Twin Electrics

[trucker]

Hi, I have recently had twin electrics fitted to my car to run the fridge whilst travelling.

The caravan switch inside the van has got 3 settings car,van and central. The hand book says that the switch should be in the central position whilst towing.

How do I know if the fridge works as the light does not come on. Ive tried this in each position wih the engine running and with the car off

Im confused. Please help a thick twin socket virgin

Kevin H

 

[mcghee]

The first thing I'd try Kevin is watching the switch in the 'van to see if it lights while someone sits in your car holding the RPM at about 2000. Some fridges will not operate while the car is idling, the voltage isn't high enough. I'm not saying this is what's happening, but it's a start.

 

[trucker]

The first thing I'd try Kevin is watching the switch in the 'van to see if it lights while someone sits in your car holding the RPM at about 2000. Some fridges will not operate while the car is idling, the voltage isn't high enough. I'm not saying this is what's happening, but it's a start.

Thanks Craig Ill try that

Kevin H

 

[Guest]

Craig,

Just remember that the 12volt operation of the fridge is pretty poor. It won't really do much more than reduce the the thawing rate and will certainly not cool the fridge from scratch. The best way is to run the fridge on electric or gas before setting off to get it nice and cold, fill it with chilled foods and it should last pretty well for most journeys. In the hot??? summer it will be even worse, but that is normal so don't be too unhappy., Most people buy food fresh on holiday, and tell the 'boss' that beer should take priority on hot days.

 

[ProfJohnL]

Hello Scotch Lad

I wonder where you get the impression that 12V is less effective than mains, or gas? As I understand it, the absorption principal as used in most caravan fridges, relies on producing heat around a critical area of the refrigerant cooling tube, and provided it is at the right temperature then the fridge will work equally well.

Reading the technical plate of a number of fridges I have seen, the 12V load is typically at typically 8A. Now when the engine is running the alternator is giving out close to 14.5V and allowing for voltage drops the fridge is likely to see a realistic 13V so using W = VA we get a practical wattage of 13V x 8A = 104W

the Mains rating has been 120W, so the 12v system is likely to be only 5/6ths as powerful as the mains, BUT, the thermostat will switch the power as the fridge demands, so in practice there should be no effective difference between 12V and Mains operation.

The gas system uses the smallest practical stable flame, and that is typically about 250W, but there are losses up the flue so the effective power will be about 150W maximum.

I do concur that it is sensible to cool the fridge down on mains the day/night before you travel, as it is impractical to leave you car running to do that job, but in practice once it is at a stable operating temperature either 12 or 230 volts will be just as effective, Gas does tend to keep the fridge cooler simply because the flame is never turned off by the thermostat.

 

[Guest]

I read the manual that came with the fridge. It states that 12 volt operation can only be used once the fridge has been chilled by using gas or mains, therefore the implication is that it is less effective. Also the 12v system does not have any thermostat, it is either on or off as the engine hits the effective revs. There are also many issues of voltage drop between car and van especially in getting enough power to run the fridge effectively and I feel the errors are sufficiently large to make the points I made valid, although they were also meant to be lighthearted. In many installations the power cable from the battery (at the front of the car) to the tow hitch is only just able to carry the load, and any earth leakages along the way will reduce the power to the fridge. Now I have happily travelled for several hours with no adverse effects on the fridge contents, although i have always noticed that ice in the freezer compartment is usually slightly melted. That is using vans and motorhomes with either Electrolux (Dometic) or now Thetford. All I wished to point out was that Kevin should recognise that his caravan fridge is not going to work as well as his domestic one, and care needs to be taken. Even on mains and/or gas the fridge can sometimes 'struggle' in hot weather.

 

[trucker]

Hi guys, thanks for your replys. I have just arrived home fronm the weekend away and I think that the fridge did work on 12v however I dont think that the fridge light works on 12v. Anyway fridge chilled before journey, and 2 hours later stil very chilled (dont know if it would have warmed up in that short time)

Kevin H