For over three years, we have been using JC Refrigeration 120VAC conversion for our Dometic 2672 refrigerator (6 cu ft). It uses an Embraco 120VAC fixed speed compressor, and its operating cycle seems to be between 1/3 to 2/3 of the time, depending on contents, ambient weather conditions, and how often the door is opened. When the compressor is on, I am seeing 90 watts to 100 watts of energy consumption. I checked my neighbor's RV, which has an 11cu ft residential refrigerator, and also has the same Embraco fixed speed compressor.
Using a Kill-A-Watt meter, I measured total consumption over the past 24 hours with moderate Aug weather (low ~70°F, high ~87°F) to be only 0.90 kwh. 900 watt hours. Roughly a 50% duty cycle.
I did not measure invertor efficiency/losses; if included, total consumption over 24 hours to roughly 1kwh.
Over the same time period, what would the total energy consumption for an equivalent sized refrigerator with a Danfoss variable speed 12VDC compressor in similar conditions? Your article indicates it draws, on average, roughly 3 amps at 12VDC, which is a little over 0.85 kwh over a 24 hour period.
What am I missing? Is the Danfoss compressor energy consumption roughly 85-90% of the energy as an Embraco compressor?
A little off topic but...we are looking at a class b camper built by a small company in Massachusetts. The builder is an electrical engineer and he uses Tesla batteries in his builds. Just curious what your opinion is on the pros and cons. Price point on the camper is great, along with the solar (800w) and battery capacities. Thanks Mike!
Yes, sorry. Typo or auto correct is a terrible thing. TO be clear 12vdc fridge of same size seems to be 2 to 3X the price of the same size 120vac residential unit.
I am just finishing replacing our old Norcold with a Unique Appliances 12 VDC model https://uniqueappliances.com/content/uploads/2023/03/UGP_385L_SPECSHEET2023.pdf It specifies the Danfoss Secop compressor. I don’t know if all of the Danfoss compressors are variable, but in initial tests, empty, mine draws about 6 amps and gets down to temperature very fast. In fact the freezer portion gets down to under the freezing point in less than 30 minutes. Thus far I am quite pleased. I am interested to learn more about the connection between Danfoss & Secop.
Sounds like the only way to go. You didn't mention it but the way you describe the motor running at the speed required to obtain the correct level of refrigeration, it sounds like an inverter compressor. This RV air conditioner on Amazon has the inverter compressor.
Great article Mike. I am currently looking to replace my current Norcold 1200 and have been debating going residential or 12v. We do not boondock often, usually just an overnight stop where hook up is not available but mainly when driving (rarely more then 6 hrs at a time) I have 600 amps of LFP battery power and an on board diesel gen (7500 watt). We are not full time. Since 12v systems are about 3X the cost of 12v of the same size do you think, for our situation paying more for 12v is worth it?
You have plenty of battery capacity and an onboard diesel generator. Plus you’re not boondocking, you just need 12 hours of overnight battery power for your fridge. And I assume you already have a pure-sine inverter onboard, correct?
So IMO there’s really no compelling reason to spend the extra money on a 12-volt DC fridge. If you can find a 120-volt AC fridge that fits, then that makes economical sense. Just be aware that some residential refrigerator manufacturers won’t warranty their fridge once it’s installed in an RV and powered by an inverter.
Yes, I have a 3k pure sine I/C (Aims PICOGLF30W12V120V). Size is limited because of floor plan regardless of 120vac or 12vdc but I have a few choices either way. Thanks for the advice and thank you for the great work you do.
Excellent, helpful article, Mike- thanks!
When will we see a Danfoss compressor in a rooftop AC unit?
There’s some rumors happening along those lines, but I don’t know enough just yet to comment on it.
Have you ever done an article on how to hook up a 19v computer monitor and laptop to charge off the 12v battery supply directly?
Not yet. Many new laptops and monitors now use USB-C for power, and 12-volt power supplies are readily available for them.
Do all 12V refrigerators use the same Danfoss compressor?
What 12V refrigerators use the Danfoss compressor?
Mike,
For over three years, we have been using JC Refrigeration 120VAC conversion for our Dometic 2672 refrigerator (6 cu ft). It uses an Embraco 120VAC fixed speed compressor, and its operating cycle seems to be between 1/3 to 2/3 of the time, depending on contents, ambient weather conditions, and how often the door is opened. When the compressor is on, I am seeing 90 watts to 100 watts of energy consumption. I checked my neighbor's RV, which has an 11cu ft residential refrigerator, and also has the same Embraco fixed speed compressor.
Using a Kill-A-Watt meter, I measured total consumption over the past 24 hours with moderate Aug weather (low ~70°F, high ~87°F) to be only 0.90 kwh. 900 watt hours. Roughly a 50% duty cycle.
I did not measure invertor efficiency/losses; if included, total consumption over 24 hours to roughly 1kwh.
Over the same time period, what would the total energy consumption for an equivalent sized refrigerator with a Danfoss variable speed 12VDC compressor in similar conditions? Your article indicates it draws, on average, roughly 3 amps at 12VDC, which is a little over 0.85 kwh over a 24 hour period.
What am I missing? Is the Danfoss compressor energy consumption roughly 85-90% of the energy as an Embraco compressor?
https://www.embraco.com/productselector/pdfs/FT008604_1.pdf
A little off topic but...we are looking at a class b camper built by a small company in Massachusetts. The builder is an electrical engineer and he uses Tesla batteries in his builds. Just curious what your opinion is on the pros and cons. Price point on the camper is great, along with the solar (800w) and battery capacities. Thanks Mike!
Please email info directly to jmichaelsokol@icloud.com and I’ll take a look.
Yes, sorry. Typo or auto correct is a terrible thing. TO be clear 12vdc fridge of same size seems to be 2 to 3X the price of the same size 120vac residential unit.
I am just finishing replacing our old Norcold with a Unique Appliances 12 VDC model https://uniqueappliances.com/content/uploads/2023/03/UGP_385L_SPECSHEET2023.pdf It specifies the Danfoss Secop compressor. I don’t know if all of the Danfoss compressors are variable, but in initial tests, empty, mine draws about 6 amps and gets down to temperature very fast. In fact the freezer portion gets down to under the freezing point in less than 30 minutes. Thus far I am quite pleased. I am interested to learn more about the connection between Danfoss & Secop.
Sounds like the only way to go. You didn't mention it but the way you describe the motor running at the speed required to obtain the correct level of refrigeration, it sounds like an inverter compressor. This RV air conditioner on Amazon has the inverter compressor.
https://www.amazon.ca/Totalral-Universal-Truck-Conditioner-White/dp/B0B3G9SZ23/ref=sr_1_3?crid=XMWJE2LYG6UT&keywords=inverter%2Bcompressor%2BRV%2Bair%2Bconditioner&qid=1691019143&sprefix=inverter%2Bcompressor%2Brv%2Bair%2Bconditioner%2Caps%2C168&sr=8-3&th=1
I had been wanting to ask you if this technology will render the softstart devices obsolete. Keep up the good work. Mike R
Great article Mike. I am currently looking to replace my current Norcold 1200 and have been debating going residential or 12v. We do not boondock often, usually just an overnight stop where hook up is not available but mainly when driving (rarely more then 6 hrs at a time) I have 600 amps of LFP battery power and an on board diesel gen (7500 watt). We are not full time. Since 12v systems are about 3X the cost of 12v of the same size do you think, for our situation paying more for 12v is worth it?
You have plenty of battery capacity and an onboard diesel generator. Plus you’re not boondocking, you just need 12 hours of overnight battery power for your fridge. And I assume you already have a pure-sine inverter onboard, correct?
So IMO there’s really no compelling reason to spend the extra money on a 12-volt DC fridge. If you can find a 120-volt AC fridge that fits, then that makes economical sense. Just be aware that some residential refrigerator manufacturers won’t warranty their fridge once it’s installed in an RV and powered by an inverter.
Yes, I have a 3k pure sine I/C (Aims PICOGLF30W12V120V). Size is limited because of floor plan regardless of 120vac or 12vdc but I have a few choices either way. Thanks for the advice and thank you for the great work you do.
I think you meant 3x the cost of 120 volts, correct?