What's important in fridge venting? Why am I doing this? - Fiberglass RV


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Old 03-04-2019, 07:57 PM   #1
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What's important in fridge venting? Why am I doing this?

I'm installing a 3-way fridge where my ice box used to be and I’m finding it a pain in the butt to vent and seal that back cavity where all the components are. As I'm making the enclosure to separate it from the rest of the camper I wondered what I'm really after here. Is the venting more important for fridge efficiency or to get rid of exhaust from burning propane? I can handle the venting part for efficiency but how airtight do I need to make this from the rest of the camper? I'm going to a lot of trouble to have this totally isolated from the rest of the camper but there are some areas where wires run through and I won't be able to seal that up completely airtight. Don't people burn propane devices in their camper all night long? How much exhaust does a fridge put out? Am I worrying too much about noxious gases leaking into my camper from operating the fridge?
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Old 03-05-2019, 04:52 AM   #2
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i think the venting issue is mostly for propane operation. it's a small box and propane creates a lot of heat to cool the ammonia. then the ammonia needs to be cooled before it can be heated again to make more cold. if not vented properly (to loose that heat) the fridge just won't run efficiently. quite a few manufacturers ignore this issue and just vent all that heat back into the fridge cavity which causes performance issues. it certainly does in my casita.

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Old 03-05-2019, 05:03 AM   #3
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I replaced my fridge in the Boler and didn't get the box in back tight and the fumes of spent propane is horrible in the camper. Dangerous too. Make sure you get this done right! Wife will not go camping in the Boler any more till I fix this problem.
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Old 03-05-2019, 09:11 AM   #4
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Proper venting, clearance distances and baffling is what will affect efficiency.

Sealing the compartment from the interior of the trailer is what will keep you safe.

The tiny flame produced by the fridge is probably not enough to burn all the oxygen in the camper, but you still don't really want it burning inside air. People who burn propane in the camper all night without proper venting are risking carbon monoxide poisoning.

The other issue is in the case of an ammonia leak from the fridge. You don't want those fumes in the camper.

Building a good box to hold the fridge, then sealing the compartment is important. Where wires go through holes, some type of silicone or insulation to fill the gap would work. As long as the "box" you build is tight, you don't need to go as far as sealing the seams with silicone or anything. The way my fridge instructs me to seal, if I remove it, is to use some sort of foam weatherstripping along the sides and top where they meet the face of the cabinets, and a line of caulk along the bottom where it meets the floor. That space seems to be important to seal tight. So this is assuming the "box" is already built, and is how you make a seal in the front face of the fridge where it meets the cabinets on the inside of the camper.

Search around for some of the threads from people who can't get their fridge to cool well enough to really use it. 95% of the time it's either a dirty burner assembly or poor venting. Often the way trailer manufacturers build the box is not correct. Seriously. I suggest you take a very close look at the instructions for the fridge you're using. Proper venting and baffling is essential to a working fridge. And I mean essential. If you don't build to the specs in the instructions, I don't care if your fridge box is a work of art. You're going to have a fridge that won't cool once the outside temps get above 60 or so. If you don't take this point seriously you're going to have a very expensive storage compartment in your trailer and no fridge.
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Old 03-05-2019, 10:24 AM   #5
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Originally Posted by Bryan L. View Post
I'm installing a 3-way fridge where my ice box used to be and Im finding it a pain in the butt to vent and seal that back cavity where all the components are. As I'm making the enclosure to separate it from the rest of the camper I wondered what I'm really after here. Is the venting more important for fridge efficiency or to get rid of exhaust from burning propane? I can handle the venting part for efficiency but how airtight do I need to make this from the rest of the camper? I'm going to a lot of trouble to have this totally isolated from the rest of the camper but there are some areas where wires run through and I won't be able to seal that up completely airtight. Don't people burn propane devices in their camper all night long? How much exhaust does a fridge put out? Am I worrying too much about noxious gases leaking into my camper from operating the fridge?
I suggest you need the vent because of heat coming from refer. just in general, I have only used the 110 and it will heat up the counter.
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Old 03-05-2019, 10:49 AM   #6
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You need the vents to expell the hot gasses created by the burners. It doesn't matter if you're running propane, 12 volt or 110 volt. The fridge needs airflow to work properly. Some people even add fans in that area to increase airflow thus increasing the fridges efficiency.
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Old 03-05-2019, 11:58 AM   #7
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I'll state again, just to drill it in, that "efficiency" isn't even really the right word. "Function" is probably more accurate. Without proper venting and airflow, the fridge will hardly function, much less function efficiently.

The instructions will show you how much space you want above, to the sides and from the back of the fridge. These are all critical.
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Old 03-05-2019, 02:20 PM   #8
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Current research finds that Carbon Monoxide (CO) combustion byproduct can cause permanent neurological damage at concentrations near 10 ppm. Your standard hardware store CO monitors will alarm on a concentration/time gradient starting around 250 ppm. Unless you buy a higher quality CO monitor that alarms at 10-15 ppm, you may never know that you are being poisoned. CO alarms like the CO-Experts that are used in airplane cabins are a great idea for trailers as well. Kids are especially sensitive to damage from low CO levels. We can also get a problematic dose of CO standing over a propane range burner while cooking, but at least we are aware of how long we have been there.


It is worth whatever effort is needed to seal off the trailer cabin from any CO source when possible. Ventilating the cabin when cooking is essential.
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Old 03-05-2019, 02:30 PM   #9
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Is this a new fridge? Is it Dometic? If so, it came with installation instructions. If you don't have those, you might find them online. Those instructions are meant to be followed.
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Old 03-05-2019, 03:47 PM   #10
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Originally Posted by ARVZ View Post
Current research finds that Carbon Monoxide (CO) combustion byproduct can cause permanent neurological damage at concentrations near 10 ppm. Your standard hardware store CO monitors will alarm on a concentration/time gradient starting around 250 ppm. Unless you buy a higher quality CO monitor that alarms at 10-15 ppm, you may never know that you are being poisoned.
Interesting, and potentially valuable information. Can you provide of link to this research? I ask because I was going by this from Consumer Product Safety Commission:

...Most people will not experience any symptoms from prolonged exposure to CO levels of approximately 1 to 70 ppm but some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea. At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.


It looks like the CO-Expert units start at about $200? I wonder about this $22 Kiddie unit.. the data sheet says:

The digital display feature allows for easy viewing of carbon monoxide levels from 30-999 PPM (parts per million). The 900-0146 will also detect and store concentration CO levels as low as 11 and up to 999 PPM with its peak level memory display.


So maybe you can read the display to find out if there are lower (non-alarm) levels.

And reading further we see,

Per UL 2034 requirements, the CO sensor will not alarm to levels of CO below 30 ppm and will alarm in the following time range when
exposed to the corresponding levels of CO.
70 ppm CO Concentration 60 240 minutes
150 ppm CO Concentration 10 50 minutes
400 ppm CO Concentration 4 15 minutes


I wonder what it is like to be in 400 ppm air for 15 minutes (before the alarm sounds).
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Old 03-05-2019, 06:59 PM   #11
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Here's a link to the Dometic installation manual with clearances shown.

https://www.dometic.com/en-us/us/pro...#documentation

Typically, the bulkheads on each side of the fridge are sealed to the hull, the counter above and the floor. Wires coming through those bulkheads can be sealed with butyl rubber or silicone or other caulking.

There is about 2 inches behind the condenser fins to the inside of the hull (see Dometic's manual). This area is vented top and bottom with large louvered panels to the outside. The ventilation vents the heat from the box and the flame, or electric heater, and vents it to the outside. This area must be vented adequately for proper function and a fan can be added to get more flow through the area and over the fins.

The Alcove that the fridge slides into is not actually sealed 100% between the room and the rear of the fridge. But the overwhelmingly likely place for all the rear heat and combustion products to go is out the rear hull vents. Some fridges used to have small chimneys for venting the flame gasses, but I think that now they just vent in the space behind the fridge, near the top. The flame is quite small and only about the size of a match flame. Again, see the Dometic instructions related to your model.

The addition of a fan really helps in hot weather and the louvers should be relatively large and free flowing.
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Old 03-05-2019, 10:30 PM   #12
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The easiest way to get help and to find resolution is to break down the installation issues into smaller resolvable situations.

So be specific, what part of the installation is giving you the most trouble? Solve that one aspect and then move onto the next aspect of trouble.

It gets overwhelming if you don't take things one step at a time instead of thinking of the issue as one great big problem. A 3-way fridge installation is not just one great big single problem. It is instead lots of small things that need to be accomplished.

Tell us, what step is the first one you want to get our advice on? What aspect of it has you stumped?

If it is how to seal around wires running through an area then first focus on that aspect. It is not all that difficult to do. The hardware store has products for that. You can drop into your local hardware store for grommets and caulking and/or weatherstripping supplies. Do know the thickness of the panel you are going through and also the relative diameter of the wires or wire bundle. They make split grommets that you can slide over existing wires. But close cell foam pieces are another option as is spray foam.

Post photos and measurements too, they let people see exactly what your situation is and that makes it easier to tell you about good options for a solution. You even can take photos on your digital camera, your cell phone or tablet camera and show those photos to store clerks. Images often communicate information faster and more accurately.
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Old 03-05-2019, 11:31 PM   #13
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Haha, where do I begin? I'm pretty sure I have it all worked out now but, yes, it's one small problem after another which explains why the fridge sat in my garage for over a year before I started this. There are a ton of things to figure out. I've been taking pictures and plan on a write-up for after Spring Break but here's some of the little things that had to get taken care of first:
1. Outlet box at end of counter was too deep and the fridge hit it when slid in.
2. Converter was mounted Halfway where the fridge needs to go and half under the bench seat. Tried to move it to completely under bench seat but cord length was too short. Had to install new cord.
3. The venting they asked for was impossible due to the belly band on the camper. I improvised so we'll see how it turns out.
4. Constructing an airtight area in an area with odd dimensions (wheel well, etc) is difficult.

Hoping to fire it up Wednesday night. Not sure I'll get my 12V line run as it looks like I need to run a dedicated line to the battery due to the high amperage.


Quote:
Originally Posted by k corbin View Post
The easiest way to get help and to find resolution is to break down the installation issues into smaller resolvable situations.

So be specific, what part of the installation is giving you the most trouble? Solve that one aspect and then move onto the next aspect of trouble.

It gets overwhelming if you don't take things one step at a time instead of thinking of the issue as one great big problem. A 3-way fridge installation is not just one great big single problem. It is instead lots of small things that need to be accomplished.

Tell us, what step is the first one you want to get our advice on? What aspect of it has you stumped?

If it is how to seal around wires running through an area then first focus on that aspect. It is not all that difficult to do. The hardware store has products for that. You can drop into your local hardware store for grommets and caulking and/or weatherstripping supplies. Do know the thickness of the panel you are going through and also the relative diameter of the wires or wire bundle. They make split grommets that you can slide over existing wires. But close cell foam pieces are another option as is spray foam.

Post photos and measurements too, they let people see exactly what your situation is and that makes it easier to tell you about good options for a solution. You even can take photos on your digital camera, your cell phone or tablet camera and show those photos to store clerks. Images often communicate information faster and more accurately.
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Old 03-05-2019, 11:35 PM   #14
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Thank you all for your comments. Yes, I have the Dometic manual and I'm following it but it's not as easy as it sounds. How do you construct box larger than the fridge and then get it through a smaller fridge-sized hole? This was definitely a bigger project than anticipated to add this after it has left the factory. This might explain why there are very few, if any, tutorials on how to exactly go about doing this. It's a royal PITA.
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Old 03-06-2019, 08:48 AM   #15
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What's this you say about the belly band being in the way? Not ideal, but...not necessarily a problem. I hope you vented it higher, not lower. Lower will not function. Higher may actually create more chimney effect and work better than "stock".

Click image for larger version

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Views:	30
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Good luck! I know how you feel, more or less. I've had a lot of fridge issues, but also gutted & rebuilt a camper so I've been through some of this.
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Old 03-07-2019, 02:04 PM   #16
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more on CO hazards

To respond to Gordon2's question about CO poisoning, I ran across this from the CDC. (Not that the CDC or anyone else can be automatically trusted to post unbiased science on anything. Most easily found science publishing is corporate science designed to sell products or mitigate legal liability, and full disclosure is very rare.) The usnews article makes the point I was going to make that low level CO poisoning mimics many other common ailments and doctors often miss this possibility.

https://www.atsdr.cdc.gov/ToxProfiles/tp201-c3.pdf


https://health.usnews.com/health-new...noxide-dangers


I come from a high-performance homes/HVAC guy perspective on this, having tested hundreds of homes for combustion safely hazards and finding them often enough that this is something to be looking out for. I used to carry my CO-Experts alarm with me just to see the CO levels in homes.
The cheaper CO alarms could be called "death alarms" because when they finally alarm it is time to GET OUT NOW BEFORE YOU DIE! This is obviously not a bad thing, but our health is being damaged at far lower CO levels that we have no human senses to detect.


The narrative I have heard is that the first generation home CO alarms were very sensitive and began to go off all over America. Firemen and then HVAC contractors would respond and often not be able to find the cause of the alarm. This led to the home alarms being dumbed down to reduce the number of "false alarms."


This was before the day you could walk into a home with a digital manometer reading fractions of a Pascal and follow an established test protocol for finding combustion safety hazards caused by Mechanical Air Distribution (heating equipment, exhaust fans, clothes dryers interacting with atmospheric draft combustion appliances). Probably most HVAC contractors still don't know how to do this home combustion safety testing, and nobody will pay them to do it, so it doesn't happen.


The short version is that it makes sense to avoid any CO exposure whenever we can. A CO alarm sensitive to 10 ppm makes that possible.
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Old 03-08-2019, 10:48 AM   #17
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What's this you say about the belly band being in the way? Not ideal, but...not necessarily a problem. I hope you vented it higher, not lower. Lower will not function. Higher may actually create more chimney effect and work better than "stock".

Attachment 128205

Good luck! I know how you feel, more or less. I've had a lot of fridge issues, but also gutted & rebuilt a camper so I've been through some of this.
OMG! I'm sorry, but that has got to be the ultimate ugliest vent cover installation ever installed on any RV or trailer I have ever seen. Looks like something either a 5 year old, or an "RV Tech" at Camping World, would do
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Old 03-08-2019, 11:29 AM   #18
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It is ugly, I agree. And I definitely find that even with the superior build quality of Bigfoot, when you start looking "behind the scenes", there are still a lot of rough cuts and sub-par finish work. But then I guess none of us expect anyone working at an RV shop to be a pro finish carpenter.

The install was ugly, but probably looked pretty acceptable when brand new. What makes it really ugly is the fact that it's an almost 30 year old trailer, where they had to use a metal cover in order to fit the bend at the belly band, and since I've owned it, I've had that cover off at least 50 times. Bending and reshaping and re-butyl taping. Then I installed that black cable hatch to increase air flow after finding a newer, higher flow plastic vent cover won't fit that belly band bend without more fabrication than I feel like doing. It ain't pretty but it works!
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Old 03-08-2019, 04:52 PM   #19
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Bryan, the job you're contemplating has some similarities with what I had to do last summer on sister-in-law's Trillium 1300.
Trailer was bought with a defective fridge. The original fridge was a Dometic RM211. This is an old model now discontinued. Compared to modern small fridges, it is higher and wider but not as deep. Replacement fridges (Norcold 323 or Dometic RM2195) have a smaller frontal area but are deeper by about 3 inches.

Another thing we found after we bought this trailer is it had been damaged by fire, and the fire actually came from the old fridge burner. In a Trillium, the rear of the fridge slides in a shroud made of FG that actually seals the rear of the fridge against the trailer's side vents. Any heat or gases from the fridge have to go out through the vents. But the fire had damaged this shroud and I had to repair it. Turned out I rebuilt 2/3 of it.

First thing I did is built a plywood enclosure who's exterior height and width would be the same as the old fridge and fit the opening in the cabinet, and interior's dimension would fit the new fridge once wrapped with a layer of thermofoil insulation (aluminium bubble wrap). I mostly used 3/4" plywood for the box.

I repaired the damaged FG shroud with some sheet metal I had lying around, some rivets and urethane adhesive. The upper part of the shroud and the side where the fridge's burner was were the most damaged. Using sheet metal also added heat protection from the burner. Then I installed the shroud inside the cabinet, against the trailer's outside wall, and sealed it with some more urethane glue. Then I slid my plywood adapter box in place, against the shroud, using some more screws/rivets/adhesive/aluminium tape to seal it. Now this whole assembly is literally part of the camper as much as the FG cabinet. Everything is sealed (aluminium tape work good for this) meaning any rising gases or hot air have to exit through the upper vent, nothing can go inside the cabinet or the camper. The lower vent is also sealed, so any water splashing through the vents will drain outside at the lower vent, and most importantly any propane gas leaking will not pool somewhere inside at the bottom of the trailer, under the cabinet, or inside the Trillium's structural 'pontoons', as it can only "drain" outside.

Using a piece of thin aluminium sheet I added a baffle against the wall of the trailer, between the upper and lower vents, as the distance from the wall and rear of the fridge was greater than the installation specs from Dometic (the fridge is mounted a deep as possible in the cabinet, with the bottom of the fridge against the bottom of the lower vent (zero clearance). Due to the fact that the trailer wall is slanted (trailer is wide at the waist) at the top of the fridge the clearance is like 3 inches, and Dometic required something less). The baffle forces the rising air to go through the cooling fins.

I also had to replace the copper gas line (from outside under the floor the the fridge), as the newer fridge's fitting was a bit farther and the original pipe couldn't reach it.

The front of the fridge sticks out by about 3 inches compared to the original, this is unavoidable. I managed to make it look good!

I guess I probably took much more precautions to seal the enclosure and protect everything from heat than necessary, especially if I look at how a similar-size fridge was installed in my popup camper.
But in any case, the new fridge was used all summer on propane and AC, it worked nicely, and I know my installation is totally safe.
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Old 03-09-2019, 12:24 PM   #20
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Using a piece of thin aluminium sheet I added a baffle against the wall of the trailer, between the upper and lower vents, as the distance from the wall and rear of the fridge was greater than the installation specs from Dometic (the fridge is mounted a deep as possible in the cabinet, with the bottom of the fridge against the bottom of the lower vent (zero clearance). Due to the fact that the trailer wall is slanted (trailer is wide at the waist) at the top of the fridge the clearance is like 3 inches, and Dometic required something less). The baffle forces the rising air to go through the cooling fins.

I added a similar baffle in my trailer as well. The air flow was less than optimal in the way the factory installs the fridge. Too much open space behind the fridge to get a good laminar air flow directed up through the fridge's cooling coils. I used some aluminum sheet metal (vent stack) that I cut to fit, and a bunch of Reflectix that I crammed in all around as well. The new baffling has improved my fridges cooling ability tremendously by creating a laminar air flow and by choking down the space near the cooling fins to direct more air across them.
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