Posting a message to the forum will remove the above advertisement

Discuss Time delayed 100mA RCD in the Electrical Forum area at ElectrciansForums.co.uk.

Please make sure you checkout our forum sponsors, many do discounts for members and, they keep the forum free to use.
  1. Sb8389
    Offline

    Sb8389 Regular EF Member

    Location:
    Nottingham
    Hi guys
    Quick question
    Does anyone know the max trip time for a 100mA time delayed RCD
     
  2. spinlondon
    Offline

    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    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.
     
  3. Sb8389
    Offline

    Sb8389 Regular EF Member

    Location:
    Nottingham
    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.
     
  4. spinlondon
    Offline

    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Again, it depends on the circuit.
    If it's the upfront RCD, 2 secs.
    Maximum Ze/Zs is 500 ohms.
     
  5. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    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.
     
    • Agree Agree x 1
    Last edited: Apr 19, 2017
  6. spinlondon
    Offline

    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Sorry, yes 1 sec, used to be 2 secs.
    I did remember in my first post
     
  7. Richard Burns
    Offline

    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    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.
     
  8. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    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.
     
  9. Sb8389
    Offline

    Sb8389 Regular EF Member

    Location:
    Nottingham
    The 100mA has being used upfront and a dual RCD board has being fitted with obviously 30mA protection for all final circuits.
     
  10. Richard Burns
    Offline

    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    Yes, it will comply for distribution circuits (1s), for which it appears to be being used, but not for final circuits (0.2s).
     
    • Agree Agree x 1
  11. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    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
     
  12. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    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?
     
  13. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    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.
     
  14. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    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?
     
  15. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    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?
     
  16. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    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.
     
  17. Ian1981
    Offline

    Ian1981 Electrician's Arms

    Location:
    North east
    Yeah he did but as usual the thread went elsewhere :)
     
    • Funny Funny x 1
  18. spinlondon
    Offline

    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    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.
     
  19. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    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'.
     
    • Like Like x 1
Loading...
Similar Threads - delayed 100mA Forum Date
100ma RCD TNS - Condition Report Electrical Wiring, Theories and Regulations Sep 25, 2017

Share This Page

Users found this page by searching for:

  1. electrcian max time delay

  • Electricians Directory Post a Domestic Job Post a Commercial Job