How can this be

24 May 2007
Reaction score
United Kingdom
A TT supply, tails from meter into Henley Block supplying house CU (split with main S100mA and 30mA side) and single 30mA RCD. This single RCD supplies (via SWA) garage supply which is a normal garage CU (30mA RCD main switch with a 16A and a 6A MCB) The garage has its own earth rod and has a Ze of 64OHMS. The armour is earthed at the garage end. The client is adamant that the garage CU, which does have some nuisance tripping, (mixture of new and rather old wiring) is tripping the house CU (main 100mA RCD). I say this is unlikely as the only common element is the main tails from the meter. Is this likely?
Sponsored Links
I suppose if there is a fault on the SWA cable it may trip the 100mA TD RCD. What sort of results do you get back from all of the RCDs? Hopefully you will be able to see that they will discriminate.
I take it things like lighting etc are on the 100mA TD side, I'd be tempted to look there.
Alternatively, you could fit a 100mA TD in another CU fed from the henley blocks for the garage supply, this will prove if it is the garage or not!

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links