Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 28 replies
  • Subscribers 32 subscribers
  • Views 2420 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Up front S type RCD tripping

Grobbyman
Rural setting. Two adjacent houses from the same pole.

The one I've been called to has had intermittent tripping problems on the 100mA S type RCD, it's TT, since just before christmas.

Seems to be no rhyme or reason and consumer unit 30 mA RCD's (two) not affected.

Called in on Friday and tested the upfront and tripping times good, ramp tested at 60mA.

Disconnected the only circuit not covered by the consumer unit RCD'd (garage) and asked them to keep an eye on it.


Called Friday night and told me it's tripping again.


Asked next door, who are in the process of rebuilding, whether anything new about christmas time.


Seems they got a new induction hob with boost facility then.


Turned it on, pressed the boost and low and behold next doors S type tripped.


Seems to do it everytime.


Doesnt affect the premises RCD's (30mA's).


Any explanations?


Had a look at the pole can't see anything amiss.


Regards


George
Parents
  • 0
    Are both houses TT, and is there any shared metal ?

    I assume the induction hob is doing two things, one is to inject some current into that houses CPC from the live, and the other will be to introduce a voltage drop in the neutral back to the transformer.

    The tripping house may be seeing its neutral to earth voltage twitching in step with the inrush of the cooker, either because the earth is  shared with the two properties, or becauuse the supply neutral is shared ?

    If it too has things with capacitance N-E this may make the RCD think it sees in imbalance.


    How much wiring is there between the type S and the 30mA RCDs that do not trip, and how high is the leakage (can you measure L-N imbalance with a clamp meter around both)  with the installation running before it is tripped - any chance of a partial N-E fault  due to water ingress or  pinched wire or something getting it uncomfortably close to that 60mA.

    Mike.

Reply
  • 0
    Are both houses TT, and is there any shared metal ?

    I assume the induction hob is doing two things, one is to inject some current into that houses CPC from the live, and the other will be to introduce a voltage drop in the neutral back to the transformer.

    The tripping house may be seeing its neutral to earth voltage twitching in step with the inrush of the cooker, either because the earth is  shared with the two properties, or becauuse the supply neutral is shared ?

    If it too has things with capacitance N-E this may make the RCD think it sees in imbalance.


    How much wiring is there between the type S and the 30mA RCDs that do not trip, and how high is the leakage (can you measure L-N imbalance with a clamp meter around both)  with the installation running before it is tripped - any chance of a partial N-E fault  due to water ingress or  pinched wire or something getting it uncomfortably close to that 60mA.

    Mike.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines