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RedneckExpress · 08-19-2006, 08:17 PM

For a while I had asked about mounting fans to the cooling fins in an ammonia absorption fridge to help with air circulation. Thanks to a lot of people I got great advice on adding a "Draft Induction" system to my fridge in addition to my interior fans as well as a tip on relocating the thermostat wires to allow the fridge to run colder than it normally would have. The combination of all three helped my 32 year old G.E. Fridge quite a bit.

The interior fans helped to make it so that the fridge is now equally cold, stuff on the door stays cold as well as stuff in the back of the fridge.

The exterior fans helped move the hot air that would stagnate in the exhaust stack in the back of the fridge, which reduced its cooling capacity.

My fridge now stays icy cold even in direct sunlight on the camper and when the interior of the camper is 90+ degrees, the fridge stays down where it should be.

Now, onto the project, as always, click on any of the pictures for a larger view.

For my project, I decided I would need about 4 fans for the combination of the interior and exterior. So, I went to our local Fry's electronics here in oregon and picked up a 4 pack of 80mm x 80mm Case fans for $15.

These fans each move about 6 CFM of air, but only draw 0.16 amps of 12 volt power. The combination of all 4 running all the time consumes ~15AH's a day, if my math is remotely accurate (0.16 amps x 4 fans = 0.64 amps drawn x 24 hrs = 15.36 AH), so for my average 4 day camping trip that would burn around 60 AH's of battery, right now, I have 1 group 27 Battery that has show amazing vitality in that it ran my camper with 2 people and showering daily and cooking and doing dishes and lights for 4 days without being run down. I will be adding a second bank of batteries to the camper here in the near future to add additional capacity (2 Trojan SCS225 Batteries @ 130 AH each).

I also picked up a 2 pack of grates for the interior fans to keep food packages from getting stuck into the fan blades by accident. To simplify installation, I glued the two interior fans together and then attached the covers with the screws they came with in the center bolt holes. The outer holes will be used to secure the fans to the fridge fins.

To secure the fans in place I super glued 4 nuts to the correct spots on the fins. I used a fairly small nut and screw combo so that I wasn't attaching a large chunk of metal to the thinest part of the fins. I routed the wire for the 12 volt supply through the existing access hole in the back where the thermostat wires came through. I used fully insulated blade connectors to connect the fan to the wiring, so that if I needed to remove the fans for cleaning, I could completely unattach them and take them out of the fridge.

The fans are now in place, secured firmly by the four small nuts you saw in the previous picture. They're centered in the fins as the right side tends to get coldest first and also the milk spot on the shelf is just to the left of the left fan, so the positioning was perfect to prevent blockage of air flow.

For the exterior and interior fans, I installed 2 LED illuminated toggle switches I picked up from Bi-Mart for $1.99 each, rated for 20amps. I chose two different colors for the different fan banks, blue interior (Cold Air Fans), red exterior (Hot Air Fans).

These switches are all in the right hand side of the fridge, so the wiring was short, as just below the fridge is the fuse block and I just tied into an existing 20 amp fuse.

My exterior cooling fans are mounted between the door and the coils so they pull air in through the louvers and blow it up over the coils and through the top. Not the most perfect looking setup, but then it was a PITA to get those to balance in place while snugging the zip ties...

All in All, the project probably cost about $23 to add a good system of air discharge both hot and cold. At some point, I may add a third fan to the interior block on the right, but for now the 2 in the center work great and I still have room to put taller containers around the fans without blocking any.

RedneckExpress · 08-19-2006, 08:17 PM

For a while I had asked about mounting fans to the cooling fins in an ammonia absorption fridge to help with air circulation. Thanks to a lot of people I got great advice on adding a "Draft Induction" system to my fridge in addition to my interior fans as well as a tip on relocating the thermostat wires to allow the fridge to run colder than it normally would have. The combination of all three helped my 32 year old G.E. Fridge quite a bit.

The interior fans helped to make it so that the fridge is now equally cold, stuff on the door stays cold as well as stuff in the back of the fridge.

The exterior fans helped move the hot air that would stagnate in the exhaust stack in the back of the fridge, which reduced its cooling capacity.

My fridge now stays icy cold even in direct sunlight on the camper and when the interior of the camper is 90+ degrees, the fridge stays down where it should be.

Now, onto the project, as always, click on any of the pictures for a larger view.

For my project, I decided I would need about 4 fans for the combination of the interior and exterior. So, I went to our local Fry's electronics here in oregon and picked up a 4 pack of 80mm x 80mm Case fans for $15.

These fans each move about 6 CFM of air, but only draw 0.16 amps of 12 volt power. The combination of all 4 running all the time consumes ~15AH's a day, if my math is remotely accurate (0.16 amps x 4 fans = 0.64 amps drawn x 24 hrs = 15.36 AH), so for my average 4 day camping trip that would burn around 60 AH's of battery, right now, I have 1 group 27 Battery that has show amazing vitality in that it ran my camper with 2 people and showering daily and cooking and doing dishes and lights for 4 days without being run down. I will be adding a second bank of batteries to the camper here in the near future to add additional capacity (2 Trojan SCS225 Batteries @ 130 AH each).

I also picked up a 2 pack of grates for the interior fans to keep food packages from getting stuck into the fan blades by accident. To simplify installation, I glued the two interior fans together and then attached the covers with the screws they came with in the center bolt holes. The outer holes will be used to secure the fans to the fridge fins.

To secure the fans in place I super glued 4 nuts to the correct spots on the fins. I used a fairly small nut and screw combo so that I wasn't attaching a large chunk of metal to the thinest part of the fins. I routed the wire for the 12 volt supply through the existing access hole in the back where the thermostat wires came through. I used fully insulated blade connectors to connect the fan to the wiring, so that if I needed to remove the fans for cleaning, I could completely unattach them and take them out of the fridge.

The fans are now in place, secured firmly by the four small nuts you saw in the previous picture. They're centered in the fins as the right side tends to get coldest first and also the milk spot on the shelf is just to the left of the left fan, so the positioning was perfect to prevent blockage of air flow.

For the exterior and interior fans, I installed 2 LED illuminated toggle switches I picked up from Bi-Mart for $1.99 each, rated for 20amps. I chose two different colors for the different fan banks, blue interior (Cold Air Fans), red exterior (Hot Air Fans).

These switches are all in the right hand side of the fridge, so the wiring was short, as just below the fridge is the fuse block and I just tied into an existing 20 amp fuse.

My exterior cooling fans are mounted between the door and the coils so they pull air in through the louvers and blow it up over the coils and through the top. Not the most perfect looking setup, but then it was a PITA to get those to balance in place while snugging the zip ties...

All in All, the project probably cost about $23 to add a good system of air discharge both hot and cold. At some point, I may add a third fan to the interior block on the right, but for now the 2 in the center work great and I still have room to put taller containers around the fans without blocking any.

GaryKD · 08-20-2006, 04:24 PM

Congrats, nicely done.

Ragman · 08-21-2006, 05:26 AM

Joe, Thanks for the pictures. I have one fan connected one of the lower racks, which does a fair job. But I really like the way you have done yours. I will take on the project of changing mine. I can see that it would be lots more efficient. Look forward to seeing your outside pictures when you get around to it.
Thanks again for the great post.
Larry

rocinante · 08-21-2006, 09:05 AM

Wow. big job. I notice my new hi-lo has this switch for the fan. Never noticed it on my other rv"s bothe class c and class a.

RedneckExpress · 08-22-2006, 07:40 PM

It took a lot of patience getting the nuts glued into place, that was the hardest part of the whole project, made the wiring look easy in comparison. I was just thankful I was able to route the wire through the already existing hole, I wasn't looking forward to the idea of trying to drill through the fridge housing and then needing to reseal the hole with caulk afterwards.

P.S. I've updated the first post with the exterior fan picture, they're not nearly as nice looking since they were just zip tied in place.

BlauMax · 08-23-2006, 07:50 AM

I'm curious about how well the super glued nuts are holding to the fin area. Super glue is not, as I understand it, a good choice for something like this applicaion. Course, I have a lot to learn..

I think I would have chosen to try to use an epoxy.. maybe something like JB Weld?

Your tutorial is GREAT

bldrbob · 08-23-2006, 08:50 AM

Looks good.My only concern would be vibration going down the road causing wear on the coils .I know they are steel and harder than the zip ties and fan case but a little sand or dust could cause a problem.

BOB

RedneckExpress · 08-23-2006, 11:31 PM

The zip ties are not tight, there's play in them so that they aren't chaffing the pipes, also only one side is attached to the coils, the other side is tied to the vent stack that runs up the left side of the picture.

The super glue is holding solid as a rock, I had tried loctite epoxy prior to the superglue, but didn't dry fast enough to get them to mount right and then never was hardened, it acted far too much like rubber cement and twisted back off when I was just tightening a screw with my finger tips, no pressure on it at all.

I thought about JB weld, but decided after 3 tries and a lot of mess cleaning afterwards with the epoxy, I'd go with a non mix adhesive and used loctite metal rated super glue.

Jeff_in_The_Dalles · 08-26-2006, 04:17 AM

Hey, neat project. The switch location looks super-clean.

I'd also be a bit concerned about the fan near the coils, and I wonder if slack in the zip ties might do more harm than having them tight (so they couldn't move or chafe on a bumpy road). Those cooling units aren't cheap, or easy to replace, so if it were mine I'd prefer to have the fans no where near any of the coils.

What kind of vent do you have above the fridge? If it's one of the roof ones, maybe you could pull the lid off and tuck the fans under there?

As far as the super-glue goes, if it holds, great. If not, you could always zip tie the fan below the fins. I suspect that creating just a little airflow inside will give you the maximum efficiency gain you can achieve with an interior fan, so if space (or power) is that much of an issue I would bet you would keep all what you gained with one fan.

Anyway, that is a really cool idea and nice job.

RedneckExpress · 08-26-2006, 12:45 PM

The roof vent is a permanently attached bit of plastic on the roof, to get it off would require a sawsall and a new roof. In the exterior fans they are zip tied together and only one of them actually comes into full contact with the coils and its the one hanging below the coil, when I get a chance to take it off the truck again, I'm going to reposition them a bit anyway, I put the exteriors in while it was on the truck which was a less than fun experience, mostly due to the door constantly biting into my head.

The main reason they are on the front of the fins blowing out vs blowing up from underneath was, there was plenty of cold in the back of the fridge, just not much of it moving forwards. So, I used a technique I had tried with a TEC based cooler I had that had improved its performance greatly.

Mexray · 09-10-2006, 06:16 PM

Nice installation...however, I wonder if only one fan would have done the job inside the fridge? It only takes a small amount of air movement to insure the cool air reaches all areas.

I have used one of those small 'D' battery powered portable fans inside the fridge on our boat with great success.

Using two fans on the outside coils is a good idea, as you probably can't get too much air flow (within reason) back there. Anything to help the convection of rising warm air probably improves the efficiently of the fridge greatly.

Nice job.

RedneckExpress · 09-10-2006, 09:41 PM

I used two because they were lower CFM rate fans, and I wanted to pull air from more than one surface of the cooling fins. I looked at those little D powered ones, and they only blow air Up, which is not what I wanted. I needed air to be blown forward toward the door so that the air continually cycles across then down to keep everything in the fridge evenly cold, not just the stuff in the back.

BlauMax · 09-11-2006, 07:07 AM

I also have one of the small portable units sold at CW. Since cold air is heavier than warm air, I put the fan toward the bottom of the frig to circulate the colder air up. Seems to work well or me.. however, I really do like the idea of having a unit powered by the coach battery.