Mains tripping

[ericmark]

Changing to RCBOs without even testing the existing RCDs

Not sure why this thread has been flagged up, but testing a RCD for not tripping is not as easy as one would think. I have put my RCD tester on the RCD, and it has shown well within spec, but changing it has removed the tripping problem.

Not a clue why, I know some RCDs were advertised as resisting spikes on the supply, so one assumes some did not. I have had one RCBO fail, and would not reset in my own house, and again in my own house had unexplained trips. But since all RCBO in the consumer unit, I could continue without any urgent hunting for faults.

For years, all I had was the RCD tester, an old one with no ramp test, so it tripped at 30 mA and did not trip at 15 mA was only test, so since not measuring the leakage, all I knew was it was less than 15 mA I did not have a clue if under 9 mA as required for back ground leakage, and this

543.7.1.1 Equipment having a protective conductor current exceeding 3.5 mA but not exceeding 10 mA, shall be either permanently connected to the fixed wiring of the installation without the use of a plug and socket-outlet or connected by means of a plug and socket-outlet complying with BS EN 60309-2.

fell on deaf ears, I had not way to measure 3.5 mA or for that matter even 10 mA my clamp-on meter measured in incruments of 10 mA so it was all trust to the lord. OK I had a insultation tester but they measure using DC, so do not show back-ground leakage.

But the installation certificate and minor works, did not require us to record the back-ground leakage, so it was simply not measured.

We were in 2008 don't have earlier versions to hand, required to

(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation

this is the whole reason we have circuits, and it did seem having only two RCDs was in essance meaning we only had two circuits, the MCBs only formed sub-circuits. But at that time, we really had no option, duel RCD consumer units were our only option, so all we could do is consider how the RCD would split the other circuits.

So with a house like this, wired sockets split front and back, and lights split up and down, to ensure someone who gets a shock from a socket circuit is not also plunged into darkness, only option was sockets on one RCD and lights on the other. With homes wired between the RCD and the RCBO they were often wired with sockets split up/down so they could match the lights so upper sockets were with lower lights, etc. This means with a RCD trip, people may be forced to run extension leads up/downstairs, but it was a risk assessment by the electrician.

Today with RCBO again we can split sockets side to side of the house, reducing the trip risk of extension leads up/downstairs.

So yes I would change to RCBOs before testing, in fact I did, there was one fault, where the neutrals were swapped on the upper and lower lights, and I found it reasonably quickly, and likely been like that since the house was built.

Testing before will show faults before we start, but if all faults are to be corrected, then why test twice? It all needs testing after the RCBOs are fitted, so testing before is only so one can price for correcting faults, so just add expense so that an estimate of cost can be generated, I see no electrical reason to test before starting, it is only done for costing.

 

[ebee]

the mains is tripping immediately when the washing machine

not really true then.sometimes does but sometimes doesn`,?