I had a chance just recently to perform a very accurate test on how fast my van fridge pulls down the internal temperature from start up to stable condition. This occurred because I was getting fridge going 24 hours before intended departure into the wilds off grid. Circumstances changed at the last minute (did not go!) and I had the chance to do two separate tests - one with 240 VOLT POWER and the other with GAS.
The Penguin was in my front yard, level both ways for max efficiency, but in full sun. Indeed, in the afternoon between 1330 and 1530 hours, the fridge side was copping the full force of the sun. No attempt was made to shade this area, as there was nothing in the fridge or freezer and I wanted to see just how the cooling went.
The attached chart shows some very interesting results for my fridge which may not be typical of others. My Thetford is climate rated as "T", has two small internal fans to move air around (one at bottom of fridge and the other to the side of the evaporator blowing the air across the face). This ensures a very even and constant temp throughout the inside of fridge section. In addition, I have 2 X 120mm fans attached to vents (one on each) which are thermostatically controlled by 45C sensor on cooling fins. The fridge had recently been fully cleaned externally and additional insulation added to internal sides and roof of space for fridge. (see separate post) A proper baffle was in place as well as a deflector plate at the top vent to ensure easy exit of hot air and provide unrestricted air flow.
On the 240 volt test, the door was NOT opened at all and I was able to obtain all the internal and external temps from the wireless display. The internal sensor was placed on top shelf near wall further-est away from fan. The external control and display was in the van away from the sun on the eastern side. The van was fully open (all windows etc) during the day and closed at night but roof still up and vent open. The ambient temperature shown was the shade temp in the open van, the outside temp in sun would have been much hotter! The fridge thermometer was excellent as it showed the temperature "trend" sensed every 10 minutes for both inside and ambient - better than the wireless Companion one I had before and at half the price (approx $16.50 on Ebay, link shown below. )
The first thing one notices is that the fridge cooling is "no sprinter" compared to the compressor fridges, but once down to operating temperatures, managed to hold its own in pretty severe conditions. Mind you, the door was not opened at all, except in the GAS test, where you can see that the fridge "treads water" until it cools the items down a bit. Also, note that the freezer section takes absolute priority and until it reaches its operating temp, (approx minus 15C??) there is very little cooling available into the fridge portion. In fact, the fridge temp rises slightly above ambient on start up before commencing the slow pull down operation. I guess you could help the fridge portion to cool down faster if you placed a couple of freezer bricks etc in the freezer compartment until the fridge compartment was close to where you wanted it. But once the freezer bricks were removed, anything then loaded in the freezer would have to be already frozen so as not to affect the fridge section below!! The gas did not get the temperature down as low as the 240 volt power, but remember, the gas had items added into the freezer and fridge compartments.
A week after these tests, I departed to my destination and the fridge had to handle similar temperatures, but the van was under some shady trees. Doing some rough calculations, I estimated that a 90 litre compressor fridge would conservatively use 40ah per day (3 amps/hour for 60% of 24 hours daily), in 35C temps including opening and loading warm drinks etc. Over a 7 day period, one would need approx 280ah from storage or generated power. All it cost me was less than 4 kg of gas - less than $7.00. Yes, @Drover, that post about getting a 9kg bottle filled for $15.00 at Anaconda if you provided the bar code from Gas Fill Aust was correct!!)
To sum up, if the absorption fridge was a race horse, you would never enter it in a sprint race with compressor fridges or even in a longer race on a good hard fast track with plenty of solar or charging facilities available. But on a soft wet track with overcast and prolonged rainy conditions, the "tortoise", with the right jockey, might make it a close finish at the final post!!
https://www.ebay.com/itm/Wireless-D...1&algo=REC.SEED&ao=1&asc=20160908131621&meid=
The Penguin was in my front yard, level both ways for max efficiency, but in full sun. Indeed, in the afternoon between 1330 and 1530 hours, the fridge side was copping the full force of the sun. No attempt was made to shade this area, as there was nothing in the fridge or freezer and I wanted to see just how the cooling went.
The attached chart shows some very interesting results for my fridge which may not be typical of others. My Thetford is climate rated as "T", has two small internal fans to move air around (one at bottom of fridge and the other to the side of the evaporator blowing the air across the face). This ensures a very even and constant temp throughout the inside of fridge section. In addition, I have 2 X 120mm fans attached to vents (one on each) which are thermostatically controlled by 45C sensor on cooling fins. The fridge had recently been fully cleaned externally and additional insulation added to internal sides and roof of space for fridge. (see separate post) A proper baffle was in place as well as a deflector plate at the top vent to ensure easy exit of hot air and provide unrestricted air flow.
On the 240 volt test, the door was NOT opened at all and I was able to obtain all the internal and external temps from the wireless display. The internal sensor was placed on top shelf near wall further-est away from fan. The external control and display was in the van away from the sun on the eastern side. The van was fully open (all windows etc) during the day and closed at night but roof still up and vent open. The ambient temperature shown was the shade temp in the open van, the outside temp in sun would have been much hotter! The fridge thermometer was excellent as it showed the temperature "trend" sensed every 10 minutes for both inside and ambient - better than the wireless Companion one I had before and at half the price (approx $16.50 on Ebay, link shown below. )
The first thing one notices is that the fridge cooling is "no sprinter" compared to the compressor fridges, but once down to operating temperatures, managed to hold its own in pretty severe conditions. Mind you, the door was not opened at all, except in the GAS test, where you can see that the fridge "treads water" until it cools the items down a bit. Also, note that the freezer section takes absolute priority and until it reaches its operating temp, (approx minus 15C??) there is very little cooling available into the fridge portion. In fact, the fridge temp rises slightly above ambient on start up before commencing the slow pull down operation. I guess you could help the fridge portion to cool down faster if you placed a couple of freezer bricks etc in the freezer compartment until the fridge compartment was close to where you wanted it. But once the freezer bricks were removed, anything then loaded in the freezer would have to be already frozen so as not to affect the fridge section below!! The gas did not get the temperature down as low as the 240 volt power, but remember, the gas had items added into the freezer and fridge compartments.
A week after these tests, I departed to my destination and the fridge had to handle similar temperatures, but the van was under some shady trees. Doing some rough calculations, I estimated that a 90 litre compressor fridge would conservatively use 40ah per day (3 amps/hour for 60% of 24 hours daily), in 35C temps including opening and loading warm drinks etc. Over a 7 day period, one would need approx 280ah from storage or generated power. All it cost me was less than 4 kg of gas - less than $7.00. Yes, @Drover, that post about getting a 9kg bottle filled for $15.00 at Anaconda if you provided the bar code from Gas Fill Aust was correct!!)
To sum up, if the absorption fridge was a race horse, you would never enter it in a sprint race with compressor fridges or even in a longer race on a good hard fast track with plenty of solar or charging facilities available. But on a soft wet track with overcast and prolonged rainy conditions, the "tortoise", with the right jockey, might make it a close finish at the final post!!
https://www.ebay.com/itm/Wireless-D...1&algo=REC.SEED&ao=1&asc=20160908131621&meid=
