04/12/2023
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Caravan electrics: avoid tripping out

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Have you ever tripped out your mains electricity supply on site? Most people have at one time or another

There is no doubt that mains hook-up can add much to our caravanning comfort but the campsite's supply can deliver only a fraction of the power we use in our houses. If we use too much – CLICK – off it goes, and we're left to sort out the mess.

Tripping the supply can make you unpopular on a campsite, especially if you have to go and get a member of the campsite's staff to put the supply back on again. Worse still, you may even have tripped the supply to neighbouring pitches.

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Caravan electrics: overload and earth faults

There are two ways in which you might trip the supply. The first, and most common, is through overload. In other words, taking more power than the supply can handle.

The second is through an earth fault, which may be caused by a faulty appliance or cable.

In this article we'll look at both and what you can do to avoid falling victim.

The typical supply to a modern house is rated at 80 or 100A but the best you'll see on a campsite is just 16A. Older campsites, and many continental ones, may have only 10A or even six.

With limited power to play with, we need to think carefully before switching something on. We need to have some idea how much power it will consume. As a rule, items that produce heat use a lot more power than those that don't.

Which electrical items can I use?

As a guide, the amps available on the campsite multiplied by the voltage equals the wattage that can be used. For example, a 10A pitch x 230 (volts) = 2300W. If, for example, you’d switched on the 2kW heater and then attempted to make a cup of tea with a 750W kettle, the bollard will trip.

How do electrical systems work in a caravan?

First thing to note is that in most caravans there are two electrical systems; 240V mains electric and 12V battery system.

Overload trips are controlled by miniature circuit breakers or MCBs for short. These are the modern-day replacement for fuses. Just like a fuse, they will tolerate a small overload for a short period but will trip immediately with a large overload, including what may occur with a short.

Overload trips may take a minute or more to activate depending on how much overload there is. This means that, if you accidentally switch something on, you may have time to switch it off again before power is lost.

Earth fault trips are instantaneous. They have to be, because an earth fault could result in electrocution. In normal operation the current in the live and neutral wires should be identical. All the current that flows down one wire should return via the other, having done its job in powering the kettle, the heater or another appliance.

When an earth fault occurs, some of that current leaks away to earth and creates an imbalance. It's that imbalance sensed by something called a residual current device (RCD), which then trips the supply.

The amount of imbalance needed for a trip is small, just 30 thousandths of an amp (or ampere, to quote the full name). This is designed to prevent death through electrocution as might otherwise happen if you touched something that had become live.

Caravan electric hook-ups

All caravans with a mains installation have to have an RCD by law. The campsite supply also must have such a device but it may be shared by more than one hook-up point so, if you trip it, your neighbours could be affected, too. It is good practice to operate the test button on your RCD each time you hook up.

One of the most common causes of earth faults on a caravan is electric kettles. If your supply RCD trips the instant you switch the kettle on, the chances are the kettle is faulty and should be replaced.

If you can't positively identify and isolate the cause of an earth fault, do not continue to try to use the caravan's hook-up. The most important piece of advice here is to get your caravan electrics looked at by a qualified electrician.

Top tips:

  • If you have a TV, make sure it will run off 12V and power it that way. Then, if the mains trips during your favourite soap, you can carry on watching courtesy of the leisure battery.
  • If your supply is just 6A, never switch on more than one item at once; if 10A, two items and, if 16A, three items. It won't prevent all trips but it will help.

How to monitor electrics in a caravan

Load monitoring devices: It is possible to buy load-monitoring devices that measure the current at the supply point and relay the information by wireless to a small display panel. Primarily designed for home use to tell you the cost of electricity being drawn, you can also set them to show you the loading in kilowatts (kW).

Once fitted, you can easily see how much power your caravan is using and adjust it to stay within your limit. The only thing to bear in mind is that there may be a short delay in the information being displayed. This is because, to save battery life, transmissions are not continuous but made every few seconds.

The Owl monitor we tried transmitted every six seconds but could be set to transmit every 60 seconds. It also had an auto power save mode that ensured it transmitted every six seconds only if the power changed, otherwise it transmitted every 60 seconds.

Load controlling devices: The Alde load monitor is a good device to help master your caravan electrics (if you have Alde heating). This consists of a sensing coil threaded through the live wire feeding the caravan. Installation should be by a qualified electrician. It senses the current and sends the reading down a wire to the digital control panel where you can see it.

You can then select the current rating of your supply in the range of five to 17A. If the set level is exceeded, the boiler is powered down in stages to prevent tripping of the supply. Of course, it's still perfectly possible to overload and trip the supply but the Alde boiler will not be to blame.


What uses the most electricity in a caravan?

When you are used to having a stable and constant supply of electricity at home, it may come as a shock to learn which appliances are the most power hungry. A hair dryer rated at 1600W will consume 70 times the power of an 18.5in LED TV rated at 23W. Microwave ovens can use more power than you might think, too. The reason is their rated power is an indication of what goes into the food rather than what is taken from the mains, which can be nearly twice as much.

With all these things to bear in mind, it can be difficult to know just how much current you may be drawing at any one time. A rough guide: 1000W equates to just over four amps at 230V.

The following table shows the typical power used by some common items:

Appliance Watts Amps Appliance Watts Amps
Truma space heater (high/low) 2000/1000 8.7/4.3 Truma Ultrastore water heater (850w) 860 3.6
Truma Combi heater (high/low) 1800/900 7.8/3.9 Whale Rapid Heat water heater 1500/750 6.5/3.3
Alde boiler (2kw & 3kw?) 3150/2100 13.7/9.1 Whale heater 2000/1000 8.7/4.2
Thetford cooker hotplate 800 3.5 Small microwave 900 3.9
Domestic fan heater high/low 2000/1000 8.7/4.2 Sandwich toaster 750 3.1
Domestic kettle 2400 10.5 Hair dryer 1600 7.0
Travel kettle 750 3.3 Curling tongs 50 0.2
Fridge 120 0.5 Fridge/freezer 220 1.0
Small two-slice toaster 1000 4.3 Avtex 18.5in LCD TV 23 0.1
Power supply unit 700 max 3.0 max Laptop computer 50 0.2


Troubleshooting electrics in a caravan

When there is a problem with your 12V electrics, check these basics first:

#1 Inspect battery connections:

  • Examine cables for cleanliness and tight connectors.
  • Ensure cables don't disconnect with a gentle tug.
  • Look out for corrosion around battery terminals.

#2 Check voltage:

  • Use a multi meter to measure leisure battery voltage.
  • A reading above 12.6 when fully charged is ideal.
  • Voltage below 12.6 indicates the need for charging.
  • If charging is ineffective, consider replacing a battery over five years old.

#3 Identify power-draining appliances:

  • Confirm battery capability to hold a charge.
  • Check for unintended power consumption by appliances.
  • Use the caravan switch to cut power to appliances via the fusebox.

#4 Inspect the fusebox:

  • Connect the battery to a multi meter.
  • Document your fusebox configuration.
  • Remove and reinsert fuses one by one to find the problematic circuit.
  • Sandpaper old fuses if needed; replace if they're faulty.


Final thoughts

Getting to know your way around the caravan electrical system is one of the first things you should do. Once you know how to test for faults and do a little investigation on your own, it will be easier to identify whether you can make fixes yourself, or whether the caravan needs a professional to fix it.

Being mindful of the appliances you are using is another good tip when it comes to not overloading the electrical system.


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