How does a fridge work while I'm off-the-grid?

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Angiekaye

Member
Joined
Oct 30, 2017
Posts
21
Location
Bay Area, CA
So I've been living in my Rv for a few weeks now and haven't really used my fridge cause I don't know a lot about it. I don't have a place to hook up right now, so I'm living off the house batteries, generator in the RV and a smaller solar generator Yeti400.  My RV has a propane tank on it.

Here's what I know about the fridge. It works. It has a switch that says Electric - Off - Gas.  I can only use the electric part if I'm hookup right? And the Gas is only when my propanes on? If I were to use my propane, how long could the fridge last? It seems like the fridge isn't really usable for long-term boondocking, right?

Thanks!
Angie
 
Gas-electric refrigerators work really well off-grid.  They don't have a compressor like a normal house refrigerator, instead they use a process called adsorption (or absorption) where you apply heat at one location to get cooling at another.    In electric mode the heat is provided by an electric heating element and yes, you have to be plugged into power (or running the generator) to use it.

But the refrigerator's native mode is using propane to create the heat.  It uses very little propane and your other propane uses (stove, hot water heater, furnace) will determine how often you need to fill the propane tank.  The refrigerator by itself can run several weeks to several months before it drains the tank.

The refrigerator also uses a small amount of 12 volt power to run it's control board, less than a single LED light.  Again, not enough to worry about - your other 12 volt uses will determine when you have to charge your battery.

The refrigerant is an ammonia and water mix that is heated in a boiler, then the ammonia vapor rises by convection to the freezer where it condenses back into liquid form and absorbs heat from the inside of the refrigerator.  Then gravity draws the liquid ammonia down to the bottom of the cooling unit, it is re-combined with the water and flows back to the boiler to begin the cycle again.

It's a very reliable process that has been around for about 100 years.

The weak point of the absorption cycle is the convection and gravity stuff.  The refrigerator MUST be within a few degrees of perfectly level for the refrigerant to properly flow through the system ... water won't run uphill.  If you operate it while the RV is off-level, the water and ammonia mixture won't be able to get back to the boiler and it can run dry and overheat.  If it does, it will create hard flakes that can plug the cooling passages, damaging or ruining the cooling unit.

 
Right, the fridge  Is useable on 120 volt only when hooked to shore power or running a generator.

Wrong, it will run on propane indefinitely. If it has not been run on propane for a long time, check to be sure the burner is clean and no obstructions in the flue.  Turn it on propane and you should hear the lighter click. Then, make sure you can see a small flame and the flue is hot.
 
The amount of gas used by a propane fridge is very small, about equal to a standing pilot lite on a stove or furnace. You could run that fridge for months on a single tank of propane. Your other uses of propane, water heater, stove, oven, etc. will determine how long your tank lasts. Take the fridge use into account for sure, but just no need to worry about it.
 
halfwright said:
Right, the fridge  Is useable on 120 volt only when hooked to shore power or running a generator.

Wrong, it will run on propane indefinitely. If it has not been run on propane for a long time, check to be sure the burner is clean and no obstructions in the flue.  Turn it on propane and you should hear the lighter click. Then, make sure you can see a small flame and the flue is hot.

Perhaps. You will hear the light click if it is a reasonably new fridge. The older ones had pilot lights that you had to light manually. Some were a little difficult to get lit.

Joel
 
Super helpful everyone. Okay, my goal this week is the get levelers under my tires so then I can start using the fridge. (I'm glad I know that about making sure the fridge is level before using). And I'm so happy I can start using the fridge now!!! And not worry about running the propane tank dry in a few days.

One more question: I have a habit of turning the house batteries off when I leave for the day to save battery. The propane and house batteries aren't connected are they? So if I turn off the house batteries, the fridge will still be on if I am using propane, right?
 
Angiekaye said:
One more question: I have a habit of turning the house batteries off when I leave for the day to save battery. The propane and house batteries aren't connected are they? So if I turn off the house batteries, the fridge will still be on if I am using propane, right?

No! There is a control board for the fridge that operates from 12V. With the batteries off, there is no 12V, and the fridge won't function. Don't worry about the current draw. It will be just fractions of an amp.

Joel
 
I might add that RV refrigerators take a while to cool.  We usually start ours two-three days before a trip and start loading it after a day with cold things that have been in the refrigerator for a while such as cold drinks.  I add the less-cool items closer to leaving.  Because you're parked for while I wouldn't add anything for at least two days and maybe even three to make sure it's really cold first.  We have small thermometers (Camping World and other RV stores) in each section so we know how cold it's getting.

It might be helpful if you let us know the make, model and age of items you ask about.  The two big RV refrigerator makers are Norcold and Dometic.  Some are two-door and some are four-door models.  Some also have Auto on the switch which you can set to automatically switch between electric (plugged in or generator) and propane when no electric is available.  When boondocking we tend to leave it on propane.

ArdraF
 
Okay!  The refrigerator is a Norcold. I took a picture of the fridge and the details on the inside. But maybe everyone's familiar with this one.

My hope is to start using the fridge soon. My RV is now pretty level after driving my right 2 tires up on blocks, so I just need to turn the propane on and the fridge will work? My propane tank says it's 3/4 full. 
 

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Angiekaye said:
Okay!  The refrigerator is a Norcold. I took a picture of the fridge and the details on the inside. But maybe everyone's familiar with this one.

My hope is to start using the fridge soon. My RV is now pretty level after driving my right 2 tires up on blocks, so I just need to turn the propane on and the fridge will work? My propane tank says it's 3/4 full. 

Yup, pretty much.  Make sure the valve on the propane tank is fully open, this seals the knob shaft against leakage.

You probably have some air in the propane lines if the system has been off for a while.  Try lighting a stove burner using a BBQ lighter - the burner may blow nothing but air for several seconds until the propane reaches it.  The reason for lighting the stove first is it uses much more propane than the refrigerator so it takes less time to purge the air out of the lines.

Then switch the refrigerator to Gas and see if it lights.  You should hear several slight clicks as the igniter lights the flame in the rear of the fridge.  The Check light should go out when the flame lights.  If the light stays on, turn the refrigerator off to reset the circuit board and try it again.

It can take several hours for the system cool the refrigerator.  First thing you'll feel is the rear wall of the freezer getting cold, after the freezer is cold, cooling will migrate down to the refrigerator.

BTW, the answer to how much propane the refrigerator will use is on the nameplate.  Propane contains about 90,000 BTUs per gallon and the nameplate says the refrigerator uses 1500 BTUH (BTUs per Hour).  That means it uses a maximum of 1/60th of a gallon of propane per hour, or 60 hours at full cooling per gallon of propane.

But the cooling system won't run full time unless you're in 100+ degree heat.  So you can stretch that figure by at least twice or three times as long in normal temperatures.
 
ArdraF said:
...................It might be helpful if you let us know the make, model and age of items you ask about.  The two big RV refrigerator makers are Norcold and Dometic.  Some are two-door and some are four-door models.  Some also have Auto on the switch which you can set to automatically switch between electric (plugged in or generator) and propane when no electric is available. When boondocking we tend to leave it on propane.

ArdraF

A word of caution:
I am reading reports of Winnebago MH's (model years in the 2012-2016 maybe additional years as well) having the gas/elect fridge wired though the inverter.  So being on auto and just unplugging from shore power does not allow the fridge to switch to gas.  The fridge just drains the battery though the inverter. That is unless you didn't notice the fridge was still running on elect and switched it to "gas only".
 
AStravelers said:
A word of caution:
I am reading reports of Winnebago MH's (model years in the 2012-2016 maybe additional years as well) having the gas/elect fridge wired though the inverter.  So being on auto and just unplugging from shore power does not allow the fridge to switch to gas.  The fridge just drains the battery though the inverter. That is unless you didn't notice the fridge was still running on elect and switched it to "gas only".
I couldn't read the placard in the picture but I bet the OP won't have a problem with that. :))
Just wondering, Angiekaye have you got your hot water heater working?
Bill
 
I am reading reports of Winnebago MH's (model years in the 2012-2016 maybe additional years as well) having the gas/elect fridge wired though the inverter.
I doubt if they come that way from the factory, at least not intentionally, but the fridge icemaker is usually plugged to an inverter outlet so as to allow the icemaker to work off-grid.  Sometimes the fridge electric mode heater gets plugged into the inverter outlet, either accidentally or because the owner wants to avoid LP gas mode while traveling. That's fine as long as the engine alternator is running, but not so good once you park.
 
WILDEBILL308 said:
I couldn't read the placard in the picture but I bet the OP won't have a problem with that. :))
Just wondering, Angiekaye have you got your hot water heater working?
Bill

No, I haven't got the hot water running yet. I take showers at work right now and wanted to focus on getting everything running first. But I need to learn eventually:)
 
sadixon49 said:
The amount of gas used by a propane fridge is very small, about equal to a standing pilot lite on a stove or furnace. You could run that fridge for months on a single tank of propane. Your other uses of propane, water heater, stove, oven, etc. will determine how long your tank lasts. Take the fridge use into account for sure, but just no need to worry about it.

I have a four-door Norcold refrigerator and it uses 1/2 gallon of propane a day, which is more than I expected.  Since the OP's refrigerator looks to be about half the size of mine, I'd make a wild guess that it uses about 1/4 gallon/day.
 
OK, I turned on the propane for the first time today. (I've been afraid I'd blow myself up:). So I turned it on, and lit the stove top to get the air out of the line (as someone suggested).  The stove worked great. But then the fridge wouldn't ever start. It tried. It kept clicking to try and start. The x would go on and off. Then I would try turning it off and on again. Maybe I'll try it again tomorrow and see how it goes.
 
I have a four-door Norcold refrigerator and it uses 1/2 gallon of propane a day, which is more than I expected

That does seem excessive. Are you sure it isn't a 1/2 lb rather than  a 1/2 gallon? The flame isn't much bigger than an oven pilot light.

Of course, temperature in the RV and door-open frequency can have a big effect on consumption rates.
 
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