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BS 1363 13A Socket Continuous Max Load

sparkiemike

Let me start by saying this is NOT about the maximum load of a double socket outlet, that has been done before!

At a recent Elex “seminar” Darren Staniforth from Scolmore made a comment that BS1363 socket outlets were only tested for 8A continuous load. This was news to me because my 1995 version of BS1363-2 says for the Temperature rise test the connected load will be 14A for a minimum continuous period of 4hours or longer until stability is reached and max duration of 8hours. 

If I recall the comments at Elex correctly, he then went on to say the latest version of BS1363 made provision for socket outlets to have a continuous load of 13A to cater for equipment like EV chargers ("granny cable") and these “plug and play” 13A hot tubs that seem so popular now. Also that some manufacturers (maybe Scolmore?) were now making socket outlets to accommodate these large loads of long continuous periods.

So my question is, does anybody know what BS 1363-2:2016+A1:2018 says about continuous loads that is different from before? And if there is a change which manufacturers are making socket outlets to the latest standard?

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    “Yesterday I once again replaced a B32 MCB supplying a 8.5kW shower with a B40, because it was running permanently overloaded, I frequently see this done.”

     

    I will ditto that one, running on the curve is not very good.

     

    Examples of 13A plugs.

    I`ve seen 13A plugs (and SFCUs) running 3KW immersion heaters for years no problem

    BUT, I`ve seen quite a few that have gone not so well too.

    Bathroom cylinder cupboards do run quite a bit higher ambient than say a living room so fair go. But a nasty make of plugtops, sockets and SFCUs about drastically reduce your starting chances too

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    The correct current rating of the over current device for a 13 amp single socket is 16, 20 or 32 amps, if you fit a 10 amp OCD plugging in a 10 amp EV charger would run it at full capacity for an extended period, which is not good design and if a garden shredder or the like is plugged in that draws a full 13 amps it will be overload.

    Over twenty years ago before I qualified as an electrician I installed a outdoor double socket at home with an indoor 13 RCD FCU supplying it, I plugged a garden shredder in with a 3kW induction motor and ran it for some time, then the RCD FCU packed up.

    The RCD FCU and the SRCD devices are rated at 13 amps for resistive loads and 3 amps for inductive loads, so I had to replace the RCD FCU and plugged the shredder in elsewhere, then when I replaced the consumer unit I replaced it with a 20 amp double pole switch, so it’s now protected by a B32 MCB In the consumer uni.

    For an outdoor EV 13 amp socket such as the Masterplug unit I would choose a double pole C16 30 mA Type A RCBO or a DP B20 30 mA Type A RCBO to replace that BG such as a Wylex compact RCBO to accommodate garden equipment, pressure washers, etc that may have a higher starting current.

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    Yesterday I once again replaced a B32 MCB supplying a 8.5kW shower with a B40, because it was running permanently overloaded, I frequently see this done.

    But was it tripping off?

     

    Z.

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    Sparkingchip: 
    A 10 amp RCBO or MCB cannot be run fully loaded at 10 amps for an extended period, it has to be derated, therefore a 10 amp EV charger needs a 16 amp protective device.

    433.1.1 does not say that. It simply says Ib ≤ In ≤ Iz so Ib and In are allowed to be equal.

    What is not permitted is a small overload of long duration - 433.1.

    If a nominally 10 A MCB could only carry a sustained load of say 8 A, it should be rated at 8 A.

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    I wonder whether these 13 amp outdoor EV sockets have a flip over lid that can accommodate the sort of moulded on 13 amp plug that is on the end of a “granny cable”?  I ask because the 13 amp plug on the “granny lead” supplied with our Kia will not allow the “lid” on a MK socket to close.  Only needed to use it once whilst waiting for a Zappy to be fitted.

    Clive

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    AncientMariner: 
     

    I wonder whether these 13 amp outdoor EV sockets have a flip over lid that can accommodate the sort of moulded on 13 amp plug that is on the end of a “granny cable”?  I ask because the 13 amp plug on the “granny lead” supplied with our Kia will not allow the “lid” on a MK socket to close.  Only needed to use it once whilst waiting for a Zappy to be fitted.

    Clive

     

    Does the Kia granny lead have an oversized plug that won’t fit under the cover because it is oversized due to being more substantial and is better made that most 13 amp plugs?

  • 0

    Chris Pearson: 
     

    Sparkingchip: 
    A 10 amp RCBO or MCB cannot be run fully loaded at 10 amps for an extended period, it has to be derated, therefore a 10 amp EV charger needs a 16 amp protective device.

    433.1.1 does not say that. It simply says Ib ≤ In ≤ Iz so Ib and In are allowed to be equal.

    What is not permitted is a small overload of long duration - 433.1.

    If a nominally 10 A MCB could only carry a sustained load of say 8 A, it should be rated at 8 A.

    First off the Masterplug unit has a 13 amp socket outlet that is not restricted to charging an EV at 10 amps, so a 10 amp OCD is not suitable as it could easily be overloaded by 30% with a 13 amp load.

    Secondly, BS7671 doesn’t tell you how to select MCBs, you need to look beyond the regs book and refer to manufacturers data and derate MCBs accordingly.

    2d5661ce1040b65c6ae751ac97b2f222-huge-1754a566-4736-4049-901a-7d5187936ad5.jpg

     

    https://www.hagerelectro.com.au/files/download/0/32587_1/0/TECHINFO_MCBS.PDF

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    How many plug in appliances fitted with a 13 amp plug that draw more than 8 amps are there in most home?

  • 0
    Well, it is oversized in depth compared to other moulded 13A fused 3-pin plugs, but whether it is more substantial electrically and better made overall cannot be determined without destroying it.  I would say that a MK 13A plug with silver plated fuse fuse clips and also terminals which don't severe the conductors in the "hole" when you tighten up the terminal, are better made than the cheaper 13A plugs that are on the market. 


    Perhaps we should be looking as to where the heat comes from?  I remember buying a printer in either Hong Kong or Singapore where the UK style 13A plug did not have provision for a fuse.  That design would certainly eliminate I²R losses in the fuse and its connections. (I will have to check whether the Kia granny has an inbuilt fuse or whether it relies on the electronics in the box near to the plug for overload protection.)

    Clive



  • 0

    Likely a thermistor in the plug top 

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