RCD tripping in consumer unit

[steve_moran38]

I have a standard consumer unit with lighting and socket MCB's positioned along the buzz bar. I have an RCD (80amp) protecting 2 MCB's both 32A - 1 for kitchen sockets and 1 for sockets elsewhere and boiler. I have just fitted a new induction cooker rated 45A with a 10mm cable direct back to its own MCB and positioned it on the buzz bar under the control of the RCD. So now have 3 MCB's protected by the RCD. It has now started to trip regularly. However I can deactivate any of the 3 MCB's and it works. Any ideas why this may be occuring ? Don't think it's a load issue but may be wrong.

 

[Spark123]

An RCD (RCCB) will detect imballance between L&N and trip, it doesn't detect overcurrent.
One possibility is the cooker is slightly leaky hence causing the tripping, possibly an accumultative effect over the 3 circuits pushing the RCD over the trip level.
It might have been better to install the cooker on it's own RCBO (RCD and MCB combined) on the non RCD side of the CU. Then when it trips you only lose the cooker, assuming of course you can get an RCBO for your board.

 

[ban-all-sheds]

I have just fitted a new induction cooker rated 45A with a 10mm cable direct back to its own MCB and positioned it on the buzz bar under the control of the RCD.

What were the results of your insulation resistance and RCD testing before you put this circuit into operation?

 

[steve_moran38]

thanks spark123. I understand what you're saying but the RCD doesn't trip when I have the cooker and 1 other MCB active. If I move the cooker MCB to the non protected side and it is this then will it trip the master switch ?

 

[Taylortwocities]

No, the master switch is a switch. It has no current limit or other fault-detecting properties.

It is important to get the answer to BAS's above question

What were the results of your insulation resistance and RCD testing before you put this circuit into operation?

I wouldn't go changing anything else until we know what the parameters are.

 

[Spark123]

Not sure what your "Master Switch" is? Can you post a photo?
Chances are that it is an isolator - these are basically an on/off switch and do not trip.
The only problem with moving the MCB to the non-RCD side is the requirement to protect any unprotected concealed cable in a wall/partition with an RCD. Also if there is a socket present on the CCU it should be on an RCD.
If you live in england/wales, installing a new circuit is notifiable under part p.

 

[martinxxxxxx]

I have just fitted a new induction cooker rated 45A with a 10mm cable direct back to its own MCB and positioned it on the buzz bar under the control of the RCD.

What were the results of your insulation resistance and RCD testing before you put this circuit into operation?

You seem to have ignored this very important question. It is not only a good idea to test circuits before you use in order to comply with the law, it is more important to make sure that they are working correctly (probably why there is a law covering the activity in the first place). Although staying the right side of the law is important too. If you did not test the new circuit the first time round. Then shuffling things about until they work does not strike me as a very sensible way to go about solving the problem. I think you should do some test and get to the root of the problem.

Martin