100mA RCD tripping problem
- Thread starter dx90
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Richard, the RCD and the 60947 main switch are interchangeable. But JD is correct. In TT the 100mA RCD must preceed any enclosure that is metal.
I see this often where a metal enclosure with a switchfuse has been installed next to the meter with a long (16mm eg) tail to a remote CU.
RCD has to go between the meter and the switchfuse.
I see this often where a metal enclosure with a switchfuse has been installed next to the meter with a long (16mm eg) tail to a remote CU.
RCD has to go between the meter and the switchfuse.
Richard1
can you please explain in some more detail on what you mean?
Has my CU been put in wrong?
If yes then how should it be according to the regs?
My CU is plastic not metal.
securespark
What do you mean by there is no compliance with this?
I did ask him about a TD RCD and he just bypassed what I said. He said he could fit a 300mA RCD that might stop the tripping but he thought it might not and that they are expensive to buy.
can you please explain in some more detail on what you mean?
Has my CU been put in wrong?
If yes then how should it be according to the regs?
My CU is plastic not metal.
securespark
What do you mean by there is no compliance with this?
I did ask him about a TD RCD and he just bypassed what I said. He said he could fit a 300mA RCD that might stop the tripping but he thought it might not and that they are expensive to buy.
I will confess that I am an RCBO enthusiast. the 100mA RCD could then be taken out and replaced with a DP isolator (but kept on the shelf in case it is needed in future)
What do other members think about putting the remaining 4 circuits on RCBOs? I admit it should be overkill, and parts would cost £160, but it seems to me it has a very high probability of (1) stopping the nuisance tripping that put the who installation off and (2) pointing its finger at the guilty circuit.
Were it not for the cost of having the electrician come back on repeat calls (which would probably cost more) it would be possible to buy just two RCBOs, and swap them between circuits for a week or so.
I know it's easy for me to say because I have crates of the things
What do other members think about putting the remaining 4 circuits on RCBOs? I admit it should be overkill, and parts would cost £160, but it seems to me it has a very high probability of (1) stopping the nuisance tripping that put the who installation off and (2) pointing its finger at the guilty circuit.
Were it not for the cost of having the electrician come back on repeat calls (which would probably cost more) it would be possible to buy just two RCBOs, and swap them between circuits for a week or so.
I know it's easy for me to say because I have crates of the things
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Could some one please explain how my CU is wired/feed so I can understand better?
I think the main power comes into the 100mA RCD and then feeds the 30mA rcd.
Where can I buy some wylex NSB TYPE B RCBOs?
I have looked and can't fine any.
Do I keep the 100mA RCD and just change the 4 MCBs for 4 RCBOs?
Once I understand it fully and know exactly what I'm doing I will then be able to do a proper job with it.
I think the main power comes into the 100mA RCD and then feeds the 30mA rcd.
Where can I buy some wylex NSB TYPE B RCBOs?
I have looked and can't fine any.
Do I keep the 100mA RCD and just change the 4 MCBs for 4 RCBOs?
Once I understand it fully and know exactly what I'm doing I will then be able to do a proper job with it.
dx90 said:Could some one please explain how my CU is wired/feed so I can understand better?
I think the main power comes into the 100mA RCD and then feeds the 30mA rcd.
YES. A busbar comes out of bottom of the first RCD, and feeds the first set of breakers; and a thick copper link goes from the load side (bottom) of the first RCD to the Supply side (top) of the second RCD. the Neutral from the first RCD goes into the first neutral strip, and a thick copper link goes from here to the Supply side (top) of the second RCD. the Neutral from the bottom of the second RCD goes to the second Neutral strip, and it is very important that the neutrals of all the circuits on that side, go to that strip.
Where can I buy some wylex NSB TYPE B RCBOs?
I have looked and can't fine any.
Not me, sorry
Do I keep the 100mA RCD and just change the 4 MCBs for 4 RCBOs?
If I were you, I would fit a 100A DP isolator instead, once you have the RCBOs fitted. Same source. Say it's for a NSB CU. Wil be about a fiver.
Once I understand it fully and know exactly what I'm doing I will then be able to do a proper job with it.
It is very important to have the power to the CU cut before you do that work. my prefernce is to have a 100A DP isolator in the tails between the meter and the CU so that it can be safely isolated. The suppliers fuse must be out before this is done. Your supplier can probably arrange this for about £60, or might possibly do it free.
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To comply with regs, there should be discrimination between RCD's. ie they must not trip together, or the 100mA one must not trip instead of the 30mA one. Without a TD incomer, there is every chance this could happen.
It must be a TD RCD the 100mA one. Or fit two independent feeds to the RCD's.
It must be a TD RCD the 100mA one. Or fit two independent feeds to the RCD's.
Hi DX90
I had to fit a wylex plastic NH series consumer unit to a TT system 3 weeks ago, because there was no isolating switch, I tried to purchase a 100ma Time delayed RCD to swop out the main double pole isolator, I could not find one that was compatable with the NH enclosure, so I rang wylex help desk , they advised that with this consumer unit not to remove the main switch as it could lead to faulty RCD action, but to install the 100maTD RCD (100/2) in a separate enclosure,
I had to fit a wylex plastic NH series consumer unit to a TT system 3 weeks ago, because there was no isolating switch, I tried to purchase a 100ma Time delayed RCD to swop out the main double pole isolator, I could not find one that was compatable with the NH enclosure, so I rang wylex help desk , they advised that with this consumer unit not to remove the main switch as it could lead to faulty RCD action, but to install the 100maTD RCD (100/2) in a separate enclosure,
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Wylex produce a dedicated TT CU....NHSTM range
And their 2 pole 100mA TD RCD code is WRMT 100/2.
We often buy a standard split-load board & swap out the incomer with a WRMT 100/2.
And their 2 pole 100mA TD RCD code is WRMT 100/2.
We often buy a standard split-load board & swap out the incomer with a WRMT 100/2.
MK do a special extra insulation kit specifically for having a TT incomer in a metal enclosure.Taylortwocities said:
As I understand it anything before the main RCD cannot be protected by EEBADS so it must be protected by class 2 insulation but class 2 insulation does not nessacerly preclude the outer case being metal.
Being pragmatic. I have TT system; RCBOs on shower and main (socket) circuits with 30mA RCCB on the remainder and no problems. With JohnB all the way. I have had a fault on one RCBO which tripped but left all else working. I don't know (and am not sure how to prove) that this would always show discrimination and eliminate your problem, but it is reassuring to know the system works safely. HTH
JohnB?
that's a Sloop.
http://www.jacquedee63.com/sloopjohnb.html
http://www.youtube.com/watch?v=H_KY_d9MQv8
that's a Sloop.
http://www.jacquedee63.com/sloopjohnb.html
http://www.youtube.com/watch?v=H_KY_d9MQv8
You have to be a bit carefull with RCBOs on a system where they are fed from another RCD some of them don't isolate the neutral so in some circumstances a N-E fault can end up still present after they trip which in turn can trip a RCD further upstream even if it's a time delay type.
Afaict usually double module RCBOs isolate the neutral but single module ones do not.
Afaict usually double module RCBOs isolate the neutral but single module ones do not.
Just an update, on things this way. I am in the process of elimination by unplugging an appliance one at a time every time it’s not in use, to see what one is causing the tripping. But this method is very slow. I will ask more questions and keep you up to date as I go along.
Thanks
Thanks
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