Discuss Zs measurements in the Cert column in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
What would you put.and see if can get correct.what Max Zs would you put in the column for Max measurement for the MCB
Are you testing TT or PME.I would put 1666 for the Rcd measurement & the normal Zs measurements for the MCB’s
PME CheersAre you testing TT or PME.
in your tick box for Max measurement tested.
Well that’s the dilemma & some disagreement here… To be fair I’ve seen both measurements recorded on Certs… personally I prefer the Zs for the MCB, with the 1666 only for the MCB1667 ohms for any circuit protected by a 30mA RCD
I personally don't see any value in using the MCB max permitted Zs values when there is an RCD protecting the circuit. Following 411.4.204, table 41.5, and 643.7.1 (a) and (b) means that I don't have to provide a Zs value, either measured or calculated, to prove ADS, assuming I have confirmed continuity of CPC. It frees me up to focus on other parts of the testing.Well that’s the dilemma & some disagreement here… To be fair I’ve seen both measurements recorded on Certs… personally I prefer the Zs for the MCB, with the 1666 only for the MCB
Yea that’s my thinking, scares me looking @ those 1666 measurementsI would argue that the RCD component of the circuit is there for additional protection - therefore you'd always use the appropriate Zs to achieve a disconnection time under ADS except if the default stated values by the manufacturer are those for RCD anyway.
In theory, a max impedance of 1666 on a 230v nominal supply does give you a current of slightly less than 5x but vastly exceeds 1x so it shouldn't matter..... but ..... we press the test button on RCD's for a reason whereas ADS just dependably sits there.Yea that’s my thinking, scares me looking @ those 1666 measurements
Agree so why would anyone wanna put 1666 in the column regarding TN SystemsIn theory, a max impedance of 1666 on a 230v nominal supply does give you a current of slightly less than 5x but vastly exceeds 1x so it shouldn't matter..... but ..... we press the test button on RCD's for a reason whereas ADS just dependably sits there.
But frankly if you're even anywhere close to working with numbers that high then you've got bigger issues anyway, not least of which is Vd.
I think the technical argument there is that the RCD would be additional protection not basic protection under ADS??If ADS is satisfied by the mcb then use the mcb If ADS is satisfied by the RCD then use that.
415.1.2 The use of RCDs is not recognized as a sole means of protection and does not obviate the need to apply one of the protective measures specified in Sections 411 to 414.415.1.2 just means if you have an EN 61008 device then you must have an overcurrent device incorporated into it, l believe.
Why? Because that is the maximum Zs for the circuit. The RCD doesn't know or care whether the earthing arrangement is TN or TT, or if you prefer the values for MCB, it's going to trip anyway, and that is its max Zs.Agree so why would anyone wanna put 1666 in the column regarding TN Systems
Especially when the actual measured Zs is going to be a low Ohm reading
I find this odd but it is the way of things now. If you have your R1 + R2 you may as well put in the Zs anyway by way of calculation.Also: Because where a circuit is protected by an RCD, there is no need to provide a Zs reading, either measured or calculated. Once you have proved that the RCD works, and that the CPC is continuous by either R2 or R1+R2, then you have met disconnection times.
Why bother? It's not useful data, as you can only check it against 1667ohms.I find this odd but it is the way of things now. If you have your R1 + R2 you may as well put in the Zs anyway by way of calculation.
While that is technically true it is a path that leads to ECIR by socket tester results - wet string below 1.6k ohm? Pass!Why? Because that is the maximum Zs for the circuit. The RCD doesn't know or care whether the earthing arrangement is TN or TT, or if you prefer the values for MCB, it's going to trip anyway, and that is its max Zs.
Also: Because where a circuit is protected by an RCD, there is no need to provide a Zs reading, either measured or calculated. Once you have proved that the RCD works, and that the CPC is continuous by either R2 or R1+R2, then you have met disconnection times.
Reply to Zs measurements in the Cert column in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.