Do EHU's always trip when overloaded.

[Parrot Face]

Strange question i know but we were on the aire at Millau last week with temps around -2c at night so we kept the heating on. I accidently turned the kettle on but surprisingly it didn't trip but the fridge started flashing and went off electric as if it was trying to go to battery. Was left wondering if when overloaded it limited the power supplied to van???

 

[Odd-no-more]

It's possible the MCB may have not tripped as it should and an overload could cause a voltage drop which could be detected by the fridge but not by a heating element

 

[autorouter]

Was the heating from electric or gas? What was the wattage of the heating and the kettle? The voltage outside UK is usually 230V not 240V, and frequently is 220V. On campsites with demand from other campers the voltage can drop even further, to 210 or 200V.

That's getting near the point where the fridge control board gives up and decides mains is no longer available. With luck it will then decide to switch to gas, but sometimes the software isn't quite so clever and it just turns off.

The voltage has dropped from 240V to 200V, ie a drop of 40/240 x 100 = 17%. The amps will also drop by 17%.

An MCB doesn't necessarily trip instantly on overload. If there's a short circuit and there's a huge overload, it trips very quickly. For a slight overload there is a thermal trip which can take several minutes. The exact rate is shown by the overload curve, and there are a number of different curves. The usual ones are B and C. A 16A MCB will have B16 or C16 written on it to show which curve it uses. B is used for most domestic circuits, but C is sometimes used if there's a big electric motor on a circuit - a compressor or washing machine for example.

So a tolerant trip curve and a drop in voltage might have given you a few minutes of power before it trips.

 

[Odd-no-more]

What he said

 

[Parrot Face]

Thanks for these replies. I feel better now as it's not likely to be a fridge problem.

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