Discussion in 'Electrical Forum' started by Sb8389, Apr 19, 2017.
Discuss Time delayed 100mA RCD in the Electrical Forum area at ElectrciansForums.co.uk.
Does anyone know the max trip time for a 100mA time delayed RCD
It depends on the earthing system, and the tape of circuit the RCD is protecting.
Distribution circuits and final circuits 32A and greater, 5 secs, unless it's a TT installation, when it's 1 sec.
Final circuits less than 32A, 0.4 secs and 0.2 secs for TT.
Its a TT system and the reading i got was 446ms so just got me thinking what the max was i had 500ms in my head but was not sure.
Again, it depends on the circuit.
If it's the upfront RCD, 2 secs.
Maximum Ze/Zs is 500 ohms.
Max 500ms min 130ms
No good being 2 seconds as max disconnection times on a TT are 0.2 seconds and 1 second
Max resistance of Ra would be 500 ohms before 50v touch voltage is exceeded.
50/0.1 = 500 ohms for 100 mA rcd.
Sorry, yes 1 sec, used to be 2 secs.
I did remember in my first post
Spinlondon has described the maximum tripping times for circuits that are protected by ADS with an RCD. The circuits would also need overcurrent protection.
Ian1981 has described the trip times for the RCD as a item in its own right irrespective of its circuit connections.
Your trip time of 443ms would meet the requirements for the device as an RCD but would not meet the requirements for disconnection time for a final circuit on a TT system.
If it is only a 1 second disconnect time required then it will comply as it will trip with in 0.443 of a second.
The 100mA has being used upfront and a dual RCD board has being fitted with obviously 30mA protection for all final circuits.
Yes, it will comply for distribution circuits (1s), for which it appears to be being used, but not for final circuits (0.2s).
Sorry you said fi
If it's a metal consumer unit the 100mA will protect the internal link tails incase they short out to the metal case so will comply as it will be a 1 second disconnection time required
I'm confused, easily done.
A S Type Time delay RCD, to BS EN 61008-1 or 61009-1, trip times are 130 minimum to 500 maximum (ms), as per Table 3A. It cannot be adjusted, it does what it says (on the tin). So why are we discussing which circuits to put it on?
A time delay is ok for circuits with a 1 second disconnect time only on tt.
So circuits up to 32amps has to be 0.2 seconds disconnect time so if the rcd tripped above 200ms then although the rcd satisfies manufacturers times it won't satisfy the 0.2 disconnect time required for the circuit.
Hmmm, understand that. I also understand sockets, cables in wall less than 50mm etc etc, require 30mA RCD. I also note the use of 30omA RCD for fire protection, etc. An S Type 100mA has only one use?
The time delay is purely protecting the internal tail links in the metal consumer unit.
The consumer unit has 2 30mA rcds in it as stated by the OP I think.
So using a time delay 100mA on a domestic split load board in place of main switch.
Is that what you mean or i may be babbling?
Pretty much; S Type can only be used for a distribution circuit, although I might be wrong? OP was just asking for min/max times of S Type.
Yeah he did but as usual the thread went elsewhere
Time delayed RCDs are used for discrimination.
If the upfront RCD was not time delay, then a fault which would cause a downstream device to trip would most likely also cause the upfront RCD to trip.
Might as well only have the one RCD for the whole installation.
I understand that spinlondon, just wondered why there's been so many posts, when the OP just wanted 'the max trip time for a 100mA time delayed RCD'.
Separate names with a comma.