Residential Refrigerator

[lbrjet]

My math shows 152 DC amp hours per 24 hours. 75.8 watts per hour.

[TitanMike]

Originally Posted by Chuck_S

Some raw data for the refrigerator in my garage (not RV) with a label reading 6.5 amps for the power use:

Kilowatt hours: 3.23
Hours: 41.16

Hopefully one of the math majors here to tell me how many amp hours at 12vDC this would use. My math isn't making sense as it says it will pull an average of something like 65 amps DC all the time which would exhaust a standard battery in minutes as the voltage drop would be so low even a Harbor Freight inverter would shut down.

Strictly curiosity. I do use a 2000w inverter wired directly to my truck's battery for power tools where no shore power is available. Handier than a generator and only needs a 10mm wrench to bolt it to the battery. Here it is running my compressor to blow the water of the system to winterize the trailer. Nothing to do with running a refrigerator, or course, just a little inverter porn.

-- Chuck

If the label on your refrigerator shows it draws 6.5 amps, that's only when it's actually running the compressor to cool. Only time the compressor will run all the time is if the door is left open and the refrigerator can't reach it's set cold temp.

The average duty cycle (time on versus time off) for a refrigerator is 50%. Perhaps less on late model Energy Star rated refrigerators.

Using the 50% duty cycle, a 6.5 amp rated refrigerator is only drawing half that amount in "amp hours". 3.5 amp hours at 120 volts is more like 42 amp hours at 12.5 volts (and allowing for an 80% conversion through the inverter).

The above is based on "averages". In specific cases it can be a lot lower if the refrigerator isn't opened frequently or can be a lot more if the door is opened every time someone needs a beer (put them in an ice chest and leave the door closed).

There's no argument that residential refers are not idea for boondocking, especially longer off grid stays. That said, they CAN work if one knows their limitations, had adequate battery capacity to keep them running at least overnight (until you can run the generator) or with adequate solar power.

In the end, everyone's "Numbers" will be different because everyone's refrigerator habits are different. In my case I only open the refrigerator 3-4 times per day. Only to get what I need for a meal or restock it. A habit ingrained in me from my family's first rv refrigerator which was really just an ice box with a huge block of ice in it. My energy requirements (if I had a residential refer) would be a fraction of that for a user that opened the door every 30 minutes like happens with a large family.

[tomkatb]

P=IV. So your 6.5 amps at 110 volts ac Is about 700 watts are consumed in one hour of the fridge running.

700.=12.5 volts x dc amps is about 56 dc amps per hour. Plus 20% average inverter inefficiency or roughly 68 amps of dc from a battery per hour.

However unless you put two cases of warm beer in the fridge it will not run all the time.

If you load the fridge with warm items and leave Houston on the forth of July you will discharge a 100 amp battery in a little Less than an hour, 50 available. Your results in Alaska will be different.

You do know a refrigerator is a heat pump! As they are designed for homes they have no outside vent for the heat.

Most rv fridges are more efficient than that. When the compressor is not running they draw less. Like 200 watts.

Solar panels put out 100 watts at their best. 8 would provide power for a few hours on a good day. Nothing on a bad day.

Typically the average rv uses 50-100 amps of battery(glampers). You can do better.

Batteries are the weak link.

[Husky10101]

I have a 2019 39RKFB and I installed 6 - Renogy 165W solar panels and an Outback solar controller. I have 10 - 105AH Lion Energy 1300 lithium batteries. I kept my WFCO 1800W inverter but so far it has been enough to run what I need. I also installed soft starts on the AC units. The RV came pre wired from the inverter to run the residential Ref., powered recliners, living room entertainment center, and the bedroom TV. Guess the TV's were important to Forest River. I also wired one AC into the inverter circuits. Last thing I did was to install a sub panel for the inverter circuits. The Ref is on one circuit, the recliners & living TV are on one circuit, the bedroom TV is on one circuit, and the AC is on one circuit. This way I am able to switch off everything but the ref. when boondocking. I am able to start the AC and run it and the ref. at the same time. I tested it with the ref., tv's, and the recliners turned on and the AC off for 18hrs. Started my test @ 1400 hrs and after the 18hrs the batteries still had 84% left in them. The daytime temp was 72 and night time in the 40s so not hot.

[tomkatb]

That is dandy solar lithium set up.

It is unlikely to ever need ac plug in for modest weather.

Proves the possibility Of solar and lithium. Cost benefit analysis did not work for us. Every situation is different.

We are going to a national park next Week in Tennessee. We get a view plus electric and water for $10 a night. That national parks senior pass thing.

Unfortunately free campsites in the Midwest are pretty rare.

[TitanMike]

Originally Posted by tomkatb

That is dandy solar lithium set up.

It is unlikely to ever need ac plug in for modest weather.

Proves the possibility Of solar and lithium. Cost benefit analysis did not work for us. Every situation is different.

We are going to a national park next Week in Tennessee. We get a view plus electric and water for $10 a night. That national parks senior pass thing.

Unfortunately free campsites in the Midwest are pretty rare.

I agree it's a dandy setup and also agree that the cost benefit analysis doesn't work for all. The $10 k worth of batteires ($995 ea) can be a show stopper for a lot of people.

From the mfr' site, the batteries are only 23# each. Ten of them weigh less than those setups with four GC-2's (est >260#) with almost three times the usable power.

A lot to like--------------- except the price of course

[dalford]

I have a Whirlpool residential fridge. The model label says full load amps to be 6.5 amps. Obviously it does not run at full load amps or even close to that all the time.

I have a Vectron BMV-712 battery monitor and have measured the DC draw of everything in our 5th wheel. When the fridge is running, ie compressor on, the draw is 8.5 amps from the battery. Just about 100 watts/hr. It runs about 20 mins every hour. Now the run rate would very on use (open/close, ambient temp, etc).

I guess my point is the power consumption specified on the label and the empirical data are quite different.

Funny thing, the light in the fridge is incandescent and it draws 2 amps....25 watts. Changed it for a LED light.

[CincyGus]

Originally Posted by tomkatb

Residential fridges are not real practical for any rv boondocking.

Most rv's are plugged in every night.

And there you have it. If you're going to boondock, run away from the resi frdige. If you park camp or don't mind running your genny, you might find the additional space worthwhile.

Residential fridges pretty much lock you into either plugging in to a pedestal or a Genny at least every other day. If you spend enough on solar panel array and/or 6-8 LI batteries, you can likely stretch that to 4-5 days, depending on your other electrical needs.

[dalford]

Originally Posted by CincyGus

And there you have it. If you're going to boondock, run away from the resi frdige. If you park camp or don't mind running your genny, you might find the additional space worthwhile.

Residential fridges pretty much lock you into either plugging in to a pedestal or a Genny at least every other day. If you spend enough on solar panel array and/or 6-8 LI batteries, you can likely stretch that to 4-5 days, depending on your other electrical needs.

X2^^^ we don’t boondock per say. Maybe a night at a Harvest Host or at a campground that allows generator use but even those are generally <3 days.

I don’t know how many boondockers go for prolonged trips >3 days without a generator.

If you are a casual boondocker you can make it work, I have but with a focus on battery management with generator use.

[CUTiger80]

All great comments and very useful information and experience. This site is the best.
Now that we’ve been looking a little harder, we have found a few used units with floor plans that we like that have gas/electric refrigerators. Is there a downside to having the Gas/electric RV refrigerator? The used prices are about the same and it appears that the size (18 cu ft) is the same.
Opinions on this twist??

[TitanMike]

Originally Posted by CUTiger80

All great comments and very useful information and experience. This site is the best.
Now that we’ve been looking a little harder, we have found a few used units with floor plans that we like that have gas/electric refrigerators. Is there a downside to having the Gas/electric RV refrigerator? The used prices are about the same and it appears that the size (18 cu ft) is the same.
Opinions on this twist??

The only downside i can think of is poorer performance in super hot weather.

The propane/electric units are absorbtion type refrgerators and the cooling process is achieved using a "boiler". Efficiency can be improved somewhat by improving air flow in the vent "chimney" with fans.

Residential types use a compressor.

With absorbtion units it becomes difficult to remove heat from the system when ambient temps are high.

On the residential units heat is not added so dissipating heat from external coils is more efficient in hot weather. There is a downside of sorts there as heat is being dissipated inside the rv. Since the source of the heat is from refrigerating the inside of the refrigerator, and the source of the heat thats being removed was from inside the RV, it's somewhat of a wash.

[NMWildcat]

Originally Posted by TitanMike

The only downside i can think of is poorer performance in super hot weather.

The propane/electric units are absorbtion type refrgerators and the cooling process is achieved using a "boiler". Efficiency can be improved somewhat by improving air flow in the vent "chimney" with fans.

Residential types use a compressor.

With absorbtion units it becomes difficult to remove heat from the system when ambient temps are high.

On the residential units heat is not added so dissipating heat from external coils is more efficient in hot weather. There is a downside of sorts there as heat is being dissipated inside the rv. Since the source of the heat is from refrigerating the inside of the refrigerator, and the source of the heat thats being removed was from inside the RV, it's somewhat of a wash.

I've heard this point of view before, but never experienced it. We use our RV frequently in the SW summers in 100°+ heat. I have honestly never had any problem with our absorbtion RV fridge staying as cold as it should be. I use a fridge thermometer and it always stays within the 'good' range no matter what the outside temp is.

[dalford]

Differences besides the boondocking issues that have already been discussed in this thread and only you can determine how much you will boondock and which system works best for your needs.

I have had both types and now have a residential and will never go back to an RV fridge. I usually go to hookup sites but have managed dry sites for a few days with generator use.

What do I like about my residential fridge over my past RV fridge:

Cools down from being off to ready to pack food in less than 2 hours max.. RV fridge takes 24 hours.

Freezer always cold. My ice cream is hard. My food is frozen solid and gets frozen quickly. I had to freeze food before I put in my RV fridge. It would freeze if not frozen but put a big load on the cooling system and took forever to freeze.

It is recommended to have everything cold before loading into RV fridge, again a cooling load thing. Residential, just put it in. Just like you do with the fridge in your house.

My beer is ice cold. RV fridge seemed always marginal on fridge temp. Others have better luck but that was my experience with two different Dometic fridges.

I can stand in front of fridge and stare inside without worrying about the unit taking 2 hours to recover from my longing for something not in there..lol. Can’t do that with RV fridge.

I’m not always fiddling with a temp adjustment vane hooked to the vanes in the fridge trying to adjust temp. I just twist the thermostat know cooler or warmer, just like at home.

Freezer ices up on RV fridge. Have to defrost. Residential is frost free.

Cost of replacement is small compared to RV fridge but some have had issues with getting the old one out and new one in. My RV is 5 years old with no issues, knock on wood..lol.

That’s just my 2 cents worth off the top of my head...

[dalford]

Originally Posted by NMWildcat

I've heard this point of view before, but never experienced it. We use our RV frequently in the SW summers in 100°+ heat. I have honestly never had any problem with our absorbtion RV fridge staying as cold as it should be. I use a fridge thermometer and it always stays within the 'good' range no matter what the outside temp is.

NMwildcat, what brand fridge do you have? My buddy has a Norcold unit but it is a big side by side and he had to add cooling fans to his but it still does not keep his ice cream hard.

I think these bigger units are also an issue. A lot of space to cool. My RV fridges worked ok but they were just standard Dometic unit. My residential is also about the same size, not a side by side. Still so much better temp control than my RV fridge. If I was boondocking as much as you I would definitely have an RV fridge.

[NMWildcat]

Originally Posted by dalford

NMwildcat, what brand fridge do you have? My buddy has a Norcold unit but it is a big side by side and he had to add cooling fans to his but it still does not keep his ice cream hard.

I think these bigger units are also an issue. A lot of space to cool. My RV fridges worked ok but they were just standard Dometic unit. My residential is also about the same size, not a side by side. Still so much better temp control than my RV fridge. If I was boondocking as much as you I would definitely have an RV fridge.

We just have the standard size Dometic with a roof vent and thermistor. My BIL has a larger side by side absorption with a side vent in a slide. His came from the factory with extra fans and seems to have no problems either. We always have Klondike bars in the freezer and they seem to be the same hardness as at home.
I'm not saying that either type fridge is better or worse, they both have their good and bad points , but either can work just fine in whatever weather you throw at them.
It just kinda rankles me when I read posts like the previous poster saying absorption fridges don't work well in high heat weather. I've had lots of experience that says that normally is not a problem.

[dalford]

Originally Posted by NMWildcat

We just have the standard size Dometic with a roof vent and thermistor. My BIL has a larger side by side absorption with a side vent in a slide. His came from the factory with extra fans and seems to have no problems either. We always have Klondike bars in the freezer and they seem to be the same hardness as at home.
I'm not saying that either type fridge is better or worse, they both have their good and bad points , but either can work just fine in whatever weather you throw at them.
It just kinda rankles me when I read posts like the previous poster saying absorption fridges don't work well in high heat weather. I've had lots of experience that says that normally is not a problem.

I agree... hey, I’ll drink a cold beer from your fridge anytime... and I love Klondike bars..

[babock]

I wish my Dometic didn't struggle but it sure does. Not sure if it's just how it is installed or what. It's why I am installing fans to help it out.

My next fridge will be a 12v compressor type. More efficient than converting 12v to 120vac and I gain a lot of fridge volume.

Since I have lithium batteries and more solar than I really need, power would not be an issue.

[Chuck_S]

My 15 year old Dometic top freezer doesn't breathe hard in the summer because absorption refrigerators are LP (propane) devices with 120vAC auxiliary heaters. The 120vAC operation is handy and "free" if you're already paying for an electric campsite but does not produce the same heat and consequently not the same cold as LP. Simple to run them on LP in the summer. They'll run for weeks on a single propane cylinder. SOP for us. And it runs on LP on the road anyway.

The Dometic has been a literal lifesaver a few abnormally hot weekends when power at the park browns out or quits entirely as everyone runs their ACs and sucks the park power dry! I got cold beer. I got popsicles. We only have time to camp a few weekends a year and it's usually summer weekends when I want a working refrigerator and a not excessively hot cabin.

I usually bring popsicles and ice cubes from home and we all know how horrible popsicles are if they get soft. There's plenty of room in the freezer. If needed there are ice trays I can use to make more ice. Never been a problem.

I've found these work better with a fan inside the refrigerator. Standard camp store item. Also in my former popup I found an external fan really helped exhaust the outside heat but this has not been necessary in my Roo with the high stack to the roof.

Residential fridges have air circulation inside eliminating the need for a little fan but dump all the heat they remove directly into the cabin.

Not even a discussion item for us.

-- Chuck

[Husky10101]

I agree about the cost of lithium batteries, but I was able to buy them on the pre Christmas sales at $600.00 each which I admit, that is a lot. I am retired and will I get my money back when I sell the RV, no way. I had several bids on installing a 5500W Owens generator instead of the solar and it was pushing $5,500.00 - $6,000.00. I am retired and I don't have lifts or hoists needed to get a generator in place. Also we used to own a DRV fifth wheel with the 5500W generator, and had to run it if we tried to boon dock and it used so much propane it was crazy. So yes I spent about the same on Lithium batteries ad a generator install, but I was able to do everything myself. The 6 solar panels were $160.00 each and the controller was $452.00, all bought pre-Christmas sales. Already had bulk welding cable and misc. parts. And because we live in the RV and it qualifies as our primary residence to the IRS, (separate bath, kitchen, and bedroom) I was able to take advantage of the energy tax credit. So I feel I did OK in place of a generator and the batteries are garmented for life. If I had a DP or a toybox where the generator ran on the fuel tanks, then it would be a difference story.

[Cypressloser]

I have 7 years experience with res. fridges (LG) and will never ever go back to a Nevercold or Dometic. Good deep cycle batteries (not the dealer installed junk) with enough usable capacity combined with solar or a generator to charge the batteries is all it takes to stay off grid. If solar isn't an option then charge the batteries directly using a stand alone charger with the generator. A major issue with factory installed inverters is they are way too far from the batteries and the wiring is too small to handle the current, resulting in a huge voltage drop.