DIY: How to make your own 12V Fridge

[user 2252]

Hello. I have a Dometic 3 power sources fridge. Being new to this MoHo thing, I was wondering about running it on 12v. The thing works well on 240v hook up and on gas. But when we are either stationary engine off in a carpark etc. or on the move, the 12v led flashes, red triangle flashes and beeper sounds. So it's not working on12v. All other 12v stuff works and leisure battery shows 12v and vehicle battery shows 12.5v. Not sure what to look for next. Many thanks for your time.

Look inside the refrigerator (where you keep your food) for a label with a model number and serial number printed on it. Use those numbers to search for documentation at Dometic.

 

[tx2sturgis]

It gets even more confusing when you discover there are phases of AC power. Most all RVs in the United States use a 30 amp or 50 amp single phase 120 volts.

Actually, 50 amp RV service is using two 120v lines, or phases, and there is 240v accessible in the RV across the two phases.

 

[user 22017]

The power pedestals at any campground/RV park and all RV's are wired the same......120 Volt

Residential supplied power is standard 240 volt

Well, i got that reading all wrong. lol And now I can;t find the article. Maybe it never happened=/

 

[bullfrog !]

Actually, 50 amp RV service is using two 120v lines, or phases, and there is 240v accessible in the RV across the two phases.

I hate to tell you but most RV pedestals I have checked simply have a jumper in between the two terminals on the plug, you do not get 240 volts between them, in fact many simply jumper from the 30 amp plug to the 50 amp plug rather than running an “extra” wire. They basically originally had a 30 amp plug as few RVs came with a 50 amp plug. When More RVs started to come with 50 amp plugs even though none had appliances that required 240 volts they simply added a 50 amp plug in to the pedestal and jumpered from the 30 amp plug in to make it work without having to run an additional wire. It has it seems become a common practice, which is why I recommend you check any plug before you plug in your RV. I have had to replace a couple of air conditioners as my motor home was one of the first that came with a 50 amp plug as it came with a front and rear air conditioner which is why I now check.

 

[abnorm]

What I should have said is....................

Standard RV's use the power provided as 120 volt circuits.......there's no 240 volt load in the traditional RV

Sorry TX ..........that's still Single Phase

 

[tx2sturgis]

Yeah I typed out 'two phases' but I was meaning to add 'split phase', since there really is no AC power called 'two phase' in use today, only single phase, split phase, and three phase, so I was assuming it would be interpreted as the split phase (240v sent on two legs 120v each) that I was referring to.

 

[tx2sturgis]

I hate to tell you but most RV pedestals I have checked simply have a jumper in between the two terminals on the plug, you do not get 240 volts between them, in fact many simply jumper from the 30 amp plug to the 50 amp plug rather than running an “extra” wire.

Just because you find that stuff in the wild, does not mean its 'correct'.

And yes...stuff happens.

A wise and/or experienced RVer always carries a plug-in circuit tester. And I always encourage RV guests to test the 30 amp RV receptacle here at my place before they plug into it.

Some top-of-the-line Class A motorhomes have the option for a residential 240v dryer, but of course that dryer will only work on 50 amp (correctly wired) shore power hookups, or the built-in 240 genset found on those units.

If the owner used an adapter to plug into 30 amp service, the 240v dryer would not work, so that option is probably not chosen very often.

When I stated that 240v is accessible in 50 amp RV's, it means the 240v is there in the RV junction box, but it does not mean that the RV plugged into it will have a 240v outlet in the coach.

BTW, in Europe, and many other countries that use 220v, it is single phase 220. Those are the funny looking electrical outlets you see in some foreign films.

But here in the good ol USA, 240v is 'split phase' as delivered to our homes and 50 amp RVs.

Sorry for the confusion.

 

[user 25174]

DIY: How to make your own 12V Fridge​

I guess the DYI thing (or maybe just me) got lost in this conversation.

 

[bullfrog !]

Yep it would be nice if we lived in a perfect world! Lol!!! The newer motor home owner’s get really upset when their dryers don’t work or their central heat and AC units “brown out” but what do you expect for $68 a night in a lot on generator power that your clock needs to be reset every few day if your fancy surge protector lasts! Lol!!! I’ve had to put a lock on my pedestal to prevent the adjoining site from plugging into the open 30 amp plug because their pedestal didn’t work! It’s the “Wild West” out here! RV parks with wiring this way are just like the older houses that still have or are still wired for 2 prong plugs. It pays to check before you plug in, just saying! Sorry for the side track but the reason to have a DIY 12 volt fridge is because of these issues in many cases. This is an older thread that has been revived and 12 volt compressor fridges are more available and inverters are available with built in features that make them a better solution than the DIY I believe.

 

[jasper]

A voltmeter connected to hot 1 and hot 2 should read 240vac if wired as shown above for four-wire 50 amps at the pedestal. If a 50 amp 4-wire receptacle has replaced an old 3-wire receptacle with a jumper from hot1 to hot 2, the voltage should read zero.

It's not just RV pedestals that cause problems. Not all electricians and especially DIYer's are aware of the 120v, 30 or 50amp RV supply. I've been called three times in the last two years on a 120v, 30 amp camper had one leg of 240vac connected to neutral and the other 240V leg connected to hot. They simply found a female that matched the male on the RV cord. One permanent dweller owner simply cut off the male end and wired it directly to a 240v circuit breaker nearby.

I recall blown fuses and a destroyed water heater element as a result, IIRC.

Thanks TX, I did not know of the 240v appliances.

 

[tx2sturgis]

DIY: How to make your own 12V Fridge​

I guess the DYI thing (or maybe just me) got lost in this conversation.

Yeah we kinda wandered off course, but this thread is getting close to 8 years old now, and like anyone or anything else with some age, its a bit wobbly and tends to ramble.

 

[tx2sturgis]

OK, I did a bit of point-of-presence and thread backtracking and the point where we went off on a tangent was when this thread was bumped and the topic swerved to talk about 120v vs 240v when an RV was hooked up to 240. (I believe they meant to say 220 or maybe 230)

Without dropping off in the weeds too much: in Europe, and other countries where this topic can be and is being discussed on this forum, it is common to use single phase 220v or 230v (notice 220/230, NOT 240) at the RV power pedestal and household power.

So while it may seem unrelated to the original topic, this tangent IS relevant for at least one user in this thread.

We have two versions of this higher voltage for our purposes here: 240v split phase used here in the USA, and 220/230v single phase commonly used in Europe and some other countries, Japan comes to mind.

Many of us have bought electronic devices that come with a charger with an adapter, usually round pins or some other configuration, that is used for single phase 220/230v in other countries.

This can be VERY relevant when it comes to 12v DIY fridge conversions because a 12v to 120v (or 220v) inverter may be needed depending on the appliance itself and the country it's being purchased in and used in.

Thanks for everyone's patience in this.

 

[maki2]

The marine industry sells electric fridge compressors, temperature controllers and chilling plates on their own. You can build your own insulated box to put the chilling plates in. Then tubing is run over to the fridge compressor. It can be handy to do it that way as the compressor can be remote mounted a few feet away from the fridge box. Plus you can super insulate your custom fridge box.

Isotherm is one reputable company that sells the individual components for making custom fridge boxes. Because it is an international supplier you can get units that are 12v or 24v.

I lived in a large marine community in Seattle and bought most of what I needed for my build in that neighborhood from marine supply stores where they sell such things so I am quite familiar with custom built fridges on boats. My best friend has one of them in his 40’ sailboat.

 

[user 25174]

Yep it would be nice if we lived in a perfect world! Lol!!! The newer motor home owner’s get really upset when their dryers don’t work or their central heat and AC units “brown out” but what do you expect for $68 a night in a lot on generator power that your clock needs to be reset every few day if your fancy surge protector lasts! Lol!!! I’ve had to put a lock on my pedestal to prevent the adjoining site from plugging into the open 30 amp plug because their pedestal didn’t work! It’s the “Wild West” out here! RV parks with wiring this way are just like the older houses that still have or are still wired for 2 prong plugs. It pays to check before you plug in, just saying! Sorry for the side track but the reason to have a DIY 12 volt fridge is because of these issues in many cases. This is an older thread that has been revived and 12 volt compressor fridges are more available and inverters are available with built in features that make them a better solution than the DIY I believe.

Seems when I open an email and one of the threads read "DYI 12 volt fridge" it's up to me to figure that it's years old.
Just interested in the topic ..
Btw I have my own fridge, but thanks for the very supportive update(s).

 

[bullfrog !]

When I see a large post number I always now look back a few posts to see if it is a revived thread as things change and I have foolishly answered a lot of irrelevant questions! Lol!!!

 

[user 25174]

When I see a large post number I always now look back a few posts to see if it is a revived thread as things change and I have foolishly answered a lot of irrelevant questions! Lol!!!

Good advice .. thanks.

 

[maki2]

The Engel fridges were designed in Australia and made in Japan but also sold suitable for use in the USA and other countries. There are other brands of

There is definitely is such a thing as a 220v (240v) RV hookup, but not in the USA. You just need to go to Europe, Australia and Asia to find them. My Engel fridge has the built in circuitry to run on both the USA standard 110v electrical as well as the 220v elsewhere. I would just need the right power cords if I ever wanted to ship my travel trailer to one of those countries.

 

[quilting22]

Yep it would be nice if we lived in a perfect world! Lol!!! The newer motor home owner’s get really upset when their dryers don’t work or their central heat and AC units “brown out” but what do you expect for $68 a night in a lot on generator power that your clock needs to be reset every few day if your fancy surge protector lasts! Lol!!! I’ve had to put a lock on my pedestal to prevent the adjoining site from plugging into the open 30 amp plug because their pedestal didn’t work! It’s the “Wild West” out here! RV parks with wiring this way are just like the older houses that still have or are still wired for 2 prong plugs. It pays to check before you plug in, just saying! Sorry for the side track but the reason to have a DIY 12 volt fridge is because of these issues in many cases. This is an older thread that has been revived and 12 volt compressor fridges are more available and inverters are available with built in features that make them a better solution than the DIY I believe.

Good info abt putting a lock on the pedestal !