Fridge Performance Survey

[ZachO]

Alright, thanks. We'll see if anyone will sell me such a small amount of fiberglass insulation. Maybe I know someone with some lying around.

The bottom up photo is taken through the lower vent, which would explain why you can't see it.

The baffle should be below the bottom tubes? Ok. I saw somewhere that mine might be mounted too high. So it should be right above the bottom vent. I'll get it right at some point. Yeah mine is just level with the bottom of the fins. Figured that was good enough to force air through them but if it matters, I'll move it.

[Civilguy]

Originally Posted by ZachO

Alright, thanks. We'll see if anyone will sell me such a small amount of fiberglass insulation. Maybe I know someone with some lying around.

Water heater wrap kit? Scraps from a broken package at Home Depot? Friendly folks at a residential construction site?

[redbarron55]

Does there happen to be a particular distance that the interior baffle needs to be mounted?
I noticed that on the "other" video there was a wire that hung the spiral part at some distance from the top.
Perhaps the position of it makes a difference?
If the Fridge worked on AC then possible the thermostat is not right.
I think the AC is not regulated by the thermostat.
Does the burner cycle on an off or does it never meet it's set-point and burn continuously?
If it cycles then the system may be working, but kept from cooling more by the thermostat turning off too soon?
Also on the bottom zigzaggy tubes there is a specification og the air space for them as well.
This is a kind of distillation tower for the ammonia system and it is designed for an airflow over them as well.
I think that the max clearance to the back is zero att he base of the absorber unit/
Look at page 8 of this PDF file:
http://www.thetford.com/wp-content/u...ion-Manual.pdf

4. If the distance between the rear of the refrigerator and the
inside of the enclosure is more than 1 inch, install two (2)
baffles to prevent bypass air around the condenser fins and
absorber coils of the refrigerator:
- Install one baffle that is at the lower edge of the condenser
fins of the refrigerator.
- Install another baffle that is at the lower edge of the
absorber coils of the refrigerator.

The fact that you can take that picture from the bottom means that there is too much clearance as installed





Looking up and down you don't have the proper baffles on the side, top, or bottom.
My guess is that you could use pieces of aluminized 1" duct board for the baffles.
You need both sides bottom and top.
I would also put a piece on the trailer wall to fill in the space between the coils and the trailer wall leaving a small space for air flow upward.
All of the air needs to go to the correct places and not bypass the critical parts.

[Civilguy]

My thoughts, for what they may be worth (!), are as follow.

Cold is basically the absence of heat. Cooling and refrigeration are accomplishing by moving heat from a target location such as the inside of your refrigerator. An absorption refrigerator relies on a process that requires heating an ammonia solution to faciltate this. So, we are faced with the challenges of a system where you are purposefully adding heat at one location in the system in order to remove it from another location, the inside of the refrigerator.

The diagram below illustrates an absorption refrigeration system. The diagram has arrows indicating where heat is put into the system, and where heat is removed from the system.

The only places that heat is supposed to move into the system are at the generator (boiler tube) and at the evaporator. Well, the evaporator is the thing inside the refrigerator that is removing the heat from your beer. Yes, your beer is adding heat to the system! The system’s whole job is to get that heat out of the beer, right?!

However, other than the heat exchanger and the refrigerator contents, there is no other place where you benefit from heat being added to the system. So, the goal is to remove the heat from the system in all other locations.

Let’s first look at where we are deliberately adding heat to the system to drive the process. The ammonia boiler is housed adjacent to the flue pipe within an insulated shield. This assembly is a heat exchanger intended to take heat from the electric heating coil or LP gas burner and transfer it to the boiler tube ("generator" in the diagram below).

The spiral baffle inside the flue basically assists the heat exchange process by keeping the heat from just jetting up vertically through the flue without heating the adjacent ammonia solution boiler tube (generator). This type of spiral baffle is also found in gas water heaters where it serves the same purpose of facilitating a better exchange of heat from the flue to the tank.

Once the heat has been exchanged from the flue to the boiler tube (generator), and the ammonia solution has been boiled, the goal is now to get rid of the heat from all other parts of the system! (Remember, the only other place the system where the heat is added to the system is from the refrigerator’s contents via the evaporator, so be sure to stock the refrigerator with an adequate supply of beer. This is a very important step in the process here!)

Heat is removed from the system by an upward ventilation pattern via 1) natural convection caused by warm air rising, and 2) sometimes additionally by one or more fans assisting the upward airflow. Refrigerator installation diagrams indicate low and zero clearances in order to facilitate airflow across the refrigerators condenser and absorber (hereinafter, the "tubes and fins").

Many refrigerator installations don't adhere to the recommended clearances which direct the airflow to pass through the "tubes and fins". As an example, my Casita’s factory installation's clearance is 3.5 inches at the top; the curvature in the shell lends to this excessive clearance at the top. Casita does not baffle this space off and force the airflow to pass through the "tubes and fins". So, the ventilation air passes by at a distance. Air "passing by" at a distance does not effectively remove the heat from the "tubes and fins".

Another factor is how the wall vents on these smaller refrigerators inhibit the airflow. Reduced airflow reduces the amount of heat removed. Subsequently, the hot air is trapped adjacent to the box that one is trying to cool! It's like putting your icebox in the warmest and sunniest location you can find!

Zach and me and many others have noted that simply removing the vent grill from the top helps keep the refrigerator cooler inside. I think this constricted ventilation which traps heat at the same level as the top of the refrigerator is a big factor in why refrigerators with roof vents generally seem to perform better.

Other than that, there are certainly a lot of factors involving proper LP pressure, a clean jet, thermostat performance, etc. However, I think a key problem experienced with these refrigerators is simply their limited ability to get rid of the waste heat, particularly in side vent installations, for the reasons described.

https://www.youtube.com/watch?v=udeSVyx6_9A

[Civilguy]

Originally Posted by redbarron55

All of the air needs to go to the correct places and not bypass the critical parts.

What he said!

[Joe Romas]

Civleguy
Otheres have tried to get that baffle kit sent to the US and were unsuccessful.

Your are 100% correct on airflow. In these units the heat from the flame is hotter then the heat from the refrigeration so they must be kept separate.
My chimney extension and flexible pipe directs the heat to above the refrigeration heat.

Have you been keeping up with the thread on the casita forum? If so you'll notice this is Gene's idea.

Here's a picture of my lower baffle and fan.
As I was taking the picture just now I noticed that the tubes lower were hotish also but if the baffle were lower it would restrict airflow.
Joe

[Civilguy]

Originally Posted by Joe Romas

Civleguy
Otheres have tried to get that baffle kit sent to the US and were unsuccessful.

Your are 100% correct on airflow. In these units the heat from the flame is hotter then the heat from the refrigeration so they must be kept separate.
My chimney extension and flexible pipe directs the heat to above the refrigeration heat.

Have you been keeping up with the thread on the casita forum? If so you'll notice this is Gene's idea.

Here's a picture of my lower baffle and fan.
As I was taking the picture just now I noticed that the tubes lower were hotish also but if the baffle were lower it would restrict airflow.
Joe

Joe,

I haven't read up on this subject on the Casita forum in quite some time. I bookmarked some of the key threads long ago... Like many others, I gratefully use and acknowledge Gene's and others' ideas whenever I can.

Ah, looking at the forum now, I see that you-all have been active of late; I will have to get caught up!

I do seem to recall that about the Australian parts not being shipped to the US. I also seem to recall Gene originally used some copper plumbing, which I have a lot of. However I think I like the corrugated NAPA tubing approach better. I guess that's part of the catching up I need to do, eh?

My lengthy post today was the result of taking time this morning to clarify to myself and put into words what I think I have learned over the past year or two on this subject. It was a good exercise to go back and look at the schematics and theory of absorption refrigeration. Consequently I feel more than ever that I am on the right track and hope this thread will be among those that helps others somewhere down the road.

Bottom line, even if there is a regulator issue or whatnot impacting my system, failing to properly baffle the installation and improve the heat removal from the "fins and tubes" and the flue would still leave me with a poorly performing, or at least inefficient, setup. So, I am now officially stoked to get this done before our trip to eastern WA later this month.

I see that you used a "power in" approach with the fan on your lower baffle. I have a pair of fans and a PWM board on hand. However, as battery capacity is limited, I will now-more-than-ever focus on trying to get effective baffling and a flue-chimney extension installed as these "passive" measures will also be critical to making the fans effective. After all, there's no sense burning up the amp-hours just for show unless I get one of those sparkly, lighted fans; right?

On the subjects of computer fans and cooling, the schematic I posted made me start of thinking of liquid cooling... But that's another subject for another day!

Thanks for your posts here, it's helped me a lot. I also look forward to catching up on the posts on the other forum. Unfortunately, I've got to go get back-to-work now. I'm self-employed and my boss gets kind of annoyed sometimes when I spend so much time on the forums.

[Joe Romas]

When I went fan shopping with size and current in mind I wound up with this one that has GREEN LED'S

2 smaller ones might work better but for now this one is fine.

My thinking was on the top might restrict some air flow when they are not running.

Joe

[ZachO]

I think a fan anywhere will help. It's been stated a few times by some very knowledgeable people that fans pull better than they push, and so the upper exhaust fan is the best option, but anything helps. And yeah, I guess too much stuff up there will restrict air. In my case, I assume that just means more hot air accumulates...causing the fan to turn on which then solves the problem. Albeit with more battery consumption.

My thermostat definitely controls temps on AC as well as gas and DC.

I will install a lower baffle, just above the lower vent, and extend the upper baffle all the way across, instead of just the width of the fridge like I have it now.

And I'll find some fiberglass insulation.

Luckily the stress levels are way down right now since it's been in the 60s and 70s during the day and 50s at night, so the fridge is cooling fine. But I'm keeping the pressure on myself to get this all done while I'm not running on gas, and before it gets hot again.

[charlsara]

There is another lengthy post here on electric vrs propane. This thread weighs in heavy for the electric. It is hard to beat a 12v compressor fridge. They just sit there and work. [emoji16]

[redbarron55]

Mine is a swing type and fairly noisy, but it works well.

[Glenn Baglo]

Originally Posted by charlsara

There is another lengthy post here on electric vrs propane. This thread weighs in heavy for the electric. It is hard to beat a 12v compressor fridge. They just sit there and work. [emoji16]

Hey Charlie. Here's another argument for your arsenal, or maybe not :

"Two Propane Gas Supplier Workers Electrocuted when Boom Truck Crane’s Boom Contacts 7,200 Volt Overhead Power Line"

[ZachO]

If I never boondocked, or only did for a night or two at most at a time, ever, there's no doubt I'd go with electric.

If I kept my current lifestyle and style of "camping", but money was no issue, I'd also have an electric fridge and a good battery bank and solar setup.

But since neither of those are true, propane is the clear winner. Not everyone has the issues I do, luckily. It's beginning to sound more and more like if the RV builders just installed the fridges following all the guidelines, we'd all be doing a lot less research and modifications, and just enjoying fridges that mostly work. And for spring and fall camping, even my fridge works great.

But yeah...

[Civilguy]

I am thinking my baffle needs to span the entire distance from lower to upper vent. Otherwise, there is an area in between where the airflow would not be confined to passing through the "tubes and fins" so it can do its job of carrying the heat out...

...something shaped like this as viewed from the side:

Trailer exterior shell side=>]<= Baffle facing back of refrigerator

I want that beer frosty.

[rbryan]

Originally Posted by ZachO

It's beginning to sound more and more like if the RV builders just installed the fridges following all the guidelines, we'd all be doing a lot less research and modifications, and just enjoying fridges that mostly work.

I agree with this, but even when perfectly installed, there's another factor in play here.

The two big players in the absorption fridge market in North America are Dometic and Norcold. Neither will sell a properly insulated high performance absorption fridge in North America. They sell them in lots of different markets all over the world, just not here. For the life of me I don't understand why.

The cooling units on their "tropical" rated fridges are pretty much identical to the ones they sell here - but due to a better door and way better cabinet insulation, the T rated fridges perform well in ambient temps up to as high as 105F.

Aussies for example have their pick of high performance absorption fridges - and far fewer complaints about their weak cooling performance.

[Cathi]

Well, there you go. Let's just move to Australia.

Originally Posted by rbryan

I agree with this, but even when perfectly installed, there's another factor in play here.

The two big players in the absorption fridge market in North America are Dometic and Norcold. Neither will sell a properly insulated high performance absorption fridge in North America. They sell them in lots of different markets all over the world, just not here. For the life of me I don't understand why.

The cooling units on their "tropical" rated fridges are pretty much identical to the ones they sell here - but due to a better door and way better cabinet insulation, the T rated fridges perform well in ambient temps up to as high as 105F.

Aussies for example have their pick of high performance absorption fridges - and far fewer complaints about their weak cooling performance.

[rbryan]

Originally Posted by Cathi

Well, there you go. Let's just move to Australia.

I'm game Cathi, but it would take some getting used to with winter in July and Christmas in summer.

[charlsara]

Originally Posted by Glenn Baglo

Hey Charlie. Here's another argument for your arsenal, or maybe not :

"Two Propane Gas Supplier Workers Electrocuted when Boom Truck Crane’s Boom Contacts 7,200 Volt Overhead Power Line"

Glenn. That is hardly a comparison to a 12 volt trailer system or even the 120. However my profession is safety and I have to agree that electricity kills a lot more people overall than propane. Whatever system we use, inspection and maintenance is critical.

[ZachO]

Originally Posted by Civilguy

I am thinking my baffle needs to span the entire distance from lower to upper vent. Otherwise, there is an area in between where the airflow would not be confined to passing through the "tubes and fins" so it can do its job of carrying the heat out...

...something shaped like this as viewed from the side:

Trailer exterior shell side=>]<= Baffle facing back of refrigerator

I want that beer frosty.

I agree. In theory this makes sense but I assume they suggest the two separate baffles for a reason...I could be wrong.

Interesting that better fridges are available outside the US...

[rbryan]

Originally Posted by ZachO

Interesting that better fridges are available outside the US...

Yeah, but try getting your hands on one here. Some people have simply added a couple solar panels and ripped out their absorption fridge and replaced it with a compressor fridge of similar capacity, like a NovaKool with a high quality Danfoss compressor. Problem solved, even in 110 degree heat, but of course, at a substantial cost.