Compressor fridge - considering adding internal fan

[sabconsulting]

Guys,

Resurrecting an old discussion here - that of adding an interior fan to a fridge. The difference here being a compressor fridge.

I have a Waeco CR140 - 140 litre compressor fridge. It has an exterior fan that comes on when the compressor runs, and I have ducted the air flow so it is forced to suck in exterior air through the heat exchanger and vent it out of the top vent - i.e. to prevent it just circulating hot air inside the space where it is fitted.

But I notice the compressor is still running a lot more than I would want.

Checking the other day I noticed that the back wall of the fridge was frozen even though the cheapo analogue fridge thermometer I have hanging in the fridge showed the temperature was at the top range of what you should have, at least on a domestic fridge.

I suspect I have the fridge set to quite a high setting causing it to run a lot simply to achieve an acceptable temperature in the middle / top of the fridge, but all it is doing is freezing the back of the fridge because the cold is not getting distributed well.

So I am thinking of fitting a small equipment fan internally, run off the fridge thermostat, to blow the air around (probably blowing the air in the fridge against the back wall so as to distribute the cold a bit more evenly.

Hopefully then the compressor would run for less time - the thermostat would click on and as well as the compressor the fan would run and redistribute the cold for a while. The thermostat would then sense the temperature had been reached more quickly and switch off the compressor rather than wasting my battery power.

Does this sound sensible?

Also, any advice on fans?

Thanks in advance,

Steve.

[_DJ_1]

Hey Steve!!!

One other thing you might try is check your door seals. They do lose their capabilities after time. Close the door on a dollar bill on all 4 sides, one at a time, and see if it offers any resistance pulling it out with the door closed. You can also place a powerful flashlight (Streamlight) in the fridge after dark and close the door. See any light?

Might be worth the try.

[sabconsulting]

skipbee wrote:
Hi Steve,

For what it's worth and knowing how good you are with mods. I pass this idea along for possible future use. It is known that top loading fridges are the most efficient. On the Ketch "Imagine" I fitted a 12 volt marine compressor fridge from Adler Barbour. The answer to improved cooling is more insulation. Were I younger, I would in place of our present Norcold ,build a well insulated, 7" or more closed cell, top load with a lid of the same dimension.

We sailed for years trouble free in the tropics, with a freezer baffle and spill over to fridge. We had some solar along with a wind bugger wind generator and almost never had to use the gas generator.
The present Norcold's propane feature is most useful to us, we use it
exclusively for highway travel as our 12 volt system is not too efficient and will kill the batteries when we forget to switch to propane or 115 volt, a common occurance. The main message is " more insulation=better cooling!

Love to all,

skip

Hi Skip,

Yes, if I were to start again I would go with a top loading fridge. I have been really impressed with the 40 litre Engel fridges. They seem less convenient but gravity works out to be a real benefit:

1) When you open the fridge the cold air stays put rather than just flowing out of the fridge.

2) You can pack the contents much more densely with little effort. In my upright fridge you can only achieve a certain packing density before stuff falls out when you open the door. In a top loader you can stuff all the cavities with cheese, chocolate and other good stuff without it falling out :B

You are also right about the insulation. I have already got extra insulation around the outside of the fridge with expanding foam insulation added top and bottom.

Steve.

[skipbee]

Hi Steve,

For what it's worth and knowing how good you are with mods. I pass this idea along for possible future use. It is known that top loading fridges are the most efficient. On the Ketch "Imagine" I fitted a 12 volt marine compressor fridge from Adler Barbour. The answer to improved cooling is more insulation. Were I younger, I would in place of our present Norcold ,build a well insulated, 7" or more closed cell, top load with a lid of the same dimension.

We sailed for years trouble free in the tropics, with a freezer baffle and spill over to fridge. We had some solar along with a wind bugger wind generator and almost never had to use the gas generator.
The present Norcold's propane feature is most useful to us, we use it
exclusively for highway travel as our 12 volt system is not too efficient and will kill the batteries when we forget to switch to propane or 115 volt, a common occurance. The main message is " more insulation=better cooling!

Love to all,

skip




'

[Boatycall]

I just use this... It's a simple RV Fridge squirrel cage fan from Wally Mart. It runs off a couple D batteries and lasts a REALLY long time because it runs the motor through a resistor to slow it down and use less battery juice.

Wally Mart fridge fan

[sabconsulting]

AnEv942 - nice install there.

DWeikert - The vent is definitely closed - we do use that though to keep the door slightly open and ventilated when not using the camper. I suspect the 110 litre fridges are a little more efficient than the 140 litre ones too.

JimK-NY - That 190 litre 2-door fridge does look like a really poor choice on a touring trailer for use in the outback, and with a tiny solar panel. We have 160w and on a sunny day it does power our 140 litre fridge with no problem (draws 6 amps when running :(), but we tend to be driving most days too so the alternator is also topping up the battery. If I intended to be parked up for more than a couple of days I would definitely want either an absorption fridge or a 40 litre Engel. I've had very good experience with the latter - very efficient. You are also right about the wiring. I had to install good thick wire and a very direct wire run to the battery to ensure it didn't suffer from voltage drop when firing up its capacitor, which otherwise results in it shutting down completely (with no error lights).

Steve.

[JimK-NY]

The large Waeco compressors fridges suck up huge amounts of power. If you want to hear a sad tale of trying to run one of these in a hot climate read as much of this as you can stand: http://www.exploroz.com/Members/145028.75/1/2009/Queensland_Adventures_Winter_2008.aspx?p=%2FBlogs%2FDefault.aspx

I had one of these beasts and on warm days it could easily drain 100 AHs or more. Having adequate external ventilation is a big factor. Make sure you have large openings under and above the unit for ventilation. Next check your wiring. These larger units pull about 7 amps. Depending on the distance from the battery bank, you may need an upgrade. I went to 6 gauge wiring. I finally gave up trying to feed the beast and replaced it with a small NovaKool. I cannot answer the question about an internal fan. I did try one of the battery operated refrigerator fans with the NovaKool but found it to be of no use. The smaller unit seems to maintain fairly even temperature without a fan.

[DWeikert]

I have the CR110 model and agree that it does run a lot, but I just assumed that's the nature of the 12v DC compressors.

This may be a stupid question but I have to ask. At the top center of the door there's a device that looks kind of like an edge on disk. In one position the fridge door closes tight in the other the closed door is held open just enough to vent and avoid the odors that accumulate in a standing fridge. You don't by chance have it in vent mode, do you?
See figure 9 on page 6 of this PDF
CR Series manual

[Joe417]

There's no reason not to do it. We use a battery type that sit on one of the shelves in a 6 cu. ft. Ammonia type frig. It will run for about 30 days on 2 D cells.

My wife says it does help keep the interior at a more even temp.

Can't hurt to try it.

[cewillis]

Sounds like a good idea to me, Steve.

[AnEv942]

Small hard drive fans. There are 'kits' sold to do just as you plan. Also small battery powered ones. I used HD fans from newegg.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835150005
I cut in half, wired thru SPDT/center off switch. I can run 1 or both or off. Helped a bit with over all cooling, but more in uniform cooling.