Type A rcd . EICR coding ? etc

davezawadi (David Stone):

As usual, a manufacturer's instruction Chris which is WRONG. Why does a boiler need a type A, in the case it requires additional protection? There are several points here. If bonding is in place to the gas or oil supply, why would the boiler require additional protection? Can THE BOILER introduce an external potential, which is not introduced by the gas/oil pipe? NO. Can the boiler produce a DC mains current? NO. Does it have a plug? NO. So what exactly does this instruction mean? It means that whoever wrote it has no idea about anything and providing faulty manufacturers' instructions should become a criminal offense both for the writer and the manufacturer with a prison sentence as the minimum on conviction as well as a hefty fine. In fact, this instruction was probably written in a country that does not have type AC RCDs available, and the boiler does not require anything any fancier than the minimum. Let's assume a TT installation. There is NO additional protection available except bonding or perhaps a number of RCDs in series. Most important there is no danger, so just what do they mean, and certainly no explanation of why a type AC is needed!


Aligarjon, British gas should lose its electrical certification. This is again just plain wrong. It appears that very few persons understand RCDs, DC Current, or anything else.

What on earth makes you assume the manufacturer got it wrong?


Perhaps the boiler is known to "blind" Type AC RCDs for a very simple reason. The boiler doesn't have to produce a DC mains current - but it could well have a bridge rectifier on the mains - as per a lot of SMPSUs - and therefore the manufacturer considers it's possible, for some faults on the rectifier output, to generate a fault current that is simply not suitable for a Type AC RCD  - See item 4 in Figure A53.1 (Page 192 of BS 7671).

davezawadi (David Stone):

As usual, a manufacturer's instruction Chris which is WRONG. Why does a boiler need a type A, in the case it requires additional protection? There are several points here. If bonding is in place to the gas or oil supply, why would the boiler require additional protection? Can THE BOILER introduce an external potential, which is not introduced by the gas/oil pipe? NO. Can the boiler produce a DC mains current? NO. Does it have a plug? NO. So what exactly does this instruction mean? It means that whoever wrote it has no idea about anything and providing faulty manufacturers' instructions should become a criminal offense both for the writer and the manufacturer with a prison sentence as the minimum on conviction as well as a hefty fine. In fact, this instruction was probably written in a country that does not have type AC RCDs available, and the boiler does not require anything any fancier than the minimum. Let's assume a TT installation. There is NO additional protection available except bonding or perhaps a number of RCDs in series. Most important there is no danger, so just what do they mean, and certainly no explanation of why a type AC is needed!


Aligarjon, British gas should lose its electrical certification. This is again just plain wrong. It appears that very few persons understand RCDs, DC Current, or anything else.

What on earth makes you assume the manufacturer got it wrong?


Perhaps the boiler is known to "blind" Type AC RCDs for a very simple reason. The boiler doesn't have to produce a DC mains current - but it could well have a bridge rectifier on the mains - as per a lot of SMPSUs - and therefore the manufacturer considers it's possible, for some faults on the rectifier output, to generate a fault current that is simply not suitable for a Type AC RCD  - See item 4 in Figure A53.1 (Page 192 of BS 7671).