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AFDD: Hager vs. Hager

whjohnson

Mr Savery has graced us with yet another presentation of his latest findings on Hager's AFDDs and it doesn't end well! Indeed, it may well pay interested parties to view his new terms and conditions recently incorporated into his contract with consumers where AFDDs are concerned. It seems that he is not alone, with many people now refusing to fit the things or be held responsible for any malfunctions due to the manufacturer's badly written algorithms etc.

In other news, there seems to be a rumour doing the rounds about the withdrawal of the requirements for AFDDs at some future point due to the huge number of issues being experienced with them. Allegedly the rumour has come from a NIC assessor.

www.youtube.com/watch

  • in reply to mapj1

    For out door work a butt crimp with 2 layers of glued heat shrink for LV or maybe a resin torpedo would be better if the joint is needed.

  • in reply to Sergio Fernandez

    Sounds like a much better idea. Have found the old ceramic screwitts under floors before now, usually with the twisted copper ends of the cable pulled taut and leaving half exposed copper strands to the wind. Suffice to say they went in the bin.

    On the AFDD front, it seems that Hager have issued some kind of firmware upgrade which effectively 'knobbles' the device like a chemical cosh! How useful!

  • in reply to gkenyon

    That higher risk of arc flash in the US is also further aggravated by  a rather liberal approach to ADS and let-through energies compared to ours.

    It is quite easy to estimate an upper limit on flash energy based on fuse or breaker I2t and supply voltage by assuming that at maximum flash half the supply voltage is in the arc, and the other half is in the supply wiring.

    I.e. if your bolted PSCC is 6000 then your worst case arc is a 3000 A one, with 120V across the arc - 360kW.

    Now with no fuse this would sizzle forever and be pretty stellar, but if you had

    1) say a 13A fuse of I2t of 1200 A2 secs  then we can say it would behave as if it cut off after 0.13ms - so 48 joules delivered to the arc volume and as the minimum distance not to get bad burns is set by 5 joules percm2,  we can ask what is the radius from a 48joul source, or to make the sums easier 50J so what sphere has a 10square cm area- we end up deciding it is dangerous to be closer than about an inch in terms of skin burns .

    2)  A 100A house service fuse with more like 75 000 A2 secs it is much more serious - at 3000A it takes 8 milliseconds to break, and that puts  about 3000 joules into the arc in that time so we need to spread that over more than 600cm2 - a sphere of about 4 or 5 inches accross - and more if there is any reflection / focussing by the mounting or box/enclosure that means the energy is directed to the body.

    And for those fool enough to be on the wrong side of that company fuse, well ... it gets a lot worse.

    Mike.

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