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  1. C

    Industrial Breaker Coordination

    The trip ratings of upstream and downstream circuit breakers should be same as I was told by a senior. Why cant the downstream circuit breaker be rated less than the upstream breakers. I'm not talking about the short circuit ratings, but the Ampere trip rating.
  2. GMES

    Understanding Rcds 2016-08-28

    IN THIS ARTICLE we discuss Residual Current Device (RCD) operation, which can occur due to electrical faults both downstream and upstream of the device. An RCD, when correctly selected and installed, can provide protection against electric shock due to indirect contact. RCDs are also used to...
  3. yellowvanman

    10KA or 6KA breakers?

    I know the difference between the 2 sorts but I'm thinking do I need to fit 10KA breakers in this scenario, when I've got 6KA MCBs in the van! 3 phase DB, Isc 4.9KA (phase to earth), all circuits from this DB are single phase. Will never be 3 phase in future (HMO). Worst case short circuit...
  4. Z

    Type D 40A MCB upstream of BS88 63A Fuse

    Can anyone help with the time current characteristics of which will operate first? Essentially a 40A type D crabtree pole star fed from a BS 88 g 63A fuse. Looking at the time current characteristics I reckon that the BS88 would operate at a fault current of 500A for a 0.4s disconnection whereas...
  5. P


    Morning Guys I know that if a 100mA RCD is followed by a 30mA RCD, the 100mA needs to be S type. If a 300mA RCD is followed by a 30mA RCD (Farm installation) does the 300mA need to be S Type? Cheers Pete
  6. D

    Commercial rcd discrimination

    hi guys im an apprentice and need some more understanding about rcds please may i have an example of rcd discrimination and what ratings i would use for different things and why thanks danny
  7. T

    Maximum tolerable fault current

    Just completing the testing of a transportable catering unit.(chip van). Within the NICEIC REPORT I must complete, a.MAXIMUM TOLERABLE FAULT CURRENT(is the same as PSCC)? b.MAXIMUM TOLERABLE UPSTREAM ELI.(is this the same as Zs)? If so how do I achieve these values when the Power...
  8. J

    Ze testing using a MFT 1553

    Am I correct in thinking that when doing a Ze test using a 1553, the dial needs to be set on the 'Hi' setting in the green loop section of the dial settings? Cheers
  9. E

    2 RCD's

    Hi guys I was just thinking about what someone put about a question I asked a couple of days ago. I asked about putting an RCD proceted fused spur on a ring main to feed an outside light. they said the RCD fused spur will be fine as long as its not protected by another RCD on the cu. My question...
  10. J


    can anyone explain how an upstream supply fault can make an rcd trip?....shakey maybe:confused:
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