Advice on fixing this outside mess

[nicebutdim]

All I’m doing is asking for some advice and trying to help a friend restore power to his sheds.

Here's some I posted earlier, perhaps you didn't see it.

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.

 

[RDB85]

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?

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.

 

[RDB85]

What distance does this cable have to be pulled through the conduit?

It’s about 10m 4m is a straight run horizontal. Then there is a bend around the corner. 4m straight run and then 2m vertical.

 

[RDB85]

What could I use to join the two boxes. If I have a Wiska box below and the RCD Enclosure above it.

 

[Diddy]

Im still somewhat intrigued as to how you have identified a break in the origional cable

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.

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....

 

[timhoward]

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.

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?

 

[Diddy]

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?

Would installing a big --- fan blowing along the length of it help at all ?

 

[davesparks]

What could I use to join the two boxes. If I have a Wiska box below and the RCD Enclosure above it.

If you are replacing the supply cable then take it straight to one of the sheds instead of trying to patch up that mess.

Don't just repeat the mistakes of the previous installer, think the job through and do it better than they did.

 

[RDB85]

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?

Okay so I’ll. change the protective device.

 

[RDB85]

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....

The cable has been completely cut somewhere in the garage ceiling. That’s why there was no reading. But as it was late and I’d seen the RCD had tripped and noticed the water ingress. I THEN went and looked in the Consumer unit and when trying to get continuity. There was no reading.

 

[nicebutdim]

The question I'd start out with is "what does your friend want to achieve?" and work backwards from that point.

Form the bare bones of a plan on the basis of their requirements, rather a length of cable you have to hand.

 

[westward10]

It’s about 10m 4m is a straight run horizontal. Then there is a bend around the corner. 4m straight run and then 2m vertical.

Good luck with that.

 

[Diddy]

The cable has been completely cut somewhere in the garage ceiling. That’s why there was no reading. But as it was late and I’d seen the RCD had tripped and noticed the water ingress. I THEN went and looked in the Consumer unit and when trying to get continuity. There was no reading.

That is now very clear and a replacement cable may well be the "best" solution. Now you would want to enquire what amount of power these units need. If it's somewhat less than the original 40 amps then cool, downrate the cable and the protective device. If Not then you simply either find the break and repair what's there OR install a cable rated the same as what's already there. I mean lets be clear, a whole new cable including conduit and a 10+ meter run which will all take time and money for materials is usually one of my last resorts in this type of scenario......it would seem slightly "mad" for someone to have cut the original cable to such an extent that it was now totally unusable and redundant, but then again you just never know with people.

 

[westward10]

Maybe it isn't cut at all as it hasn't been observed. Maybe it runs through another isolator.

 

[RDB85]

That is now very clear and a replacement cable may well be the "best" solution. Now you would want to enquire what amount of power these units need. If it's somewhat less than the original 40 amps then cool, downrate the cable and the protective device. If Not then you simply either find the break and repair what's there OR install a cable rated the same as what's already there. I mean lets be clear, a whole new cable including conduit and a 10+ meter run which will all take time and money for materials is usually one of my last resorts in this type of scenario......it would seem slightly "mad" for someone to have cut the original cable to such an extent that it was now totally unusable and redundant, but then again you just never know with people.

Okay so I’ve looked at what is currently fitted in the shed it has a small chest freezer 0.75 a 36w LED Light and a 44w LED Light. So I’ve worked out to 830watts so about 4 amp when divided by 240v.

 

[nicebutdim]

Maybe it isn't cut at all as it hasn't been observed. Maybe it runs through another isolator.

I'd pondered exactly this, but thought it unlikely that an isolator wouldn't have been left in an accessible position. Who knows?

 

[RDB85]

My friend also informs me that his mums bought a Lazy Spa. The 40a Type B MCB has been changed to a 20 amp. Looking at the power consumption and the lights and chest freezer it’s just under 16amp. Plus the RCD which is recommends in the manual.

 

[oscar21]

I'm not sure why some people make this assumption, but it certainly calls their competence into question.

Would they make similar assumptions about the rating of an isolator?

In case you hadn't noticed plenty of people who "mess" with electrics - kitchen fitters, DIYers, Dave from the pub and remarkably quite a lot of practicing electricians have zero competence. I just thought this one set them up way too easilly to fail.

 

[nicebutdim]

In case you hadn't noticed plenty of people who "mess" with electrics - kitchen fitters, DIYers, Dave from the pub and remarkably quite a lot of practicing electricians have zero competence. I just thought this one set them up way too easilly to fail.

Why should an industry adopt new practices to accomodate people who have no business using their products? Everything they need to know is either printed on the RCD or in included instructions - I doubt an extra warning label would encourage them to become any less ignorant.

 

[RDB85]

In case you hadn't noticed plenty of people who "mess" with electrics - kitchen fitters, DIYers, Dave from the pub and remarkably quite a lot of practicing electricians have zero competence. I just thought this one set them up way too easilly to fail.

Are you referring to me?