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  1. #1
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Help with electrics.

    20191005_094849.jpg20191005_094940.jpg

    Had a heater in my q/t which went wrong and tripped the electrics in the house.
    Have changed the heater and works fine now, but if something goes wrong in the future I dont want it tripping the house electrics.
    It is a 500watt heater wired to this trip plug via the elitec 1000,from the one plug it goes to the main box which is in my garage and serves the garage only.
    The plug goes to a 5amp trip switch which didn't trip but the one in the house did.
    Ideally I want the 5amp to trip if something goes wrong,so what do i have to do please?
    Hope you understand it ok.


    John

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  3. #2
    Senior Member Rank = Mature Champion RS2OOO's Avatar
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    Frim is your man for this.

    A lot of these breakers have a far greater tolerance than their rating so I'd guess the tolerance of the trip switch is greater than the breaker in the house.

    A 5 amp fuse should be more than adequate for a 500w heater. Are you sure there's not a fault with it?

    What size is the breaker in the house that tripped? And if the circuit is RCD protected are you sure it wasn't the RCD that tripped and not the breaker?

    With my CU only the specific breaker trips after an overload, but the whole house goes out if the RCD trips.

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  5. #3
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Thanks Rs, maybe a faulty 5amp but wouldn't the trip on the plug have blown instead?
    The one on the house is the main one with just on/off on it and it tripped all the power points in the house.

    Yes Frim is the electric man.
    John

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  7. #4
    Senior Member Rank = Mature Champion RS2OOO's Avatar
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    The plug looks like a 13 amp to me John, not sure if you can get 5 amp ones but would be ideal if you could.

    Yes, you'd have thought the RCD on the plug would have gone first. Did the plug definitely not get tripped then and didn't need resetting?

    What size is the breaker in your house?

    Mine are 32amp for ring circuits, 20 amp for radial circuits and 6 amp for lighting circuits.

    My Garage runs off a 32 amp breaker fitted in the house CU, but I fitted the secondary CU in the garage with a 20 amp for (radial 4mm) sockets and 6 amp for the lights. If I plug in 4x 3KW heaters in the garage then the 20 amp garage breaker goes but the 32 amp house one stays on.

    If I touch live (or earth) and neutral together in the garage then the house RCD goes and cuts all power to everything.
    Last edited by RS2OOO; 05-10-2019 at 01:17 PM.

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  9. #5
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Thanks for reply Rs not too hot on electrics but know the basics.
    Mine is the same in the house 32amp to garage,I have a second control unit in the garage and all is 15 amp bar the heater which is 5amp.

    Maybe that's what happened Rs with the faulty heater and the neutral earthed so tripping the house,could that be.
    Dont like doing as you say touching cables together

    Should have said the plug went as well.
    John

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  11. #6
    John, it sounds like an earth fault to me if I am reading your posts correctly?

    An MCB is only designed to trip on an overload but will also trip on a live to earth fault but not a neutral to earth fault. An RCD is designed to trip on both live and neutral to earth faults but not an overload. An RCBO is designed to trip on both live and neutral to earth faults as well as an overload.

    What sometimes happens is if you have a powerbreaker socket, plug in adapter or plug is if you have an RCD or RCBO linked to the same circuit that may trip and not the powerbreaker device as the RCD or RCBO may already have a small amount of earth fault on it where as the powerbreaker device doesn't if that makes sense? So basically the powerbreaker device requires 30 mA to trip if it is rated at 30 mA that is but the RCD or RCBO may trip at 20 mA even though it is rated for 30 mA.
    This is referred to as discrimination. The way round it could be to fit a 10 mA powerbreaker device if you can find one and plug your heater into that. This may help if you get small earth faults but may not if you get bigger earth faults which may still trip the RCD or RCBO.

    When I say powerbreaker device I mean a socket, spur, adapter or plug with a built in RCD. Powerbreaker adapters and plugs usually have 13 amp fuses in which can be replaced with something of a lower ampage but it's possible to trip the powerbreaker device and not blow the fuse in the powerbreaker device and vice versa depending on the type of fault you get.

    Hope this helps

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  13. #7
    Powerbreaker spurs have replaceable fuses as well before anyone says anything

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  15. #8
    Senior Member Rank = Mature Champion RS2OOO's Avatar
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    Quote Originally Posted by john1 View Post
    Dont like doing as you say touching cables together

    Should have said the plug went as well.
    I should have pointed out, when I touched the cables together the power supply to the garage was switched off. It still blew the RCD in the house though as it would have detected the change in potential via the neutral cable as all the neutrals, whether RCD protected or not, go to a single terminal in the main CU.
    Last edited by RS2OOO; 05-10-2019 at 04:15 PM.

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  17. #9
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Quote Originally Posted by RS2OOO View Post
    I should have pointed out, when I touched the cables together the power supply to the garage was switched off. It still blew the RCD in the house though as it would have detected the change in potential via the neutral cable as all the neutrals, whether RCD protected or not, go to a single terminal in the main CU.
    Thanks Rs understand the neutral bit as they are all joined together.
    John

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  19. #10
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Quote Originally Posted by Frimley Koi keeper View Post
    John, it sounds like an earth fault to me if I am reading your posts correctly?

    An MCB is only designed to trip on an overload but will also trip on a live to earth fault but not a neutral to earth fault. An RCD is designed to trip on both live and neutral to earth faults but not an overload. An RCBO is designed to trip on both live and neutral to earth faults as well as an overload.

    What sometimes happens is if you have a powerbreaker socket, plug in adapter or plug is if you have an RCD or RCBO linked to the same circuit that may trip and not the powerbreaker device as the RCD or RCBO may already have a small amount of earth fault on it where as the powerbreaker device doesn't if that makes sense? So basically the powerbreaker device requires 30 mA to trip if it is rated at 30 mA that is but the RCD or RCBO may trip at 20 mA even though it is rated for 30 mA.
    This is referred to as discrimination. The way round it could be to fit a 10 mA powerbreaker device if you can find one and plug your heater into that. This may help if you get small earth faults but may not if you get bigger earth faults which may still trip the RCD or RCBO.

    When I say powerbreaker device I mean a socket, spur, adapter or plug with a built in RCD. Powerbreaker adapters and plugs usually have 13 amp fuses in which can be replaced with something of a lower ampage but it's possible to trip the powerbreaker device and not blow the fuse in the powerbreaker device and vice versa depending on the type of fault you get.

    Hope this helps
    Thanks Frim,suppose you were busy doing the q/t.

    Understand bits but not a lot.

    Here is the story,bought a 1kw s/s heater element from China (dont shout ) when it arrived looked ok,but it only had two connecters,live and neutral,so I thought WHAT no earth so put one on the body.

    Fitted it all and tested it working ok.

    Left for a while in the water switched off,then when I needed heat switched it on and tripped everything.
    Didn't want to mess any more so took it out and put an aquarium one in and ok.
    So,have I done wrong with the earth?
    John

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  21. #11
    If you have earthed something that doesn't need to be earthed then potentially yes it is not a good idea. If the heater is double insulated then it doesn't require an earth connection as it has been made so internally it shouldn't be possible for a live or neutral cable to come into contact with the outter casing. The symbol for a double insulated item is a square with a smaller square inside it. If I was using my laptop and not my phone I would find you a link to a double insulated symbol.

    In the end you did the correct thing - disconnected the heater and asked the question

    Double insulated or not if the heater is faulty it will take out RCDs, RCBOs, MCBs and fuses etc etc.

    As it is a 1 KW heater and it's running through a controller it may be drawing a bit more than 1 KW as the controller is using power too. Not much but maybe both together enough to push the total power consumption up enough to trip a 5 amp MCB specially if it is an old one that is starting to wear out and become more sensitive than it should be? 1 KW is just over 4 amps at 240 volts.

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  23. #12
    Quote Originally Posted by RS2OOO View Post
    I should have pointed out, when I touched the cables together the power supply to the garage was switched off. It still blew the RCD in the house though as it would have detected the change in potential via the neutral cable as all the neutrals, whether RCD protected or not, go to a single terminal in the main CU.
    I always say to people the neutral earth issue knocking out RCDs etc even when an MCB is switched off puts the "arse" into RCD

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  25. #13
    Senior Member Rank = Mature Champion RS2OOO's Avatar
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    Quote Originally Posted by Frimley Koi keeper View Post
    I always say to people the neutral earth issue knocking out RCDs etc even when an MCB is switched off puts the "arse" into RCD
    Glad you said that mate cos there's a lot of sparks who'll tell you it's impossible to trip an RCD with the circuit switched off.

    Sent from my Pixel 2 using Tapatalk

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  27. #14
    Quote Originally Posted by RS2OOO View Post
    I should have pointed out, when I touched the cables together the power supply to the garage was switched off. It still blew the RCD in the house though as it would have detected the change in potential via the neutral cable as all the neutrals, whether RCD protected or not, go to a single terminal in the main CU.
    You kind of correct about the common neutral bar as in an consumer unit fitted before 2007? before the 17th Edition Regs came out consumer units had common neutral terminals and common earth terminals but when the 17th Edition Regs came out you had to fit what is referred to as a split load board which has 2 or more RCDs controlling serval MCBs each so you have RCD protection but if you get a fault you don't loose the power to everything and with these consumer units each RCD has it's own neutral bar. You also have the option to use a standard style consumer unit with a common neutral bar and fit RCBOs in it. Expensive option but less tripping issues.

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  29. #15
    Quote Originally Posted by RS2OOO View Post
    Glad you said that mate cos there's a lot of sparks who'll tell you it's impossible to trip an RCD with the circuit switched off.

    Sent from my Pixel 2 using Tapatalk
    Bell ends !!! An MCB only switches the live off but leaves the neutral connected so a neutral to earth fault will still trip an RCD.

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  31. #16
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Thanks Frim,so I bin it

    Hopeless at electrics I even bought a multimeter to try and check the heater but dont know how to use it
    John

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  33. #17
    Some RCDs will even trip with no power going to them as we have tried to test the resistance across the terminals of an RCD out of a consumer unit sitting on the desk and it still trips as is registers the voltage given off by the continuity tester as an in balance in current going through the RCD. That's how sensitive they are. I think we were testing a 30 mA double pole RCD. Maybe a 100 mA RCD could be possible to test?

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  35. #18
    Senior Member Rank = Mature Champion RS2OOO's Avatar
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    I'm guessing at 30ma even if the circuit being tested is in close proximity to another circuit it might be able to induct a current.

    Not sure if that's possible but it is in my head.

    Sent from my Pixel 2 using Tapatalk

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  37. #19
    Extreme Koi Member Rank = Grand Champion john1's Avatar
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    Hey Frim, cant you speak English or better still Irish !!!

    Sorry mate you are losing me.
    John

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  39. #20
    Get it checked first John the resistance between the live and neutral wires should be 60 ohms. That will prove the resistance is correct. Then depending how high your meter will read you need to check the resistance between the live cable and the case and also the neutral cable and the case. Normally you need an insulation resistance tester to test to the case as the readings should be above 500000 ohms or 0.5 million ohms.

    Sorry I didn't speak Irish lol but to you I may as well be speaking Latin lol

    Can you tell me exactly what tester you have so I can tell you how to use it? Never try to test for resistance on a live circuit as it could knacker the tester. Unless the tester instructions say otherwise always dead test for resistance OK.

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