Thetford fridge

Submitted: Friday, Aug 24, 2012 at 15:46
ThreadID: 97624 Views:12331 Replies:8 FollowUps:6
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We've just returned from a 4-month trip and agree with Ferryman's comments in May 2012 regarding the new 184L USA-made Thetford fridge. It's far better than our previous caravan fridges, both in internal space layout and (particularly) performance consistency. No more half-frozen lettuces!!

Despite having a 100ah gel battery operating 12v in the van, however, we experienced numerous incidents of rapid battery depletion which seriously compromised free-camping opportunities during our trip. When we contacted the caravan manufacturer en route for assistance, both we and the auto electricians we engaged were treated with abuse.

An autoelectrician has today pinpointed the fridge as the culprit. It is drawing a disproportionate amount of power from the battery.

The caravan is still under warranty and the fridge was supplied as an optional upgrade by the manufacturer.

Has anyone experienced this problem with a new model 184L Thetford? If so, is there a solution?
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Reply By: olcoolone - Friday, Aug 24, 2012 at 16:08

Friday, Aug 24, 2012 at 16:08
I take it your Thetford fridge is a 3 way (gas, 12v and 240v).

Any 3 way fridge draws big amps on 12v and will flatten your 100 amp battery in about 5 hours..... that's if your battery is fully charged.

3 way fridges are designed to be run on gas whilst stationary and away from 240v.... the 12v is only there for when travelling and the tow vehicle is running.

A gas fridge running on LPG will last about 15 days on a 9Kg bottle.

3 way fridges don't work very well in temperatures above 28-30 Deg C and they hate tropical climates.

All these things are a know fact in the caravan/RV world.

A 12/240v compressor fridge is the only real way to go.

You tow vehicle if wired correctly should only charge your van battery whilst running and the 3 way fridge should not draw of your van battery.... only the vehicles charging system.
AnswerID: 493525

Follow Up By: racinrob - Friday, Aug 24, 2012 at 16:29

Friday, Aug 24, 2012 at 16:29
olcoolone, I agree with all your comments.
Naughty I know and I don't encourage others to do it but I always put my Dometic 3 way on LPG at the start of a trip and leave it there.

rr
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FollowupID: 769123

Follow Up By: Footloose12 - Friday, Aug 24, 2012 at 17:33

Friday, Aug 24, 2012 at 17:33
Many thanks for your prompt comments.

I should have said (and didn't - sorry) that the depletion is occurring whilst we are travelling.

The fridge is drawing more power than the car is capable of replenishing to the caravan battery. We've had the car wiring checked and there's no fault there.

Whilst stationery, we run the fridge on gas, and it has still performed well, even in the North (Top End and Kimberley). The only down-side on gas is that when it's hot it heats up the fridge cavity and we need to run the fridge exhaust fan on 12v.

Your last comment is of great interest, however, if we're reading you correctly. Are you saying that the fridge should be running directly off the car whilst travelling, rather than through the caravan battery? If so, do you know if this is industry practice?

Regards,
Footloose
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FollowupID: 769127

Follow Up By: olcoolone - Saturday, Aug 25, 2012 at 15:07

Saturday, Aug 25, 2012 at 15:07
"Your last comment is of great interest, however, if we're reading you correctly. Are you saying that the fridge should be running directly off the car whilst travelling, rather than through the caravan battery? If so, do you know if this is industry practice?"

Depending on brand of caravan and who wired it up..... most times it is driven by price and seeing most caravan owners think they know everything (not directed at you) most think spending $700 is a rip off when they can get it done for $350.... little do they know they are not getting what they think they are.

We see this very often... we work on the theory do it once and do it right, I would sooner have a customer walk out of our workshop and get it done elsewhere then do below acceptable work.

You car charging system should have ample power to run the fridge on 12v and charge the caravan battery at the same time...... what sort of tow vehicle do you have and was the electrical work done by a competent auto elec or some work experience guy at the local caravan place.
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FollowupID: 769174

Follow Up By: Nomadic Navara - Saturday, Aug 25, 2012 at 18:55

Saturday, Aug 25, 2012 at 18:55
Quote from FollowUp2 - "The fridge is drawing more power than the car is capable of replenishing to the caravan battery. We've had the car wiring checked and there's no fault there."

During daylight hours the alternator should have enough output for the fridge and a lot left over for the battery. I would suggest the problem is with your wiring and not the alternator.

I suggest you run a separate very heavy cable for the battery through an Anderson plug.
PeterD
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FollowupID: 769194

Reply By: Mottleman - Friday, Aug 24, 2012 at 16:32

Friday, Aug 24, 2012 at 16:32
Thetford's website suggests 4.3kw/24hrs which is very close to 15amps on 12v... which will mean not much running on battery...

cheers
JohnN
AnswerID: 493526

Reply By: time waster - Friday, Aug 24, 2012 at 19:01

Friday, Aug 24, 2012 at 19:01
I would fit a DC-DC charger to charge the van battery, we find it excellent now having a 100% charged caravan battery and second battery in the car.

Christian
AnswerID: 493531

Reply By: Cravenhaven - Friday, Aug 24, 2012 at 19:14

Friday, Aug 24, 2012 at 19:14
Perhaps a bit more information might help others assist you.

You say the autoelectrician pinpointed that the fridge is drawing a disproportionate amount of power from the battery, can you qualify exactly how much current (power) it draws?.
Secondly, what sort of vehicle do you drive, and can the autoelectrician give any indication on just how much current the car provides to the caravan when the fridge is running.
What sort of connectors and what size cables are you using in both the car and caravan for the 12v supply and return. Do you have a switch or VDR on the main car battery to isolate the caravan when the engine is shut off.

If the vehicle alternator is capable of providing the required power, then it might just be a case of running heavier wires between the car battery and the fridge, or alternatively running a separate circuit from the car battery to the fridge (via appropriate connectors) and disconnecting the fridge from the caravan battery.
Another possibility is to fit a larger alternator to the car.
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AnswerID: 493533

Reply By: Ross M - Friday, Aug 24, 2012 at 19:36

Friday, Aug 24, 2012 at 19:36
If the car is charging correctly, the wiring to AND from the trailer and to fridge/battery is big enough to minimize VD then the battery cannot go flat.
AnswerID: 493535

Reply By: Member - Andrew W14 - Friday, Aug 24, 2012 at 20:18

Friday, Aug 24, 2012 at 20:18
There's probably a couple of simple answers to your problem.

First - the fridge should NEVER be wired to the van batteries. As you have found the current draw will stuff them up quickly. 3 way fridges should only be wired vis Anderson plug directly to the tow vehicles alternator/battery. You will of course need some sort of battery isolator for when the tow vehicle alternator is not putting out charge.

Secondly - The wiring (both from the battery to the Anderson plug and from the van Anderson to the fridge should be a minimum of 8 B&S, preferrably 6B&S. Yours will more than likely be dramatically less than that.
AnswerID: 493539

Reply By: Member - iijmartin - Friday, Aug 24, 2012 at 22:03

Friday, Aug 24, 2012 at 22:03
I learnt a lesson very early with new van/tow vehicle setup. Drove 5 hrs to find battery monitor in van squarking showing 184L Dometic 3 way fridge had used 120 amp of the two x 120AH van batteries. Surprise exactly what the fridge specs say 24 A/hr. Problem was blown fuse near car battery (which was actually only 20A fuse) so car not running any power to fridge .Fuse replaced with 30A and then auto electrician changed to auto reset fuse on return home.
Knowing a few more things since with my dual battery set up in tow vehicle plus 2 x 120 aH van batteries I would definitely go for DC-DC charger in the future
I also don't think you can assume that all van manufacturers and auto electricians use the correct sized wire
Cheers
AnswerID: 493544

Follow Up By: Cravenhaven - Saturday, Aug 25, 2012 at 08:37

Saturday, Aug 25, 2012 at 08:37
"I also don't think you can assume that all van manufacturers and auto electricians use the correct sized wire"

My BIL was showing off his new caravan last weekend and pointed out the 4mm wire that the manufacturer had installed from the Anderson plug through to the battery and 3-way fridge. He has already rewired it with 10mm wire and also separated the fridge from the van battery and run it straight to another Anderson plug. He also ran 2 lots of 16mm wire from the car isolator solenoid to the rear anderson plugs.
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FollowupID: 769148

Reply By: Member - wicket - Saturday, Aug 25, 2012 at 12:24

Saturday, Aug 25, 2012 at 12:24
If you rummage through the thetford site look for the installation instructions for the fridge you will find that it says the fridge power input should be at least 14.5v , (yes this is correct !) I bet your connection when tested won't be this high.
AnswerID: 493583

Follow Up By: olcoolone - Sunday, Aug 26, 2012 at 10:42

Sunday, Aug 26, 2012 at 10:42
14.5v is the nominal voltage they base their specs on but it will run over a broad range..... all it is is a heating element, less voltage more amps.

Not many vehicles dish out 14.5v constant....
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FollowupID: 769223

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