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S.P.D.s and Populated Consumer Units.

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Are new populated consumer units with S.P.D.s fitted designed to mainly protect the sensitive electronic equipment downstream of the S.P.D.s WITHIN THE CONSUMER UNIT? Is that the makers' MAIN intention as R.C.D.s, R.C.B.Os and other sensitive electronic devices can be damaged by Voltage surges, as compared to basic protective devices like wire or cartridge fuses or more basic M.C.B.s?

https://www.youtube.com/watch?v=5OuirPKoY0c


Z.
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    whjohnson:

    The thing is, would such devices be quick eniough to prevent a spike being induced in the secondary before the electronics on the south side of that were fried?




    Well they're usually semiconductor based, so can be extremely fast. For example, type 2's are tested against a waveform that reaches it's peak in 8 microsecs. The main thing that will affect their usefulness is the length of the leads from the SPD to the points where the circuit is "tapped into" due to the inductance of the leads.

  • 0

    Simon Barker:




    whjohnson:

    Apparently SPDs don't protect sensitive circuits on the secondary side of an isolation transformer, although the transformer itself supposedly provides some protection. Since most of the sensitive electronics usually lies after secondary winding one does wonder if these things are actually of any practical value.




     

    But the sensitive electronics won't do much if the power supply has blown.



    The thing is, would such devices be quick eniough to prevent a spike being induced in the secondary before the electronics on the south side of that were fried?




     

  • 0

    ebee:

    Years back an electronics teacher stated that for some uses CMOS etc was not used and TTL favoured because they were less suseptable.

    He pointed out thaf if, for instance, Russia set off a nuke in the air over our troops then the tanks etc would prob still function even though the soldiers inside them would have perished.




    The planes were even more of a problem. A magnetic pulse could cause all the US planes (and NATO US built planes) to fall out the sky but the Russians didn't have semiconductor technology in their planes and still used valves....

  • 0

    whjohnson:

    Apparently SPDs don't protect sensitive circuits on the secondary side of an isolation transformer, although the transformer itself supposedly provides some protection. Since most of the sensitive electronics usually lies after secondary winding one does wonder if these things are actually of any practical value.




     

    But the sensitive electronics won't do much if the power supply has blown.
  • 0
    Well we are using more electronic devices these days and they are more vunerable to discharge etc.

    So do we try or is it worth it? risk assesss makes sense then act accordingly.


    Years back an electronics teacher stated that for some uses CMOS etc was not used and TTL favoured because they were less suseptable.

    He pointed out thaf if, for instance, Russia set off a nuke in the air over our troops then the tanks etc would prob still function even though the soldiers inside them would have perished.
  • 0
    Apparently SPDs don't protect sensitive circuits on the secondary side of an isolation transformer, although the transformer itself supposedly provides some protection. Since most of the sensitive electronics usually lies after secondary winding one does wonder if these things are actually of any practical value.
  • 0

    whjohnson:

    It might help if these things actually worked! I know this is a AFD rather than a SPD but the jury is still out as far as I am concerned. Here's part 1. Parts 2 & 3 are as equally illuminating.




    I don't think its fair to compare SPDs and AFDDs. SPDs are conceptually simple: if the voltage exceeds some limit, apply a short using e.g. a hefty thyristor. AFDDs have to monitor HF patterns in the current and subjectively decide which ones are normal (power-on switch spark, sparky brushes on a motor, electronic dimming etc) and which ones are a heat-generating arc fault. Which is hard to get right.

  • 0
    It might help if these things actually worked! I know this is a AFD rather than a SPD but the jury is still out as far as I am concerned. Here's part 1. Parts 2 & 3 are as equally illuminating.

    https://www.youtube.com/watch?v=kVpXQa6EW3k
  • 0

    Chris Pearson:


    So CU change in a rural location which definitely fails the risk assessment. The space for it just allows for a dual-RCD CU, but there is no room for the extra width of an SPD. As I see it, the only solution is to have a separate enclosure for the SPD.

     

    Or use RCBOs. That frees up 4 ways from the RCDs, 2 of which are then taken by the SPD.
  • 0

    wallywombat:

    I recently installed a domestic SPD. The house was semi-rural, and definitely failed the risk assessment. As for the single-dwelling exemption: getting an SPD CU from Wylex adds about £100 to the cost. The cost of protected equipment: combi-boiler, TV, laptops x 2, smoke alarms, burglar alarm, phone chargers, LED lighting etc, easily worth more than 5 x £100. So I don't see how I could be compliant with 18th Ed without installing one.




    I couldn't argue with any of that except that some of those appliances will be on power bricks, which might be fried in the event of a surge, but the appliances themselves will not be.


    So CU change in a rural location which definitely fails the risk assessment. The space for it just allows for a dual-RCD CU, but there is no room for the extra width of an SPD. As I see it, the only solution is to have a separate enclosure for the SPD.

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