Time delayed RCD

[squinky]

Hello all! just joined the forum as I am keen DIYer!
I would consider myself to have a fairly good knowledge of DIY.
Just a quick question about a time delayed 100mA RCD.
I had a fuse board with a 30mA rcd and a 100mA time delayed rcd in the board.
I fitted a separate board and took out the 30mA circuits from the old board and fitted them to the new board.
Now in the old board I have only the 100mA time delayed trip covering the circuits.
Question is as I dont have a 30mA rcd in this board anymore will the time delayed work ok as the 100mA or do I have to get a normal type 100mA trip.
I know from reading posts on this forum that the new 17th edition boards are in and everything must be covered with a 30mA.
But I prefer to stick to the 100 if possible as its been working that way this past 10 years and I don'y really want to change the whole board!
Thanks

 

[Spark123]

The reason for using a TD RCD is to provide discrimination between the 2 devices i.e. if a fault on a 30mA protected circuit caused 150mA to flow then the 100mA device delay allows the 30mA RCD to deal with the fault.
What sort of items are you putting on the 100mA TD device? It probably wont matter that much tbh, as long as your disconnection times are met.

 

[squinky]

Thanks for the reply spark123! The circuits on the 100mA side are- cooker, oven, Immersion heater, central heating and lights.
Do you think then that the 100mA will work just as a normal 100mA trip?
It should tripout in the required time that its supposed to if there was a fault on any of the circuits?
Thanks

 

[securespark]

Have you got a TT supply?

 

[squinky]

Hi securespark! Yes checking with a hand-book which I have - it is TT. There is an earth spike within an inspection chamber out the back.
Thanks!

 

[securespark]

In that case you should not dispense with your existing RCD protection...