Heard a sort of chattering sound from the MCB (30A) supplying one of the ring mains in our house this afternoon. Turn of the MCB, turn it back on again, all is ok for a little while (maybe 10 minutes?) then it starts again.
The circuit in question is one of four ring mains in the house, it supplies the sitting room, one bedroom , a socket in the hall, in the conservatory and the dressing room. generally lightly loaded - a few table/standard lamps, TV, VCR, DVD etc.
Whilst investigating this problem I noticed that when this circuit was switched on the disc on the meter started fair whizzing round - 30 rev/minute up from the say about 3 rev/minute is was doing normally.
My quick calcs indicate that 30 rev/min implies something like 10kW/h being consumed - around 40A? , or have I made some big boo-boo?
Anyway, there is nothing on the circuit drawing anything like that (no we don't have any secret electric showers, or unknown immersion heaters etc.) These symptoms continue to occur once everything on the circuit has been disconnected.
I've not had time today to investigate this more thoroughly, the circuit is isolated now via the MCB pending time tomorrow.
So, my thought so far is that there is some fault in the fixed wiring, causing a high current draw, and that the MCB is faulty in some way, hence the noise rather than tripping.
Does the above sound a reasonable diagnosis?
I can check out the MCB by swopping it with others in the CU I guess, if it is faulty then I'm not sure if replacing it is going to be a problem or not.
The CU is a pretty old Crabtree one, you can see a couple of piccies here:
Does anyone know if I will be able to find something to fit?
Thanks