I agree gas too. 240v is nearly as good but works harder in hot weather (Shade helps that) 12v is mainly for when travel as it is set at a temp and doesn't move.
That all said, I know a few people that have hooked up their 12v to the CV batteries and use 12v during the day when sunny then back to gas at night when 'off the grid'. You need a good solar set up though really.
Keep Safe on the roads and out there.
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TUG.......2014 Holden LT Colorado Twin Cab Ute with Canopy
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I'm going to go against the flow here and say electricity is more efficient.
The generally accepted definition of efficiency is the amount of energy required to do a set amount of work, in this case cool the fridge. And according to manufacturers data it takes less energy in the form of electricity to run a 3-way fridge than gas.
Doing the numbers, and using my Dometic 3-way fridge as an example, under standard test conditions (average consumption measured at an average ambient temperature of 25°C in pursuance of ISO Standard) they say it takes 3.9 kWh of electricity, or 460g of LPG per 24hrs.
Given that 3.9 kWh of electricity is 14MJ of energy, whereas 460g of gas is 22MJ of energy, it means that on electricity you are using only 64% of the energy to get the same result. I'm not entirely surprised, as anyone who has put their hand over the gas flue when it's operating will know that a lot of the energy in the original gas is lost up the flue as waste heat.
If, however, you meant which is more effective at cooling the fridge to the desired temperature, I'd have to agree with the others and say gas. I believe this is because of the high temperature of the gasses, and the fact the flue runs the full length of the boiler and so transfers more heat to the ammonia solution than either the 240V or 12V electric elements can, because they are only in contact with the lower third of the boiler.
Edit: Corrected figure for gas consumption
-- Edited by Mamil on Thursday 19th of September 2019 02:59:24 PM
Hi Button,
I find my current & past fridges have worked equally on Gas/240v.
My Eagle (you'll find my writings in the Techies Tab) - I improved its running by shading the side where the fridge was, also added computer fans to the bottom vent (blowing) & to the top (sucking the hot air out).
All the best with yours.
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If you don't get it done today, there's always tomorrow!
I'm going to go against the flow here and say electricity is more efficient.
The generally accepted definition of efficiency is the amount of energy required to do a set amount of work, in this case cool the fridge. And according to manufacturers data it takes less energy in the form of electricity to run a 3-way fridge than gas.
Doing the numbers, and using my Dometic 3-way fridge as an example, under standard test conditions (average consumption measured at an average ambient temperature of 25°C in pursuance of ISO Standard) they say it takes 3.9 kWh of electricity, or 360g of LPG per 24hrs.
Given that 3.9 kWh of electricity is 14MJ of energy, whereas 460g of gas is 22MJ of energy, it means that on electricity you are using only 64% of the energy to get the same result. I'm not entirely surprised, as anyone who has put their hand over the gas flue when it's operating will know that a lot of the energy in the original gas is lost up the flue as waste heat.
If, however, you meant which is more effective at cooling the fridge to the desired temperature, I'd have to agree with the others and say gas. I believe this is because of the high temperature of the gasses, and the fact the flue runs the full length of the boiler and so transfers more heat to the ammonia solution than either the 240V or 12V electric elements can, because they are only in contact with the lower third of the boiler.
Very nicely put.
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Our Dometic 3 way works great on 240v, maintains or slightly lowers the temperature on 12v while traveling & struggles on gas when the mercury gets near 30 degrees.
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Our Dometic 3 way works great on 240v, maintains or slightly lowers the temperature on 12v while traveling & struggles on gas when the mercury gets near 30 degrees.
sounds like your fridge is either not level hen on gas or no ventilated enough,,
In 99% of cases 12 v is the worse performer
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My old Dometic 200L fridge, freezers thermostat is bypassed on DC it was flat Out keeping the temp it had before switching . Assume in this fridge ? 12v DC is only to maintain For short period ? Current draw was up around 20 amps .,
-- Edited by Aus-Kiwi on Thursday 19th of September 2019 09:05:48 PM
There's no technical reason that a 3-way fridge shouldn't work equally well on 12V DC as 240V AC. The principle of operation is a simple resistive electric heating element attached to the side of the boiler heating up the ammonia solution inside. In the pic on the left you can see the 'L' shaped AC and DC heating elements slotted into tubes welded onto the side of the boiler. The coloured cutaway makes it easier to see - the black is the boiler, the green the gas flue, and the red the pipe the electric element slots into. In the case of a dual voltage fridge there would be two of the red pipes, one for the DC element, and another for the AC element.
So, it shouldn't matter if it's a DC or AC element, if they are the same wattage they should put out the same amount of heat, and heat the boiler equally well, and therefore cool the fridge equally well (all other variables like ambient temp, rear ventilation etc. being the same). And that's why the manufacturers specs claim the fridge will meet test conditions equally well on DC as AC and gas, but we all know from experience that in reality our fridges rarely cool effectively on DC. So why?
It's because a number of things conspire to make sure the DC element never gets to it's intended output, and so does not perform as designed. The main culprit is voltage drop on the supplying wires. There's a long way from the car alternator/battery to the fridge in our vans, and most cars and vans are delivered with woefully undersized wiring. Then we try and push 15-25Amps through that wire for today's large 3-way fridges. Voltage drop is proportional to current and length of run, and inversely proportional to size of wire. Result is the heating element is running well below it's rated wattage because it only gets 10 volts or so and the current can't increase to compensate because it just gets burnt off as heat in the undersized wires. So, the fridge running on DC barely maintains the temperature it started at.
It's not a problem on AC as the wire runs are shorter and the current is a fraction what it is on DC, so voltage drop is negligible and the AC element can happily run at full rated wattage.
The solution is to upsize the DC wiring all the way from car battery to fridge. Mine was originally 2.5mm2 from car battery to van fuse box, then 4mm2 from there to fridge. Even though my car alternator was putting out a good 14.4V, by the time it got to the back of the fridge it was only 10V. I upgraded to a 16mm2 wire all the way and I now get a minimum of 13V at the back of the fridge and it can pull as much current as it likes without restriction. Result is the DC element running at rated wattage (actually a bit above in my case, so I have to watch I don't burn it out!) and now it cools just as well on DC as it does on AC and gas, getting down to 2deg in the fridge, and minus 18deg in the freezer.
-- Edited by Mamil on Thursday 19th of September 2019 07:47:43 PM
In this fridges case the load flattens the batteries fast due to current draw . It was connected to run when engine was running for that reason . Its a big fridge . A smaller fridge or latter more modern ? could be different . The new compressor fridge 12/ 240v is much more efficient !! Has run the last 18 months on solar alone !!
