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Regulation stating a type AC RCD can not be upstream from a type A RCD

Alan B

Hi

I found an EV charger today with built in type A RCD + RDC-DD connected to a type AC RCD in the consumer unit, the AC RCD is also protecting 3 other circuits including sockets. I know this is incorrect because the type AC RCD could be blinded by DC currents, but I am struggling to find a regulation to reference when providing information to the customer?

Thanks

Alan

Parents
  • 0

    531.3.3 "....RCD Type AC shall only be used to serve fixed equipment, where it is known that the load current contains no DC components."

    No DC components, not just up to 6mA.

    so can't be used on (new or altered) socket circuits.

    Edit; together with 132.16 Additions and alterations " ... condition of any existing equipment...will be adequate for the altered circumstances."

Reply
  • 0

    531.3.3 "....RCD Type AC shall only be used to serve fixed equipment, where it is known that the load current contains no DC components."

    No DC components, not just up to 6mA.

    so can't be used on (new or altered) socket circuits.

    Edit; together with 132.16 Additions and alterations " ... condition of any existing equipment...will be adequate for the altered circumstances."

Children
  • 0 in reply to OlympusMons
    OlympusMons said:

    531.3.3 "....RCD Type AC shall only be used to serve fixed equipment, where it is known that the load current contains no DC components."

    No DC components, not just up to 6mA.

    so can't be used on (new or altered) socket circuits.

    That probably nails it.

  • 0 in reply to Sparkingchip

    But just what is a DC COMPONENT? Is it a D.C. electronic component like a diode or transistor? Or is it a type of electrical current? AND does the regulation apply to a normal D.C. component if of an electrical type. OR just if one can appear under fault conditions?

    Also, how do we measure the DC component if of an electrical supply type to see if it exists?

    Z.

  • 0 in reply to Zoomup

    A DC component is a component within the appliance that may cause DC leakage into the AC circuit supplying it, it’s where the appliance converts the AC supply to DC via a transformer and rectifier. Examples of things that include DC components are basically anything with a PCB so washing machines, chargers, also EV chargers, TV, everything digital. Really we should have been using A type RCDs as standard ages ago because all these pesky dc currents build up the more digital tech you add to the installation. The big brown book has basically relegated AC RCDs unless you can be certain of no DC components are connected to the circuit it protects. It’s on page 157 of the big brown book. 53.1.3.3 NOTE3 “RCD type AC shall only be used to serve fixed equipment, where it is known that the load current contains no DC components”  so maybe an old fridge with a dedicated circuit.

    Does it have a PCB? Does it run on rectified power (this might include LED lightbulbs)? Are you unsure if the previous two answers are yes? If the answer to any of those three questions are yes then you should not use an AC RCD.

  • 0 in reply to IronFreely

    But the reg. refers to the LOAD CURRENTS NOT HAVING D.C. COMPONENTS, not D.C. electronic components.  It's a copnfusing unclear statement.

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