Running 3-way fridge in 220v mode off inverter while driving?

Submitted: Wednesday, Jul 04, 2012 at 18:12
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Hi,
From the outset, I state for the record that I am not any sort of electrics-competent person, but I've done enough 12v wiring around boats to get the basics of red and black string without setting fire to anything....
The Challenge: Three-way electrolux fridge/freezer. been a brilliant product and gone all over Oz with us in the back of the Prado (towing a Kimberley Kamper 2000). Fridge runs very well on gas whenever camped. Didn't go well on 12v from the outset, so have always run it while driving, in 220v mode, through an inverter. Bonus is that, using a powerboard on top of the crap on the back seat, we've also been able to charge up all the usuals (laptops, camera, phones, toothbrushes, ipod speaker set, etc,) while driving. The last inverter (Dick Smith 300w cheapo) eventually died after the damp of a boat and being rattle around the outback for ten years or so. Have bought a better quality 600w replacement. All good EXCEPT that the domestic accessory sockets on the dash get too hot and melt the bayonet from the inverter.
I have in mind running a totally separate circuit, from battery through to passenger footwell, with 50a Anderson Plug, secured to centre console wall at foot level (where we have always kept the inverter so that the bride keeps a constant eye on it, and it can't blow up without at least one of us noticing).
I'd put its own in-line fuse in the circuit (on the positive supply line, or the negative return line? any advice? does it matter?).
Advice welcomed please:
a. despite all doom-sayers saying that mains power inside the vehicle is dangerous, it's been workable for us for a long time - so if it really is a stupid thing to do could someone tell me please.
b. if I do this, what gauge of wiring should I use to avoid the same over-heating that has been happening at the accessory sockets?
c. Any other useful comment or advice would be very welcome.
cheers all,
Graham.
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Reply By: Bush Wanderer - Wednesday, Jul 04, 2012 at 18:24

Wednesday, Jul 04, 2012 at 18:24
Check out the caravanner forums and some recent caravan magazines.
This is common practice, and makes the 3 way fridges work better...have not yet tried to myself.
Don't know if it's legal or not.
BW.
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Follow Up By: KevintheKK - Wednesday, Jul 04, 2012 at 18:33

Wednesday, Jul 04, 2012 at 18:33
Thanks BW, have been looking at articles in camper mags and haven't seen much either for or against this method, but of course I don't actually read caravan mags - but I'll keep googling and see if any practical help turns up. cheers, Graham (KK).
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Follow Up By: Bush Wanderer - Wednesday, Jul 04, 2012 at 19:20

Wednesday, Jul 04, 2012 at 19:20
I know the Sahara comes with 240 volt in the rear as does my other car which is a toaureg.....book states fine to use it while travelling, so must not comply with ADR.
BW.
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Reply By: oldtrack123 - Wednesday, Jul 04, 2012 at 19:24

Wednesday, Jul 04, 2012 at 19:24
Hi Graham
The simple reason WHY your fridge runs better on 240v than 12v [especially over such a short distance] is undersized 12V cables giving excessive lost voltage @ the fridge
The same problem you have found with the lighter sockets
UNDERSIZED for the current [Amps ] involved

Yes, many do use inverters to bodgy overcome the problem, instead of FIXING the problem with the correct cables
It also makes for good sales for the inverter sellers who will tell you that is the answer

AS far as 240v is concerned ,it can be just as deadly from an inverter as from the mains power
Deaths have occurred using inverters

USE with GREAT care
One point that should be considered is the safety RECOMMENDATION:-

" ONLY HAVE ONE CLASS 1 DEVICE[has a 3pin plug] connected @ any time"

You can with reasonable safety connect multiple Class 2 devices[2pin plug] @ the same time


Peter
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Follow Up By: KevintheKK - Wednesday, Jul 04, 2012 at 19:38

Wednesday, Jul 04, 2012 at 19:38
Thanks for that advice Peter - much appreciated.
Graham.
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Follow Up By: Member - Andrew W14 - Wednesday, Jul 04, 2012 at 20:27

Wednesday, Jul 04, 2012 at 20:27
A couple of comments regarding the above:

All 3 way fridges when running on 12 volts by pass the thermostat so the thermocouple (or whatever its called) is running constantly. I believe the reason they do this is that no matter what sized wiring you have they will not run as well on 12 volts as on gas or 240 volts. So be wary of rewiring everything and thinking it will fix the fridge - it won't!

The comment that 'deaths have occurred using inverters' is just plain scare tactics - even if it were true. Deaths have been caused by many many things - inlcuding crossing the road, but that doesn't stop us doing it.

Whilst I think that 240 volts in a car is not necessarily a good idea, unsupported scare tactics are not necessarily convincing to me.

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Follow Up By: garrycol - Wednesday, Jul 04, 2012 at 20:57

Wednesday, Jul 04, 2012 at 20:57
Not quite true for all 3 ways - my 3 way uses the same power on 12v as 240 v - 120w so has the same cooing power. As mentioned wiring is the major limitation.

Being zapped in an accident is also an issue - while I don't believe paramedics have been "electrocuted"but they have certainly been zapped by inverters after accidents.
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Follow Up By: steved58 - Wednesday, Jul 04, 2012 at 21:05

Wednesday, Jul 04, 2012 at 21:05
I often wonder after an accident if the inverter is still connected what happens?
The emergency workers would be unaware of the presence of 240volt as would anyone trying to help

So is it safe ? I don't know and as such would not consider using this method without first investigating it just because it works for years does not make it safe and it is after an accident that concerns me

Just my thoughts maybe yours varies from mine


Steve
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Follow Up By: PJR (NSW) - Wednesday, Jul 04, 2012 at 22:37

Wednesday, Jul 04, 2012 at 22:37
We had an autoelectrician to run a heavy cable, fused at 40 amps, to suitable heavy duty 12V outlets up the back near the two fridges. I have been in electronics since the 70's and having been zapped with both 240 and RF in bad mobile installations (not mine) I will NOT run 240 V AC mobile. It did not kill me but no thanks.

Scare tactics or not I don't care for it.

Run a good cable and run on 12V.

We have only used the inverter once and that was on very the last night before the rewire. We do not even take it now. The voltage drop to the fridges is neglible. 13.8 at the battery gives 13.3 at the input to the inverter in the fridges. I have a cheap voltmeter wired to the guts of the fridges and stuck on the front so that I can monitor the volts. We also have three batteries in a one crank and two for auxiliary system split with e Redarc 200 amp isolator. This gives a bit less than 40 hours for the fridges. Heaps as we seldom stay inone place more than two nights.
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Follow Up By: oldtrack123 - Wednesday, Jul 04, 2012 at 22:40

Wednesday, Jul 04, 2012 at 22:40
Hi Andrew
Re"All 3 way fridges when running on 12 volts by pass the thermostat so the thermocouple (or whatever its called) is running constantly""

That comment is totally wrong ,many models of Dometics do have 12v thermostat control on 12v operation, but not ALL

Many have the same rated heating element for 12v as 240v so if it receives the correct voltage it must & does do the same job
SOME even use the same element.


Are you saying that in some mysterious way it is a less dangerous 240v than mains???

Encouraging complacency with any 240v source is stupid.

Inverters have killed & who knows how many shocks have been received.

Some of the older ones are not even fully isolated & heavens knows what some of the ebay overseas ones are

Even a fully isolated inverter is only reasonably safe WHILE IT REMAINS fully isolated

IF a fault to earth occurs ANYWHERE in the wiring ,They are no longer fully isolated & become an unprotected EN system

Such faults regularly occur in vans etc due to poor workmanship &/or unqualified labour being used to wire them



Peter
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Follow Up By: KevintheKK - Wednesday, Jul 04, 2012 at 23:16

Wednesday, Jul 04, 2012 at 23:16
Very grateful for all comment so far - thank you for your time and educative advice.
If anyone has any advice on providing a dedicated 12v supply to the inverter - ie what gauge should the cable run be, and is an Andesron plug connector a good solution at the inverter end, then I'd appreciate it. I certainly need initially to get around the problem of the accessory sockets over-heating, hence the idea of a dedicated heavier-duty circuit.
However, I'm also taking seriously the idea of running a heavy duty 12v circuit right through the vehicle to the back end where the fridge is carried, and having another go at running it on 12v while travelling.
The inverter remains, of course, a way of charging up on the go all the peripherals that need 220/240, but I appreciate the cautionary advice from all above.
Further inputs welcomed.
(Well Done Queensland, said this NSWelshman through gritted teeth!!!!!!)
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Follow Up By: PJR (NSW) - Thursday, Jul 05, 2012 at 08:48

Thursday, Jul 05, 2012 at 08:48
Hi Kevin

The blokes here ran a single 8 gauge B&S red wire to the back and picked up an earth from the chassis. They used a bolt on the side of my drawer system metal frame which is solidly bolted to the body of the car in at least 6 places. I run the compressor, water pump and two fridges of it.

The two outlets for the fridges is provided by a double (we believe its 15 amps each socket) cigarette lighter style wall outlet that I picked up years ago. I would try your local autoelec for this in your area. This particular one can lock if you get the right plug and therefore not fall out. I prefer this style because it is then compatable with phone chargers and lots of other gizmos that run 12V. You could also try a marine parts outlet or shop for one.

Food for thought:
They also installed a separate fuse box, running off the auxiliary battery, for all my 4WD circuits. It handles the compressor, battery isolator (Redarc 200 amp one), lockers (2) and lights (fog + driving) circuits. 15 amps for each except for the compressor which has a 30 amp fuse in it. Beats having fuses all over the place and trying to figure out which is which. We purchased a cheap engraver and labelled the box accordingly.

Hope this helps.
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Follow Up By: PJR (NSW) - Thursday, Jul 05, 2012 at 08:52

Thursday, Jul 05, 2012 at 08:52
Sorry forgot one thing.

If you run the cable yourself do not run it under/outside the car. Even inprotective sheeting or tubing. Keep it in the car. It could get torn apart by sticks and branches or even shredded by rocks. Such as those on the Cordillo Road.

I am sure that I do not need to tell you to spread a bit of selastic around where any cable enters or exits the firewall etc.
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Follow Up By: PJR (NSW) - Thursday, Jul 05, 2012 at 08:57

Thursday, Jul 05, 2012 at 08:57
I wish this had an editot.

Try this one. 12 V DC 15 Amp dual outlet.

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Follow Up By: oldtrack123 - Thursday, Jul 05, 2012 at 12:59

Thursday, Jul 05, 2012 at 12:59
Hi Kevin
PJR's above give a good indication of what is required
The Actual Mininum cable sizes will depend on the full run length from tug battery to fridge

Same for inverter if you wish to minimize lost energy .

Peter
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Reply By: Robin Miller - Thursday, Jul 05, 2012 at 09:04

Thursday, Jul 05, 2012 at 09:04
Some good comments above Kevin but I wouldn't unessasarily run 240v - I have seen more than the odd car go down both with shorts , and even shallow water crossings on flooded highways lead to engine stalls and people getting out of the car and this isn't good with 240v.

I like to approach problems from an engineering point of view and this means get data first.

Why not do a test with your fridge with a direct 12v connection and 240v connection and see how it performs - then its probably just a matter of using good cabling as suggested above.

If you do do this measure the (12v) voltage actually at the fridge just to be sure.
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Reply By: Member - Oldbaz. NSW. - Thursday, Jul 05, 2012 at 09:48

Thursday, Jul 05, 2012 at 09:48
G'day Graham, I have run my 25 yr old 3way Finch on 240v via a 1200watt inverter
in the back of the Jackaroo for several years, & it works like a dream. It runs off my
starter battery & is only used when car is running. I have been taken to task on this site for running such a big inverter...very inneficient & so on. I reckon my fridge draws less than 150w..the inverter barely gets warm & the inbuilt cooling fan doesnt
run. I am aware of the safety issues but dont consider this setup to pose any higher risk than 240v in any other domestic situation. I had the inverter checked by a leco
& it has inbuilt safety switches on input & output sides as well as low voltage cutout.
I run it direct off the battery with 6AWG wire, earth & live. Got it off ebay for about
$150...so that makes it rubbish to some..I prefer experience to be my guide. I'm not
recomending this to anyone, but it works for me.cheers....oldbaz.
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Follow Up By: oldtrack123 - Thursday, Jul 05, 2012 at 12:51

Thursday, Jul 05, 2012 at 12:51
Hi Oldbazz

Re :"& it has inbuilt safety switches on input & output sides as well as low voltage cutout.
I run it direct off the battery with 6AWG wire, earth & live. Got it off ebay for about
$150...so that makes it rubbish to some..I prefer experience to be my guide. I'm not
recomending this to anyone, but it works for me.cheers....oldbaz.""

Your experience may not be of much use if you get electrocuted
RUSSAN ROULETTE COME TO MIND

I would be ASTOUNDED if you $350inverter has "A SAFETY SWITCH"[RCD]
AS far as I am aware NONE DO!!.
AND A plug in type safety switch is not functional either

Have a good read of Bantam's post , I totally concur with his post

Peter


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Follow Up By: Member - Oldbaz. NSW. - Thursday, Jul 05, 2012 at 15:43

Thursday, Jul 05, 2012 at 15:43
Hi Peter, I have no wish to debate the dangers of 240v, as you obviously have broad knowledge of the subject, but to describe my use of an inverter as " Russian roulette"
would seem to be enhancing the odds of my imminent electrocution just a wee bit.
Only 6 shots in a revolver, as I recall. I suggest that my chances of killing myself, or anyone else, by my inverter use would be more like 100 million to 1. If you can give
me evidence that more than one person has died in this way in the last 5 years in Australia we can redo the odds.
My point is that nearly every other action I take in a year has much more chance of causing death than my inverter, this being so I have made a risk assessment that I
can live with.
I have no reason to doubt anything you or anyone else has stated re electrical
safety, but I have elected to go this way due to superior fridge performance, due to
thermostat operation giving stable temp control. Use is regrettably only 4/5 weeks
per year. cheers....oldbaz.
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Follow Up By: oldtrack123 - Thursday, Jul 05, 2012 at 17:19

Thursday, Jul 05, 2012 at 17:19
Hi Oldbaz
RE"My point is that nearly every other action I take in a year has much more chance of causing death than my inverter, this being so I have made a risk assessment that I
can live with""

That is your right & perogative & I have no problem with that if that decision only affected you
However others could be affected.
Death & shocks have a very narrow margin where electricity is concerned

All that Bantam, myself & others can do is point out the risks THAT DO EXIST
It is then up to each individual which path they take

You have not given ANY details as to how YOU actually have connected the inverter

IF one insists on taking YOUR path ,it can be done in a reasonably safe way for ALL who may ever be involved.
A cheap 300W max MSW inverter will do the job'


Peter
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Reply By: The Bantam - Thursday, Jul 05, 2012 at 12:18

Thursday, Jul 05, 2012 at 12:18
People continue to be in denial and willfully ignorant over the dangers of portable inverters.

The unavoidable fact is that people have been killed in Australia by portable inverters.

We have become accustomed to the very safe way that our domestic electrics are installed......most people will have no idea how strictly electrical installations are specified and the multiple levels of protection provided in a modern domestic or industrial installation.
We have a level of "plug in confidence" with 240V mains that borders on recklessness, becasue of the regulated safety of the system.

BUT, the majority of those levels of protection are simply not there or can simply not be relied upon to work where a permanent earthing system properly tested and properly bonded bonded to the greater mass of earth exists.

You can not rely on any of the fuses, circuit breakers or safety switches doing a damn thing to save your life where a portable inverter is involved.

There are plenty of people out there that say they have been doing this or that dangerous thing, but have not been hurt......that is down to either luck or statistics, depending on your view.

An live source of 240volts in a moving vehicle can be a very dangerous thing.......should that vehicle be involved in a serious acceident or a rollover that 240V supply could end up anywhere.

As for all those things that need charging.....I do not believe there is a single one that can not be charged directly from 12 volts with no 240V involved.



Now to the fridge.
the problem with 3 way fridges is they cool the internals by applying heat to the works.....not the most efficient process at the best of times......these fridges are designed primarily for gass and will always work better on gas, because gas can deliver more heat than is convienient or practical from electricity...especially from 12 volts.

3 way fridges draw quite large amounts of current from 12 volts, even then the amount of energy available is low compared to gas.....so just to keep up many simply don't bother with a thermostat.

Remember, "ya Cana change the laws of physics, Jim".....to get the same amount of cooling requires the same amount of enregy regardless of the source.

Wired corretly, the fridge should draw the same ammout of 12 Volt current on either 12 or 240V via the inverter...probably more on the inverter

As has been mentioned many 3 way fridges have the same heater wattage on bothe 240v and 12 volts.

It is Oh so common for perple to grossely underestimate the size of the wiring required to deliver adequate power to 3 way fridges...thus they commonly work poorly on 12 volts.

Likewise people frequently underestimate what is required to run an inverter.

many of these fridges have 120 to 150 watt heating elements, bigger ones may be more........that puts things 10 to 15 amp area.

Ciggy lighters where never designed to deliver continuous high currents, a good one will deliver 15 amps, but the contact quality is inherantly poor and to expect 15 amps contunous is unreasonable.
I would not rely on more than 5 to 7.5 amps continuous out of a ciggy lighter..even a good one.
Most of the ciggy lighter plugs are even poorer propositions.

A ciggy plug on any more than a 120 watt inverter is a joke, even on a 120 watt inverter run continuously expect reliability problems.

There are any number of better plugs to use, the most pratcical for 15 amps is the T plug...like a mains plug but with 2 pins arranged in a "T"

I do not like to se a 50 amp anderson that is not wired capable of delivering its full 50 amps continuous.

Now to the wiring.
If you are running the length of the vehicle say 7 meters as the wire flies.....for 15 amps the absilute minimum to run is 6mm automotive ( 4.5mm2) twin.
A better choice would be 6mm2 solar twin.
Don't expect any sort of sucess on less, and that is for exclusive use of the fridge.
AND if you are smart only while the engine is running.

cheers
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Follow Up By: KevintheKK - Saturday, Jul 07, 2012 at 18:50

Saturday, Jul 07, 2012 at 18:50
Dear Bantam and other advisers:
I am extremely grateful for the knowledge and advice that you have all offered.
While comforted by the fact that I'm not the only one who has been powering up fridge and other accessories via an inverter, I am also grateful for the risks that have been highlighted. To be totally honest, I hadn't even considered the concept of being in an (unavoidable) accident, and the rescue teams trying to cut us out of the vehicle not knowing that live 240 is running through the interior along a white string.....! Thank you for shocking me into realising the implications. (I agree with another inverter-user that statistically this is long-odds, but it is still sobering enough to make me re-think the problem...).
Bantam - thank you for your practical advice, and I'm very interested in establishing if the 12volt solution can be made to work efficiently.
(re other accessories being charged while travelling, this was always a bonus and not a need - we carry a generator for 'long-stop' occasional top-up useage, so that is the 're-charge the toys' opportunity).
Bantam - thanks again and I may need to pick your brains as I go down the road of improving the 12v supply.
Thanks again all contibutors.
Graham (and for Liz).
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