OP
brman
I agree. In a periodic no earth on a class 1 would be a C2 regardless of RCD etc. I don't think RCDs and lack of extraneous conductive parts is enough to make it a C3.
So you are right, you are still leaving a potentially dangerous fault. However I think there are a few mitigating reasons why this is acceptable.
First, as I see it, a certificate for a CU change is not certifying the complete installation. It is certifying the work done (i.e. the CU change) plus the circuits as they affect the operation. So Max Zs, IR, bonding etc is needed to ensure the CU works properly. A good example of this is from my last elecsa assessment. On testing I found a spur of a ring with a Zs of greater than 1.14ohms. if this was something I had just installed I would be failing the test and working out how to get the max Zs down. However as I was just changing the CU I determined it was due to poor design (read as mutiple ring extensions and long spurs done over the years), not bad connections, and noted on the cert that it was high but still within that required by the RCD protection.
In the same way, if I came across cables out of zones I would still do a CU change.
And, to be fair to the ESC, they are not saying that fitting an RCD is rectifying the problem. You still need to inform the client in writing that there is a potentially dangerous fault and also label the CU that there is no CPC in the circuit so only class 2 fittings can be used. All they are saying is that doesn't stop you doing a CU change.
That is the way I read it anyway
So you are right, you are still leaving a potentially dangerous fault. However I think there are a few mitigating reasons why this is acceptable.
First, as I see it, a certificate for a CU change is not certifying the complete installation. It is certifying the work done (i.e. the CU change) plus the circuits as they affect the operation. So Max Zs, IR, bonding etc is needed to ensure the CU works properly. A good example of this is from my last elecsa assessment. On testing I found a spur of a ring with a Zs of greater than 1.14ohms. if this was something I had just installed I would be failing the test and working out how to get the max Zs down. However as I was just changing the CU I determined it was due to poor design (read as mutiple ring extensions and long spurs done over the years), not bad connections, and noted on the cert that it was high but still within that required by the RCD protection.
In the same way, if I came across cables out of zones I would still do a CU change.
And, to be fair to the ESC, they are not saying that fitting an RCD is rectifying the problem. You still need to inform the client in writing that there is a potentially dangerous fault and also label the CU that there is no CPC in the circuit so only class 2 fittings can be used. All they are saying is that doesn't stop you doing a CU change.
That is the way I read it anyway