r.d.unit electrical box?

Answer 1

I think you have a sparrow in the guttering - take it out and it will work fine ;-)

Answer 2

A residual current device (RCD), or residual current circuit breaker (RCCB), is an electrical wiring device that disconnects a circuit whenever it detects that the flow of current is not balanced between the phase ("hot") conductor and the neutral conductor. The presumption is that such an imbalance may represent current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit. A shock, possibly lethal, is likely to result from these conditions; RCDs are designed to disconnect quickly enough to prevent such shocks.

Testing

RCDs can be tested to see if they are operational and/or they have been wired correctly.

It is a good idea to check RCDs monthly. One way to test an RCD is to press the button labelled "Test" or "T" on the RCD unit (which will simulate a ground fault by bypassing some current) and see if the RCD reacts by correctly opening the circuit. If it does not trip, the RCD should be replaced. Unfortunately, the test button is a fairly crude test and it is quite possible (though rare) for an RCD to trip on the pressing of the test button even when it would not pass a proper test involving passing known leakage currents and measuring the resulting trip time (and comparing those values to the requirements given in a standards document such as BS 7671). For example, an incorrectly wired RCD may still trip when the test button is pressed even though a real ground fault may not cause it to trip. Use of a solenoid voltmeter from live to earth may provide a more effective test of the RCD; such a test should be performed at least once upon installation of the device. The test should be repeated at every outlet "downstream" of the RCD to ensure that the downstream outlets are also wired correctly.

Answer 3

Never heard of it! Whats the question.?

Do you mean RCD ? if so what about it?