Random RCD trip

[multimods]

Could do with some help. Domestic RCD trip on main switchboard keeps going at random, unrelated to anything being switched on/off. Board has single Wylex 30mA trip unit about 14 years old. Takes down entire domestic supply. Sometimes goes days between trips, last night went twice within 5 minutes. Have large number of trailing sockets for computers, printers etc etc. Suspected new computer power supply, put a 30mA RCD adapter on that line. Unfortunately is an active type, so when supply next tripped, both the main board RCD went and the adapter. If I put in a passive unit, will that diagnose which line is going? If I put in a 10mA trip and it is on the correct line, might it diagnose the problem? Is there anything faster than 30ms at reasonable price? Any suggestions? Thinking of having old board replaced by unit with RCD unit on each circuit block. If is the computer power supply, is this a common problem, never personally seen it before. Thanks

 

[1john]

You got too much equipment that leaks to earth on one RCD.

 

[multimods]

Would it help to change the old board for one with an RCD on each pasrt of the domestic circuit. Presumably that would split the leakages and give a larger total permissible leakage? Electrician said 30mA too large, should be 10mA for a new board. Is that right?

 

[multimods]

Another question, pardon me. Is it worth borrowing an Earth Leakage Clamp Meter and checking each trailing lead? I don't know how sensitive they are, and if they work on a normal domestic trailing lead?

Cheers.

 

[JohnD]

Electrician said 30mA too large, should be 10mA for a new board. Is that right?

No. 30mA is correct.

However if your Consumer Unit is reasonably modern, you can fit an RCBO per individual circuit, which will prevent cumulative leakage from multiple circuits tripping a single RCD. RCBOs usually cost in the region of £30-£40 each.

Another question, pardon me. Is it worth borrowing an Earth Leakage Clamp Meter and checking each trailing lead? I don't know how sensitive they are, and if they work on a normal domestic trailing lead?

A Clamp meter measures current flowing one way in a conductor. It will not usually work on a 2-core or 3-core flex because current travels one way up one core, and the other way down the other core, and they cancel out. You can however put it round one or both meter tails, and it will tell you the current flowing in each, or the net difference if you put it round both.