Grim Reaper
Expedition Leader
I sort of walked into a deal on some 24v AC units that were on some cabinets I was interested in. Little boogers are rated 986 BTU so really not powerful enough to cool and sizable space.
Well I look up the compressors and it turns out these things will run 12v as well. Its the same brand compressor used in the Waeco 110 but this one is over twice the output http://waecousa.com/page.aspx?p=proportref
http://www.rparts.com/Catalog/Major_Components/compressors/Danfoss/danfoss.asp They are used for making fridges on Yachts. :wings:
THis is what I have for the most part but it has a Air evaporator on it http://www.westmarine.com/webapp/wc...02&subdeptNum=230&storeNum=15&productId=61965
Now most portable fridges like the ARB Waeco and use a Roll bond Evaporator but this this is an already running A/C with an air exchanger. I was looking at swapping the evaporator for a Roll-bond but I was having problems winding somebody I knew to recharge it. I'm also a cheap bastard so I want to make this as cheap as possible. I may still swap it at one point because it will mean lower power consumption.
http://www.rparts.com/Catalog/Major_Components/compressors/Danfoss/danfoss.asp
So I got thinking about my home fridge and it uses and air exchanger style evaporator so I did a little experimenting. I took the lid off my cooler and stuck the evaportaor in it and used card board to seal up the rest of the hole so a LOT of thermal loss for lack of insulation.
The first test I ran the compressor with just the evaporator in the cooler with no fan on evaporator. Stuck a remote thermometer in the box and a probe thermometer I could move around. After about 40 minutes of run time it leveled out at about 43 Degrees. Just wouldn't drop below that with another hour of run time. I stuck my IR thermometer in the Cooler and got a temp of 16 Degrees F on the evaporator. :bowdown: But the lack of air flow through the evaporator just didn't get that cold moving around my poorly insulated box. I had 24v DC fan handy It ran half speed on 12v. Hung it on the side of the evaporator to move some air through it. Out put side was running 28 degrees and the warm side of the box got down to 30 in about 15 minutes. :wings:
Today I am going Cheap cooler shopping. I need something with Perfectly Vertical sides to mount the Set up on for further experimenting. The biggest thing after doing research is that most coolers have really crappy insulation. I may ultimately end up making my own box or adding insualtion to a ready made cooler.
From what I read if I make a air tight box using 2 inch blue board foam insulation it will probably have double the insulation properties of the typical cheap cooler most of us use. That should let me get down to the mid to low 20's in the freezer area.
I also need to down size the fan on the evaporator. I need it to draw less power and run a little slower to allow a little more time to cool the air moving through the evaporator. I think a Pair of CPU fans might do the trick.
Some how out of the 3 high end Fluke meters I have all have blown fuses or other problems so I couldn't get a current draw figure It may be an issue with the wat the compresso runs that it can't get started running through the meter. From what I read this thing will pull about 65 watts at full draw. Now the Compressor is capable of running variable RPM's So I need to investigate what it takes to make that work. Right now its looking like a $200 controller.
Making my own box with the air exchanger will also let me compartmentalize and make a freezer area and a refrigerator area within the same box since I can use duct work to move the cold around to control the temps.. :sombrero:
I have a couple Honeywell industrial thermostats with remote probes on scrap equipment I can lay my hands on to regulate the temp. I got these set ups as a bonus. All I was interested in was the box they were attached to. So my total cost on the prototype will be the box I build and a pair of CPU fans.... :wings:
Well I look up the compressors and it turns out these things will run 12v as well. Its the same brand compressor used in the Waeco 110 but this one is over twice the output http://waecousa.com/page.aspx?p=proportref
http://www.rparts.com/Catalog/Major_Components/compressors/Danfoss/danfoss.asp They are used for making fridges on Yachts. :wings:
THis is what I have for the most part but it has a Air evaporator on it http://www.westmarine.com/webapp/wc...02&subdeptNum=230&storeNum=15&productId=61965
Now most portable fridges like the ARB Waeco and use a Roll bond Evaporator but this this is an already running A/C with an air exchanger. I was looking at swapping the evaporator for a Roll-bond but I was having problems winding somebody I knew to recharge it. I'm also a cheap bastard so I want to make this as cheap as possible. I may still swap it at one point because it will mean lower power consumption.
http://www.rparts.com/Catalog/Major_Components/compressors/Danfoss/danfoss.asp
So I got thinking about my home fridge and it uses and air exchanger style evaporator so I did a little experimenting. I took the lid off my cooler and stuck the evaportaor in it and used card board to seal up the rest of the hole so a LOT of thermal loss for lack of insulation.
The first test I ran the compressor with just the evaporator in the cooler with no fan on evaporator. Stuck a remote thermometer in the box and a probe thermometer I could move around. After about 40 minutes of run time it leveled out at about 43 Degrees. Just wouldn't drop below that with another hour of run time. I stuck my IR thermometer in the Cooler and got a temp of 16 Degrees F on the evaporator. :bowdown: But the lack of air flow through the evaporator just didn't get that cold moving around my poorly insulated box. I had 24v DC fan handy It ran half speed on 12v. Hung it on the side of the evaporator to move some air through it. Out put side was running 28 degrees and the warm side of the box got down to 30 in about 15 minutes. :wings:
Today I am going Cheap cooler shopping. I need something with Perfectly Vertical sides to mount the Set up on for further experimenting. The biggest thing after doing research is that most coolers have really crappy insulation. I may ultimately end up making my own box or adding insualtion to a ready made cooler.
From what I read if I make a air tight box using 2 inch blue board foam insulation it will probably have double the insulation properties of the typical cheap cooler most of us use. That should let me get down to the mid to low 20's in the freezer area.
I also need to down size the fan on the evaporator. I need it to draw less power and run a little slower to allow a little more time to cool the air moving through the evaporator. I think a Pair of CPU fans might do the trick.
Some how out of the 3 high end Fluke meters I have all have blown fuses or other problems so I couldn't get a current draw figure It may be an issue with the wat the compresso runs that it can't get started running through the meter. From what I read this thing will pull about 65 watts at full draw. Now the Compressor is capable of running variable RPM's So I need to investigate what it takes to make that work. Right now its looking like a $200 controller.
Making my own box with the air exchanger will also let me compartmentalize and make a freezer area and a refrigerator area within the same box since I can use duct work to move the cold around to control the temps.. :sombrero:
I have a couple Honeywell industrial thermostats with remote probes on scrap equipment I can lay my hands on to regulate the temp. I got these set ups as a bonus. All I was interested in was the box they were attached to. So my total cost on the prototype will be the box I build and a pair of CPU fans.... :wings:
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