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Thread: RCD tripping with lightning

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    RCD tripping with lightning

    Hi - I have read a number of threads re. RCD's and earth leakage - many thanks to those that have contributed especially AndyD. I have had more sparkys through my house than friends and i still have some issues - which i'd like some advice on. I don't plan on solving this myself but would like to be better informed when I select my next electrician.

    I have a largish house (800m2) on a 3000m2 property with five occupants and the expected lots of electrical devices. 4 geysers and about 20 outside lights.

    1. When there is lightning my RCD trips almost every time. My neighbors houses do not trip. Often times the lightning is so far away I can count a few counts between seeing the lightning and hearing the thunder. It has been like this for years.
    From what ive read I should:
    - get an electrcian that has a ramp tester
    - second RCD
    - replace original if faulty
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    2. One of my external light circuits is tripping the isolator at the DB board (located at the pool) but also the main DB board in the house. This circuit has 11x40W energy savers on it and is about 120m long. The cable is buried well underground. Worked fine for year and now seems to trip with wetness or moisture (the circuit works in winter in JHB). How can i test to see where the fault could be. What i am considering is:
    - if i cant find the fault at a light fitting i dont want to dig up the cable as the garden is established
    - run a new cable above ground to the old light fitting
    - if that the problem then replace the light fittings.

    3. Any (good) electricians on this forum that do work in Midrand that want to tackle my issues.

    Many thanks is advance for the advice.

  2. #2
    Diamond Member AndyD's Avatar
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    Is that your main DB? I don't see any overload protection....

    Can you safely turn off the supply and give us a couple of pics of the inside and a pic of the full DB including all the circuit breakers? If you can't isolate the power rather don't, please don't remove the cover when it's live. I'll pop back when I have more tim,e later.
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  3. #3
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    Quote Originally Posted by AndyD View Post
    Is that your main DB? I don't see any overload protection....

    Can you safely turn off the supply and give us a couple of pics of the inside and a pic of the full DB including all the circuit breakers? If you can't isolate the power rather don't, please don't remove the cover when it's live. I'll pop back when I have more tim,e later.
    Thanks Andy. Do you travel to JHb

    Note on the front cover of the DB board:
    Click image for larger version. 

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    The whole DB board from the front. The circuits that are down are simply due to needing them on at the moment. They are working fine.
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    Top Row of isolators:
    Had the thinggie (three green lights on) on the right installed by some chap on his recommendation -meant for lightning.
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    Middle row... They geyser timers were installed sometime in 2013 by one of eskoms guys. When i checked last year one wasn't actually connected to a geyser! (when it showed off the geyser would still be on)
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    Bottom row..
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    The two large plugs are for a UPS installation that feeds two circuits of the house only. An electrician did it but I got the feeling he was doing his apprenticeship at my cost. Works fine though.

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    and here is inside the DB board
    Click image for larger version. 

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    This is the DB board that is "Fed"from the large DB board. On the large board it has the RDC labelled as "DB2" next to the the switch RDC.
    When the large (3 switch) RDC trips this smaller DB board still has power.

    Click image for larger version. 

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    I think this is the answer to your overload question. This is outside the garage. When i switch this off the large DB board and the smaller one have no power.
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    Click image for larger version. 

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    Diamond Member AndyD's Avatar
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    Yeah, there's several obvious compliance issues such as geysers which are fixed appliances on single pole breakers, what looks like 2.5 wiring supplied by 25A circuit breaker but difficult to tell from pic, lack of isolation for UPS supply, surge protection which is just duplicating the protection you have in the external box, overload protection in subDB is way oversized for supply wiring size....I could go on but most of this is off topic as it has no bearing on your RCD nuisance tripping issue.

    One question, if the triple pole RCD (labelled 'earth leakage' top left) trips do the green lights on the surge protectors (top right) go out or do they remain lit?
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    Hi

    Reading the posts above , I could not restrain myself from answering and hopefully I have not missed RCD's in the attached pic's

    If I was called to have a look at the installation I would not bother taking out any test equipment and would expect you to be tripping on your main RCD intermittently, bordering on absolutely annoying.

    RCD's will trip when they reach 30mA of leakage to earth - Every appliance has a leakage to earth , some more than others and the worst offenders are heater elements , computers , transformers (UPS) , ants creating a nest in outside fittings , Lightning protection arrestors etc

    The sub DB appears to be fed from the main DB 3 phase RCD - If there is a fault under the sub DB RCD it could sometimes trip the 3 phase RCD in the main DB first as there does not appear to be discrimination

    If for argument sake we said that every appliance has 1mA leakage then 30 appliances connected under the RCD will trip the RCD without any actual fault.29 Appliances would allow the RCD to behave but a little moisture in the air and the extra 1mA to earth will suddenly appear and trip your unit.
    The 1mA is just for easy calculation and explanation.Each appliance varies and in any installation can change depending on what is being used at any stage and the age of the appliance.

    I would strip out the 3 phase RCD , I only see single phase equipment , and install multiply single phase RCD's - In my own house I have 5 units installed and I do not have a 800sqm house with 5 occupants

    This way you should reduce the potential leakage to earth on each unit and you can avoid putting unnecessary items onto the RCD's eg light circuits, depending on the application and installation.
    It will also make life easier to determine where the fault is actually coming from as the circuits under each RCD will be reduced instead of checking the complete installation every time there is a trip.

    We have found that in 80% of installations with 1 RCD and intermittent tripping , once we install an extra 2 or 3 RCD's we solve the intermittent tripping problem.

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    Quote Originally Posted by AndyD View Post
    Yeah, there's several obvious compliance issues such as geysers which are fixed appliances on single pole breakers, what looks like 2.5 wiring supplied by 25A circuit breaker but difficult to tell from pic, lack of isolation for UPS supply, surge protection which is just duplicating the protection you have in the external box, overload protection in subDB is way oversized for supply wiring size....I could go on but most of this is off topic as it has no bearing on your RCD nuisance tripping issue.

    One question, if the triple pole RCD (labelled 'earth leakage' top left) trips do the green lights on the surge protectors (top right) go out or do they remain lit?
    @AndyD - when the triple RCD trips the three green lights on the surge protectors stay illuminated.

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    Thanks GCE: am starting to wonder how I bought the house with an ECC.

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    Quote Originally Posted by carlog View Post
    This is the DB board that is "Fed"from the large DB board. On the large board it has the RDC labelled as "DB2" next to the the switch RDC.
    When the large (3 switch) RDC trips this smaller DB board still has power.

    Click image for larger version. 

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    I think this is the answer to your overload question. This is outside the garage. When i switch this off the large DB board and the smaller one have no power.
    Click image for larger version. 

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ID:	7037

    Click image for larger version. 

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    Where is the large DB located? (Is it in the garage, or somewhere else?)

    Quote Originally Posted by GCE View Post
    The sub DB appears to be fed from the main DB 3 phase RCD ...
    Possibly not.

    What I'm trying to figure out is whether the "large" DB is the "main" DB, and where is the main switch disconnector for the entire installation.

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