Domestic smoke detection with internal surge protection to meet 443.4.1 of BS7671 2018 AM2 2022

Question

Domestic smoke detection, some have internal surge protection built into the units i.e. Aico heads have a standard that specifies units are to be tested with fast transient bursts of +/-2kV, and slow high energy surges of +/-0.5kV and 1kV. Would this be sufficient to negate the application of a separate SPD to be fitted within a consumer unit to meet BS7671 2018 AM2 2022 443.4.1?

AJJewsbury · Accepted Answer

2kV sounds rather modest for an SPD - according to table 443.2 we should be able to expect even sensitive equipment to be able to withstand 1.5kV (normal equipment 2.5kV, DBs and sockets 4kV and equipment at the origin 6kV) so it sounds like these are merely the equivalent of "type 3" SPDs - i.e. would have to be backup up by upstream type 2s (and possibly type 1s, depending on the installation). 
 - Andy.

mapj1 · Answer

Note that the pulse duration and source impedance used for the product test may or may not match with those used for the SPDs. Hopefully there is more info - 230V land normally the En series apply 
 
 The waveform associated with a 'type II' surge suppressor look similar to one of those tests but the time axis is very different. Even so not the same and it depends which failure mode is setting the limit. 
 The design robustness needed to hold off a few kV for less than 50nanosec is a lot less than for 50usec and in turn less than 300usec. 
 'surges to xxkV' sounds great bit it is not a complete spec. 
 Mike.

Domestic smoke detection with internal surge protection to meet 443.4.1 of BS7671 2018 AM2 2022

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