running the fridge when towing

[graham_cliffe]

I have an avondale dart and I'm not sure how I configure the electrics so the fridge operates when I'm towing. I set the fridge control to battery, but I switch the 240v and 12v main controls to off. I have both the sockets connected to the car, however the fridge doesn't stay cool, if I turn the 12 volts on at the main control will this run the fridge on the car battery or the leisure battery.

I have trawled through all the books etc but can't find the answer.

 

[Steve_374341117]

I'm no expert but I believe you switch on the 12v and this runs off the car battery whilst engine is running - when ignition is switched off the fridge is no longer powered, thus preventing a drain on the car battery. Once on site you switch over to mains electric. That's what I do anyway.

 

[graham_cliffe]

I'm no expert but I believe you switch on the 12v and this runs off the car battery whilst engine is running - when ignition is switched off the fridge is no longer powered, thus preventing a drain on the car battery. Once on site you switch over to mains electric. That's what I do anyway.

Thanks I'll give it a try

 

[RickStevens]

Was the fridge cold before you switched it to 12V?

Running it on 12V will only keep it at a stable temperature, it wont cool it.

Rick

 

[sarahandher6dachshunds.]

i have a 2003 dart 556 the set up for the fridge is gas off, green switch off red switch on,pressed down.then couple to car,make sure that the switches on the front of lounge seat is off,where the rcd is,front left switch as looking at it should be pressed hitch end in.its the master switch not the rcd.the fridge light on red will light up when engine is on car,there may be a slight delay for light to come on,try revving car slightly and idle.the delay is so one does not flatten car battery and there are relays in the wiring electrics.engine of no red light.the fridge is on the car battery only not the vans battery only runs when car is running.there is no need to set temp control as fridge runs constant,prior cooling of fridge helps,use a adapter for home to connect orange hook up lead to 3 pin,buy from dealer,cool fridge on mains the green switch and set temp do this a day before holidays.on site turn red switch off and use gas or hook up.hope this helps sarah

 

[JeffandDi]

Well this answers a question I also had in a round about way.

I have only recently installed the electrics to power the fridge from the car and I know for certain it works but when we arrived on site for the first time out the fridge had not got cold. I though we were doing something wrong as well.

Am I right in saying you are suggesting the 12V supply is never going to chill it down from "room temperature" be that either via the leisure battery or the car? We store our van in a compound so cant really chill it via the gas or mains before we go away. I guess the answer is to use freezer packs and then it should keep the temperature cool on the journey...

 

[Mikey_74]

Yes Jeff and Di, your fridge shouldn't be connected to the leisure battery, it should be connected directly to the white/grey 12s plug (or newer 13pin) The element used whilst running the fridge on 12v hasn't got the power to chill the fridge, but if the fridge has already been chilled via either 240v or gas then the 12v system will maintain the temperature, what we do is, as we're loading up in the storage compound we light the gas and leave it on full for just over an hour (long enough to do the checks I do before, during and after hitch up, nose weight and general loading, bla bla) by then the fridge is quite cold and then we flick over to 12v and we're on our way

 

[graham_cliffe]

We had been away for a week, and the fridge had been on mains, so was completely cold, but by the time I got home it had warmed up to the ambient temp, so was not cold at all !

 

[graham_cliffe]

Thanks sarah

The problem is that there is no light on our fridge just 2 controls 1 for temp and 1 which is 4 position, off battery mains or gas. on my main electrical panel there are about 6 switches 1 main 240 breaker, 4 rcds for the 240 volt system 1 for the fridge 1 for the sockets 1 for the heater and 1 for the water, then 2 others 1 for 12 volts on and off and the final 1 is for the water pump

I think I have to leave the 12 volt switch in the on position, I assume from the other answers that while connected to the car this should run from the car's electrics rather than the leisure battery.

 

[ProfJohnL]

Its not quite accurate to say running fridge on 12V won't cool it down, as far as the fridge is concerned it does not know what fuel is being used, so it will perform on any of the three sources available. All the fuels do is to produce heat at the correct point of the refrigerant system. There may be a slight difference between the power sources, but provided the sources can heat to the working temperature, it will drive the refrigerant system correctly.

What is significantly different is when the different fuels will be used, the mains can only be provided when the caravan is stationary and connected with an EHU, The regulations stipulate that gas must no be used when on the move, leaving the 12V being the only source available when towing.

When stationary and using gas or mains power there is no forced ventilation through the burner and element assemblies, so the power is used to its maximum effect. Also the fridge will remain in a level attitude that is necessary for the refrigerant system to operate successfully.

By comparison when towing, there may be additional air flows through the heating assembly which may dilute the heating effect of the 12V element and there will be unnatural windage through the normal cooling vents which may disturb the normal convection current needed for the condenser phase to work properly. And when the caravan is in motion the refrigerant in side the system may be being swished around so it doesn't lie in the correct places to allow it vaporise and condense effectively.

I have used 12V to cool down an Eletrolux (Dometic) fridge on a number of occasions when for safety reasons it was unsafe to use full mains power directly to the appliance, and it works perfectly well.

 

[Glenn_5132962]

My fridge cools perfectly well on 12v. If I drive for more than an hour or so from the storage compound I have frost forming on the fins in the freezer compartment. (Pageant S7).

 

[JeffandDi]

Interesting stuff. Thanks for all the reply's. The van is a new 2010 Stirling so I would expect the fridge to be as economical with whatever power it manages to get. We shall see next trip out. I might even measure the temp before and after just to see!

 

[RobinF]

Hi Graham, I have a Avondale Dart 556/6 2004 and have the same fridge as yourself. I have at long last worked out how to use mine on 12v when towing! after various faults with my cars wiring. You DO have to have the 12v switch at the main consumer unit ON the relays inside the caravan switch the 12v to the fridge when your car is running, I have proved this by testing the voltage at the fridge with a multimeter and we just came back from a week away (fridge on mains)on a 3 hour tow and the ice cubes I had left in the freezer box to test the fridge were at long last still frozen when we got home. I store my van at home so I always pre chill the fridge before we go.

 

[graham_cliffe]

Thanks Robin, I knew it must have been something along those lines, I'll have a play over the weekend

 

[DerekBrad]

That seems to be a fairly definitive answer, and thanks Robin.This thread seems to pose the question of 'why can't manufacturers make sure that the owner's manuals cover these questions in an unambiguous way'? I consider myself as being able to follow instructions fairly well, but always felt that this fridge topic was very hit and miss.

 

[TonyH1]

The size of the wiring will have an effect on the efficiency of the 12v system. The fridge draws quite a lot of power and it's quite a length to the fridge so if the the wirings too thin you will suffer voltage drop. (Well you will any way but you can reduce it by using a heavier wire.)

It's usually the wiring to the socket that needs uprating. Some people extend the feed for the fridge right back to the battery but remember to use a fused relay to avoid draining the car battery.

 

[sarahandher6dachshunds.]

Thanks sarah

The problem is that there is no light on our fridge just 2 controls 1 for temp and 1 which is 4 position, off battery mains or gas. on my main electrical panel there are about 6 switches 1 main 240 breaker, 4 rcds for the 240 volt system 1 for the fridge 1 for the sockets 1 for the heater and 1 for the water, then 2 others 1 for 12 volts on and off and the final 1 is for the water pump

I think I have to leave the 12 volt switch in the on position, I assume from the other answers that while connected to the car this should run from the car's electrics rather than the leisure battery.

thanks for reply but the chances of us both having same year model was slim any how worth a go. sarah

 

[CheapnCheerful]

I can only echo what is said above - Fridges are very sensitive to voltage drop. On the instructions on my fridge, it has warnings about the fridge freeezing everything in it if it is used on 12V for more thn a couple of hours, on the grounds that the 12V element has as much power as the 240V element, but no thermostat to control it.

In practice I suspect the reason many fridges have less power is due to voltage drop - the power is proportional to the square of the current, which is proportional to the voltage - ie a fridge running at 11V will have a 16% drop in power despite the voltage only going down 8%, and at 10V it will have approximately 32% less power with 16% voltage drop.

Initially my fridge did not appear to work at all on 12V. I checked and there was only 10V accross the element. At this voltage I think there was insufficient heat to cause the refridgerent to circulate, and thus no cooling effect at all. I cleaned up the inline fuse for it which was getting warm due to a bad contact, and also doubled up the wiring on the 12S socket using the spare pins to provide a parrallel path. This gained me 1/2 a volt! But it was enough to mean the fridge now worked, albeit only good enough to keep things cool rather than cool things down. I am sure that if I could get the full 12V to it it would end up being just as good on 12V as it is on 240V. I intend doing a re-wire on the van with thicker cable and a shorter route with less connections - I get just over 13V from the 12S socket under load, so if I only loose 1V in the caravan, it should work quite well!

 

[ProfJohnL]

Hi, Cheap n cheerful

Thanks for putting in the figures with which I concur completely. This conclusively dispels the often stated myth that caravan fridges won't work on 12V.

I do wonder why the manufactured don't put thermostats on 12V element, its a resistive load so capacitive or inductive arcing of contacts should not be a problem, and there are plenty of manufactures offering 13A rated bimetallic or other forms of thermal switches which can be manufactured to operate at any normal fridge temperature.

 

[TD42]

This link may help regarding towbar wiring for fridges & other tow hitch wiring problems The main prob as mentioned is undersized cableing for the Fridge/ battery charging circuits

http://www.towitall.co.uk/faq/faq1.htm
Tony D

 

[graham_cliffe]

another quick question (Robin F may be able to answer this) if I have the mains connected do I need the 12v switch on for the battery to charge?

thanks

 

[RobinF]

Good question, I dont know the answer to that one but I have my van connected to mains on my drive, I have the 12v switch off and the mains rcd on and the rcd for the battery charger on. I have not had a flat battery YET! so i assume it is charging. Sorry I cant answer it correctly for you. Robin.

 

[Mike_S]

For my previous caravan (a 20002 Swift)the 12v "main switch" had to be on for the battery to charge when hooked up to the mains. On my present caravan (a 2009 Bailey Senator) the 12v main switch can be on or off - the battery charges when hooked up to mains and switched on. Using a multimeter (set on DC volts) will give the correct answer to this one. Check the voltage at the caravan battery terminals. If the battery is being charged the voltage will be above 13.5v - if not be charged it will be lower.

Mike