Increasing Airflow through Condenser.

Sorry Westend, never saw your post 6 months ago.

Yes, my generic Watts up meter( GT power) , in sub 60 degree weather, claimed it took 3 days before my small 1.8 cubic foot fridge consumed more than 24 A/h. This meter cannot accurately read draws below 0.8 amps, and does not account for the internal fan of 0.03 amps nor the small parasitic draw of the circuit board. But the amperage displayed when the compressor is running is spot on my my clamp on DC ammeter and my shunted ammeter

A few days ago I removed the fridge for a condenser and fan cleaning.


That is about 9 months of dust build up.

I placed my inline meter back on the fridge afterward, but forgot to check it after 24 hours, and forgot exactly when I installed it, and it resets back to 0 at 64 amp hours anyway.

Fridge still performs awesome, even with the dust build up. I still have the same internal fan running 24/7. I can still start freezing things at a setting of 3.5 of 7.

I keep it at about 2.2 of 7 to hold sub 36.5f internal temps, and hot weather three digit spells did not require increasing this to keep sub 39f internals.

Wonderful thread on use of fans and modifications on refrigeration! Did I understand correctly that at 60f ambient, you are drawing 24AH per 72 hrs.? That is absolutely the lowest I've heard. I think I may be in for a 120V-> 12V replacement sooner than expected.

Thanks all. I have been looking at replacement fans; quieter and lower draw, real bearings instead of sleeves. I Googled the fan model that the fridge came with; 73 cfm, 0.19 amps. 2.4 mm/H2O static pressure... according to the Chinese spec sheet. I've been looking at a Noctua and thinking of getting a pair. Together they spec at less amperage than the single Donnguan Yuhong, better static pressure, almost the same CFM for one and lower dB.. Still looking at others.

Too many irons in too many fires right now. When my son returns my DC watt meter I'll take some reading and try a new fan or two. May take a while.


landyacht318, I agree with the opinion about the engineers and the beancounters. There are very few engineers who get to practice their specialty without having to design to a cost. If a few cents can be saved it will be done to save that money. When it is a matter of dollars difference it is no contest as long as the decision will not come back to bite the company in the pocket/check book. On the other hand to someone trying to make something they own better, the cost of one or two high quality fans is irrelevant in the big picture. Happiness is worth something.

Bob Landry wrote:
in 15 years of selling and servicing Tundra, NovaKool, Vitrifrigo, Isotherm, and I'm sure there are others, I have never seen a detached cooling fan or condenser, ducted or otherwise. If anyone has one, I would love to se a photo.

Nobody said anything about "detached cooling fan". But there are passive condensers, look here.
Not "detached" from the fridge (which has never been said, if you look in the post that you quoted), but placed pretty far from the compressor. And there is a (optional?) compressor fan to install in the compressor nook, see this Service Memo: Installation of fan on R1600/R1900/R2600/R3000. Note again passive condenser on the back of the fridge on the 3rd photo - the fan is only for compressor, condenser doesn't need it.

These fridges are of course sold all over the world, this isn't something "not for exports". Which is only logical if you consider that most residential 120V fridges have same design - passive condenser at the back.

Vitrifrigo went even further, offering a detached compressor, meaning - completely detached from the fridge and connected to the system via long tube, so that you can place the compressor where air flow is better or where there is more room.

If my memory doesn't fail me, Dometic also has an option of a detached compressor with one of their boxes.

Bob Landry wrote:
They are all built on the compact footprint with the condenser mounted on the edge of the base plate and the fan located between the compressor and condenser drawing in air towards the compressor.

Not "all", but many. Those under say, 2.5 cu.ft typically have such a compact design where compressor and condenser are bundled together in a small nook. Such a solution is not the best for air flow, that's why fan is mandatory. I think the best would be to have condenser unfolded over larger surface AND a forced fan cooling. Though if passive condenser is large enough and the compressor has enough space around it, the fan becomes unnecessary.

I agree the Danfoss compressors will have little trouble if installed without enhanced airflow measures.

The Danfoss bd35f can power an 8 cubic foot fridge at max RPM IIRC, so this same compressor is coasting along powering my 1.8 cubic foot fridge.

I also feel that my unnecessary modifications have considerably added to the efficiency, and I am thoroughly impressed with its performance. In terms of battery consumption, noise, and interior temperatures.

People can choose for themselves whether they want to go through the effort of finding and installing a quieter, more efficient fan to replace whatever sleeve bearing fan fell within the broad specs at the time of assembly.
Whether more insulation and/or a cabinet recess which is optimized to bathe the condenser, compressor and controller in ambient air and evacuate the created heat is worth it. The fridge will still maintain sub 40f interior temps without them.

On many marine forums I visit it appears it was the earlier Danfoss compressor controllers which failed most often, and they were on units which used a sea water cooled condenser and had no forced airflow in the compressor/controller compartment. They since added a finned heatsink to the back of the compressor controller to help dissipate the heat generated by high duty cycles. This Controller costs about 250$ to replace.

Seems to me, the only one to profit from not taking any of these unnecessary measures, is someone who sells or services such units.

Anyone seeking to minimize battery consumption and has the skills to enhance heat removal, perhaps even without touching anything on the cooling unit itself, would be wise to do so, in my opinion.

Also the Cabinet should be designed so that one can easily remove dust hair dust and other detritus from the condenser fins and fan blades. I need to unscrew my fridge and slide it out to do so, but would build a new cabinet differently to accomplish this task easier if I were to start over.

Instead I am going to soon have a low restriction easily replaceable/ perhaps washable air filter on my intake which might eliminate the need to clean the detritus from condenser fins and fan blades.

Almot wrote:


There are fridges where condenser and compressor are not packed in a small bundle - condenser is large and placed far away from the compressor and does not require a cooling fan, and compressor has plenty of space around it. Ex, some Novakool units. But they still offer optional compressor cooling fan. Because compressor is VERY hot.

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Maybe there are some "not for export" versions made in Canada, but in 15 years of selling and servicing Tundra, NovaKool, Vitrifrigo, Isotherm, and I'm sure there are others, I have never seen a detached cooling fan or condenser, ducted or otherwise. If anyone has one, I would love to se a photo. They are all built on the compact footprint with the condenser mounted on the edge of the base plate and the fan located between the compressor and condenser drawing in air towards the compressor. Mechanically, these systems are just about bullet proof right out of the box. Maybe someone did a "shade tree" job on one but I have never seen it done. The existing design is not a bean counter creation either. Danfoss has been building their condensing modules this way since I began servicing them in the mid 90's beginning with the Adler Barbour icebox conversion kits. Beneteau Sailboats will often install a duct from a small grill to the condenser fan but that's because it's usually located in a lazeret along with batteries, an inverter, converter, reverse osmosis water maker, and other equipment that generates a lot of heat. I personally had one that ran 24/7 for 7 years in a closed cockpit locker with no external cooling with zero issues. If there is going to be a problem with these units, it's usually going to be a bad electronic unit or a condenser fan failure, none which can be directly attributed to heat buildup in the space. Mechanically, these units are extremely reliable and I can count on one hand the number of compressors I've changed out and have fingers left over .
If and when my absorption box ever fails, it's going t be replaced with one of these compressor boxes, much more bang for the buck.

Looks like they really shoehorned that cooling unit in on the back of that TruckFridge.

The Danfoss/Secop controller can handle powering 0.5 amps of fans and upto 1 amp for a few seconds. I'd suggest you hook up another low draw, low cfm fan to the controller to exhaust the hot air from the area and draw cooler air into it. The Fans available vary greatly in output for noise made and current consumed.

My System is working beautifully and in sub 60 degree weather it take more than 72 hours for the fridge to consume 24 amp hours. I've got a "Watts up" meter I can hook inline. Here it is next to my controller where I have a removable panel for winter time to keep warm air inside the living compartment and not draw cool air in past weak seals.


I've not reread this whole thread, and don't remember it all, but long story short, I never reversed the airflow. I did add more insulation to cabinet walls and fridge walls which allowed me enough room to move the fan to the other side of the condenser. These fans are much quieter pushing air through a restriction rather than pulling it through one.

I'd also made a cooling unit tunnel to direct all fan flow through condenser, and across compressor and controller. This air is then directed out a louvered vent behind the fridge, or into the next compartment of the cabinet where I have another fan exhausting air into the living space.

Having moved the fan makes it much easier to clean the dust off the fan blades and condenser twice a year. The cooling unit tunnel also protects the unit from installation/ removal stresses, as I do need to remove it to access the fan and condenser. 4 screws and disconnect a powerpole connector and it slides right out easy peasy

It is said that the best way to increase fridge performance is by making sure the condenser is not sitting in air it itself has already warmed. I feel that just letting it stew in its own juices with a few passive vents in the area is like a vehicle radiator with the grill blocked off and wondering why the engine runs hot.

Mine has 0% chance of running preheated air through the condenser or across the compressor, and I'm sure if the bean counters allowed the engineers to design it this way, they would, but what does a bean counter care if your fridge consumes 24 amp hours per 24 hours, or 30 A/H. There is enough wiggle room on their spec sheets, and there is no truth what so ever in advertising anyway. Besides that, they can't design the cabinet where the fridge will reside and the manufacturer making recommendations as to how to design the cabinet for most advantageous airflow for maximum efficiency will make 90% of the public thing it was not designed properly in the first place, rather than as a compromise and good enough for those who don't understand the physics.

Doing these mods is not trying to outthink the engineers, it is undoing the damage done by the beancounters to the engineer's designs, what they would do if allowed free reign, in my opinion.

My Engel is what, 8 years old going fast on 9,, The only thing I've done with it other than use it and occasionally defrost it is.. Well last summer during a defrost I took it outside and set it on the Picnic table.. Got out the Crafstman 160 PSI Huffer Puffer (air compressor) and the jet nozzle and blew like Gabriel (Put on a dust mask first) Looked like a dust storm for a while.

Blew it clean I did.

Shortly after we got it, and when we decided to sell the house. We shut down our big upright freezer (The model I have is a freezer OR frige depending on where I set the knob) and used it in the house as our house freezer.. Way less power than the big boy. Ran it on 120 then. Normally run it on 12 since at 3 amps it's not worth switching over.

Oh, and also last summer when the 12 volt failed, I snagged a computer power cord from my spares kit and ran it on 120 till I found the 12 volt issue,,, Which reminds me I have another issue on that distribution panel I need to address.

Old thread, but there is so little knowledge about 12V fridges in RV that it doesn't hurt digging it up again.

Those compact compressor/condenser bundles have not too good design of airflow, but it's difficult to improve. Cool air is drawn through the warm condenser and this is right. But then this air, warmed up after the condenser, is directed towards the hot compressor. Are you still with me? :) a warm air is supposed to cool down a hot compressor. Alright, compressor is VERY hot, so cooling it with warm air is still better than not cooling at all.

There are fridges where condenser and compressor are not packed in a small bundle - condenser is large and placed far away from the compressor and does not require a cooling fan, and compressor has plenty of space around it. Ex, some Novakool units. But they still offer optional compressor cooling fan. Because compressor is VERY hot.

Do not reverse the flow, you'll make it worse.

In your fridge, hot air after compressor escapes upwards as is the nature of a hot air, and should better be given some way to vent out through either roof of wall above the fridge. In the worst case, let it flow into the trailer above the top of the fridge and dissipate in the trailer volume.

The main purpose of the fan is to cool the condenser. The compressor gives off heat and it would not make sense to draw warm air from the compressor over the condenser coil.