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Overvoltage and Surge Protection for a house in Malta with 3 phase 63A supply

wpqs

I would appreciate some comment on the design of Overvoltage and Surge Protection for a house in Malta with 3 phase 63A supply (see below), particularly the need for a MCB in DB-A to protect the cable running to the MCB in DB-X. This seems like overkill. It was originally specified as a Type B RCD. What are your views? Any other comments are welcome.

Notes:

1. The cables to supply the house run along the facades of the houses in the street, so it seems sensible to protect against lightening strike or other - hence the surge suppressor

2. Overvoltage protection is needed as otherwise the house insurance is void. The concern relates to loss of neutral connection,

3. Malta follows IEE Wiring Regulations, but has some local variations

Parents
  • 0

    One further point: The electrician suggested that the rating of the contactor to isolate the supply to the house during over-voltage should be rated at 100A although the MCBs and supply are all rated at 63A. Do I really need 100A rating? 

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  • 0

    One further point: The electrician suggested that the rating of the contactor to isolate the supply to the house during over-voltage should be rated at 100A although the MCBs and supply are all rated at 63A. Do I really need 100A rating? 

Children
  • 0 in reply to wpqs

    It will depend on how often it is called to interrupt the full load current. A '63A' or '100A'  contactor will carry 63/100 amps under some controlled condition, usually a well behaved resistive load and at a defined ambient temperature, often 30C,  but it is not intended to interrupt that current without the contacts becoming slowly degraded each  time. If the load is reactive (inductors - think motors, or capacitors, think electronics and some kinds of light fitting) the surge currents may be much higher than the average, and some de-rating is required or the contacts get burnt up unusually fast.

    The use of the next size up means that concerns about longevity and or a warmer environment are mitigated, and avoids having to think hard about the location or extra ventilation. The electrician may also be thinking about avoiding call backs if he or she has seen problems in the past. If upgrading at design time the price increase is usually modest, if a model is selected where both ratings are for the same frame size, as it is essentially beefier contacts in the same box.
    Mike.

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