not sure where the 7.2 comes from?
240 Volt and 30 mA ( 0.03 Amp ) is 240 x 0.03 = 7.2 ( assuming my maths is correct )
not sure where the 7.2 comes from?
Silly me of course, I used 230 volt and 300 mA so that's why did not match. My maths not very good either, odd can imagine numbers but calculus never could work it out, still use a slide rule, only to show off though, calculator much better. Just need to log that one up to experience?240 Volt and 30 mA ( 0.03 Amp ) is 240 x 0.03 = 7.2 ( assuming my maths is correct )
... it would, but only if the amount of current involved was not enough to cause an OPD to operate, anyway - and I would have thought that, in practice, any current high enough to result in a fire would usually (always?) be high enough to trip an OPD.In my opinion the RCD reduces the risk of a fire happening by limiting the amount of energy in the fault path to ground.
As I've said, although I may be missing something it sounds very odd to me. As I've said, I'm not convinced that a current lower than that which would trip a circuit's OPD (without van RCD) would be adequate to start a fire.But the idea of a 300 mA RCD or less to prevent fire still seems odd, ....
For a start, that wasn't (and probably was nowhere near) a 'fire'. I have to say that I find it very hard to believe that 30 mA (or, indeed, 300 mA) flowing through anything in an electrical installation would cause any thermal damage, let alone a fire.... although I know it works, I found a socket which had been damaged by water ingress that had part melted the casing behind the socket that had been made safe due to the 30 mA RCBO tripping, but signs of plastic distorting with just 30 mA or 6.9 watt, so what would happen to 300 mA or 69 watt?
and I would have thought that, in practice, any current high enough to result in a fire would usually (always?) be high enough to trip an OPD.
I think that is getting close to 'barrel scraping'Think of a 5 watt lamp such as a Christmas tree lamp, that can ignite material in close contact with the lamp. .... Then think of a thin wire as part of the fault path to ground
I have to say that that surprises me but, if true, makes one wonder why the required only 300 mA RCD 'fire protection'(in most of the {seeming very few} situations in which such protection is required at allI think they did some direct testing that established that a common source of earth faults is surface tracking on insulation and currents as low as 50-100mA have been found to be sufficient to cause ignition and fire.
I think that is getting close to 'barrel scraping'
Very true - such is the nature of the world.Not all adverse incidents ( accidents ) happen due to something at the top of the barrel.
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