Improved refigerator performance

[fryedaze]

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.

 

[Rambler]

Pretty nifty install.

Is that Malibu? I like your boating style already.

 

[fryedaze]

Thanks, Thats the admirals Malibu. My Crown and Knob Creek single barrel are just out of the picture.

 

[bshanafelt]

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.

 

[Rambler]

Not a Crown drinker. Knob Creek, Bulleit, and most any single scotch works for me.

 

[FlyWright]

Very professional looking installation, Dave. Thanks alot for posting this...now I have ANOTHER item to add to my 'gotta-look-into' list!!

 

[Pineapple Girl]

I'm with Al, gotta look into this. My reefer runs a LOT. Very nice job!

 

[Shoalwaters]

I'm with Al, gotta look into this. My reefer runs a LOT. Very nice job!

Excellent post - fan and insulation for me.

 

[Marin]

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.

 

[fryedaze]

Keep in mind folks, this .16 amps. The benefits are great and the draw down on battery power are minimal.

 

[windmist]

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

 

[Forkliftt]

Great Research

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?

 

[fryedaze]

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.

 

[Marin]

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.

 

[fryedaze]

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.

 

[FF]

Another brands of fridges might be a better replacement choice as some vent into the cabin , so no aux fans required.

 

[fryedaze]

Danfoss comp speed change

Sorry pics are fuzzy. Here is the manual link. http://dometicenviro.com/marinerefrigerator/PDFs/L-2120.pdf

 

[JD]

Sorry pics are fuzzy. Here is the manual link. http://dometicenviro.com/marinerefrigerator/PDFs/L-2120.pdf

So Dave what determines the correct speed for any one unit?

 

[fryedaze]

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

 

[FF]

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.

 

[fryedaze]

Here are link on compressor speed contol. Danfoss BD35 and BD 50 compressors have variable speed capability and can run at speeds between 2,000 and 3,500 RPM. The longer and slower these compressors run, the more efficient they get, so it makes good sense to exploit this feature.

Speed Controllers for Danfoss BD 35/50 Compressors
http://coastalcoolaids.com/images/Compressor_Speed_Control_with_Guardian_and_Merlin_v2_with_pics.pdf
http://www.ra.danfoss.com/Technical..._bd35f_r134a_12-24vdc_06-2011_dehc100d702.pdf

 

[fryedaze]

<P>FF, is that 60-100 amp-hrs in a 24 hr period? My unit draws a max of 7 amps when running on 12 VDC.</P>

 

[rwidman]

Adding to the ventillation of the refrigerator coils will certainly help its efficiency, but you're just transferring the heat load to the cabin or galley. It's usually not much of a problem because it's a large space, but the heat removed from the inside of the refrigerator has to go someplace.

I've always thought the best plan would be to transfer the heat to seawater just like the airconditioner typically does. I believe such units are available but they are not very common, probably because of initial cost.

I suppose it would be possible to cobble something like this up by attaching copper tubing to the refrigerator coils and pumping seawater through the tubing and dumping it overboard.

Would it be worth the trouble? I don't know.

 

[FlyWright]

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.

FF, Is that 60-100 Amp Hours per day?

 

[Larry M]

...I've always thought the best plan would be to transfer the heat to seawater just like the airconditioner typically does. I believe such units are available but they are not very common, probably because of initial cost.

I suppose it would be possible to cobble something like this up by attaching copper tubing to the refrigerator coils and pumping seawater through the tubing and dumping it overboard.

Would it be worth the trouble? I don't know.

We had a water cooled system on our last boat. Efficient as long as the water temperature was less than 90F. When we were on the hard, we had to shut it off.

Waeco makes an affordable water cooled system. SeaFrost also does but more money.

After living with a 12 VDC water cooled refrigeration/freezer system for 10 years and now having a 12VDC air cooled refrigeration/freezer system for 5 years (BD-35F and BD-50F). We prefer the current system. It's about the same in amps/day but better temperature control, more dependable, one less thru hull, no water pump and it works great on the hard.

 

[Larry M]

FF, Is that 60-100 Amp Hours per day?

I would say yes. We have a Danfoss BD-35 compressor for the refrigerator and a Danfoss BD-50F for the freezer. Our total amps, for 24 hours, is ~125-140 amps.

 

[motion30]

a tip I found to work on two different units.. remove the defrost tray in the fridge unit if it has one . Seem to help a bit as tray blocks almost all of the coil

 

[Marin]

I've always thought the best plan would be to transfer the heat to seawater just like the airconditioner typically does.

These are actually fairly popular up here, usually in larger or newer boats.

 

[rwidman]

The other upgrade to the typical marine refrigerator is the cold plate design where the system freezes a plate when there is excess energy available (engine running or shore power available) and then uses the stored cold (technically incorrect language, but easier to understand) to reduce compressor run time when on battery power.

 

[fryedaze]

Ron I just help a friend put a system in his sail boat that can use air or seawater. Its a Seafrost. It only uses .5gpm and it has the same danfoss BD 35 compressor I have. It is VERY efficient. I runs less than 2 hours a day, but the insulation package we put in between R50 and R100. We used VIPs (vacuum insulated panels). One inch gets you R40-50.The system has a smart controller that varies the speed of the compressor based on performance.

Dave