Is it not the labelling that is confusing the OP? The 'yellow thing' (the SPD) is not labelled, but the adjacent B40 MCB is labelled 'Surge Suppressor". Despite that, the B40 must be protecting some circuit - which I might guess could (despite the absence of appropriate labelling) be a shower circuit, perhaps?Protecting the yellow thing. Which is protecting your electric gadgets
Is it not the labelling that is confusing the OP? The 'yellow thing' (the SPD) is not labelled, but the adjacent B40 MCB is labelled 'Surge Suppressor". Despite that, the B40 must be protecting some circuit - which I might guess could (despite the absence of appropriate labelling) be a shower circuit, perhaps?
@conny : do you have an electric shower?
Kind Regards, John
Oh, I didn't realise that.Some manufactures use an Mcb to protect the spd, rather than rely on the main fuse!
Fair enough. However, in view of what Andy has said, maybe it is as 'simple' as he suggested (and correct in terms of the labelling) - i.e. that the 40A MCB is merely 'protecting' the surge protection device (the yellow thing on the right), rather than protecti9ng any circuit.No John. It runs off an oil fired boiler. I hate that it just says sockets without stating which floor or room.
I've always been skeptical about the idea of parallel connected SPDs. If a surge comes in that is too big for the SPD to shunt then the SPD has to be disconnected (either by internal protection or an external breaker) to stop it going up in smoke, but that leaves the connected load with no protection.However, does not "protecting the SPD" with an MCB actually impair its intended function?
Exactly my point. However, in reality is it likely that any spike/surge short of a 'direct lightning strike' (in which case all bets would be off!) would/could result in enough current for an SPD to 'go up in smoke'?I've always been skeptical about the idea of parallel connected SPDs. If a surge comes in that is too big for the SPD to shunt then the SPD has to be disconnected (either by internal protection or an external breaker) to stop it going up in smoke, but that leaves the connected load with no protection.
If it's downstream of an RCD, it will only protect anything (let alone 'the whole install') if the RCD has not operated (or been manually 'switched off').Isnt that why they have replaceable plug in modules (the dual width ones) and indicator windows. ... You don’t often see these on dual rcd boards. And yes i suspect it is connected to one rcd b/bar. The length of the cable must be kept to a minimum, but it’s still protecting the whole install.
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