Refrigeration

[Shoney]

Hi all,

Working on a van conversion at the moment and had some question's regarding refrigerator's. I purchased a 3-way refrigerator that can run on 12vDC/110vAC/LPG. Is the 110vAC option more efficient in terms of amp hours? According to the product specifications, the electrical power is 90 watts. The way I calculated it, at 12vDC (90w/12v) it would be 7.5 amps, which would make it 180 Ah to run for 24 hours. At 110AvAC (90w/110v) it would be 0.8 amps, which would be 19.6 amp hours to run for 24 hours. Have I calculated this correctly? Are there more energy efficient refrigerator's I should consider?

 

[Boutdun]

Check out “Snowmaster”, i think made in calif. talk to Todd, 512-698-6169. I could not be more pleased with th 62 qt. I have. Even is wired for 110 or 12v, I keep mine on 12v. There was a untuned where a guy tested 5 of the best brands, this one came in #1.

 

[jonyjoe303]

90 watts is 90 watts, but with the 110 AC, it would be more since you need to account for the inverter. But even at DC, it won't be 180ah per 24 hours. The compressor only runs when needed. It won't be a constant 90 watts for an hour, maybe 10 to 15 minutes run time per hour.

Depending on the model of fridge and how cold you keep it, you might use 50ah per day or less. My 12 volt fridge kept at 26f uses about 12ah per 24 hours, at 16f it uses between 18 and 24ah per 24 hours, at 12f it uses over 30ah per 24 hours.

On my fridge I hotglue foam insulation to the exterior of the fridge to increase its efficiency. When I increase the fridge temp from 16f to 26f, it took 3 days before the compresser ran again. It used less then 5ah in 3 days. The insulation worked extremely well.

The only drawback with 12 volts, you need to have good stable power. My fridge compressor stops working if it encounters too much voltage drop. If you have problems, just use the 110 volts, that will give the fridge stable power.

 

[highdesertranger]

propane refrigerators do not have a compressor. highdesertranger

 

[[email protected]]

Shoney, the refrigerator you bought is a gas absorption model that can run most efficiently on LP gas, it can also run nearly as efficiently on 120 volt house power. The 12 volt operation will drain a battery very quickly unless you are generating power while driving. I have had 15 over the last 30 years in rv's and other than a twice a year cleaning they are bullet proof.

 

[Drmiller100]

The 12 volt compressor fridges take a lot less power. 1 ah at 12.6 volts is 12.6 watts per hour.

Comparing, at 12 volts your are talking 24 ah for 24 hours

Iceco, dometic, etc

 

[eDJ_]

Question about these absorption refrigerators.   Do they run constantly or have to run constantly.  Are there any that are cycled with a thermostat ?   Asking for myself or any others who don't know and would like to.

 

[highdesertranger]

I know the older ones ran constantly. I hear the newer ones do cycle. highdesertranger

 

[Shoney]

Thank you, I didn't realize that about refrigerators. that helps to simplify things for me.

 

[Spaceman Spiff]

Question about these absorption refrigerators.   Do they run constantly or have to run constantly.  Are there any that are cycled with a thermostat ?   Asking for myself or any others who don't know and would like to.

New absorption refrigerators run on a thermostat when using electricity and run constantly on propane.

 

[Tom_M]

New absorption refrigerators run on a thermostat when using electricity and run constantly on propane.

My 2005 fridge cycles when on propane. It has electronic spark ignition and a 12 volt solenoid gas valve. When cooling is needed the spark is started and the gas valve opens. Once the proper temperature is reached the gas valve closes.

 

[Shoney]

So lets say I have a 2.1 cubic foot mini fridge and I wanted to mainly run it on 12 volt with solar and propane as a backup. what can I expect the duty cycle to be? Is there a way I can find out?

 

[user 423]

^
One day I was charging my house battery with my generator. My charger has a digital readout that displays the amps being fed into the battery.

The outside temp was in the mid-80s and the fridge would cycle fairly frequently. Each time the compressor kicked on, the reading on the amp meter went down X number of amps.

Charging the batteries takes several hours, so if you sat there and monitored how many times and for how long the compressor kicked in, you would have a pretty good idea of what the duty cycle is. The difference in the readings is what the fridge pulls in amps. For mine it was about 2.5 amps. Max for my unit is 3.75 amps.

I have an Alpicool C20 that has added insulation and is used as a fridge set at 38 deg.F.

 

[Shoney]

Another question. The fridge specifies a nominal gas consumption of 25g per hour. Should i vent the exhaust outside the van? I have a roof vent and fan, as well as the diver and passenger windows to circulate air.

 

[abnorm]

The propane absorption fridge requires an airtight interior enclosure that is vented to the exterior with high and low vents for circulation

 

[bullfrog]

You are dealing with a small flame made by burning propane. The draft will greatly determine how well it works. On my old one even cobwebs could cause problems as well as not being level. I would highly recommend following the manufacturer’s installation instructions as how well it works is dependent on proper installation and there are some fire/safety hazards involved.

 

[highdesertranger]

also running an absorption refrigerator off of 12v is very inefficient. you would need a huge battery bank and a way to charge it, i.e. acres of solar. highdesertranger