The RCD is tripping after few minutes of the light is on.

[biswajit]

I have done the new wiring in my garage with a new distribution box having a RCD and 4 MCB's. And now when I switch a light on, it works for 5 to 10 minutes and then suddenly RCD trips. Please advice what I can do to find the fault. Many thanks.

 

[DPG]

I have done the new wiring in my garage with a new distribution box having a RCD and 4 MCB's. And now when I switch a light on, it works for 5 to 10 minutes and then suddenly RCD trips. Please advice what I can do to find the fault. Many thanks.

Could you post your test results - we may be able spot something.

 

[Mike Johnson]

Switch off the three MCB's that do not supply the light, if after a time the RCD still trips then its a fault on the lighting circuit or unlikely a faulty RCD, if it does not trip then switch on another MCB and wait a while, if again the RCD does not trip, then repeat the same on the last MCB, this should identify the faulty circuit, in reality I would replace the MCB's with RCBO's this will isolate the fault to one circuit automatically and allow further investigation of that one circuit without cross faults causing confusion.

 

[nicebutdim]

Switch off the three MCB's that do not supply the light, if after a time the RCD still trips then its a fault on the lighting circuit or unlikely a faulty RCD, if it does not trip then switch on another MCB and wait a while, if again the RCD does not trip, then repeat the same on the last MCB, this should identify the faulty circuit,

The above won't eliminate anything if the fault is between neutral and earth.

 

[mainline]

in reality I would replace the MCB's with RCBO's this will isolate the fault to one circuit automatically and allow further investigation of that one circuit without cross faults causing confusion.

That would only be true if the rcbos were DP type ones.

 

[Mike Johnson]

Instead of just criticising why don't you two be pro-active and give some help.

 

[DPG]

OP, what testing has been done? Either during installation or for fault finding? What MFT do you have?

If you give us a bit more info we may be able to help.

Or is this a full DIY install with no testing?

 

[mainline]

Instead of just criticising why don't you two be pro-active and give some help.

Misinformation shouldn't just be ignored.

 

[Mike Johnson]

What misinformation, if the fault is on the phase side the information given is correct, read the first post, the RCD is tripping.

 

[mainline]

What misinformation, if the fault is on the phase side the information given is correct.

You gave a definitive answer that they could isolate the faulty circuit by turning off the mcb which isn’t correct.

You then said that it could be disconnected automatically by using an rcbo that’s not correct either as the N to E fault will still exist for SP type rcbos.



It wasn’t a criticism it was being helpful to the OP as your post stood it could serve only to cause the OP confusion thinking that the fault had been isolated.

I would also add that the proper way would be to disconnect and test the circuits rather than the way you suggested.

If the OP hasn’t a test meter I suggest getting one and preferably in the hands of a competent electrician.

 

[nicebutdim]

Instead of just criticising why don't you two be pro-active and give some help.

I don't believe doing so would be appropriate, without further information from the OP.

 

[Mike Johnson]

Read the first post, the OP is DIY and it's the RCD tripping so not an N to E fault.

 

[nicebutdim]

Read the first post, the OP is DIY and it's the RCD tripping so not an N to E fault.

The OP has just wired his garage and installed a new DB. There are any number of potential issues and I don't believe it's wise to provide much in the way of advice until we have more detail from them.

I'm not sure how you think an RCD works, but detecting an imbalance between line and neutral most definitely includes a neutral to earth fault.

 

[davesparks]

Read the first post, the OP is DIY and it's the RCD tripping so not an N to E fault.

RCDs can trip on N to E faults and the OP being DIY doesn't magically prevent this from happening.

 

[biswajit]

Could you post your test results - we may be able spot something.

I have not done any test other than continuity and polarity test. Please suggest what other test I need to do and I will try to find details of how to do those.

 

[biswajit]

The above won't eliminate anything if the fault is between neutral and earth.

I need help. This is first time I have done electrical wiring after my 42 year old Electrical Engineering understanding. So please help how I can resolve the issue. I have now done the test as you advised and found one particular circuit in a MCB is having fault. Like if I put some load in there the RCD trips. I need help to understand how to find the cause. Please be considerate as I am new to this DYI thing. I have also noticed the other two MCB's are causing the fault as I previously mentioned. Like RCD trips after few minutes of light switched on. And now I found that those two circuits MAY NOT be faulty at all. I am sauying this because I have also tested with just RCD is on and all three MCB's are off. And still my RCD trips after few minutes. That suggests my incoming power supply wire may have faults. How can I find what is causing this RCD trip while all MCB's are OFF.

 

[biswajit]

RCDs can trip on N to E faults and the OP being DIY doesn't magically prevent this from happening.

Please help me to solve my problem. like I may not understand your abbreviation so please be patient and kind with me.

 

[mainline]

Please help me to solve my problem. like I may not understand your abbreviation so please be patient and kind with me.

You need to do an IR (insulation resistance) test of each circuit.

 

[UNG]

I need help. I am sauying this because I have also tested with just RCD is on and all three MCB's are off. And still my RCD trips after few minutes. That suggests my incoming power supply wire may have faults. How can I find what is causing this RCD trip while all MCB's are OFF.

You obviously have a neutral earth fault which without the correct test kit will be difficult to find
As a DIY your best option would to completely discoonect all the circuits and reconnect them one at a time and switch on the RCD after connecting each one this should find the problem circuit

 

[westward10]

Have you notified Building Control of these works?

 

[Jock from the north]

I have not done any test other than continuity and polarity test. Please suggest what other test I need to do and I will try to find details of how to do those.

Follow the eic test result page .start with ring continuity including figure of 8.then choose between phase and earth connected together on al circuits or wonder lead method.r1 +r2 is preferred method for your type of install as it proves polarity.then do your ir test at 500 volts removing all lamps and vulnerable equipment .then start your live testing .loop impedance, rcd test at 30ma on type a setting .preceeeding this you would be carrying out the same tests for supply to dB maybe not rcd test if armoured supply.you will need a mft for this but it will NAIL down fault.no pun intended .