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Electric shower fault

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    #32
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Sleeper12 wrote: »
    My very first comment. :)

    Dont get overly excited just yet:D


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    #33
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Sleeper12 wrote: »
    Question for the electricians on the page. If full consumer board was fitted by reci electrician last year and he installed a 32amp should he come back and fit correct one for free?
    Can't OP contact RECI itself if he can't get him back?

    They probably should come back. Id say getting them back is another story probably.


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    #34
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    Sleeper12 wrote: »
    Question for the electricians on the page. If full consumer board was fitted by reci electrician last year and he installed a 32amp should he come back and fit correct one for free?
    Can't OP contact RECI itself if he can't get him back?

    It would depend on the cable size feeding whatever it is feeding.

    The CPD protects the cable, not the load.


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    #35
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Steve wrote: »
    It would depend on the cable size feeding whatever it is feeding.

    The CPD protects the cable, not the load.

    The funny thing is about fixed appliances such as a shower, there is no real possibility of the cable becoming overloaded.


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    #36
    Sleeper12
    Registered Users Posts: 17,097 ✭✭✭✭Sleeper12


    Steve wrote:
    It would depend on the cable size feeding whatever it is feeding.

    Steve wrote:
    The CPD protects the cable, not the load.


    But 32amp is always undersized for an 8.5kw shower regardless of the cable size & the length of the run? Or am I wrong on that? I'm happy to be corrected on this. Genuinely curious


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    #37
    Sleeper12
    Registered Users Posts: 17,097 ✭✭✭✭Sleeper12


    Bruthal wrote:
    Dont get overly excited just yet


    I'm just poking fun. Op won't know for a few weeks yet if replacing rcbo sorts the problem.


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    #38
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Sleeper12 wrote: »
    But 32amp is always undersized for an 8.5kw shower regardless of the cable size & the length of the run? Or am I wrong on that? I'm happy to be corrected on this. Genuinely curious

    Yea but the cable should be sized for the 40 amp breaker.


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    #39
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Sleeper12 wrote: »
    I'm just poking fun. Op won't know for a few weeks yet if replacing rcbo sorts the problem.

    I know, so am I. With the OP now saying its a 32 amp rather than the original 40 amp mentioned, and mentioned that it seems to happen more often when showers are longer, its likely the problem.


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    #40
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    Sleeper12 wrote: »
    But 32amp is always undersized for an 8.5kw shower regardless of the cable size & the length of the run? Or am I wrong on that? I'm happy to be corrected on this. Genuinely curious

    Doesn't matter what the load is, if the cable is too small it will melt if you put a bigger breaker in than it can handle.

    Showers (8kw) should be wired using 10sq but there could have been 6sq installed which means max 32A CPD.


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    #41
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Steve wrote: »
    Doesn't matter what the load is, if the cable is too small it will melt if you put a bigger breaker in than it can handle.
    Slightly ott there imo.


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    #42
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    Bruthal wrote: »
    The funny thing is about fixed appliances such as a shower, there is no real possibility of the cable becoming overloaded.

    There is if 6sq (or smaller) is used. OK for short bursts but not for prolonged use.


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    #43
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    Bruthal wrote: »
    Slightly ott there imo.

    Ok, to be more precise, it wont actually melt, it will harden and the insulation will break down and crack over a long period of time which will eventually cause it to short and heat up... even then it won't melt but will do it's thing (provided its LSF) and turn straight into carbon and do it's best to not propogate a fire into the rest of the environment... :P

    It's easier to say 'it will melt' to a non electrical person :D


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    #44
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Steve wrote: »
    Ok, to be more precise, it wont actually melt, it will harden and the insulation will break down and crack over a long period of time which will eventually cause it to short and heat up... even then it won't melt but will do it's thing (provided its LSF) and turn straight into carbon and do it's best to not propogate a fire into the rest of the environment... :P

    It's easier to say 'it will melt' to a non electrical person :D

    Well what I mean is, if you put a 200 amp breaker on a 6 square cable to a shower, it still wont automatically start melting, or harden.


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    #45
    Steve
    Moderators, Category Moderators, Entertainment Moderators, Sports Moderators Posts: 22,584 CMod ✭✭✭✭Steve


    Bruthal wrote: »
    Well what I mean is, if you put a 200 amp breaker on a 6 square cable to a shower, it still wont automatically start melting, or harden.

    Correct, but if you were only replacing the consumer unit (which is the scenario described), how do you know what is on the far end?
    If you see 1.5sq, more than likely it is a light circuit but it may not be.. do you put a 20A breaker on cos maybe they've connected a 3kw heater in the attic? No, you put a 10A on because its 1.5sq :)


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    #46
    John T Carroll
    Closed Accounts Posts: 757 ✭✭✭John T Carroll


    Steve wrote: »
    Ok, to be more precise, it wont actually melt, it will harden and the insulation will break down and crack over a long period of time which will eventually cause it to short and heat up... even then it won't melt but will do it's thing (provided its LSF) and turn straight into carbon and do it's best to not propogate a fire into the rest of the environment... :P

    It's easier to say 'it will melt' to a non electrical person :D

    I did alot of basic calcs a good few years ago before I installed my Electric Shower and here are a few extracts (just my calcs, mind).

    8.5 KW Shower running at a nominal 230V with a 10 Meter run (20 Meters "To & From")
    Using 10 M2 cable. Shower Output: 8.41 Kw, Circuit current: 36.76A, Cable losses: 0.71 watts/Foot
    Using 6 M2 cable. Shower Output: 8.35 Kw, Circuit current: 36.62A, Cable losses:1.17 watts/Foot


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    #47
    Sleeper12
    Registered Users Posts: 17,097 ✭✭✭✭Sleeper12


    Steve wrote:
    It's easier to say 'it will melt' to a non electrical person


    I like this one better. :)


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    #48
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Steve wrote: »
    Correct, but if you were only replacing the consumer unit (which is the scenario described), how do you know what is on the far end?
    If you see 1.5sq, more than likely it is a light circuit but it may not be.. do you put a 20A breaker on cos maybe they've connected a 3kw heater in the attic? No, you put a 10A on because its 1.5sq :)

    Good point. But presumably any installer will actually check what appliances are on what breakers, and test run them.

    A 40 amp breaker wont really overload a 6 square cable to melting point with an 8.5kw shower on it. If it did, then the 10 square will also be overheating.

    But anyway, you make a good point. The electrician may have seen a 6 square cable, and wouldnt put anything more than a 32amp rcbo on it.


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    #49
    John T Carroll
    Closed Accounts Posts: 757 ✭✭✭John T Carroll


    John T Carroll wrote: »
    I did alot of basic calcs a good few years ago before I installed my Electric Shower and here are a few extracts (just my calcs, mind).

    8.5 KW Shower running at a nominal 230V with a 10 Meter run (20 Meters To & From)
    Using 10 M2 cable. Shower Output: 8.41 Kw, Circuit current: 36.76A, Cable losses: 0.71 watts/Foot
    Using 6 M2 cable. Shower Output: 8.35 Kw, Circuit current: 36.62A, Cable losses:1.17 watts/Foot
    Sleeper12 wrote: »
    I like this one better. :)

    This is the one I was really looking for:
    9.5 KW Shower running at a nominal 230V with a 10 Meter run (20 Meters To & From)
    Using 10 M2 cable. Shower Output: 9.38 Kw, Circuit current: 41.05A, Cable losses:0.855 watts/Foot
    Using 6 M2 cable. Shower Output: 9.31 Kw, Circuit current: 40.88A, Cable losses:1.46 watts/Foot


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