Fridge working on 12 V whilst towing

[Rubix]

Went on our first proper trip away last week. Spent 2 1/2 hours driving there (no stops) and I know that the fridge was chilled sufficiently on mains before we left (5 deg C approx)

By the time we got there it had risen slightly to around 8 deg C.

When on site we has mains hook-up and I noticed that the voltage varied from 225 to 240 throughout the week. At home the temp (when empty) was fine, but when on site it got up to almost 10/11 deg C at times (lower at night).

It was around 8 deg C when we left to come back home, 3 1/2 hours drive with 1/2 hour stop and it was up to 12 deg C when back home.

First question is

1. As I suspect the 12 Volt operation is up the duff is there a way I can check this while at home (where we store it) by measuring current whilst connected to the car ?

2. Is the 240 V operation that susceptable to low voltage dips, that it can rise in temp.

3. We tried not to pack it solidly, and I read that not much should be put in front of the cooling fins inside, is this right ?

Thanks for your help.

 

[MikeP]

1. You can connect an ammeter in-line and see what current it is drawing. We have a simpler method as we have a simple caravan. With the engine running above tickover if we switch the fridge on the interior 21W bulb dims a bit, which tells us that the fridge is drawing.

2. Don't know.

3. You need to let some air circulate, but on the other hand "a full fridge (or freezer) is an efficient fridge". It's always useful to pack some frozen cartons of fruit juice ... that will keep the temp down on a ferry for a couple of hours with no power at all.

To be honest, I'd expect some temperature climb on a warmish day. If the 240V and 12V elements are not one and the same, then it will take a little while for the 12V element to heat up and produce a cooling effect. Another test is to start the fridge from ambient on (say) a 2 hour journey, and see if there is frozen condensation on the evaporator in the ice box by the end of the journey.

 

[rob_jax]

Hi,

The heating elements (that move the cooling fluid around the fridge) for 12 V and mains operation are equally rated in most caravan fridges

For example, our Dometic has a 110 watt 12 V heater and a 110 watt mains heater - so I'd expect performance on both to be similar - and indeed they are (with our van).

But the real difference with a number of vans is that when towing at anything above walking place, airflow past and into the fridge vents can seriously disrupt the cooling.

You may want to experiment with using winter covers when towing, and making sure that the back of the fridge is truly sealed from the inside of the caravan (no draughts). One common error is to allow too much open space behind the fridge - the fridge needs a "chimney" type space to make the air move and not a big empty room

But you would have expected the caravan designer to have done this for you.

Robert

 

[Rubix]

Thanks for your comments.

Mike, your first point wouldn't work on my van as the interior 12v appliances (lights) don't work when connected to the car as the relay disconnects them.

One thing I did just think of. I assumed the rise in temp was due to the dip in mains voltage, but the awning did get quite warm in the day, and so I guess this would have affected the temp in the fridge as it would be taking in warm air as oppsed to "fresh air".

Robert, I will try your idea about winter covers.

If I was to measure a current being drawn when the fridge is turned on (and the car connected) can I assume it is working, or would a 12 V element draw current if faulty too ?

Thanks again.

 

[rob_jax]

Rubix,

Cooling performance on the road really does depend on the airflow past the vents - so you will need to experiment

The mains and 12 volt heaters are just simple cartridge heaters - they either work or they don't - so a DVM re-configured to measure high currents will give a good indication.

Expect at least 10 Amps to be flowing - so care with any connections

Also if you have the "push and hope" 12S car to caravan connector - make sure this is in top condition - clean, no corrosion, and that the pins are making good contact into the sockets.

Check for any signs of melting or over-heating around the central pin (pin 7) - this is the fridge return and is also used to align the plug and socket (really dumb idea) - and is prone to getting knocked.

Robert

 

[Ken_374312330]

I've connected a small red led across the 12v leads on the back of the fridge and mounted it on the panel above the fridge. The led comes after the fridge switch, so it won't light unless the fridge 12v switch is on!

When the car is hooked up and ready to go, just look in through the window to check that the led is lit. Later I realised that inside the front window would have been a better place for the led, then I could see it from the car.

I have also mounted an old 12v computer cooling fan on the inside of the top fridge vent (blowing outwards). On hot days, this makes a considerable difference to the fridge temperature. I have only used it on site, but it might make a difference while on the move.

Ken

 

[WatsonJohnG]

Ken I did the same thing when our fridge was minus the warning lights and also installed a 230V neon for mains warning

It wasn't the most user friendly idea when they left off the warning lights and the best system was when you had a red and green illuminated switch for 12V and mains

The winter covers have been mentioned but I wonder if they were removed at all

I have seen lots of people on rallies who weren't made aware on handover that you needed to take them off above 8degC

 

[Rubix]

Rob_jax,

previously said by you :

"Cooling performance on the road really does depend on the airflow past the vents - so you will need to experiment"

I was looking in John Wickershams Caravan books, and he talks about using winter covers, but I thought these were to be used when the outside temperature was low (I think below 8 deg C was mentioned) part of my original problem was warm temps inside the awning on site (but on 240V) but also when driving.

Would the increased airflow whilst driving make the fridge "thnik" it was cooler, and hence your suggestion for using covers ?

Thanks again.

 

[rob_jax]

Hi Rubix,

When stationary, you should only need the winter covers when the outside air temperature is below, say 5

 

[Ewan_5130997]

I like the idea of fitting neon indicators for the fridge in my Bailey Ranger 550/6. I have no idea, however, how to go about it. Is it relatively easy?

 

[WatsonJohnG]

Hi ewan it is easy if you know what you are doing and can get access to the top of the fridge

Looking at the plan of the 550/6 in the Bailey catalogue it appears that the fridge is under the cooker rings.

This means either removing the rings and unscrewing the gas pipe or pulling the fridge out to get at the top where the terminals are clearly marked.

If it had been under the sink things would have beeen a lot easier.

You use a neon on 230V connected to the live and neutral after the fridge selector switch and an LED warning light on the 12V after the selector switch in the 12V +ve and -ve leads

If you aren't sure its best to get an electrician to do the job for you

 

[Ewan_5130997]

Thanks.

In the 550/6, however, the fridge is on the opposite side of the van from the cooker and sink. It sits under a work surface where we sit the tv. I presume it will be easy enough to remove. Are the back of the selector switches usually easily accessible?

There is a panel above this work top that has two mains sockets, a 12v socket and the TV point on it. It clips out easily so I might look at fitting the led and neon on the panel.

 

[WatsonJohnG]

Hi Ewan

It wasn't apparent from the catalogue where the fridge was and under the cooker rings seemed the spot

If you look down on the top of the fridge all the wiring connections should be easily visible

I can't find a pic on the Thetford website

 

[Ewan_5130997]

Thanks again. I'll have a look first chance I get.

Ewan