Home Electrical advice query not car not motorbike

[markw]

What trip rating does your RCD in the house have? If it's say 100mA , or even 30 mA, see if you can get a really tightly monitored RCD for the spur you want to put in. Say 10 mA. This way, only the 10mA RCD should trip in the event of an earth fault on that spur, leaving the rest of the installation unaffected.