Portable Fridge 3 way

Submitted: Saturday, Mar 05, 2005 at 17:30
ThreadID: 20977 Views:2934 Replies:7 FollowUps:16
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Has anyone a comment on running a 3 way fridge on 240 via an inverter while travelling in the car. Could this work and would it be more efficient than running direct on 12 volt.

Cheers, Mark
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Reply By: Tuco - Saturday, Mar 05, 2005 at 18:06

Saturday, Mar 05, 2005 at 18:06
Running your fridge this way is VERY INNEFICIENT! For a start you have to convert the 12V DC to 240V AC with the inverter. You will get losses through heat in the inverter to start with. You will need a LARGE inverter to supply sufficient current to run the fridge on 240V. Once you have the inverter running in your vehicle - you also have a potentially dangerous piece of equipment in the vehicle. 240V KILLS - 12V doesn't!
Why not just run it on 12V - thats what it is designed for. Properly wired 12V 3way fridges work very well. Unfortunately the DC wiring and plug that comes with most brands are not heavy enough, and many people will find that the 12V performance is less than satisfactory.
AnswerID: 101230

Follow Up By: MarkC - Saturday, Mar 05, 2005 at 21:06

Saturday, Mar 05, 2005 at 21:06
Thanks for the reply, just tossing around alternatives. I noticed that some compressor types like Reefer use an inbuilt inverter as they believe a 240 volt compressor is more effecient than a 12 volt compressor. If my 3 way (I know it's not a compressor type) is properly secured by tie down straps & behind a cargo barrier and the inverter is correctly wired by a qualified electrician I really can't see why this would be any more dangerous than any other 240 volt appliance that is in my home. My fridge on 240 _Affordable_Storage_Drawers.aspx 90watts, so according to JayCar I only need a small inverter ( they could be telling porkies) to power the fridge. So I'm still confused as why this would be a very inefficient way. Is it that on 240 the fridge has to be dead level but on 12volt there is more tolerance to the travel of a car. I'll appreciate any feedback.

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Follow Up By: Black Jack - Friday, Apr 01, 2005 at 01:01

Friday, Apr 01, 2005 at 01:01
This question is off the point of this thread but...
I found one of your threads in the archives regarding using Dick Smith wire W 2017 for a 12 v lead for the Chescold fridge. Can I use this wire from the battery to the rear of the car as well?

FollowupID: 361948

Follow Up By: Tuco - Saturday, Apr 02, 2005 at 20:11

Saturday, Apr 02, 2005 at 20:11
Hi Jack - yes you could use the W2017, however for a long run like from battery to rear bumper you would be better using something heavier. W 2017 is shown in the DSE catalogue as having a cross sectional area of 3.5 mm2. Most people advocate having at least 6mm2 with long DC runs to the rear bumper. I'm using W2306 (18.8 mm2) in a single run only. I use the vehicle chassis/body for the earth return. Both my caravan and camper trailer are wired with W2302 (7.1 mm2) and I use 50 Amp Anderson plugs for the connections. I do not use the heavy large 7 pin round trailer plug for the DC supply at all.

W2017 is essentially 'monster' OFC speaker cable - but is very effective for carrying DC and the multi strands make it very flexible and easy to use in the likes of a Chescold DC cable - where it may need to be coiled up and stored.
When I had a Chescold 70 Litre fridge freezer - I did away with the pathetic DC connector on the rear of the fridge, and wired W2017 directly to the !2V heater coil. The increase in voltage at the coil - AND fridge performance was amazing.
FollowupID: 362100

Follow Up By: Black Jack - Sunday, Apr 03, 2005 at 10:09

Sunday, Apr 03, 2005 at 10:09
Thanks for the reply. I have read just about everything said on ExplorOz regarding Chescold and have followed the suggestions exactly. I had already followed your suggestions and had wired in the W 2017 directly to the DC coil. Next I have to do is wire the car. I have looked at the heat exchange design and I am looking at wrapping alfoil around the coils and upper pipes of the heat exchanger, making sure the wires from the two coils are not affected. Then wrap the insulation around that. I am looking to trap more heat in for longer. Can you see a problem with this idea? I heated the alfoil over a gas stove and it didn't melt, so I figure the heat exchanger would not have enough heat to cause a problem.

Thanks again
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Follow Up By: Tuco - Sunday, Apr 03, 2005 at 22:00

Sunday, Apr 03, 2005 at 22:00
Hi Jack - before you go ahead and do the alfoil wrap, check the performance that you are getting with just the wiring change.

If you do more than one change at a time, you may never know which change was effective or not. I'm not saying that the foil wont work, just that it is better to change only one thing at a time before retesting.

We only use an absorbtion fridge in the caravan ( Dometic 2 way gas/240V) - but use an Evakool ED70 12V in our 4x4. It works much better than the Chescold, and we keep it powered with Kyocera 120 W solar panel.

cheers - Tuco
FollowupID: 362202

Reply By: Member - Jimbo (VIC) - Saturday, Mar 05, 2005 at 18:10

Saturday, Mar 05, 2005 at 18:10
Often wondered the same Mark and I'd try it out if the element in my old Chescold wasn't wellington booted.

If the inverter is big enough to supply enough power, why shouldn't it work?

Keep in mind if you need an inverter over 150 watts you'll need to run it direct from a battery.


AnswerID: 101231

Follow Up By: MarkC - Saturday, Mar 05, 2005 at 21:15

Saturday, Mar 05, 2005 at 21:15
Hi Jim,

Thanks for reply, I also have a Terracan and for a while I thought I was the only one. It's good to find other Terracan owners, I hope you are having as much fun with yours as I am with mine.
Bak to the fridge question, my 3 way only _Affordable_Storage_Drawers.aspx 90watts on 240 so a small inverter should do. I replied back to Tuco as he was adamant that this way was pretty inefficient. Just looking at alternatives as I have the inverter and was goiny to install it in the cargo area anyway.

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Follow Up By: Member - Jimbo (VIC) - Saturday, Mar 05, 2005 at 21:42

Saturday, Mar 05, 2005 at 21:42

My Jerry Can is a gem. I love it.

Sure the inverter may be inefficient, but whilst you're driving and your alternator will produce more power than you can use, who cares? Then when you stop you switch to gas. If you've already got an inverter, give it a go, why bugger around with special 12 volt wiring?


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Follow Up By: MarkC - Saturday, Mar 05, 2005 at 23:18

Saturday, Mar 05, 2005 at 23:18
Thanks mate, my thoughts exactly, I'll give it a go and let you know how it works.

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Reply By: brett - Saturday, Mar 05, 2005 at 22:14

Saturday, Mar 05, 2005 at 22:14
You'll probably end up drawing more current at 12V with the inverter than the fridge running off 12V, so you may as well plug the fridge straight in to 12V. The power is only used to heat an element in the fridge, makes no difference if you use the 12V element or the 240V element. These fridges need to be dead level to work properly and this is very hard to do in a moving car. Most people think they only work well on gas and 240V and not very well on 12V, the reason for this is they only ever use 12V in the car when the fridge isn't level.
AnswerID: 101263

Follow Up By: MarkC - Saturday, Mar 05, 2005 at 23:24

Saturday, Mar 05, 2005 at 23:24
Hi Brett,

According to the manual my fridge _Affordable_Storage_Drawers.aspx 90watts on 240 & 75watts on 12volt. I can appreciate if I get the 12volt wiring right with no voltage drop the fridge will work OK on 12 volt, just seeing if their is an alternative to upgrading the wiring as I have the inverter.

Thanks for the input,
FollowupID: 359246

Follow Up By: ozromer - Tuesday, Mar 08, 2005 at 09:22

Tuesday, Mar 08, 2005 at 09:22
This bit about being dead level does not accord with either my experience or with the handbook for a Dometic fridge that I had in my old caravan. The book says that these fridges work OK on 12v whilst a boat or vehicle is moving because the liquid ammonia/hydrogen phase sloshes around and prevents significant cycling of the vapour phase into the condenser area.
My experience is that it is very often difficult to find a 'van site that is level in both directions, but the fridge still worked when a few degrees off level. In fact I deliberately tried the off-level setting at home during a dispute with a frdge repairer and got good performance when a fair bit off level.
Do agree though that 240 volts be treated with great respect. Depending on the body's resistance (and it will be lowered by getting wet at the campsite) a 240 shock can be fatal. On the other hand the safe limits for DC, even in wet conditions, are 32 volts RMS (root mean square) and 45 volts peak, which makes 12 volts very comfortable to live with.
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Reply By: Member - David 0- Sunday, Mar 06, 2005 at 21:21

Sunday, Mar 06, 2005 at 21:21
All been said above. Don't go there. Cover the windows to keep the sun of it, get it cold, keep it full of cold stuff and run it on 12V.
AnswerID: 101377

Reply By: Member - Jimbo (VIC) - Sunday, Mar 06, 2005 at 21:31

Sunday, Mar 06, 2005 at 21:31
Just a thought, my understanding is that it is amps that kill you, not volts. A spark plug develops around 30,000 volts which gives you a nasty jolt up your arm, but won't hurt you. Just like those little toys you can buy that will generate enough kick from a AA battery to make you jump but will do you no harm.

Can a 150 watt inverter do you any serious damage? I doubt it, but may stand corrected.

AnswerID: 101381

Follow Up By: Mad Dog (Australia) - Sunday, Mar 06, 2005 at 22:14

Sunday, Mar 06, 2005 at 22:14
A 150 watt invertor can put a lot of dirt on top of you Jim, don't mess with it. It only takes milliamps at 240 volts to kill you. I have a bad habit of testing the charge in 9 volt batteries with my tongue, apparently a few with weak hearts have been knocked flat doing this.
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Follow Up By: Mad Dog (Australia) - Sunday, Mar 06, 2005 at 22:50

Sunday, Mar 06, 2005 at 22:50
Have a read of this Jim, interesting stuff.

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Follow Up By: Member - Jimbo (VIC) - Monday, Mar 07, 2005 at 07:51

Monday, Mar 07, 2005 at 07:51
Thanks Ray
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Reply By: MarkC - Sunday, Mar 06, 2005 at 22:32

Sunday, Mar 06, 2005 at 22:32

Thanks to all who have taken the time to reply, this sure is a great forum. No one has actually said why using an inverter is dangereous apart from the obvious that 240 can kill. If the fridge is OK, the inverter is OK and all is wired correctly why is it so deadly or am I missing the point! Compressor type fridges seem to operate OK using inbuilt inverters, is this any less dangereous than using an external inverter? Having said all this this I guess the prudent choice is to let my auto electrician make the final decision. Once again thanks for all the feedback.

AnswerID: 101392

Follow Up By: Member - Jimbo (VIC) - Sunday, Mar 06, 2005 at 22:41

Sunday, Mar 06, 2005 at 22:41

I often let the kids use the laptop, via an invereter to watch DVD's. I wire it safely, with fuses and I cant think it is ant more dangerous than using a TV at home.

Why is 240 more dangerous in a car than in a bedroom I ask.


FollowupID: 359331

Follow Up By: Mad Dog (Australia) - Sunday, Mar 06, 2005 at 22:48

Sunday, Mar 06, 2005 at 22:48
Probably only more dangerous if it's a Heath Robinson installation with no concern for safety.
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Follow Up By: AdrianLR - Monday, Mar 07, 2005 at 13:03

Monday, Mar 07, 2005 at 13:03
A danger is that the inverter will often be sitting on the floor which is the first thing that gets wet if you happen to stall during a river crossing and get water in the car. The fuses may blow before damage is done but there isn't the equivalent of an Earth Leakage Detector or Residual Current Device that would protect you in you bedroom (assuming recent house wiring). Also, the design of the inverter will impact the level of danger - if the 12v ground isn't isolated from the 240 ground/neutral (as in some cheap inverters) then there is higher risk of the chassis being one half of a 240v circuit.

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Reply By: MrBitchi - Monday, Mar 07, 2005 at 14:51

Monday, Mar 07, 2005 at 14:51
Also, inverters are only about 80% efficient so 90w at the fridge means about 120w at the battery. All the extra power just goes in heat.
I'd always use 12v instead of 240v in the car where possible. It's more efficient and safer. One half cycle of 240v can kill you.
Yes I know we all use 240 inverters for laptops etc but why take the risk if you don't have to?

Cheers, John.
AnswerID: 101445

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