Nova Kool R3800 AC/DC Refrigerator

[RossWilliams]

My Roadtrek does not appear to have any venting to the outside. As someone pointed out, a vent in the side detracts from appearance. So I wouldn't assume that lack of a vent, even on an Advanced RV where price isn't much of an issue, necessarily means they are sub-optimal. It does indicate they aren't really necessary and I think you are likely to be better off sealing the exterior.

[GallenH]

Interesting. As that would imply other measures that need to be taken for anyone doing a retrofit. In a way it makes sense. In the "mild" climate of Phoenix we elected to put our standup freezer inside as opposed to in the garage for similar reasons. We worried about the time it spent running and what that meant for its longevity. Aside from the longevity factor there's a more critical concern for power usage on a RV.

[booster]

I think there are quite few explanations that may be true for venting.


* Compressor frigs have been traditionally for boats. Exterior venting could be a really bad thing for a boat The are mostly designed to take in air at the bottom front and exhaust out the top front.



* Exterior vents are expensive to put in so the manufacturers save a lot of cost by eliminating them.


There are some benefits and some detriments to outside vents besides the above.


* They are more efficient if it is cooler outside than inside, which can save a lot of energy particularly at night.


* The can be a bit quieter as the compressor area is sealed of from the interior of the van.


* It is often easier to get larger airflows through condenser and compressor areas with outside vents.


* If it is very hot out, and especially if parked with the frig side to the sun and don't have the external skin of the compartment insulated, you can use more energy with external vents.

[Bud]

booster, and folks that choose a new B (probably you too) would not choose outside vents - Better looking and more Stealth. Well, maybe not. You might perfect it by adding vents for Hot weather and close em at 20 degrees.

[booster]

Originally Posted by Bud

booster, and folks that choose a new B (probably you too) would not choose outside vents - Better looking and more Stealth. Well, maybe not. You might perfect it by adding vents for Hot weather and close em at 20 degrees.

Good point about if we were all starting from scratch. I doubt any of us would be willing to pay to get outside venting if we had to pay the full cost of it.



I was listing the pros and cons for those that are retrofitting into an existing van the would already have the external vents in place. In that case, I think a pretty good case can be made for using the external vents, if of course the venting of the frig is done properly. The same applies if going to the inside of the van, how well it works is going to depend to a large extent to how well it is vented.

[rowiebowie]

Originally Posted by GallenH

So from this discussion about venting: What do the current mfgs of RVs that have compressor fridges as stock do with regard to venting? Are there no exterior vents to the fridge compartment? I believe I read somewhere on this forum that space on the inside beneath the fridge is vented on some but honestly can't remember.

Many rv makers (in my case Airstream) install compressor refrigerators without the manufacturer's recommended venting. In my case, Novacool recommended 30sq. inches of ventilation both on the bottom and the top of my model. Airstream chose to ignore this with zero bottom ventilation. The top ventilation is provided by the grill around the microwave (which sits directly above the front of the fridge) and does not provide an efficient path for the release of heat. Combined with a lack of insulation behind the upper portion of the exterior wall behind the fridge results in 125 degree temps in that confined area as it sits on my driveway.

I added lower ventilation and insulated the exterior wall to reduce temps by 10 degrees. I also wired a fan that pulls hot air from the upper fridge cavity back into the coach. The fan is on a thermostat (on @ 100/ off @ 85 degrees). The plan is the fan will replace the hot air with whatever the temperature is in the coach, which should never exceed 80 degrees while traveling.
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[mikeehlert]

.....how well it works is going to depend to a large extent to how well it is vented.

This is the fundamental need. If i were building from scratch would have sealed compartment around refrigerator and microwave intake through floor, exhaust thru roof, and a couple thermostat controlled fans.

If it gets so cold in there in winter that the compressor doesn’t need to run fine.

[booster]

Originally Posted by mikeehlert

.....how well it works is going to depend to a large extent to how well it is vented.

This is the fundamental need. If i were building from scratch would have sealed compartment around refrigerator and microwave intake through floor, exhaust thru roof, and a couple thermostat controlled fans.

If it gets so cold in there in winter that the compressor doesn’t need to run fine.

I agree, the floor and roof vent would be the best setup, especially if you have fan boost when needed, as wind and driving can create stalled airflow. Compressor frigs generate tiny amounts of heat compared to absorption units, so gravity venting gets much more difficult because there is so little heat to generate upflow.

[booster]

Originally Posted by ripaco

I have a NovaKool 4500 in my 2004 Leisure Travel. Two lifeline 6V 220AH in series for a total of 220AH at 12V. 200 watts of Renogy solar panels on the roof with Bogart Engineering SC2030 solar controller and BE TM2030 Trimetric monitor so I can view exact amperage going in or out of the battery. It also uses a very accurate algorithm to show the exact percentage of charge in the battery (look it up on the Bogart engineering website if you are curious). NovaKool states that the running amps are 4.4 but I see around 3.4. The compressor refrigerator is not designed to use outside air to reject the heat from the condenser coil. It should have inside air with adequate ventilation as stated in the installation instructions. When I replaced the gas absorption refrigerator, I sealed up and insulated the outside vents but left them removable for access to the compressor and controls. I also insulated the van interior outside wall where the refrigerator is installed. two weeks ago I was dry camping 4 nights at 9100 feet elevation. It was overcast over half of the day every day. Ambient temperature was mid 50s by morning and low 80s in the afternoon. During the whole trip, I ran the generator around 20 minutes total. The battery never got below 87%.

Excellent post and great information. I don't think we want to load up this thread about frigs with other information, but it would be very good for all of us, I think, to see what settings you have in your Trimetric components as this has come up in the other, sometimes not so pleasant, thread on battery monitor accuracy and settings. Please consider going to that thread and posting you settings as it could be very useful, and that thread appears to have settled down now.

[avanti]

To repeat what I said in my original post on this topic:
I would NEVER recommend installing outside vents for a compressor fridge if I were starting from scratch, for all the reasons that have been mentioned. My van doesn't have them either--during the build, I kept reminding the upfitter not to cut those holes!

What I said is that if you already have vents and upgrade to a compressor unit, you should use them. They will certainly work better, except perhaps in the winter. This is perfectly obvious--the idea that it could be better overall to use inside air that you have just paid to cool is crazy talk. And, if you are not running your A/C, the air coming in the vent will almost ALWAYS be cooler than the inside of your van.

Compressor fridges don't NEED vents, and that is a wonderful thing. But, this doesn't mean that they wouldn't benefit from them if they happen to be available.

[eric1514]

Originally Posted by avanti

...
What I said is that if you already have vents and upgrade to a compressor unit, you should use them. They will certainly work better, except perhaps in the winter. This is perfectly obvious--the idea that it could be better overall to use inside air that you have just paid to cool is crazy talk. And, if you are not running your A/C, the air coming in the vent will almost ALWAYS be cooler than the inside of your van...

This is why I used the existing vents when I upgraded to a Novakool 3100. When I'm camping, the air outside is almost always cooler than the air inside the van. If it's 70-80 outside, it's 80-90 inside.

[RossWilliams]

Originally Posted by eric1514

This is why I used the existing vents when I upgraded to a Novakool 3100. When I'm camping, the air outside is almost always cooler than the air inside the van. If it's 70-80 outside, it's 80-90 inside.

That is true for me as well. When its 40-50 outside, its 60-70 inside. One way to look at this is do you want a window that is permanently open.

[eric1514]

Originally Posted by RossWilliams

That is true for me as well. When its 40-50 outside, its 60-70 inside. One way to look at this is do you want a window that is permanently open.

The chimney created by the lower and upper vents is sealed off from the inside of the van by the back of the fridge, the back of the microwave and cabinetry. I made sure the seal is as airtight as I could make it with weather stripping and caulk because as you say, it is potentially a permanently open window otherwise. I was also concerned about carbon monoxide as the exhaust exits very close to the lower vent, although, if I'm producing CO, I'm also moving and the gas won't lazily make its way to the vent two feet away.

[mikeehlert]

Originally Posted by eric1514

The chimney created by the lower and upper vents is sealed off from the inside of the van by the back of the fridge, the back of the microwave and cabinetry. I made sure the seal is as airtight as I could make it with weather stripping and caulk because as you say, it is potentially a permanently open window otherwise. I was also concerned about carbon monoxide as the exhaust exits very close to the lower vent, although, if I'm producing CO, I'm also moving and the gas won't lazily make its way to the vent two feet away.

Think that is a pretty good sounding installation. Does it work well for you?

[RossWilliams]

That makes sense Eric. Of course, when its cold out I would rather have the heat from the fridge stay in the cabin. We have run our furnace way more than our air conditioning but heating is a lot easier than cooling.

[GallenH]

I'm curious: A stock way to vent with no exterior vents appears to be that you use an intake beneath the fridge and then vent through the top of the cabinet usually through the microwave cabinet which has a front grill and would allow good airflow back into the interior.

Can you feel this airflow? Is it warm?

[avanti]

Originally Posted by GallenH

I'm curious: A stock way to vent with no exterior vents appears to be that you use an intake beneath the fridge and then vent through the top of the cabinet usually through the microwave cabinet which has a front grill and would allow good airflow back into the interior.

Can you feel this airflow? Is it warm?

Certainly you can feel the warmth. And, if you don't have adequate convective air flow, it will get very hot behind the fridge. My exit path is through a closet, and it didn't provide enough flow. I installed a pair of computer muffin fans whose speed is modulated according to the temperature behind the fridge. Solved the problem definitively. Also very quiet, since the fans are usually barely moving.

[mikeehlert]

Originally Posted by GallenH

I'm curious: A stock way to vent with no exterior vents appears to be that you use an intake beneath the fridge and then vent through the top of the cabinet usually through the microwave cabinet which has a front grill and would allow good airflow back into the interior.



Can you feel this airflow? Is it warm?

Mine gets air from under the seat via a grill and exits both around the microwave and above the microwave. There is a computer type fan on the compressor to push air past the coils. Yes the air coming out is warm.

[booster]

Our externally vented unit takes in air at the lower side vent and out the upper side vent built into the Roadtrek kitchen window.


The air coming out the vent is maybe 5-10* above ambient so just noticeable as warm. It is a ducted into the condenser and compressor module and sealed for air bypass, so no air leakage to disrupt the air circulation.

[eric1514]

Originally Posted by mikeehlert

Think that is a pretty good sounding installation. Does it work well for you?

It's hard to say and I've only used it for a couple of trips since I did the install a month or so ago and I don't know what to compare to. The fridge is able to maintain 35-36 degrees in 40 to 90 degree temperatures. Above that and it will creep up to 37-38 and run continuously. That usually happens on hot days in the afternoons. After sunset, things return to normal with about a 40-50% duty cycle. Over night, I'm guessing it runs about 25% of the time. I will use 40-60 Ah per day. Not great, but not bad.

The plus side is that it is almost completely silent (I've wired an LED light to tell me when the compressor is on as it is difficult to tell) and I'm not adding heat to the cabin. It was mentioned that the heat might be welcome in winter but the duty cycle would be so low that the heat output would be negligible.