Discuss A lighting CB wont re-set and shower CB rating query. in the Australia area at ElectriciansForums.net

alw94

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I completed the wiring on an extension of some relatives of mine and certified it about 5 months ago. Now, the main part of the house has some old wiring and I have fixed, repaired and moved sockets and lights but I haven't carried out any testing on this side of the house. The extension wiring is mine from start to finish and is all checked out. I have just had a call to say that a week ago both RCDs tripped and that that since then the CB for downstairs lights won't re-set. Now, instead of phoning me, they contacted Southern Electric as they have one of those monthly service contracts. He has commented on the shower I fitted (9.5kw shower/10mm cable) being on a 50a CB. At the time I was looking for a 45a CB but, as far as I remember, Wyles don't do a 45a CB, so did a bit of checking and plumped for the 50a CB thinking that this and the 10mm cable would also allow for any changes in future. The guy from Southern Electric had to phone his boss who have recommended as 32a CB. This can't be right can it? Looking at other posts I think I'm on safe ground. Any comments from you folk?

Now, he hasn't checked anything else - actually, it's not clear at all just what he has done - but the downstairs lighting circuit still won't re-set. All I have done to this circuit before was to change a pendant and used this circuit for the smoke alarm in kitchen and hall. Considering that all was well for 5 months this problem has only occurred after both RCDs tripped. Could it be as simple are bulbs blown causing problems? I've asked them to switch all lights off, re-set CB and then go around switching on one room at a time but they are not even sure of some of the lights are on or off as they are dimmers. I live 200 miles away and they want me to go down to sort it out but am really pushed to find the time. Any helpful tips from you folks about assessing the possible problem before making the trip?

It, of course, is making me feel uneasy about whether I've done something wrong but short of not quite tightening wires up, I can't really see what. It doesn't help that it took 5 days for them to come to me. Instead they went to Southern Electric, an apprentice friend of their son and other people who all have a comment to make. When I first spoke to them they apparently had problems with sockets I fitted but I think we've got to the bottom of those and they are ok.
 
shower wise i#m in the same dilemma as i can only git a 40 or 50 amp rcbo as i'm using 10 ml and its just taking 42 amps and the 32 is completely wrong
 
manufacturers like to exagerate the current draw of their appliances.....same for cookers n all....hence your diversity you can apply....first 10A then 30% of anythin left...unless using a cooker with a socket built in then you add 5A...seeemples.....
 
Checked a 10.5kW shower the other day and it was pulling 43A and on a 40A rcbo with 10mm cable. mcb was warmish (only just so prob anout 40 degrees) after running for approx 20min. I guess it would be better on a 45 or 50A rcbo but that was on full hot for more than normal so I decided to ok it.
 
Checked a 10.5kW shower the other day and it was pulling 43A and on a 40A rcbo with 10mm cable. mcb was warmish (only just so prob anout 40 degrees) after running for approx 20min. I guess it would be better on a 45 or 50A rcbo but that was on full hot for more than normal so I decided to ok it.
well under normal operating conditions...cant see the users turning it up full.....and burning themselves....this is the thing....you get people wanting these showers with crazy outputs and they never get anyware near there full potential...mad innit.......
 
Agreed glenspark, that is why I left the 40A rcbo. Any way the operating temp is around 50-60 degrees I recall with a trip time of around an hour at I=1.15xIn or thereabouts.
 
Cheers for the quick replies. I need to check it was a 9.5kw because something made me go up to the 50a rather than the 40a. It may be that it was a 10.5 but I haven't got my notes to hand. If I phone them they won't know either. I used this for my assessment and nothing was mentioned then.

Any tips on the lighting circuit as, if I have to go, it'll have to be done in a day, as I haven't the time to stay longer. Not looking forward to this as it's a 5am start and won't get back to 9-10pm depending on what needs to be done.
 
Cheers for the quick replies. I need to check it was a 9.5kw because something made me go up to the 50a rather than the 40a. It may be that it was a 10.5 but I haven't got my notes to hand. If I phone them they won't know either. I used this for my assessment and nothing was mentioned then.

Any tips on the lighting circuit as, if I have to go, it'll have to be done in a day, as I haven't the time to stay longer. Not looking forward to this as it's a 5am start and won't get back to 9-10pm depending on what needs to be done.
so did you ask the inevitable question.."have you had any work done sinse i was here last"?.....IR mate on the offending circuit......at the board first to verefy theres either a short circuit or a breakdown in insulation and remember to disconnect anything electronic being fed from this circuit first wont you mate as you could fry it..lol....
 
then if/when you have verefied theres an IR problem then you can seperate the circuit at the various points on the string......till you find the portion thats causing it....test strappers in both directions wont you n all as it may be something they`v hammered into the wall...hanging pictures or whatever..lol.....
 
10mm twin and earth depending on the installation method ie clipped direct can be rated at 63 amps check the current capability of the cable in the way that it's installed a 50 amp breaker may be fine, regardless of the power of the shower being less
 

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