced air flow through the removable screen vs the much more open weave screen.
Are you installing muffin fans above the refrigerator condenser exhausting up-- if so, that would help compensate for the reduced air flow.
Good point Brett, for those who still have an absorption fridge. I guess I forgot to mention that we have a marine style compressor based fridge that uses a Danfoss compressor and thus the reduced airflow is not a concern in our case.
Don
I have a Danfoss, too. From SeaFreeze - Sea Freeze of America (http://www.seafreezeinc.com/)
But it has to remove "heat" from the fridge. And that heat has to go somewhere.
I did not modify what was there for the absorption fridge. The access panel on the side of the FT is still there. And the stock vent is still there on the roof.
Keep in mind what "Danfoss" means. It's something those with a boat depend on. There's no such thing as have someone stop by to fix it if its broken, if you're in the middle of the Pacific.
best, paul
The outside vent on the side of the coach is of course still there, and would by itself be enough airflow to remove the heat under normal circumstances. The vent up top does significantly add to the convection effect by being elevated above the cooling unit, and the reduced airflow over what would be required by a propane cooling unit is not a concern to me, otherwise I would have chosen a more open weave screen and made a 360º frame to stretch it. The one I chose actually has a good ratio of open space to material, probably better than 50% if not more like 75% open space. So fiure the 5" by 20" opening is only 5" by 10". That isn't much smaller than the opening of the chimney flue on the brick chimney at my old house! Used to have some rip roaring fires in that... I am not worried.
Don,
I agree-- you are just fine. Did not recall that you had replaced the absorption refrigerator. Significantly reduced heat load with your Danfoss compressor refrigerator vs absorption refrigerator.
My marine refrigerator uses two Danfoss compressor units. Just to me certain the heat escapes easily, I had a 12 volt exhaust fan added at the roof vent, controlled by a thermostat.
Tom,
Given how easily I can access the are above the fridge with my easy removable cap and vent screen, I could easily add one of these anytime ::) Wouldn't hurt, and anything to reduce the load on the compressor would likely save energy even if it use some to do so.
Don
Mine is logically wired as an AND function, needing the compressor running AND the temperature over the limit before activating.
That is interesting Tom, how does the thermostat get the signal from the compressor? Is there a current sensor? Do you have any links to the fan control system used in yours?
Don
Sea Freeze custom built the refrigerator with a tap to drive the vent fan. I wish I had a schematic, but believe it has a relay that is energized whenever the compressor is running.
Remember, this is a 12 volt only refrigerator.
Then I suspect that the Danfoss compressor may include the tap in its harness or on the control board... Will check it out one of these days.
Don