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Old 03-13-2022, 01:58 PM   #1
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A different approach to internal refrigerator fans

This is about the approach I took to adding air circulating fans to inside my RV’s refrigerator. If you are looking to do the same, hopefully this will provide some ideas and understanding. Included for completeness is some info I previously posted in other member’s threads.

To be frank, I was initially confused about all the various discussions regarding adding on fans. After reading a number of posts and doing some internet research I have come to understand there are two basic approaches with Absorption RV Refrigerators that help then perform better. And this applies only to the Absorption types of refrigerators. This does not apply to the home style refrigerator using a compressor.

1. Air circulation around the external components. The heat absorbed from inside the refrigerator needs to be dissipated to the atmosphere. This occurs via an external heat exchanger which is behind the vented cover on the side of the RV. A natural ‘chimney effect’ draft takes place as the refrigerant gas passes through this heat exchanger heating up the air around it which causes the air to rise to the roof vent and exit. It creates a draft just like a fireplace and this airflow is what gets rid of the heat that was absorbed from the interior of the refrigerator. If the roof vent is partially blocked or there is an improper design / ducting in the ‘chimney’ it will minimize this draft effect and reduce the efficiency of the process. Thus one approach is to enhance this natural draft by adding fans either on the Vent Cover blowing air into the space and across the Heat Exchange (and subsequently up the chimney) or by adding fans at the roof vent sucking air up the chimney. In either case it enhances the overall efficiency of the unit with measureable results as indicated in a number of posts.

2. Air circulation internal to the refrigerator. These range from a battery operated ‘fan in a cage’ devices from your local RV Store to professionally handmade ‘hang off the cooling fins’ fan boxes that tap into the 12DCV of the refrigerator that you can buy online from the folks who make them. And of course everything in between that DIYs make themselves. The need for some sort of forced air circulation seems self-evident to me as there is no natural ‘chimney stack’ to encourage it. Upon reflection, with the refrigerator filled with constantly changing and odd shaped items, I am amazed it works as well as it does. I have been using the battery operated ‘fan in a cage’ for years but with my love to tinker, it was time for a project using computer fans.

However, I took a slightly different road from the typical use of PC fans. The concern I had with the fans mounted to the face of the Cooling Fins inside was twofold. One, I did not want to lose storage space and since these fans mount to the face, they take up valuable storage real estate. Two, these fans typically run at high speeds > too fast and too much air flow in my opinion. And even if they turn off when the door is opened, they will take some time to spool down and thus possibly ‘force’ cool air out the door. So, it occurred to me to use a fan small enough fan to fit in the unusable space on TOP of the colling fins and at the same time have a gentler air flow.

About PC fans. Having built a number of PCs I am well familiar with PC fans. They come in a variety of styles and sizes. Some are 2, 3 or 4 wires. In general two types of speed control are used: (1) PWM (Pulse-Width Modulation) and (2) varying the DC input voltage. As the as the name implies PWM fans uses a control signal to regulate speed, so more hardware needed for these. And for the typical 2 wire, speed can usually be regulated by varying the input voltage, but only to a point. Any fan has a minimum threshold to ‘turn on’ and get moving. Once spinning it can generally go to a lower voltage for slower speeds, but I was looking keeping it simple. So I needed a low voltage ‘turn on’ threshold that was also low enough to move the air in a nice and gentle manner. And as mentioned above, I was looking for a small fan that would fit on top of the cooling fins. This is a free space where nothing is ever stored and l liked the idea of taking the warm air at the top (heat rises) and moving it vertically down across the fins. Since the fins are absorption devices sucking the heat out (vs. blowing the cold in), it has a nice appeal to move the air this way. Thus the fan has to be thin and have a small footprint to fit in the space. Fortunately, smallish fans readily exist for mini pcs, 3D printers and the like. So I bought a variety to test out their start up voltage which I was hoping to get as low as 5VDC. I planned on getting the 5VDC from a small Buck Convertor (12VDC > 5VDC) that hopefully would cause a typical 12VDC fan to run fairly slow. The Raspberry Pi fans seemed ideal as they have a 3.3 to 5V range but they are really tiny. And turns out they are simply too small. I also found some thin 40mm square fans both in 12 and 24V. Idea of trying the 24V version was to get the fan speed even slower but was unsure if it would start at 5V. And the 12V versions have a listed start voltage of 6V. Turns out both the 12V and 24V started up on the 5V Buck device. I settled on using the 24V (its 40 x 40 x 10 mm). Note: appreciating there is a voltage drop across a circuit and the longer the wires the greater the drop, I did these tests with 6 feet of 20 AWG wire between the source and the fans… so was a 12-foot loop, much longer than its installed state.

* Side note about these fans. They are brushless and thus do require at least 3 wires and an electronic controller to operate, but technology is such that the controller and its 3-wire output is 100% contained within the case of the fan itself. Waaay cool. If there is a desire out there, I can do a post on how these fans work.

Below are pictures of the fan unit that will fit on top of the cooling fins made from a 2” wide piece of aluminum flat stock from Home Depot. Was able to mill out the fan holes and put in the bolt holes on a ProtoTRAK machine that was available to me.

Fan/voltage selection. In testing out both the 12V and 24V versions of the PlusPoE branded fans I ran them off at their rated voltage as well as 5V. See table for results. Not surprisingly the change is fairly linear. While I have an anemometer the ‘breeze’ generated by one of these fans is so slight that it does not really register. So if we assume that the air flow is also linearly proportional to the speed (and we believe the manufacturer’s rated flow) then we get the next table. Since the calculated air flow of the 24V running at 12V is close to the 12V running at 5V, one could go an even simpler route and eliminate the 12V to 5V convertor all together. However in running both of these configurations on the bench for some time, I preferred the 24V running on 5V based on the lower RPM (which resulted in less vibration) and the seemingly gentler air flow. However, I plan on installing a toggle that allows to switch between 5V and 12V to do some testing and in case the fans simply run too slow at 5V to be effective.

I also considered only having the fans come on only when the refrigerator is actually in its cool cycle but decided not to. A few reasons: (1) these fans have a stated life of 30,000 hrs so that translates into 8 to 10 years running continuously during the season, (2) I figured that constantly circulating air will result in more even temperatures throughout and (3) the power consumption is negligible. I measured 0.2A to run all 5 fans using at 5VDC. It’s 0.9A at 12VDC. So even if boondocking, it’s practically nothing. These measurements were taken at the source (a fully changed battery reading 12.6VDC).

The initial install will not turn the fans off when the door is opened. I’ll do that later on if this all works out as I expect. I have 2 remote temperature sensors that use RF to signal the external display unit so I will be able to monitor the temps at various locations throughout the refrigerator.

About the wiring. I initially considered cutting off the fan plugs and soldering the wires all together on a power leader. But if a fan fails, becomes a real pain. The plugs are a “JST” type at 2.5mm spacing, thus a 2.5 JST male plug was needed. I also will install a connection plug between the power leads for the unit and the wires that will be fed down the drain tube to get power. This will allow for easy removal of the entire unit if need be. And due to the design of the fans I was able to put a small hole near the corner that fit a small zip tie to keep it neat.

To hold the unit down, the plan is to use 2 lengths of small threaded rod that will extend from the flat stock to the bottom of the fins and fastened with stainless steel nylon locking nuts and washers on the bottom. So, it creates a sort of sandwich with the fins in the middle.

More to follow when installed and tested this coming season.

There is still time if you want to get going on your project!

***
Components used:
  • Aluminum Flat Stock: 2” by 1/8” cut to 17” length (based on fin length) milled, drilled and tapped to fit the fans. 6-32 at stainless steel socket head cap screws used to mount the fans.
  • Fans: PLUSPoE Brushless DC Colling Fan 24VDC 40mmx40mmx10mm
  • Male Plugs to mate to fans: found a ‘kit’ that consisted of 5 male & 5 female with leads plus another 5 male without leads. Google “5 Pairs JST-XH 2.54mm 1S 2 Pin Balance Plug Lead Socket Male and Female Connector with 10cm Silicone Wire Cables for Woodland Just Plug Lights 3D Printer”
  • 5V Convertor: 12v to 5v Volt Converter, DROK DC Voltage Regulator Board Power Supply Module, DC 6.3-22V 12 Volt to 5 Volt 3A 15W Waterproof Car Volt Step Down Buck Converter
  • Wire sleeve: Alex Tech Split Sleeving, ¼” diameter
  • Power Leads: 20AWG Bntechgo Ultra Flexible Silicone Tinned Copper Wire
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Old 03-13-2022, 02:40 PM   #2
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Nice work!
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Old 03-14-2022, 07:16 AM   #3
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Fantastic

Great process and sexy solution. I am using the DIY computer fans blowing on the internal coil but it takes up space and the fan blades are exposed for easy touching. I am now going to ivestigate the space above the coil that you used. Thanks for the idea and build level quality challenge.
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Old 03-14-2022, 07:32 AM   #4
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Great job!
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Old 03-14-2022, 08:02 PM   #5
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I like the fan idea, but how much air flow do you need for this concept to be effective? My thought was maybe one small fan would get enough circulation in the box and that would be sufficient. I don't know that the airflow needs to be directly forced over the fins although I can see why that would be better but it would use more electricity with the multiple fans required. Anyone have any thoughts?
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Old 03-14-2022, 10:30 PM   #6
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My trailer has a 2014 Dometic model DMR702. The wife packs it as full as possible. The refrigerator works so well that if set on high items in the fridge compartments start to freeze. The moral of the story is don't worry about fans, pack it full and check once in awhile to make sure it's not set too cold.
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Old 03-15-2022, 10:29 AM   #7
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A different approach to internal refrigerator fans

Brain fart…never mind.
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Old 03-15-2022, 10:44 AM   #8
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Quote:
Originally Posted by kingoffixin View Post
I like the fan idea, but how much air flow do you need for this concept to be effective? My thought was maybe one small fan would get enough circulation in the box and that would be sufficient. I don't know that the airflow needs to be directly forced over the fins although I can see why that would be better but it would use more electricity with the multiple fans required. Anyone have any thoughts?
It doesn't take much and I suspect the OP will find they need to dial down the airflow considerably with that many fans.

One has to watch airflow and not get to the point where you have turbulence and also trying to exchange or force air movement out any seal leakage. You don't want to pressurize the interior.

If you've ever seen the little battery operated interior fridge fans you'd see they don't move A LOT of air, just some and that's all that's needed.

Very nice work by the OP BTW.
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Old 03-15-2022, 05:40 PM   #9
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Quote:
Originally Posted by ESGWheel View Post
This is about the approach I took to adding air circulating fans to inside my RV’s refrigerator. If you are looking to do the same, hopefully this will provide some ideas and understanding. Included for completeness is some info I previously posted in other member’s threads.

To be frank, I was initially confused about all the various discussions regarding adding on fans. After reading a number of posts and doing some internet research I have come to understand there are two basic approaches with Absorption RV Refrigerators that help then perform better. And this applies only to the Absorption types of refrigerators. This does not apply to the home style refrigerator using a compressor.

1. Air circulation around the external components. The heat absorbed from inside the refrigerator needs to be dissipated to the atmosphere. This occurs via an external heat exchanger which is behind the vented cover on the side of the RV. A natural ‘chimney effect’ draft takes place as the refrigerant gas passes through this heat exchanger heating up the air around it which causes the air to rise to the roof vent and exit. It creates a draft just like a fireplace and this airflow is what gets rid of the heat that was absorbed from the interior of the refrigerator. If the roof vent is partially blocked or there is an improper design / ducting in the ‘chimney’ it will minimize this draft effect and reduce the efficiency of the process. Thus one approach is to enhance this natural draft by adding fans either on the Vent Cover blowing air into the space and across the Heat Exchange (and subsequently up the chimney) or by adding fans at the roof vent sucking air up the chimney. In either case it enhances the overall efficiency of the unit with measureable results as indicated in a number of posts.

2. Air circulation internal to the refrigerator. These range from a battery operated ‘fan in a cage’ devices from your local RV Store to professionally handmade ‘hang off the cooling fins’ fan boxes that tap into the 12DCV of the refrigerator that you can buy online from the folks who make them. And of course everything in between that DIYs make themselves. The need for some sort of forced air circulation seems self-evident to me as there is no natural ‘chimney stack’ to encourage it. Upon reflection, with the refrigerator filled with constantly changing and odd shaped items, I am amazed it works as well as it does. I have been using the battery operated ‘fan in a cage’ for years but with my love to tinker, it was time for a project using computer fans.

However, I took a slightly different road from the typical use of PC fans. The concern I had with the fans mounted to the face of the Cooling Fins inside was twofold. One, I did not want to lose storage space and since these fans mount to the face, they take up valuable storage real estate. Two, these fans typically run at high speeds > too fast and too much air flow in my opinion. And even if they turn off when the door is opened, they will take some time to spool down and thus possibly ‘force’ cool air out the door. So, it occurred to me to use a fan small enough fan to fit in the unusable space on TOP of the colling fins and at the same time have a gentler air flow.

About PC fans. Having built a number of PCs I am well familiar with PC fans. They come in a variety of styles and sizes. Some are 2, 3 or 4 wires. In general two types of speed control are used: (1) PWM (Pulse-Width Modulation) and (2) varying the DC input voltage. As the as the name implies PWM fans uses a control signal to regulate speed, so more hardware needed for these. And for the typical 2 wire, speed can usually be regulated by varying the input voltage, but only to a point. Any fan has a minimum threshold to ‘turn on’ and get moving. Once spinning it can generally go to a lower voltage for slower speeds, but I was looking keeping it simple. So I needed a low voltage ‘turn on’ threshold that was also low enough to move the air in a nice and gentle manner. And as mentioned above, I was looking for a small fan that would fit on top of the cooling fins. This is a free space where nothing is ever stored and l liked the idea of taking the warm air at the top (heat rises) and moving it vertically down across the fins. Since the fins are absorption devices sucking the heat out (vs. blowing the cold in), it has a nice appeal to move the air this way. Thus the fan has to be thin and have a small footprint to fit in the space. Fortunately, smallish fans readily exist for mini pcs, 3D printers and the like. So I bought a variety to test out their start up voltage which I was hoping to get as low as 5VDC. I planned on getting the 5VDC from a small Buck Convertor (12VDC > 5VDC) that hopefully would cause a typical 12VDC fan to run fairly slow. The Raspberry Pi fans seemed ideal as they have a 3.3 to 5V range but they are really tiny. And turns out they are simply too small. I also found some thin 40mm square fans both in 12 and 24V. Idea of trying the 24V version was to get the fan speed even slower but was unsure if it would start at 5V. And the 12V versions have a listed start voltage of 6V. Turns out both the 12V and 24V started up on the 5V Buck device. I settled on using the 24V (its 40 x 40 x 10 mm). Note: appreciating there is a voltage drop across a circuit and the longer the wires the greater the drop, I did these tests with 6 feet of 20 AWG wire between the source and the fans… so was a 12-foot loop, much longer than its installed state.

* Side note about these fans. They are brushless and thus do require at least 3 wires and an electronic controller to operate, but technology is such that the controller and its 3-wire output is 100% contained within the case of the fan itself. Waaay cool. If there is a desire out there, I can do a post on how these fans work.

Below are pictures of the fan unit that will fit on top of the cooling fins made from a 2” wide piece of aluminum flat stock from Home Depot. Was able to mill out the fan holes and put in the bolt holes on a ProtoTRAK machine that was available to me.

Fan/voltage selection. In testing out both the 12V and 24V versions of the PlusPoE branded fans I ran them off at their rated voltage as well as 5V. See table for results. Not surprisingly the change is fairly linear. While I have an anemometer the ‘breeze’ generated by one of these fans is so slight that it does not really register. So if we assume that the air flow is also linearly proportional to the speed (and we believe the manufacturer’s rated flow) then we get the next table. Since the calculated air flow of the 24V running at 12V is close to the 12V running at 5V, one could go an even simpler route and eliminate the 12V to 5V convertor all together. However in running both of these configurations on the bench for some time, I preferred the 24V running on 5V based on the lower RPM (which resulted in less vibration) and the seemingly gentler air flow. However, I plan on installing a toggle that allows to switch between 5V and 12V to do some testing and in case the fans simply run too slow at 5V to be effective.

I also considered only having the fans come on only when the refrigerator is actually in its cool cycle but decided not to. A few reasons: (1) these fans have a stated life of 30,000 hrs so that translates into 8 to 10 years running continuously during the season, (2) I figured that constantly circulating air will result in more even temperatures throughout and (3) the power consumption is negligible. I measured 0.2A to run all 5 fans using at 5VDC. It’s 0.9A at 12VDC. So even if boondocking, it’s practically nothing. These measurements were taken at the source (a fully changed battery reading 12.6VDC).

The initial install will not turn the fans off when the door is opened. I’ll do that later on if this all works out as I expect. I have 2 remote temperature sensors that use RF to signal the external display unit so I will be able to monitor the temps at various locations throughout the refrigerator.

About the wiring. I initially considered cutting off the fan plugs and soldering the wires all together on a power leader. But if a fan fails, becomes a real pain. The plugs are a “JST” type at 2.5mm spacing, thus a 2.5 JST male plug was needed. I also will install a connection plug between the power leads for the unit and the wires that will be fed down the drain tube to get power. This will allow for easy removal of the entire unit if need be. And due to the design of the fans I was able to put a small hole near the corner that fit a small zip tie to keep it neat.

To hold the unit down, the plan is to use 2 lengths of small threaded rod that will extend from the flat stock to the bottom of the fins and fastened with stainless steel nylon locking nuts and washers on the bottom. So, it creates a sort of sandwich with the fins in the middle.

More to follow when installed and tested this coming season.

There is still time if you want to get going on your project!

***
Components used:
  • Aluminum Flat Stock: 2” by 1/8” cut to 17” length (based on fin length) milled, drilled and tapped to fit the fans. 6-32 at stainless steel socket head cap screws used to mount the fans.
  • Fans: PLUSPoE Brushless DC Colling Fan 24VDC 40mmx40mmx10mm
  • Male Plugs to mate to fans: found a ‘kit’ that consisted of 5 male & 5 female with leads plus another 5 male without leads. Google “5 Pairs JST-XH 2.54mm 1S 2 Pin Balance Plug Lead Socket Male and Female Connector with 10cm Silicone Wire Cables for Woodland Just Plug Lights 3D Printer”
  • 5V Convertor: 12v to 5v Volt Converter, DROK DC Voltage Regulator Board Power Supply Module, DC 6.3-22V 12 Volt to 5 Volt 3A 15W Waterproof Car Volt Step Down Buck Converter
  • Wire sleeve: Alex Tech Split Sleeving, ¼” diameter
  • Power Leads: 20AWG Bntechgo Ultra Flexible Silicone Tinned Copper Wire
Lot of work, hope it works like you want. One slight correction though, heat doesn’t rise. Hot air does.
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Old 03-15-2022, 05:59 PM   #10
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We found that these inexpensive little fans go a long way in buffering the temperatures inside our RV fridge. Chasing a consistent temp wasn't a big problem after placing it on the shelf near the cooling fins. There is of course, the need to change the setting when the ambient temperature changes significantly.

https://www.amazon.com/Beech-Lane-Mu...33&sr=8-2&th=1
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Old 03-15-2022, 06:15 PM   #11
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@ ‘air’ commuter: LOL, yes you are right, heat naturally moves towards cooler and hot air rises. Was figure of speech and I stand corrected

Some more info on this:

A key to even and more rapid cooling is separation and air circulation. Imagine 4 ‘blocks’ of room temperature items and they are placed, one next to and up tight against the other, in the refrigerator. It will take some time for these 4 items to cool down since, for the two between blocks, 2 of their 6 sides are not exposed to the cooler air but instead butted up against the other room temp blocks. And similar, the two end blocks have one side against the other blocks. If the blocks were spaced out, all 6 sides of each block are exposed to the air in the refrigerator. Now imagine that the air is magically stagnate: is does not move at all. Since air is a great insulator, it will take a long time for these items to cool down. The reason is that blocks will warm the air around them and this air will only start to cool down based on that high insulating quality of air. But if this air is on the move, then the warmed air around the block will be replaced with cooler air. This circulation of cool air around all 6 sides of the block will result in a more rapid and even cool down.

One of aspects of using the 5V on the 24V fans is their very slow speed. When running (at 5V), each fan has a whisper of a breeze. You can just feel it on your cheek if one of them is held close. Move it a foot away, no way. My hypothesis is that this gentle blowing across most of the fins accomplishes two key aspects: (1) it will move any warm air that has risen to the top of the refer (left side, center, right side) and (2) it will maximize the effectiveness of the absorption fins.

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Old 03-16-2022, 06:04 PM   #12
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Quote:
Originally Posted by kingoffixin View Post
I don't know that the airflow needs to be directly forced over the fins although I can see why that would be better but it would use more electricity with the multiple fans required. Anyone have any thoughts?
@kingoffixin
I measured the power required for running all 5 fans and its less then 3 watts when running at 5V. And this was measured at the battery (.2 amps at 12.6V) so takes into account the Boost/Buck device and all the resistance in the 12 foot loop of wire. That translates to over 300 hrs on the RV battery assuming that was the only load.

As a reference, a typical RV 12V incandescent light draws about 1.5amps or 18 Watts.

Also, space for the fans is one of the issues being addressed, and on top of the fins is ideal from the 'it is unused space' with the added benefit of maximizing the total effectiveness of the fans/absorption fins combination (or at least that is my theory ).
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Old 03-17-2022, 11:25 AM   #13
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Wow!
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Old 03-22-2022, 08:24 PM   #14
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Measuring the difference

I have been thinking about how to determine if this device will make a difference. I currently have two RF type temp sensors with an external display. But they do not record any history of temp data. On another thread, the poster talked about BT type of sensors that also report out to a remote display (your smart phone) but have some data history. Who knew?! That is what I like about these forums: discovery and shared experiences. So, I found a set on Amazon and got it. Pictures below. (SwitchBot 4-Pack Smart Hygrometer Thermometer, Bluetooth Wireless Room Temperature Humidity Sensor with App Alerts).

What I like about it is the small size of the sensing devices, that there are 4 of them and will store 30 day of data in the device that can be downloaded.
Now I will be able to better evaluate ‘fans on’ and ‘fans off’ dynamics.

Cannot wait!
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Old 06-11-2022, 05:14 PM   #15
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Update June 2022

I have been delayed in completing this fun project due to (1) truck broke (2) boat broke and (3) COVID. So, this is brief update on the wiring that I have now figured out. Recall I was looking to have these fans on continuously when the refer is turned on (gas or electric) and thus did not want them running when the refer is off, like when prepping the trailer for winter. So, a relay was needed. Also was hopeful to not have the fans running when the door is open. While this was put to the back burner, my delay allowed me to investigate this and now I will be doing this from the get go. So, Fans On whenever the refer is turned on (not just ‘in cycle’) and Fans Off when the door is opened to minimize spillage of the cool air. Neat. But it did require another relay. And while I was looking to use solid state (SS) relays, the ‘off when door open’ aspect required a Normally Closed (N.C.) relay when is problematic in a SS relay. Within the next month I hope to have it all set up and will report on both the installation and the impact. In the meantime, here is the wiring diagram.
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Old 06-18-2022, 11:39 AM   #16
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Update 18 June 2022

Had an opportunity to play with the temp sensors as well as test out the wiring diagram.

Temp Sensors. I placed all 4 of them next to one another in the freezer to start with and let them sit while we were away for the week, so the freezer remained closed. Since they store their history that can be download, Idea was to determine if they all tracked the same. One had a couple of degrees delta to the others, so I kept that one for the freezer. I then put the other 3 in the refer, next to one other, and let them sit overnight. Again, the idea was to see how they tracked together. Conclusion is pretty darn close. Using the sensor whose temp was between the other two as the ‘reference’ the others were off by about half a degree. Pretty good! And with Excel, I can apply a ‘correction’ factor, so I did. Below is the chart of the 3 Refer sensors. Since I am interested in both the rate of change (do they respond to changes in temperature the same) as well as the actual temperate, this was an important test.

Fan Controls. While I was hopeful to get all this done, I was short a few items, so I only temporarily wired it up. This allowed to test out the wiring diagram and make sure all would work as expected. And it did! Below are a couple of pics of this test. One of the challenges is how to mount all this so not an issue going down the road. Found a nice home for the relays on the cover for the control board. I’ll provide some additional pics when all installed and tidied up. The fans are running a such a slow speed I could not hear them and had to use a flashlight to make sure they were spinning. Thus, in retrospect, perhaps I did not need to have the “Door Open > Fans Off” feature, but heck, it was fun to figure out!
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Old 07-01-2022, 04:18 PM   #17
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Mission Accomplished!

Finally, was able to get this completed. And frankly I spent a lot more time on this project then I expected or is warranted. One of the more frustrating aspects was the refer drain tube. It completely fell apart due to being so brittle. It was made from that thin corrugated white plastic tube and just due to age became hard and brittle to the point where touching it caused it to fall to pieces. And the location of the drain nipple out of the refer is high up in the cavity necessitating all work done with extra-long tools which I fortunately had. Else would have needed to pull out the refer which I was unwilling to do! Getting it right took a couple of weekends of trial and error, etc. but I got it!

Here are some pics of the finished project. The next steps will be to see if this effort makes any difference which will take some time to measure with fans on and off.

Overview of the install from the outside.
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Close up of the relays and wiring. I put in plugs wherever needed to allow for servicing.
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Wires from the fans exiting via the drain tube.
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Wire from light. Was able to snake it via same path as refer temp sensor.
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Plate held in place via 2 x threaded rods ‘clamping’ onto the fin.
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Old Today, 06:10 PM   #18
NXR
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Nice work. When I bought my ARP Fridge Defend I bought the model that can power two outside blowers and two inside blowers. The ARP box only supplies power to the blowers when the fridge's cooling unit is turned on.

The internal blowers are two little 2" jobs that Velcro to the top and get aimed at the cooling fins. I installed mine exactly as shown on this page: https://www.arprv.com/rv-fix-fridge-circulation-fan.php

One interesting thing about this particular ARP Fridge Defend model is that it disables Norcold's automatic defrost mode that otherwise occurs every 49 hours. The defrost mode shuts the cooling unit down until the fridge rises to 42 degrees F (and the freezer temp also goes up).

That defrost mode is to keep frost from accumulating on the cooling fins. Last year we had the fridge turned on for 4 months straight and had zero frost on the fins. The internal blowers also noticeably reduces the recovery of the internal temp after loading food, etc.

The internal fans, regardless of how you do it, do make a good difference.

Ray
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