Can this device be installed in an installation and comply with B.S. 7671?

Humm. Presumably it attempts to generate a leakage current that's equal in magnitude but opposite in polarity to the imbalance it senses. I can't help thinking that it'll risk hiding real earth fault currents in the same way - so defeating the RCD not only for unintentional tripping, but intentional as well. I realise it claims only to work for frequencies above 150Hz and for a limited current (a few amps) so simple earth faults before the inverter is likely not to be fully cancelled and so the RCD should hopefully still trip - but what of earth faults after the inverter or where the residual current has additional (higher frequency) components due to the downstream electronics? The fact they don't suggest that shock protection isn't compromised isn't reassuring.


If the idea is that shock protection from faults only before the device is reliable, then I can't help thinking that a simpler answer might be to use double/reinforced insulation for the supply and just omit the RCD altogether.


As for BS 7671 I can't think of a regulation that would expliciity prohibit its installation - but clearly some 'engineering judgement' (good workmanship at the design stage?) should be applied and might caution against such things.


  - Andy.

Humm. Presumably it attempts to generate a leakage current that's equal in magnitude but opposite in polarity to the imbalance it senses. I can't help thinking that it'll risk hiding real earth fault currents in the same way - so defeating the RCD not only for unintentional tripping, but intentional as well. I realise it claims only to work for frequencies above 150Hz and for a limited current (a few amps) so simple earth faults before the inverter is likely not to be fully cancelled and so the RCD should hopefully still trip - but what of earth faults after the inverter or where the residual current has additional (higher frequency) components due to the downstream electronics? The fact they don't suggest that shock protection isn't compromised isn't reassuring.


If the idea is that shock protection from faults only before the device is reliable, then I can't help thinking that a simpler answer might be to use double/reinforced insulation for the supply and just omit the RCD altogether.


As for BS 7671 I can't think of a regulation that would expliciity prohibit its installation - but clearly some 'engineering judgement' (good workmanship at the design stage?) should be applied and might caution against such things.


  - Andy.