Type A rcd . EICR coding ? etc

Hi Lyle


The reasonably "foreseeable test" should not apply if the appliance is manufactured in compliance with the LV directive because this gives specific requirements to prevent these kinds of faults. I do not see any of the fault types suggested as reasonably foreseeable because the manufacturer should have designed the possibility out of the product. If the fault is foreseeable he should provide protection against it IN THE PRODUCT, not expect it to be provided by a third party, and particularly as the instructions do not admit this danger. It is fairly easy to fit a "crowbar" across the supply which is triggered by such leakage which removes the danger by blowing the mains fuse (and I note that internal fusing appears not to be fitted, which I would expect). The instructions keep on referencing BS7671 in areas where it is out of scope, pushing overall safety onto someone else. This is a bit like saying I make a class 2 appliance but someone else must protect it against an Earth fault to the casing because I have not designed the class 2 insulation to be adequate under all foreseeable conditions.


Washing machines and similar appliances have used phase control etc. of their motors for many years, yet I have not heard of any accidents due to RCD failure because of leakage. Is this just luck or is it because the design is adequate? Unfortunately, I think that BS7671 is being asked to deal with all possible dangers from "the use of electricity", including the appliances connected, which is way out of scope. We are seeing that "Risk Shifting" is becoming common, particularly in areas such as product liability. There is an easy solution available, if you need a DC supply, then isolate it via the electronics. It may cost slightly more, but for low-power devices not very much. Just as an example I recently bought a new 300W power supply for £25, and 10W supplies cost £5. I have just been quoted £3000 to fit a replacement gas boiler, and I can buy it for £1000. Realistically a few pounds extra for the boiler to be properly isolated is not a problem because a 50W transformer would cost £5 in volume. Perhaps this is all too simple? (And I should get Gas Safe registration!).


I have several RCD testers including the Megger MFT as I said. One of these gives readings up to 2 seconds for disconnection, the MFT just says TRP if longer than 100 ms.


The solution to this is to add a regulation to BS7671 which simply states that "Appliances which may leak DC currents into the Mains wiring system may not be connected to RCD protected circuits". This puts the problem back with manufacturers to ensure that their products are safe and cannot affect our safety measures.

Hi Lyle


The reasonably "foreseeable test" should not apply if the appliance is manufactured in compliance with the LV directive because this gives specific requirements to prevent these kinds of faults. I do not see any of the fault types suggested as reasonably foreseeable because the manufacturer should have designed the possibility out of the product. If the fault is foreseeable he should provide protection against it IN THE PRODUCT, not expect it to be provided by a third party, and particularly as the instructions do not admit this danger. It is fairly easy to fit a "crowbar" across the supply which is triggered by such leakage which removes the danger by blowing the mains fuse (and I note that internal fusing appears not to be fitted, which I would expect). The instructions keep on referencing BS7671 in areas where it is out of scope, pushing overall safety onto someone else. This is a bit like saying I make a class 2 appliance but someone else must protect it against an Earth fault to the casing because I have not designed the class 2 insulation to be adequate under all foreseeable conditions.


Washing machines and similar appliances have used phase control etc. of their motors for many years, yet I have not heard of any accidents due to RCD failure because of leakage. Is this just luck or is it because the design is adequate? Unfortunately, I think that BS7671 is being asked to deal with all possible dangers from "the use of electricity", including the appliances connected, which is way out of scope. We are seeing that "Risk Shifting" is becoming common, particularly in areas such as product liability. There is an easy solution available, if you need a DC supply, then isolate it via the electronics. It may cost slightly more, but for low-power devices not very much. Just as an example I recently bought a new 300W power supply for £25, and 10W supplies cost £5. I have just been quoted £3000 to fit a replacement gas boiler, and I can buy it for £1000. Realistically a few pounds extra for the boiler to be properly isolated is not a problem because a 50W transformer would cost £5 in volume. Perhaps this is all too simple? (And I should get Gas Safe registration!).


I have several RCD testers including the Megger MFT as I said. One of these gives readings up to 2 seconds for disconnection, the MFT just says TRP if longer than 100 ms.


The solution to this is to add a regulation to BS7671 which simply states that "Appliances which may leak DC currents into the Mains wiring system may not be connected to RCD protected circuits". This puts the problem back with manufacturers to ensure that their products are safe and cannot affect our safety measures.