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is a surge protected extension/powerstrip any use without upfront SPDs

psychicwarrior

hello goodly morrow

If a T3 SPD, 'must not' be used, as per 7671,  without upfront (T1+)T2 SPD  (for want of better words) ,  what real value is a plugged in surge protected extension lead/powerstrip  (which is a T3 in effect one presumes) without a T2 somewhere upfront ?

Or is it really just a sacrificial item and really is better to have.

Perhaps the components are pretty useless and cheap in most of the consumer grade surge leads/strips.  May be connected devices (via power blocks and transformers etc) can cope just as well  ;-)

Engineering references and regs are not going to use the anything is better than nothing finger in the air style and have to present a considered, tested and  co-ordinated approach. The consumer market takes a different view it seems and makes little to no effort (does it) to advise that surge protected powerstrips/leads 'must not be used' without upfront SPD,  but if course such is not part of fixed wiring any way so no need, or is there a need . 

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    As pointed out by AJ and Ive found similar,  there is a distinct lack of tech spec  of critical values (e.g. Up)  on sales pages.  Digging around manufacturers pages   for some has revealed limited info too.

    The internet (if you can trust it), suggests that powerstrips  are T3-like intended, in so much as they are 'point of use' .  How well they co-ordinate with any fixed wiring SPD provisions, who knows .

    One brand stocked by CEF states it conforms to BS 5733, BS EN 61643-11   (I don’t have the BS docs but is 61643  about SPD types conformance etc). 

    As an aside, the 'insurance' offered tends to come with all sorts of small print  - so the internet says  ;-)

    I was wondering too, if the PSU that a lot of  electronic kit use would survive or sacrifice just as well as most consume grade powerstrips/leads with surge protection built in  (to a standard, or just cheap parts ... who knows).  If the idea of a T3 'must not use without a T2'  recommendation is because it would get destroyed and be a fire risk etc, then what goods a powerstrip  too.    As said though, may be manufacturers have it sorted although given the power of profit, it might not be as effective as the marketing suggests  on some at least ;-)

  • 0 in reply to psychicwarrior
    psychicwarrior said:
     (I don’t have the BS docs but is 61643  about SPD types conformance etc). 

    Appendix 1 of BS 7671 refers to BS 5733 on page 412 and BS EN 61643 on page 427.

  • 0 in reply to psychicwarrior
    psychicwarrior said:
    One brand stocked by CEF states it conforms to BS 5733, BS EN 61643-11   (I don’t have the BS docs but is 61643  about SPD types conformance etc). 

    BS 5733 has nothing to do with SPDs and overvoltage protection  and, for the purposes of this discussion, is not really a valid.

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  • 0 in reply to gkenyon

    however, its good to know it meets '5733, as a lot of cheap Chinese extension leads and adaptors etc don't. It sets a minimum standard for the housing strength,  and performance in a fire...the insulation of live part and creepage and clearances between them. But no, nothing  SPD specific.

    That is indeed in  61643, and yes, part  11 is all about SPDs for AC systems.

    Mike.

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