Discuss Advice on fixing this outside mess in the UK Electrical Forum area at ElectriciansForums.net
I suppose everything has a price point. It could be quite a bit more expensive overall to manufacture a 100A rated RCD compared to a 25AI had the same problem a few months ago, my mate was looking at some wiring in a food wagon and he rang me for advice on what to do next, he says there is a 32A RCD protecting the installation without any breakers and I said well if its a 32A RCD then it must be an RCBO so its covered but he was adamant it was just an RCD, when he sent me a picture and I looked a bit closer it dawned on me that it was indeed just an RCD.
If it said 63A or 80A etc the you would automatically assume its just an RCD without any other protection, its just the fact that it has a low value on it that I think loads of people will think its an MCB as well, same as the 20A and 25A ones that are also knocking about. Just doesn't make any sense to me to have all that different tooling to make different rated RCD's when a 100A would cover everything, the cost on saved metal must be minuscule.
Other than having been disconnected is there anything wrong with the existing cable?With that now the culprit. I’ve ordered a vent plug for the Wiska Box. Some Wago 222 Connectors and something to connect the Wiska Box and RCD enclosure.
In hindsight singles would probably be better but I’ve got 30m of NYY and the price of cable and also selling the NYY.
Why are you going to replace the cable?
Are you going to reconnect it?
In hindsight singles would probably be better but I’ve got 30m of NYY and the price of cable and also selling the NYY.
This whole scheme has alarm installer written all over it.
Don't conform to stereotype.
Hmm as an electrician I tend to check the source of power 1st and then work from there. You also seem convinced that you need to run a new cable...but only in your last post do you state/imply that the armour cable has been cut "somewhere".
If something is outside your normal work/comfort zone sometimes it is better to just accept it and get a person in that knows this type of work well.
Not knowing how to do something isn't embarrassing or anything like that, But winging it and guessing is wrong on so many levels. You could get someone in and even learn from them for next time.....
I’m not trying to. But you really don’t like anyone that works in that field. Also the original install was done by a qualified spark. What’s wrong with NYY or do you have a better suggestion.
It’s a bit obvious that a new cable is needed as it’s anyone’s guess as to where it’s been cut. Maybe as the RCD was off I also decided to look in the enclosure. As you know it’s outside and all.
The posts in this thread indicate you knew this was obvious a whole day before learning the cable has apparently been cut.
Incredible foresight on your part
It was a tongue in cheek post, but not entirely inaccurate.
Your suggestion of replacing the cable cable prior to the apparent discovery that it has been cut. You reasoning behind using NYY was based on 'having all cable of the same construction' and later 'because you had some to sell'. I'd love to understand the reasoning behind all of this, but accept that I'll never know the facts.
As for what I'd do? Well I'd make decisions based on what exists and what needs to be achieved. The very things people have been trying to learn from you since yesterday, but apparently you're only bringing you make that assessment after already deciding on part of a planned way forward.
I'm all for trying to draw a line as many on here would like to help you. My gentle suggestion is to just admit mistakes and move on. It's not like we don't all make mistakes too. I'm sure you've already learned things from this. e.g. assume nothing and work methodically when fault finding (find out what does work first)Okay so what currently exists is an RCD and an outside box. Two radials done in 4mm NYY. And a 1.5mm SWA that’s been cut. I’ve 30m of NYY which I’ve decided to use as selling it online is a right pain and with the price of cable going up it’s not worth buying new cable when the NYY seems appropriate cable to use.
I’ve also got some 25mm Galv Conduit and an assortment of Saddles and End and Through Boxes.
All I’m doing is asking for some advice and trying to help a friend restore power to his sheds.
All I’m doing is asking for some advice and trying to help a friend restore power to his sheds.
Galv conduit would certainly provide good mechanical protection. @timhoward raises the issue of CCC - I don't know the differences between SWA and NYY off the top of my head, nor the correction factor when enclosed in conduit, but you may need to increase cable size and also that of the conduit.
I'm all for trying to draw a line as many on here would like to help you. My gentle suggestion is to just admit mistakes and move on. It's not like we don't all make mistakes too. I'm sure you've already learned things from this. e.g. assume nothing and work methodically when fault finding (find out what does work first)
So, you currently have a B40 device for the supply circuit. Is this RCD protected in the garage board or not?
Have you got a cable that's CCC exceeds 40 amps after appropriate deratings?
Until you have the supply circuit design sorted you can't move on to the details.
Brief research shows that 4mm NYY-J clipped direct is rated under 40 amps, so by the time it's in galv conduit I'd doubt this is going to cut it. So you may need to rethink the protective device and/or the cable.
Does that get you started?
What distance does this cable have to be pulled through the conduit?
Cut it where ? Inside the consumer unit or elsewhere. Is it the case that the cable is inches short now or is there an as yet unidentified break in the original cable? Ir came back nothing ? Unsure what that means. Continuity came back nothing - I assume that means you didn't get a reading when you tested each core to say earth for continuity ?Right so I’ve done some further investigation back at the consumer unit in the garage. Tested for Continuity and IR and got nothing. Open up the Consumer unit to find that when it was converted into a room. They decided to cut it. So the feed that goes from there to the RCD is no more.
The NYY-J is what was left over from the previous installation for both shed radials.
Agreed. Has the penny dropped that this presents a problem?I know we all make mistakes. I’ve learnt from it. Every day is a school day as the saying goes. If designing the circuit the CCC Table 4D2A
3 core in conduit is 27 amps in Conduit and 32 amps Clipped Direct.
Would installing a big --- fan blowing along the length of it help at all ?Agreed. Has the penny dropped that this presents a problem?
If the cable is at risk of starting to melt above 27 amps loading, is a 40 amp MCB of any help to avoid this scenario?
What could I use to join the two boxes. If I have a Wiska box below and the RCD Enclosure above it.
Agreed. Has the penny dropped that this presents a problem?
If the cable is at risk of starting to melt above 27 amps loading, is a 40 amp MCB of any help to avoid this scenario?
Im still somewhat intrigued as to how you have identified a break in the origional cable
Cut it where ? Inside the consumer unit or elsewhere. Is it the case that the cable is inches short now or is there an as yet unidentified break in the original cable? Ir came back nothing ? Unsure what that means. Continuity came back nothing - I assume that means you didn't get a reading when you tested each core to say earth for continuity ?
But how could you test for continuity without opening up the consumer unit 1st ? You do know to do a continuity test you must somehow create a loop for the test to be conducted. Be that through a long lead or using traditionally the earth as your potential loop .....and so on.
I still think you should be mentored for this instance just so that you have the practical knowledge next time. But if my questions and what I have said sound harsh there IS a point to them - You could be turning a 30 min fix into a day long job....even if you are doing it for a friend and doing it free of charge so no ulterior motive....It's simply preferable to fix what is there (If no unidentified break in the cable elsewhere) as opposed to starting again ....I/We are trying to save you some time and possibly money and as already mentioned maybe even saving you from installing a cable in a manner that renders the install "incorrect" with regards to cable size and OC protective device selection....
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