Maximum sustained current perrmitted from 13 amp plug ?

The tester alternates and displays all the test results in sequence.


One thought is that the Coronavirus lockdown may affect the current drawn, if this is a hotel or similar premises and is currently closed the voltage will be higher than under normal circumstances.


Andy B

My guess would be that current rating, rather like voltages, are nominal rather than precise actual. A certain margin is expected.


As you say, the voltage may be increased by 10% or more over 230V - and would still be considered 230V nominal.


Similarly there are margins built into overcurrent protective devices - e.g. an MCB shouldn't trip when carrying current 13% above its rating (at least not for conventional time - usually an hour), Likewise cables would be expected to carry those sorts of currents above their ratings for such periods without significant damage (otherwise our whole approach to overload protection - I_n ≤ I_z falls apart). So it would be logical for the same to apply to accessories such as plugs and sockets (unless their product standards say otherwise).


So I'd suggest that in general up to a 10% or even 13% excess actual current, due to voltage variation, provided it wasn't expected to persist for more than say an hour, should be considered acceptable.

    -  Andy.

I don't think that the test which was carried out is in any way a PAT fail. It is ridiculous to worry that a kettle takes slightly more than 13A at something above nominal voltage, and if the volts were low at 208V a 3kW appliance could quite reasonably take about 14.5A. A 13A plug will carry about 20A for short periods, and this does not cause serious overheating, because of the usual reason forgotten by electricians of thermal inertia and thermal capacity. These items will have passed the manufacturers test, be CE marked etc, and if you want to complain it would be very difficult as you would be claiming the CE mark was invalid, probably from a British manufacturer (wherever it was made) for a British brand. I suggest your PAT contractor is an Id**t and requires re-education and should not be employed again. As the PAT tester does not know what kind of appliance is connected, how does it set the maximum current anyway? It is normally a user setting, so perhaps it is incorrectly set at 13A -+ no tolerance at all as it is accurate to 0.000001%? The whole basis of this current test is nonsense.


For the other comments BG, you are making the same mistake yourself. A heater which takes slightly over 13A (say 14A) is in no way dangerous to plug or anything else. The whole 13A fuse system uses a 13A fuse to prevent overload, The fuse blows at about 17A after about an hour, and this is the safety valve for everything. If I wanted to make it fuse quickly at about 14A, I would have to use a fuse with a continuous rating of about 9A, which you will notice we do not. Why is it that almost no one here seems to understand temperatures, overload currents, fuse characteristics, and thermal capacities here, they are an important fundamental piece of electrical engineering!


Items with a negative input impedance (switch mode power supplies) take more current at lower voltages, but again are adequately protected by fuses of 13A for appliances. This may be plug in induction hobs, chargers, vfd motors etc. Forget the working current, 3 kW maximum is the expected power, a much better indicator of proper operation than the current. Remember the test instrument accuracy (probably no better than 3%) and probably more like 5 or 10% for indicated power, and remember the power factor may not be 1.

Mapj1,

ref " N-E reversal at the plug, a mistake that RCDs have almost eliminated."

Could you elaborate on that please? I`m findinding difficulty grasping the reason.

Thanks

In the days when VOELCBs were common, and most non TT supplies had nothing at all, we had a shiny new scout HQ with a 30mA RCD for the lot.

This was used for leader training, events so on a weekend course,  adults brought in their own shavers radios, rechargeable torches and all sorts.

At that time a lot of kit was in circulation with the older red black green mains leads and people were far more in the habit of swapping plugs from round to square and vice versa,  most did this very well, but a few folk seemed to do their plug fitting in the half light using a nail file and bread knife or something.


On more than one occasion, someone brought something in with the plug mis-wired with an  earth neutral swap, that 'worked OK at home'  that because the black wire was under the earth pin,. perhaps unsurprisingly disappointment when it all went dark, and there was denial from everyone that it could possibly be something that someone had brought in. Funniest like that was a red-green reversal, so the case was live and the load live to earth.

If it really had worked at home, then there must have been further faults in his  home.

Hah. Now I feel stupid. I was thinking of a L N reversal. That`ll teach me to read properly. I`m of Red, Black, Green age meeself

Many years ago the Post office downrated all 13A plugs used on its property to 8A as they believed that was all they were good for.

Some interesting points made, thanks for the replies.

Had I tested the new kettles I would have  been inclined to pass them in view of the very short term use.


I can not however agree with those who state that a space heater drawing 14 amps is OK. I have seen far too many 13 amp plugs that have failed under very modest overload, or even long term full load. Under modest overload the plug or the socket will often fail before the fuse operates.


It would appear that most appliance manufacturers take a similar view, as most new appliances are limited to about 10 amps, possibly due to warranty claims or adverse publicity about melted plugs.

3Kw heaters are now hard to find as are 3Kw tumble dryers.