Improving Fridge Cooling

[pulpwood007]

I did a search and read some of the posts regarding modifications to RV refrigerators. Seems like there are several ways to improve cooling, and some that don't work so well.

I would like to hear any about modifications that you have made to to your Dometic or Norcold fridge that improved the cooling in hot weather. Especially how many degrees you were able to drop the temps to.

[dryfly]

NRALIFR:

That thermoworks monitor looks cool. Do you just route the wires through the door gasket? Does that leak cool air?

[NRALIFR]

.

[NRALIFR]

These were taken when I was in a state park near Tucson not long back, and the outside temp was over 100*. No awnings deployed, and no shade on the camper either. The freezer probe is clipped to the center shelf near the back of the compartment. The fridge probe is clipped to the shelf closest to the fins. The temperature at the bottom of the fridge will be 6-8 degrees warmer.





:):)

[Edd505]

dougrainer wrote:

bob_nestor wrote:
First, absorption units do better on propane and 110v than they do on 12v. The 12v is only there to try an maintain temps while traveling.

Second, minimize putting warm things in, so limit the number of times and the length of time you have the unit open and try not to put a lot of things in at the same time that aren't already cooled down.

Third, they all work by transferring the heat to the outside via the cooling coils in the back of the unit. For most installations that uses just normal airflow over the coils - since hot air rises it brings in cooler air at the bottom and exits at the top. Units installed with a top roof vent work better than units with the top vent on the side. Most manufacturers don't follow the recommendations for clearances in the back where the coils are and usually allow too much space. Limiting the space to the recommendations using baffles and such helps with the airflow. Adding fans can help, but be careful. Just moving a lot of air may not be as effective as moving the right amount of air over the coils. Faster air can create a turbulent airflow and a laminar airflow is what you want for maximum heat transfer.

Finally, since the unit's performance is based on the ability to transfer the heat outside thru the coils, the temp difference between the air at the coils and the outside air is important. Try not to park your RV in such a way that the sun is heating the area where the refrigerator is located. And remember that at most the unit can probably create about a 40 degree F temp difference, so it will work better when the outside temps are around 70 than it will when the temps a pushing triple digits.

Are you stating that if the outside ambient temp is 95 degrees then (using your 40 degree), the Interior refer temp will at best be 50 degrees? If so, go back to school and learn RV refers. While outside ambient will affect the capability of an RV refer, I have to check and repair refers in 100 degree Texas heat all thru the summer. With all parameters(install and ventilation at spec), I can get a good cooling unit to produce 28 to 32 degrees in the lower section. There is No such thing as a "40" degree difference in RV refers. Doug(41 years working on RV's and Refers)

Mine must be broke, I get zero in the freezer & 35-36 in the refer.

[dougrainer]

bob_nestor wrote:
First, absorption units do better on propane and 110v than they do on 12v. The 12v is only there to try an maintain temps while traveling.

Second, minimize putting warm things in, so limit the number of times and the length of time you have the unit open and try not to put a lot of things in at the same time that aren't already cooled down.

Third, they all work by transferring the heat to the outside via the cooling coils in the back of the unit. For most installations that uses just normal airflow over the coils - since hot air rises it brings in cooler air at the bottom and exits at the top. Units installed with a top roof vent work better than units with the top vent on the side. Most manufacturers don't follow the recommendations for clearances in the back where the coils are and usually allow too much space. Limiting the space to the recommendations using baffles and such helps with the airflow. Adding fans can help, but be careful. Just moving a lot of air may not be as effective as moving the right amount of air over the coils. Faster air can create a turbulent airflow and a laminar airflow is what you want for maximum heat transfer.

Finally, since the unit's performance is based on the ability to transfer the heat outside thru the coils, the temp difference between the air at the coils and the outside air is important. Try not to park your RV in such a way that the sun is heating the area where the refrigerator is located. And remember that at most the unit can probably create about a 40 degree F temp difference, so it will work better when the outside temps are around 70 than it will when the temps a pushing triple digits.

Are you stating that if the outside ambient temp is 95 degrees then (using your 40 degree), the Interior refer temp will at best be 50 degrees? If so, go back to school and learn RV refers. While outside ambient will affect the capability of an RV refer, I have to check and repair refers in 100 degree Texas heat all thru the summer. With all parameters(install and ventilation at spec), I can get a good cooling unit to produce 28 to 32 degrees in the lower section. There is No such thing as a "40" degree difference in RV refers. Doug(41 years working on RV's and Refers)

[wa8yxm]

There are basically two mods both are fans

I put a set of fan INSIDE the Fridge blowing on the fins. Not only improves cooling but reduces "Frosting" a well.. They are specifically designed for the fridge and attach to the fins.. need to modify it by adding one more fan but that will happen later.

Outside fan may also help but my RV service tech pointed out the fiber crud that built up on the heat exchanger in an area you can not reach) turns out I can blow it out but take a look at your air conditioner condonser coild

Coleman the outside
Most other makes the fan side (you need to remove covers

The crud offsest the effect of the fan.

[doxiemom11]

Not sitting so the sun hits that side of your unit is a big plus. When we had no choice, we added a small fan in the exterior compartment to help push the hot air up and out. That helped quite a bit. This was in 95-108 temps full sun. Norcold 1200. In the future, we will just try not to be in those conditions again.

[pianotuna]

The only thing I see different from 120 volt to gas is time to first cycle. On 120 volt that is 4.5 hours. It is slightly sooner on gas.

Oddly, 12 volt on mine works *great* if I'm plugged into 120 volt. The amps draw on 120 volt is around 34 amps--and when plugged in the 12 (really 13.6) volt draw is about...34 amps.

I'm tempted to get a 12 volt boost device and put it on the 12 volt side of the fridge.

[pianotuna]

cooldavidt wrote:
Correct me if I'm wrong- I think a 12v fridge comes only in beer cooler sizes. Totally impractical to run an RV fridge on 12V alone.David

You are incorrect--though there are small units availble:

https://youtu.be/jMCdrE-4jBI

[pulpwood007]

bob_nestor wrote:
First, absorption units do better on propane and 110v than they do on 12v. The 12v is only there to try an maintain temps while traveling.

Second, minimize putting warm things in, so limit the number of times and the length of time you have the unit open and try not to put a lot of things in at the same time that aren't already cooled down.

Third, they all work by transferring the heat to the outside via the cooling coils in the back of the unit. For most installations that uses just normal airflow over the coils - since hot air rises it brings in cooler air at the bottom and exits at the top. Units installed with a top roof vent work better than units with the top vent on the side. Most manufacturers don't follow the recommendations for clearances in the back where the coils are and usually allow too much space. Limiting the space to the recommendations using baffles and such helps with the airflow. Adding fans can help, but be careful. Just moving a lot of air may not be as effective as moving the right amount of air over the coils. Faster air can create a turbulent airflow and a laminar airflow is what you want for maximum heat transfer.

Finally, since the unit's performance is based on the ability to transfer the heat outside thru the coils, the temp difference between the air at the coils and the outside air is important. Try not to park your RV in such a way that the sun is heating the area where the refrigerator is located. And remember that at most the unit can probably create about a 40 degree F temp difference, so it will work better when the outside temps are around 70 than it will when the temps a pushing triple digits.

I cannot tell a lot of difference in performance on LP vs. 120VAC. I try to achieve laminar airflow by using the same amount of CFM at bottom of coils and at top (exhaust). Within reason, I'm not sure why having more air passing over the coils would be a negative issue.

Living in Texas, I sure need more than a 40 degree differential from the ambient outside temps. I've been able to achieve that at times but not always. Humidity seems to play a large role.

My previous trailer exited at the top, and required me removing the fridge and building new baffles. My new Grand Design trailer exits on the side of the slide, and looks as though they followed manufactures specs so I don't feel that's an issue.

I'm definitely going to add some fans but also looking at the ARP Fridge Defend system. I may use my muffin fans and not their squirrel cage type.

I have yet to determine if the add on fridge interior fans do that much.

Thanks for all the replys.

[theoldwizard1]

bob_nestor wrote:
... at most the unit can probably create about a 40 degree F temp difference, ...

I think that number is a bit optimistic, but the bottom line is you won't be getting "ice cold" beer out of one on a 90F day !

12VDC compressor refrigerators DO EXIST !

However, a good, Energy Star, high efficiency residential refrigerator, an inverter, some decent house batteries (minimum TWO 6V golf cart batteries, 4 is better) so solar panels (or a couple of hours with a generator and battery charger) and you will be a much happier camper.

[dougrainer]

MitchF150 wrote:
Interesting.. I find gas works better for me, especially when it's really hot outside (80*+ and even in the 90's*). With the additional fan setup I now have, it really helps while on gas.

Mitch

BOTH LP and 120 have the SAME BTU output. But, there are variables that affect 120 operation. LOW 120 voltage(below 115) will cause lower BTU heat output, which causes people to think LP is better. So, you need to monitor the 120 voltage with a DIGITAL Meter, NOT those cheap needle wall RV plug in types. When the voltage drops below 115, operate on LP. Voltage drops are common in parks that are in hot climates with a LOT of RV'ers. Doug

[MitchF150]

Interesting.. I find gas works better for me, especially when it's really hot outside (80*+ and even in the 90's*). With the additional fan setup I now have, it really helps while on gas.

Mitch

[cooldavidt]

Correct me if I'm wrong- I think a 12v fridge comes only in beer cooler sizes. Totally impractical to run an RV fridge on 12V alone.

I do what you do. Electric if available, gas when I am moving or stopped for short periods. I find gas does not cool as well as 120v under the same conditions.

David

[MitchF150]

David. I run it mostly on gas. I start it on gas, will leave it on gas during the trip and only switch to 120v once it cools down in the evening and over night (I usually will have at least electric hookup where I go)

Then, during the day, switch back to gas. Yes, running the A/C during the day really helps too.

My water heater is gas/electric too and I start it on gas and then switch to electric for the duration while camped after it's up to temp.

I meant the fans run on 12v.. The fridge does not have a 12v option, and I wouldn't use it anyway, since it has to work so hard to keep cool on gas!

Good luck! Mitch