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Old 10-17-2012, 10:28 AM   #1
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Improved refigerator performance

The Tundra T 80 frig setup on our boat did not keep the items in the crisper drawer cold. This was due to the compressor unit directly behind it and inadequate ventillation of the enclosure. The temperatures behind the frig were 145F. My fix was to install a 5.5 inch, 65 CFM, .16amp computer fan. The fan has dropped the cabinent temps to 10 degrees above ambient. It is set up to run when the condensor fan runs. The condensor fan has a .5amp shutoff curcuit, so it was important to have a low amp fan.
During my investigation I learned that my compressor has multiple speeds that can be manually set. Its a Danfoss. I also adjusted the speed of the compressor speed to 3000 rpm. Without the new fan this adjustment dropped my freezer tenp from minus 5 to minus 14F. My frig was running almost continuously before this adjustment.
Prior to these changes the best my frig would do was 39F in the top of the frig. After the changes with the fan and the compressor I found the frig at 22F in less than a days operation. Of coarse this required me to make thermostat adjustment. Prior to this it was set at the highest setting and can all the time.
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Old 10-17-2012, 10:51 AM   #2
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Pretty nifty install.

Is that Malibu? I like your boating style already.
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Old 10-17-2012, 10:55 AM   #3
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Thanks, Thats the admirals Malibu. My Crown and Knob Creek single barrel are just out of the picture.
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Old 10-17-2012, 11:34 AM   #4
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Agreed - great ventilation - supply AND exhaust makes all the difference.

Don't forget to add insulation to the box as well if possible. Even the foil faced bubble wrap from the Box stores helps alot.
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Old 10-17-2012, 01:17 PM   #5
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Not a Crown drinker. Knob Creek, Bulleit, and most any single scotch works for me.
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Old 10-17-2012, 03:34 PM   #6
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Very professional looking installation, Dave. Thanks alot for posting this...now I have ANOTHER item to add to my 'gotta-look-into' list!!
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Old 10-17-2012, 04:31 PM   #7
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I'm with Al, gotta look into this. My reefer runs a LOT. Very nice job!
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Old 10-17-2012, 05:47 PM   #8
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I'm with Al, gotta look into this. My reefer runs a LOT. Very nice job!
Excellent post - fan and insulation for me.
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Old 10-17-2012, 09:14 PM   #9
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FWIW when we got our GB we noticed that the then-one-year-old Norcold under-counter refrigerator/freezer seemed to run a lot. So we timed it and found that on an average summer day it ran about seven minutes and then was off about seven minutes. I thought this was an awfully short cycle time but had no previous experience with marine/RV refrigerators to compare it to. So we e-mailed Norcold.. They responded promptly and said that the on-off cycle we had measured was normal for our unit.

A few years later there was a discussion on the GB owners forum similar to this one, about the benefits of ventilation for refrigerators on boats. While we have not added a fan--- which is a very good idea and one I think Dave conceived and executed beautifully--- we did drill a bunch of two-inch diameter holes in the interior cabinet divider that separates the refrigerator compartment from the under-sink compartment. There were already a series of similar holes at the top of the divider so having more down below at least helped with the air circulation.

From what I have learned on the GB forum and other places the lack of insulation in the typical marine/RV refrigerator is the single greatest source of thermal inefficiency and the main cause of short on-off cycles. I don't know if there are some makes of marine refrigerators with better insulation than others, but it would be nice to know if there are.
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Old 10-17-2012, 09:31 PM   #10
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Keep in mind folks, this .16 amps. The benefits are great and the draw down on battery power are minimal.
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Old 10-17-2012, 09:35 PM   #11
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From what I have learned on the GB forum and other places the lack of insulation in the typical marine/RV refrigerator is the single greatest source of thermal inefficiency and the main cause of short on-off cycles. I don't know if there are some makes of marine refrigerators with better insulation than others, but it would be nice to know if there are.

For a marine refrigerator I think it would be hard to beat the Sea Freeze line located in Bellingham of all places. I have heard nothing but good but be prepared to pay about twice what a Never Cold costs.

Sea Freeze of America - Marine Refrigeration - Refrigerators

As the old adage goes - You get what you pay for.

Ron
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Old 10-17-2012, 09:37 PM   #12
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Great Research

Quote:
Originally Posted by fryedaze View Post
The Tundra T 80 frig setup on our boat did not keep the items in the crisper drawer cold. This was due to the compressor unit directly behind it and inadequate ventillation of the enclosure. The temperatures behind the frig were 145F. My fix was to install a 5.5 inch, 65 CFM, .16amp computer fan. The fan has dropped the cabinent temps to 10 degrees above ambient. It is set up to run when the condensor fan runs. The condensor fan has a .5amp shutoff curcuit, so it was important to have a low amp fan.
During my investigation I learned that my compressor has multiple speeds that can be manually set. Its a Danfoss. I also adjusted the speed of the compressor speed to 3000 rpm. Without the new fan this adjustment dropped my freezer tenp from minus 5 to minus 14F. My frig was running almost continuously before this adjustment.
Prior to these changes the best my frig would do was 39F in the top of the frig. After the changes with the fan and the compressor I found the frig at 22F in less than a days operation. Of coarse this required me to make thermostat adjustment. Prior to this it was set at the highest setting and can all the time.
Dave, well done! We have the same model and it NEVER cooled well. It replaced the failed Norcold comparable unit that came with the boat. I also added a computer fan recently to help compensate for the inadequate air space and this seemed to help. I am VERY interested to find out how to set the Danfoss up for the 3000 rpm. Can you tell me how you did it?
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Old 10-17-2012, 09:53 PM   #13
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My manual indicates that you can change speeds by inserting different resistors into the ciurcuit, but my controls have a smalll curcuit card that is plugged into the speed controls and allows you to select speeds by plugging into the different speed connections. I will get pictures tommorrow.
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Old 10-17-2012, 09:55 PM   #14
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For a marine refrigerator I think it would be hard to beat the Sea Freeze line located in Bellingham of all places. I have heard nothing but good but be prepared to pay about twice what a Never Cold costs.
Thanks for that link Ron. I've filed it with the other potential refrigerator companies against the day when our Norcold finally decides to call it quits. Amazingly it's been working fine for 14 years now with one short hiccup period three years ago. I attribute that in part to the fact it has never been turned off since we bought the boat in 1998.
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Old 10-17-2012, 10:02 PM   #15
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Ok one more item for all you tech geeks. I have a temp and humidity data logger on order that should be here in a week. I will run a test with an without the fan to demonstrate the power consumption and share will my trawler friends.
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Old 10-18-2012, 07:22 AM   #16
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Another brands of fridges might be a better replacement choice as some vent into the cabin , so no aux fans required.
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Old 10-18-2012, 09:06 AM   #17
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Danfoss comp speed change

Sorry pics are fuzzy. Here is the manual link. http://dometicenviro.com/marinerefri...DFs/L-2120.pdf
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Old 10-18-2012, 11:44 AM   #18
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Sorry pics are fuzzy. Here is the manual link. http://dometicenviro.com/marinerefri...DFs/L-2120.pdf
So Dave what determines the correct speed for any one unit?
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Old 10-18-2012, 11:49 AM   #19
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JD, I'm no expert on this equipment, so I cant answer the tough refrigeration technical questions. I just tinkered with it until I got better results. For all I know it may fail down the road due to my tinkering.
Dave
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Old 10-19-2012, 06:18 AM   #20
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Sea Freeze lit sez 60-100A DC consumption with no cabin temps specified.

60-100A is NORMAL for most fridges, a bit higher for inverter fed AC box store fridges.
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