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RCD Testing x5 150mA (or higher for Hager RCCB)

sparkiemike
Following on from John Peckham's recent post, I have recently installed several of Hager's consumer units with their new 100A 30mA Type A RCD (CD285U)


When testing the RCDs I noticed the trip times were much higher than previously experienced. Hager have said that RCCB needs to be tested at 250mA https://www.hager.co.uk/news-exhibitions-case-studies/18th-edition/updated-guidance-rccb-testing/97806.htm


In addition, if you have a Fluke you may notice that when carrying out a earth loop test (in no trip mode) the Fluke will fail to get a reading and trip the RCD. Apparently Hager have had a several reports of this and when I called could not explain it.
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    I thought it needed a MCB upfront of it and I wasn't expecting to see it connected into the main switch as it is



    Those sorts usually have a one-shot thermal fuse in them (that if broken, cause a red bar to appear the window). This allows it to be used without MCB as long as the upstream device is "good enough". For example the Wylex SPDs that come in their CUs don't need protection if the upsteam fuse is <= 125A.


    As an aside - I'm surprised by the orientation of that Hager SPD - if it had been manufactured with L,N below and E above, all three connection leads could have been substantially shorter, and for transients, the inductance of the leads has a large effect on the voltage that is passed through. For example, a typical type 2 SPD might achieve down to 1.5Kv across its terminals, but add in 1m of L+E leads, and that might increase to 3kV at the other ends of the leads. So rather than 1.5K reaching equipment, 3kV reaches it. It looks like maybe 30cm of unnecessary cabling there, which might be letting through another 0.5Kv.
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    I thought it needed a MCB upfront of it and I wasn't expecting to see it connected into the main switch as it is



    Those sorts usually have a one-shot thermal fuse in them (that if broken, cause a red bar to appear the window). This allows it to be used without MCB as long as the upstream device is "good enough". For example the Wylex SPDs that come in their CUs don't need protection if the upsteam fuse is <= 125A.


    As an aside - I'm surprised by the orientation of that Hager SPD - if it had been manufactured with L,N below and E above, all three connection leads could have been substantially shorter, and for transients, the inductance of the leads has a large effect on the voltage that is passed through. For example, a typical type 2 SPD might achieve down to 1.5Kv across its terminals, but add in 1m of L+E leads, and that might increase to 3kV at the other ends of the leads. So rather than 1.5K reaching equipment, 3kV reaches it. It looks like maybe 30cm of unnecessary cabling there, which might be letting through another 0.5Kv.
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