Faulty RCCB on old TT system

[edrobbo8]

I have a problem to sort out - it is a TT system with a faulty 80A 10mA RCCB after the meter and before the consumer unit. The board is very old style MCBs with no RCDs present.

The customer called me up because until about 6 weeks ago the front garden lights were causing the RCCB to trip. I went round to look at it and pressed the push to test button and it worked, plugged the Megger into a socket and it would not trip it on x1 or x5, the ramp test did nothing either.

So, to comply with current regs, can this faulty RCCB be replaced with a similar unit, or is it a new board?

 

[telectrix]

nothing to stop you replacing the RCCB. it's classed as maintenance. and why 10mA? are you sure it's not 100mA and you've typo'd or misread?

 

[Deleted member 9648]

Sraight swap for a 30ma to get out of trouble.....new CU with up front S type and RCBO's in an ideal world.

Edit.....just a thought...is there actually an earth?....if it trips on the test button it should operate with earth leakage. What was the Ze/Ra?

 

[edrobbo8]

Ze was 98 Ohms, so reasonable considering dry weather (this was a week or so ago). I am fairly certain it was 10mA which I thought was strange, but was in a rush so could have been 0.1A! Going back there on Saturday so will double check. Ideally yes new CU but money money money!

 

[edrobbo8]

I was going to replace with a Wylex insulated enclosure and DP 80A 30mA RCD.

 

[Had8Lives]

The old RCCBs only reacted to Live to Earth Faults (see the diagram inside the terminal cover). The test button connects a resistor across live and earth which energises the trip coil and switches off the power. I believe an RCD Test leaks current between neutral and earth, so won't trip an OLD RCCB. :smart:

 

[Guitarist]

I was going to replace with a Wylex insulated enclosure and DP 80A 30mA RCD.

You shouldn't really be replacing an old CU with a new one that has only 1 RCD.
If you want to replace it, then do so with either a high integrity board or a dual RCD board. Better still, and if space is limited, a board with a 100mA S-type main RCD and 30mA RCBO's.

 

[edrobbo8]

Thanks Guitarist, I was going to replace only the faulty RCCB with a 30mA RCD to cover the whole installation - as telectrix said it's maintenance! If I was replacing the whole board then I would use a split load board with dual RCDs.

 

[Engineer54]

Thanks Guitarist, I was going to replace only the faulty RCCB with a 30mA RCD to cover the whole installation - as telectrix said it's maintenance! If I was replacing the whole board then I would use a split load board with dual RCDs.

Not a particually good idea on any TT installation!!

Guitarist ...Better still, and if space is limited, a board with a 100mA S-type main RCD and 30mA RCBO's.

A much better protective set-up where a TT system is employed!!!

 

[rich.250]

Or just put a s type in place of the main switch in dual board...