).So you absolutely do need ventilation for a compressor refrigerator, BUT you don't need the exact same thing. After all, you are no longer burning a fire back there, and the byproducts of combustion aren't being vented. Instead you are just supply cool air for intake and then exhausting heat. For the BD35, according to Danfoss, I believe they are looking for 25 square inches on both the in and out side (if you are using screening or a louvered vent there is a subtraction factor; in other words, a 5" x 5" hole with screening over it is not 25 square inches of ventilation). I think the DP2600 has the larger BD50 compressor, and that will have a spec for ventilation area in/out (the compressor is made by Danfoss).
The Vitrifrigo manual does give some guidance and specs. Most of these are for interior venting, since more of these go in boats (and you can't have a vent along the side of a boat in the same way that you can on an RV). They do essentially say that exterior venting is great if you can get it. In case you don't have this document, here is the page, copied. The dimensions are metric (since they are made in Italy).
On the other hand, that lower vent on our Chinooks can sometimes have issues. There is no way to positively keep all water out, and at least on my generation of Chinook, there wasn't a good outcome when water would get in. Basically the bottom of the compartment was lower than the lowest drain-to-the-outside area. Boo. When I still had the propane fridge, I used flashing to make a sort of self-draining vent door, but knew that I would want to eliminate that vent when I went compressor. On the other hand, I've never had any water come in the roof vent. So I felt that keeping that was an option.
You'll want to decide about that for your own rig, of course.
For my smaller unit (Vitrifrigo C130, BD 35 remote compressor), I need to provide at least 25 square inches of intake and exhaust. That's after taking off any deductions for screening, slats or whatever. I haven't decided for sure whether to go for all inside venting, or all outside venting. The "easiest" thing would be inside intake and roof exhaust, but I'm not super keen on mixing the two. I am not enough of an expert to know for sure whether or not it would be a problem, but I can imagine possible bad scenarios and just don't feel totally comfortable with a "mixed" venting scenario. I'm more comfortable with all out or all in. Considering that I have had a BD 35 running inside all the time now for two years (small "cooler shaped" refrigerator with BD 35 compressor which is a pre-cursor to the "real" refrigerator), I'm less worried about the potential heat gain with all-inside venting than I was at first (thinking it might heat up the rig in summer). But on the other hand if I go with all exterior venting then I should be able to hear the compressor/fan less (it's pretty quiet, but I like sensory deprivation levels of silence
). With all exterior venting, I should be able to isolate the sound more (vs. having 50 square inches of "sound ventilation" into the interior).I won't go into all the specifics for my various design ideas, because they are different given that the C130 has an external compressor (I can put it in another place because it's not attached to the refrigerator).
For the DP 2600 I would probably choose one of two options. But, like with my friend's installation of the DP150, we had to assess once we had it in hand and then make a decision.
1) Use original "chimney" venting scheme from the propane refrigerator. If there is extra depth, then perhaps put some rigid extruded polystyrene insulation behind the refrigerator, then a thin ply "wall" then the chimney area. In this case you'd want to exclude interior air from this exchange.
2) Go to all interior venting as shown in some of the Vitrifrigo diagrams. Basically, a path for air to come in at the bottom front of the refrigerator (if there is room over the generator box), slide up the rear, and then come out to the inside over the top of the refrigerator. This eliminates all complications of exterior vents/leakage/etc. And perhaps allows for more insulation. Just have to look at the space and the options. One potential use for the roof vent "flat" is to fit a "real" stove vent hood, if that's a priority.
If the refrigerator doesn't get enough venting, I think the compressor will run warm and increase the duty cycle (boo). It's important that the "intake" of the compressor NOT be able to take in pre-warmed air (from the exhaust). Sometimes you can make a hood type thing (like the intake on a car) or etc. The supplied fan (at least on BD35) sucks air in.
The Danfoss compressor has a few nifty goodies you can tap into, optionally. There are some very good youtube videos by "Penguin Refrigeration Limited" that explain and show it all.
1) If you put a fan across two specific terminals on the compressor, it will come on when the compressor comes on. Not saying this would have been my exact choice, but my buddy elected to keep only the lower vent opening from the propane setup, and he mounted a second fan that comes on when the compressor comes on and exhausts air (the fan that's included with the compressor sucks air in).
2) If you put an LED light across two terminals it will flash codes if there are errors.
3) There is a resistor on the compressor terminals. I forget the exact numbers/terms at the moment, but they set it up with a sort of middle ground one that runs things at a certain speed and duty cycle. I think the refrigerator is actually more efficient at a slightly higher (but lower speed) duty cycle, which you can achieve by changing the resistor (this is official, not an off the books hack). But they figure some people might be worried by thinking it is running "too much." And besides, just like anything else pre-made, they have to pick something as the stock setting.
Another important thing is the the electronics of the compressor DO NOT want to see voltage drop. They are sensitive to that. IIRC they say to run straight to the battery, but then everyone says that and if you complied you'd have a hundred ring terminals on your battery. Basically, they don't want a breaker shared with a bunch of other things, and no long/thin wire run. It could lead to early demise of the (expensive) compressor. On my rig, the original 8AWG run for the propane refrigerator was just okay, and that's with much larger (refit) cables going from the fuse block to the batteries. I'm thinking I may run a new wire across under the coach, or possibly re-purpose the generator start wire (6AWG). The trouble with a new inside wire is that it's a just about equally long run "around the horn" either way (forward or aft) to the refrigerator. No good way to "cut across" inside. Going around, it's hard to get behind the shower, and a 6AWG over the overcab is kinda big. I guess all of the ways have their plusses and minuses, and too, maybe the 8AWG would be okay. It could certainly be worse.
I'm far from an expert on this, so if anything sounds "off," do double check me. I also have not yet installed my C130. Only planned
I have been running a cooler shaped refrigerator with the same compressor (easy way to see how much energy I'd need since this was my first "can't be stopped" demand back when I set up my test solar charging system). And my buddy whose DP150 we installed really likes it. In fact, he's getting a different RV and is planning to get the same one again (I think he'd upsize to the DP2600 if he regularly traveled with 2-3 people).
