Can you run a 3-way fridge from 240V whilst driving?

DaveA1963 · Member

Can you run a 3-way fridge from 240V whilst driving?

2happy · Member

What source are you using presently? But in any short answer is yes it will run fine on the inverter whilst mobile. You may want to [re)look at 12v once you have your new dcdc charger fitted. Ours works great on 12v. Returning home on wednesday in SE QLD, the ambient was 32 and inside fridge was at 0.1 degrees running on 12v (actually measured 13.1v at the connection)

One issue with using 240v is that you have more inherent loss of charge (to run the inverter) than directly off low voltage, hence it will take a little longer to recharge your house battery. Irrespective of power source all of the absorption fridges work off a heater be it 12v, 240v, or gas flame. So whether you're mobile or stationary there is no difference. Note that it is more important to keep the unit somewhere near level though.

DaveA1963 · Member

Thanks for your very informative reply! That's really helped me.

We presently use 12V when moving and otherwise, it's mainly been used on 240V, which works fine. I have tried it on gas, just to see if it worked, and that would appear to be fine too.

I have a two-way spirit level and am absolutely anal about having the van level when setup. It drives my poor wife to distraction!

We aren't going to have a chance for the manufacturer to look at it for quite some time, so I'm keen to try the inverter method and see if we can keep the fridge at a safe temperature. I'll basically only use this method when actually travelling and if I can get it working properly on 12V, I'll go with that. Having said that, if I've got solar and the DC-DC pumping power back in to our 190Ah lithium battery, I should be able to put in more than I'm taking out, if that makes sense?

-- Edited by DaveA1963 on Saturday 24th of February 2024 10:50:40 AM

Are We Lost · Guru

My Dometic 186L fridge specs show 325 watts on 240v and 275 watts on 12v. Maybe yours is similar. That 50 wattt shortfall is probably enough that it does not keep temperature.

Ian G · Senior Member

You may want to look at the 12 volt issue, you haven't mentioned how you are supplying your 12 v, I assume it is from the vehicle battery via an anderson plug. A common problem is the wire size being too small and a large voltage drop as these fridges can draw 20 amps. When the fridge is running on 12v and the vehicle running you should have around 13 volts at the fridge for it to run correctly.

valiant81 · Guru

Hi all; Chech the 12 Volt wiring from your car to the fridge as a voltage drop over the distance and your fridge will not perform as exspected. But what you are expecting from your fridge may be just out of the capacity of your fridge. We have over the years had 3 Jayco caravans ( the first was a Jayco swan, followed by 2 X Jayco discovery caravans ) and all had the same 95 Liter 3 way fridge. Our current caravan is now just over 12 years old.

We have found that these fridges are very poor at trying to maintain temp. Even when on a powered site and using power, the fridges took several day to come back down in temp. This and this alone is one of the reasons why we purchased a couple of 40 Liter compressor fridges that run off 12 volt or mains power. Both fridges sit in the back of my 4x4 and connected to the 12 volt system in the car. Free camping as we do, both fridges are moved under the awning of our caravan and connected to the 12 volt system in the caravan ( 2 x 220 Ah of batteries and 1000 watts of solar input ( just upgraded from 240 watts )). We have been free camping for up to 2 weeks at a time and only started to run out of power after a couple of days at the end with not a lot of solar gain and this was the reason why we have upgraded the solar to 1000 Watts.

As for the 3 way fridge in our current caravan we run it on gas, and the wife mainly uses it for food that is not so temp sensitive ( dog food and vegetables etc ). I also have a small 2kva genset that i have used and connected to a 30 Amp battery charger in the past to recharge the house batteries, when the solar has been insufficient.

-- Edited by valiant81 on Saturday 24th of February 2024 04:53:40 PM

Whenarewethere · Guru

When calculating wire resistance. It is the total length of + & - . So if your 12v cable is 12 metres, it is actually 24 metres (there & back so to speak).

You need the correct cross sectional area so it isn't working too hard, ie too much resistance.

The resistance calculators will often state a cable size a fair bit under size. At least from fridge issues. A 0.5 volt for example voltage drop is too much.

The voltage drop is too much in most cases for a fridge. At least double cable cross sectional area which will halve the voltage drop.

Run a new 12v parallel cable to the socket/s. If they are not 50amp Anderson plugs, replace them (actually not needed, but the 120amp & 175amp Anderson plugs are smoother to plug & unplug).

P.S. If you need to solder Anderson plugs a heat gun is brilliant. Also great for heatshrink tube, but at a lower temperature.

Whenarewethere · Guru

valiant81 wrote:
This and this alone is one of the reasons why we purchased a couple of 40 Liter compressor fridges that run off 12 volt or mains power. Both fridges sit in the back of my 4x4 and connected to the 12 volt system in the car.

My 28L compressor fridge (whether 40 or 60L are similar) with its poor volume to outside surface area ratio. With a bit of extra insulation used 15AH per 24 hours. Why people bother with gas fridges, I don't get it.

https://thegreynomads.activeboard.com/t65059593/extra-fridge-insulation-wattage-test/

-- Edited by Whenarewethere on Saturday 24th of February 2024 05:38:24 PM

Are We Lost · Guru

Whenarewethere wrote:
Why people bother with gas fridges, I don't get it.

Because the sun does not shine every day. At this moment I am sitting in my car with the engine running, charging my laptop and phone. It has been overcast with very little feed to the van battery for a day and a half. With 2 laptops and TV we ran it low last night and again during the overcast day today.

In the meantime, the 3 way fridge is happily keeping our stuff frozen/chilled, running on gas. The fridge is 186 litres and pretty full. How many amp/hours would a 12v fridge that size consume in hot weather? If it did not run on gas we would have had to taken the van to a power source. More battery capacity and solar would help, but that is more on the roof or portable and more cost and installation.

Of course, it is solvable to last another overcast day but at a cost.

-- Edited by Are We Lost on Saturday 24th of February 2024 06:46:32 PM

Whenarewethere · Guru

Fix your solar network.

We run our fidge, charge camera batteries & phones, run lights off a tiny system for 4 days before I bother to plug the solar cells in.

Even with overcast situations & 2 panels in series, x 3 in parallel, you will get enough to keep head above water.

Our straw is long enough for sh_t weather. Not difficult stuff.

Are We Lost · Guru

Whenarewethere wrote:
Fix your solar network.

I checked the specified consumption for the current similar sized Dometic 12v fridge. At 32 degrees ambient it supposedly consumes 66 amp hours per day. With two days of wet and overcast with virually zero solar input that would totally exhaust a typical battery. AGM to much extra weight. Lithium too much extra cost. Then I would need more solar to charge it faster. For someone long term on the road it would be worth considering.

Not justifiable for me.

Whenarewethere · Guru

You could add insulation to the fridge to reduce energy consumption. A lot of yachts will have 200mm of insulation & they don't have much space.

Our fridge has about 80mm on average & we will also chuck our crap over it in hot weather. Making sure vents a free.

There are diminishing returns on insulation thickness. But at 66 amps per 24 hours at 32°C one needs to look at the quality of the setup.

elliemike · Guru

If you are on level ground with the van hitched up. Is the Fridge ( van) actually level !.

When travelling the van (Fridge) will not be stable and certainly not maintain being level constantly for the journey. Running on 12v, 240v or gas, The fridge must be reasonably level to work .

I have been informed in the US and Canada in very Hilly or Mountain Range driving, some owners switch the fridge off to prevent blockage of pipework. Due to the Trailer or RV being out of level for hours on steep roads.

Recommended level by Dometic. Left to Right = Fore and Aft. Front to back = is side to side (Port and Starboard)

Showing results for Dometic three way Fridge level tolerance
Search instead for Dometic three way Fridge level tolerance

"Thank you for contacting Dometic. The refrigerator should not be more than 3 degrees unlevel left to right, or 6 degrees unlevel front to back.

We do not recommend having the unit unlevel for more than 1-2 hours as this can increase the chances of a blockage.10 Mar 2017

-- Edited by elliemike on Sunday 25th of February 2024 10:57:51 AM

Are We Lost · Guru

Whenarewethere wrote:
But at 66 amps per 24 hours at 32°C one needs to look at the quality of the setup.

This is the manufacturer's specification, no doubt based on a perfect installation .... 2.8 amps average consumption. Probably most installations will consume more than that. The rating for an equivalent to my 186L fridge is 9.5 amps.

Putting in thick insulation would obviously benefit fridge performance, but the fixed size compartment would mean substantial reduction in capacity.

I don't need the extra insulation as you suggest. I don't need "to fix" my solar as you suggest or add panels. I don't need to swap my controller for a bigger one, or get extra battery capacity. Today is the third wet/cloudy day in a row, with just enough power generated through solar to slowly bring the battery charge back up while running my laptop.

I'm really thankful my fridge works just fine on gas.

Too many compromises/expense/weight for me to consider 12v only.

Whenarewethere · Guru

elliemike wrote:
If you are on level ground with the van hitched up. Is the Fridge ( van) actually level !.
When travelling the van (Fridge) will not be stable and certainly not maintain being level constantly for the journey. Running on 12v, 240v or gas, The fridge must be reasonably level to work .
I have been informed in the US and Canada in very Hilly or Mountain Range driving, some owners switch the fridge off to prevent blockage of pipework. Due to the Trailer or RV being out of level for hours on steep roads.
Recommended level by Dometic. Left to Right = Fore and Aft. Front to back = is side to side (Port and Starboard)
Showing results for Dometic three way Fridge level tolerance
Search instead for Dometic three way Fridge level tolerance
"Thank you for contacting Dometic. The refrigerator should not be more than 3 degrees unlevel left to right, or 6 degrees unlevel front to back.
We do not recommend having the unit unlevel for more than 1-2 hours as this can increase the chances of a blockage.10 Mar 2017

3 degrees left to right is a bit of an issue as road cross sectional slope is 3° & in general no more than 4°, but can sometimes be up to 6°.

But it's basically 3° minimum on all roads. So you may need to prop up the fridge a bit if the left side of the caravan is sloping down a whisker to start with.

Road planning & design manual (attached image):

elliemike · Guru

Whenarewethere wrote:
elliemike wrote:
If you are on level ground with the van hitched up. Is the Fridge ( van) actually level !.
When travelling the van (Fridge) will not be stable and certainly not maintain being level constantly for the journey. Running on 12v, 240v or gas, The fridge must be reasonably level to work .
I have been informed in the US and Canada in very Hilly or Mountain Range driving, some owners switch the fridge off to prevent blockage of pipework. Due to the Trailer or RV being out of level for hours on steep roads.
Recommended level by Dometic. Left to Right = Fore and Aft. Front to back = is side to side (Port and Starboard)
Showing results for Dometic three way Fridge level tolerance
Search instead for Dometic three way Fridge level tolerance
"Thank you for contacting Dometic. The refrigerator should not be more than 3 degrees unlevel left to right, or 6 degrees unlevel front to back.
We do not recommend having the unit unlevel for more than 1-2 hours as this can increase the chances of a blockage.10 Mar 2017

3 degrees left to right is a bit of an issue as road cross sectional slope is 3° & in general no more than 4°, but can sometimes be up to 6°.

But it's basically 3° minimum on all roads. So you may need to prop up the fridge a bit if the left side of the caravan is sloping down a whisker to start with.

Road planning & design manual (attached image):

I think it is 3 deg. looking at the front of the fridge. 6 deg. from the fridge door to the back of the fridge.

Whenarewethere · Guru

Yes, but that is not much tolerance.

It might be worth pre tilting the fridge factoring the how level the caravan is & another bit for the typical road.

I am surprised just how little tolerance there is.

A compressor fridge has 3O°

watsea · Guru

The QLD TMR design guidelines give road crossfall, depending on the type of road, as 2-4%, mostly as 3%.
3% is about 1.7 degrees. 4% is about 2.25 degrees.