eDJ_
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It looks like the animation link corrupted
http://www.hvaceducationaustralia.com/Resources/Images/Absorption System.gif
http://www.hvaceducationaustralia.com/Resources/Images/Absorption System.gif
Why doesn't my 'fridge work well on 12v?
- Thread starter TMG51
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highdesertranger
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the drop in replacements for the smaller ones are on engels website. http://www.engelcoolers.com/fridge-freezers . notice at the bottom of the page the also have a retrofit kit to retro yours or build your own. I have seen other manufacturers that have drop in replacements to, I thought dometic was one of them. I would go strait to the manufacturers web site to see what is available. get the part number and do a search for that number. highdesertranger
Looks like the Isotherm CR-130 and the Truck Fridge TF130 are the only two compressor fridges (so far) that would fit in my opening without rebuilding the whole interior. Interesting, the Truck Fridge is half the price. I wonder how performance compares. I don't see any reviews.
http://truckfridge.com/tf130.html
http://truckfridge.com/tf130.html
His outfit worked on Propane, 115 volt AC, but not so great on 12 VDC sitting in the driveway.
But when on the road and underway the 12 VDC did a good job. He had to stop and check
to see that it wasn't freezing things on longer trips. Often he turned it off for an hour or two
before turning it back on when underway just so his stuff wouldn't freeze. I don't know if this
is typical or if others have experienced this with their outfits or not ?
[/quote]
I had this happen a number of times in a 1990 Chinook.
But when on the road and underway the 12 VDC did a good job. He had to stop and check
to see that it wasn't freezing things on longer trips. Often he turned it off for an hour or two
before turning it back on when underway just so his stuff wouldn't freeze. I don't know if this
is typical or if others have experienced this with their outfits or not ?
[/quote]
I had this happen a number of times in a 1990 Chinook.
Spaceman Spiff
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ZoNiE said:
I have 200W solar and 208 AH battery. I run an old Norcold 2.1 ft³ compressor refrigerator (at 34° F) and a Maxxfan as my largest loads. My batteries are at 100% by noon.
eDJ_ said:
That is a problem with the temperature feedback control (or temperature setting), not the refrigeration unit. Your friend is acting as a coarse manual temperature controller by turning on and off the refrigerator (which is what the controller should be doing).
TMG51 said:
Truckfridge is basically the same as Vitrifrigo and is the cheapest 12V compressor frig I have found. Lots of good reviews on trucking and sailing sites. Everything is more expensive on marine sites.
-- Spiff
LeeRevell
Well-known member
That TruckFridge unit looks pretty good. "24 Watts per hour", hmmmm....... works out to about 2A per hour.
Found this handy Watts to Amps conversion website online:
http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm
Found this handy Watts to Amps conversion website online:
http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm
SternWake
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12v Compressor fridges of the same size, and in upright format, are all very comparable to each other in power consumption, and all of them will list misleading amp draw figures.
Some will say how much they will consume over an hour, some will say how much they consume when the compressor is running.
12v fridges with the danfoss/Secop compressor, the bd35f, have an adjustable compressor speed. This is done by changing the resistance on the thermostat circuit to the compressor controller.
Slowest speed is 2000 rpm which consumes about 2.4 amps, and highest speed which is 3500 rpm and this consumes about 6.5 amps.
The faster the speed the faster the initial cool down, and the shorter the run times when the compressor does cycle on.
The slower the speed the slower the cool down and longer run times when the compressor does cycle on.
The slowest compressor speed which maintains the proper temperature and also runs less than 50% of the time, is most efficient.
There are Many similarities between Dometic, vitrifrigo, Isotherm, truckfridge and a few others, chief being the box, and the compressor itself.
However the condenser and evaporator(cold plate) and thermostats all differ brand to brand, and their plumbing, how they are mated to the compressor is also different. My VF actually has a filling port if it gets low on refrigerant. I see some others just crimp the ends of the tube and solder it to seal it rather than have a fill port.
While My Vitrifrigo c51is came with a 120MM fan screwed/mated to the radiator like finned condenser, and covers the whole condenser, the Truckfridge's come with a 92MM fan which only covers a portion of the condenser and it is just Zip tied to the condenser.
I've Added extra insulation to my VF, modified the fan position to the other side of the condenser so it pushes air through it instead of pulling, and upgraded the fan to one with much better ratings.
This fan pulls cool filtered air from the floor below the fridge, and this air has no chance to be recycled once it has been pushed through and heated by the condenser and compressor. This is an area which can easily double the electrical consumption of a compressor fridge. If the cooling unit bathes in hot air it itself has heated, it has to run longer to remove the same amount of heat within the box. Properly ventilate the cooling unit. This is almost never done properly when 12v compressor fridges are installed in the factory, whether RV or Boat and has started the negative myths surrounding 12v compressor fridges. Installation and initial design error of the cabinet into which it is to reside.
I've also added a 0.03a 40MM fan to the interior, which runs 24/7. It takes 12v from the LED light. it makes a huge difference in evening out internal temperatures, assists cooling down warm items placed within much faster, and allows me to lower the tstat setting from 4 of 7 to 2.2 of 7 to maintain 36.5F or lower. This internal fan is a very small heat source, and as such does not make the fridge use less battery power.
I've added a significant amount of extra foam board insulation around the whole box, and the cabinet in which it resides is also insulated. The weak spot is the door and not too much to be done about it. And the electrical consumption is slight enough I am not worried about the door which sweats in humid conditions, even though this is a sign that it is not insulated as well as it could be.
But my 1.8 cubic foot fridge rarely consumes more than 0.6A per hour in my normal usage. I never worry about it. It is always cold and my 200 watts of Solar makes many times as much electricity as needed to run just the fridge. In fact I am also running an ARB chest style fridge freezer at the moment as well as my VF, even though I do not need to.
My DC only fridge came with an AC/DC option for another 100$. I put that extra 100$ toward my 40 amp 12v adjustable voltage power supply, so any time I have 120vAC available, I can charge my batteries, and power ALL DC loads. 100$ more just for the AC option on ONLY the fridge, seemed like a waste to me.
The only time the AC/DC option would be a nice feature, is if I moved into an apartment and wanted to use the fridge in the apartment. With 40 amps available from my power supply/charger, the 2.8 to 2.2a needed by my fridge would slow down charging, by a very small figure if the battery was depleted enough to max out the power supply.
Not gonna happen, so since one needs a charging source anyway, I recommend Not paying extra for the AC DC option if it is significantly more expensive than a 12v DC only fridge.
I have removed the 270 OHM resistor provided with my VF c51is to reduce compressor speed from 2500 to 2000. When the compressor first cycles on, it consumes 2.8 amps or so. About 5 minutes later when the compressor is about to cycle off, amp draw has lessened to 2.2amps.
So Do not obsess over the manufacturer listed amp draws. They are variable and you are not going to find one fridge significantly more efficient than another, and their proper installation with regards to cooling unit ventilation, can make or break any fridge's efficiency.
I Considered the Truckfridge, but then I decided Vinchenzo in Italy probably took more pride in his workmanship than Did Chin Ho outside Beijing, so I spent the extra for the VF, and no regrets.
The TF design of the cooling unit, would not have allowed me to swap the fan to the other side of the condenser, which not only was much quieter, but also more effective as computer fans are much better at pushing air through a restriction than they are at pulling air through one.
Absorption fridges run on 12v never work well, and are complete power hogs. Absorption fridges provide a 12v option as it is illegal to run the propane function when driving. Especially through tunnels or when filling the gas tank. Most 12v absorption heating elements draw 8 to 14 amps, and this is continuous. And even at that huge electrical consumption, will fight the losing battle of interior temperature. An Absorption fridge run on 120vAC, will consume a lot more electricity than a household compressor fridge of the same size. Absorption fridgesmake great use of fossil fuels for cooling, and their electrical options for cooling redefine inefficient.
Not wasting solar wattage is often brought up on this forum, but only by newbies. Those of us with solar surpluses might go as far as cranking up the fridge until the late afternoon, or charge the laptop battery or other things, but we do not stress out if we have more solar than our present needs dictate. it is not worth the effort, and having too much solar, is a good thing. It will make your batteries happier the faster in the day that they are recharged.
One mistake that many people make is they believe their solar charge controller when it states the batteries are full. A hydrometer will usually reveal this to be wrong. The solar controller rolling back to float voltage and flashing the full charge indicator, means only that the controller has held absorption voltage as long as it was programmed to do so, and, for fear of overcharging and greedy lawyers, they are all programmed timidly, and the user needs to bump up Absorption voltage and duration at which it is held, especially when cycling the battery deeper. The deeper the discharge of the battery, the more important it is to have the correct absorption voltage held for longer. Charging a battery from 85% to 100% is a whole different animal than a battery cycled to 50%, So one Cannot mindlessly believe their charging source when it flashes the full charge indicator.
A blinking green light, does not equal 100% state of charge, unless confirmed by a Hydrometer, or when AGMS are employed, when the AGM batteries accept less than 0.5 to 1% of their rating at the manufacturer recommended absorption voltage. No ammeter? You are blind.
I can program my solar controller to flash the green light and hold only float voltage by 9 AM. It does not mean the batteries are full. I could convince 99.5% of people that is exactly what it means though.
Flashing green lights/full charge indicators, are chronic liars. Don't let them make a fool of you. If you do, you will not get as many cycles from your batteries, and have to replace them prematurely.
And works 'just fine' only means 'has not failed yet'.
Worked just fine for 500+ deep cycles, is truly 'just fine', but no lesser claim qualifies.
Some will say how much they will consume over an hour, some will say how much they consume when the compressor is running.
12v fridges with the danfoss/Secop compressor, the bd35f, have an adjustable compressor speed. This is done by changing the resistance on the thermostat circuit to the compressor controller.
Slowest speed is 2000 rpm which consumes about 2.4 amps, and highest speed which is 3500 rpm and this consumes about 6.5 amps.
The faster the speed the faster the initial cool down, and the shorter the run times when the compressor does cycle on.
The slower the speed the slower the cool down and longer run times when the compressor does cycle on.
The slowest compressor speed which maintains the proper temperature and also runs less than 50% of the time, is most efficient.
There are Many similarities between Dometic, vitrifrigo, Isotherm, truckfridge and a few others, chief being the box, and the compressor itself.
However the condenser and evaporator(cold plate) and thermostats all differ brand to brand, and their plumbing, how they are mated to the compressor is also different. My VF actually has a filling port if it gets low on refrigerant. I see some others just crimp the ends of the tube and solder it to seal it rather than have a fill port.
While My Vitrifrigo c51is came with a 120MM fan screwed/mated to the radiator like finned condenser, and covers the whole condenser, the Truckfridge's come with a 92MM fan which only covers a portion of the condenser and it is just Zip tied to the condenser.
I've Added extra insulation to my VF, modified the fan position to the other side of the condenser so it pushes air through it instead of pulling, and upgraded the fan to one with much better ratings.
This fan pulls cool filtered air from the floor below the fridge, and this air has no chance to be recycled once it has been pushed through and heated by the condenser and compressor. This is an area which can easily double the electrical consumption of a compressor fridge. If the cooling unit bathes in hot air it itself has heated, it has to run longer to remove the same amount of heat within the box. Properly ventilate the cooling unit. This is almost never done properly when 12v compressor fridges are installed in the factory, whether RV or Boat and has started the negative myths surrounding 12v compressor fridges. Installation and initial design error of the cabinet into which it is to reside.
I've also added a 0.03a 40MM fan to the interior, which runs 24/7. It takes 12v from the LED light. it makes a huge difference in evening out internal temperatures, assists cooling down warm items placed within much faster, and allows me to lower the tstat setting from 4 of 7 to 2.2 of 7 to maintain 36.5F or lower. This internal fan is a very small heat source, and as such does not make the fridge use less battery power.
I've added a significant amount of extra foam board insulation around the whole box, and the cabinet in which it resides is also insulated. The weak spot is the door and not too much to be done about it. And the electrical consumption is slight enough I am not worried about the door which sweats in humid conditions, even though this is a sign that it is not insulated as well as it could be.
But my 1.8 cubic foot fridge rarely consumes more than 0.6A per hour in my normal usage. I never worry about it. It is always cold and my 200 watts of Solar makes many times as much electricity as needed to run just the fridge. In fact I am also running an ARB chest style fridge freezer at the moment as well as my VF, even though I do not need to.
My DC only fridge came with an AC/DC option for another 100$. I put that extra 100$ toward my 40 amp 12v adjustable voltage power supply, so any time I have 120vAC available, I can charge my batteries, and power ALL DC loads. 100$ more just for the AC option on ONLY the fridge, seemed like a waste to me.
The only time the AC/DC option would be a nice feature, is if I moved into an apartment and wanted to use the fridge in the apartment. With 40 amps available from my power supply/charger, the 2.8 to 2.2a needed by my fridge would slow down charging, by a very small figure if the battery was depleted enough to max out the power supply.
Not gonna happen, so since one needs a charging source anyway, I recommend Not paying extra for the AC DC option if it is significantly more expensive than a 12v DC only fridge.
I have removed the 270 OHM resistor provided with my VF c51is to reduce compressor speed from 2500 to 2000. When the compressor first cycles on, it consumes 2.8 amps or so. About 5 minutes later when the compressor is about to cycle off, amp draw has lessened to 2.2amps.
So Do not obsess over the manufacturer listed amp draws. They are variable and you are not going to find one fridge significantly more efficient than another, and their proper installation with regards to cooling unit ventilation, can make or break any fridge's efficiency.
I Considered the Truckfridge, but then I decided Vinchenzo in Italy probably took more pride in his workmanship than Did Chin Ho outside Beijing, so I spent the extra for the VF, and no regrets.
The TF design of the cooling unit, would not have allowed me to swap the fan to the other side of the condenser, which not only was much quieter, but also more effective as computer fans are much better at pushing air through a restriction than they are at pulling air through one.
Absorption fridges run on 12v never work well, and are complete power hogs. Absorption fridges provide a 12v option as it is illegal to run the propane function when driving. Especially through tunnels or when filling the gas tank. Most 12v absorption heating elements draw 8 to 14 amps, and this is continuous. And even at that huge electrical consumption, will fight the losing battle of interior temperature. An Absorption fridge run on 120vAC, will consume a lot more electricity than a household compressor fridge of the same size. Absorption fridgesmake great use of fossil fuels for cooling, and their electrical options for cooling redefine inefficient.
Not wasting solar wattage is often brought up on this forum, but only by newbies. Those of us with solar surpluses might go as far as cranking up the fridge until the late afternoon, or charge the laptop battery or other things, but we do not stress out if we have more solar than our present needs dictate. it is not worth the effort, and having too much solar, is a good thing. It will make your batteries happier the faster in the day that they are recharged.
One mistake that many people make is they believe their solar charge controller when it states the batteries are full. A hydrometer will usually reveal this to be wrong. The solar controller rolling back to float voltage and flashing the full charge indicator, means only that the controller has held absorption voltage as long as it was programmed to do so, and, for fear of overcharging and greedy lawyers, they are all programmed timidly, and the user needs to bump up Absorption voltage and duration at which it is held, especially when cycling the battery deeper. The deeper the discharge of the battery, the more important it is to have the correct absorption voltage held for longer. Charging a battery from 85% to 100% is a whole different animal than a battery cycled to 50%, So one Cannot mindlessly believe their charging source when it flashes the full charge indicator.
A blinking green light, does not equal 100% state of charge, unless confirmed by a Hydrometer, or when AGMS are employed, when the AGM batteries accept less than 0.5 to 1% of their rating at the manufacturer recommended absorption voltage. No ammeter? You are blind.
I can program my solar controller to flash the green light and hold only float voltage by 9 AM. It does not mean the batteries are full. I could convince 99.5% of people that is exactly what it means though.
Flashing green lights/full charge indicators, are chronic liars. Don't let them make a fool of you. If you do, you will not get as many cycles from your batteries, and have to replace them prematurely.
And works 'just fine' only means 'has not failed yet'.
Worked just fine for 500+ deep cycles, is truly 'just fine', but no lesser claim qualifies.
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