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Topic Title: Existing Job....
Topic Summary: I'm 1000000% sure this is wrong but wanted to check!
Created On: 05 December 2012 07:54 PM
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 05 December 2012 07:54 PM
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djaonline

Posts: 26
Joined: 26 October 2012

Hi everyone,

Just been to look at a job installing sockets within a conservatory and saw something that came to my attention....

Very recently the customer had a new installation to a shed installed and I was scratching my head as to where the power was being fed from, the customer showed me and passed me the NIC EIC certificate issued, Here is the setup that was installed


From DB1 there is a 20A Radial Circuit protected by RCD
From a socket on the radial a 13A fuse spur has been installed
This 13A fuse spur has a SWA out of it to DB2 in the shed
DB2 then has 3 circuits
32A Radial on 2.5mm for Shed Socket
32A Radial on 2.5 for Outside Socket
6A Radial on 1.5 for shed light

Can I have some opinions/slash feedback as like I said in the summary I'm very very sure this is the wrong way to carry out this installation, I wouldn't carry it out this way and I have only been qualified 4 months, I hate picking at other people's work but it really caught my eye
 05 December 2012 08:01 PM
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daveparry1

Posts: 5879
Joined: 04 July 2007

It depends how much current they want to use in the shed, they will be restricted to a max of 13amps by the fused spur. Sometimes people only want enough power for a light and a socket for the lawnmower or electric drill etc in which case there's no problem,

Dave.
 05 December 2012 08:17 PM
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mossep

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As dave siad, it could be pefectly fine, all depends on what they want to do in the shed. There are many ways to skin cats!

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www.mossep.com
 05 December 2012 08:18 PM
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OMS

Posts: 18917
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Originally posted by: djaonline

Hi everyone,
Just been to look at a job installing sockets within a conservatory and saw something that came to my attention....
Very recently the customer had a new installation to a shed installed and I was scratching my head as to where the power was being fed from, the customer showed me and passed me the NIC EIC certificate issued, Here is the setup that was installed

From DB1 there is a 20A Radial Circuit protected by RCD

OK - then no problem with that - it sets an approximate limit on the peak shed capacity of around 5kW or 20A

From a socket on the radial a 13A fuse spur has been installed

Ok - sets a limit on the shed supply at 13A or 3kW

This 13A fuse spur has a SWA out of it to DB2 in the shed

OK - no problem with that - there is 30mA protection present as well as overload protection by the 13A fuse (backed up by the 20A MCB)

DB2 then has 3 circuits

OK - a bit mental but there you go

32A Radial on 2.5mm for Shed Socket

OK - the MCB is overated for the 2.5mm2 cable but the 2.5mm2 cable is still protected by the upstream 13A fuse for overload protection (and probably short circuit protection as well). The upstream RCD is giving additional protection and ADS - in essence, the MCB is only being used as a vague illusion of splitting up circuits

32A Radial on 2.5 for Outside Socket

Ditto above


6A Radial on 1.5 for shed light

Again, the MCB and cable combination is overated but not unsafe - overcurrent protection and additional protection are in place locally and upstream

Can I have some opinions/slash feedback as like I said in the summary I'm very very sure this is the wrong way to carry out this installation,

My observation would be that a single fault on an appliace plunges the user into darkness when the RCD trips - but that may not be a particular problem

I wouldn't carry it out this way and I have only been qualified 4 months, I hate picking at other people's work but it really caught my eye

Don't be afraid to call into question what you see - just recognise there is more than one way to skin a cat - and some are messier than others.
Get in the habit of checking against regulations as to why you think something is wrong

ie it's wrong because regulation XYZ says this - but what I'm seeing is that - it's a discipline that will stand you in good stead when you start tackling PIR's fault finding and remedial works during your career.




Try and find reg numbers for why you think the above is not OK - and also look for the reg numbers that perhaps you can link to my response - if you get stuck - shout - plenty people on here be willing to help. You'll learn lots, trust me - there is no substitute for a little self directed learning

Regards

OMS

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Failure is always an option
 05 December 2012 08:28 PM
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djaonline

Posts: 26
Joined: 26 October 2012

I do now understand what they have done just a strange design as I guess there is no need for 2 32A MCB's & a 6A. I have a lot to learn but glad I asked the question, I will still be extending kitchen ring as the house is split into 2 radial circuits, and I feel this is a better way

Thanks
 05 December 2012 08:33 PM
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daveparry1

Posts: 5879
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There was no need to install a c/unit in the shed, they could have just fed the socket from the swa and put a fused spur in to supply the lights!

Dave.
 05 December 2012 08:41 PM
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OMS

Posts: 18917
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Originally posted by: daveparry1

There was no need to install a c/unit in the shed, they could have just fed the socket from the swa and put a fused spur in to supply the lights!

Dave.


Yup - cheap, effective and totally compliant for about 99% of people who just want the convenience of a light and a bit of local small power in the shed.

Still - no doubt the original installer rinsed the client on the basis of "It's regs luv, gotta do it this way"

Regards

OMS

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Failure is always an option
 05 December 2012 10:37 PM
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Zs

Posts: 2627
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Originally posted by: OMS

Don't be afraid to call into question what you see - just recognise there is more than one way to skin a cat - and some are messier than others.

Get in the habit of checking against regulations as to why you think something is wrong

ie it's wrong because regulation XYZ says this - but what I'm seeing is that - it's a discipline that will stand you in good stead when you start tackling PIR's fault finding and remedial works during your career.






Try and find reg numbers for why you think the above is not OK - and also look for the reg numbers that perhaps you can link to my response - if you get stuck - shout - plenty people on here be willing to help. You'll learn lots, trust me - there is no substitute for a little self directed learning

Regards



OMS


Trust this forum dja. It has been my making and will be yours. never run away because somebody tells you you are stupid and makes your cheeks go pink (that will happen, but where are half of them now?) just keep on asking and then looking things up, and googling them.

Only when I got to the 32A breakers in the shed bit of yours did I wince. In terms of overload the 13A fuse is overseeing that installation and at least it is likely to be under-rated. Anything like a skilsaw or a karcher jet washer will take out that 13A fuse as you pull the on switch. But a simple greehouse heater and a light will be ok.

You are absolutely right, it is carp and to me it looks like the stock from the back of the van has been used without much thought for the breakers in the sub distribution board. That DB isn't doing much at the moment so you could take it out and use a fuse for the plugs and one for the lights. But probably best just to leave it in place. But the circuit is protected, after a fashion, by the 13A cartridge. They were robbed by that installer and his van-stock.

You could possibly give them more electrical welly in the shed by removing the fused spur and changing it for a small DB with appropriate breaker. How far away is the shed? How many Amps is the cable capable of delivering? We'll help you get to that number. Do they need any more than 13A?

I have a few jobs from my early years which I would like to revisit. None of them dangerous but all of them not well designed.

Keep asking and keep reading. I used to look on this forum in absolute awe and only ever asked things. Nowadays I speed read it and reply to questions like yours. But I try to look in every day. This forum is so valuable. So hang in with us. We go around in circles and we must be just about due for a question about the size of the earthing conductor between electrode and MET I reckon.

Zs

Edit: Who is the longest standing member/contributor to this forum who is still active on here? I'm thinking GB at the moment.

Edited: 05 December 2012 at 10:57 PM by Zs
 05 December 2012 11:08 PM
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ebee

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GB is everybodies uncle.
There area few other uncles too.
They tend to keep the rest of us on the straight and narrow

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 06 December 2012 05:08 AM
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Legh

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If the 20A radial in the house feeds one socket and then onto a fused spur. IMO, you could remove the fused spur, replace it with a JB (adaptable box).
Then down grade the 32A breakers in the shed to 10A. That might provide more discrimination. (not much under S/C conditions). Most domestic loads run at less than 2kW
Earth fault discrimination might be a different proposition, since the 20A radial is covered by a RCD which is most likely covering other circuits. I would personally like to see any circuits going outside to be separately protected for earth fault conditions, but that's just a personal preference.

There are various combinations that would be feasible and in line with the requirements with the regs.

However, a good design is what you would be looking for.
1/ Overload and S/C protection
2/ Earth fault protection
3/ Discrimination with series connected protective devices
4/ Segregation of circuits

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 06 December 2012 08:49 AM
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oneye

Posts: 158
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There could be various reasons why the shed feed is as wired, including reasons already mentioned.

I would like to believe the shed feed is temporary with the intention of a {planned} better link directly back to the main DB. My immediate neighbour has a shed which is not large dimensionally, but has lathe, heating and lighting, tools and extension to his house burglar alarm which I set off one day with the hedge trimmer.
 06 December 2012 09:44 AM
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whjohnson

Posts: 699
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I can understand the conundrum with the 32A mcbs and the 2.5 radials being a problem, but this?

Again, the MCB and cable combination is overated but not unsafe - overcurrent protection and additional protection are in place locally and upstream


What is wrong with he 1.5mm/6A mcb combination?

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 06 December 2012 11:01 AM
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OMS

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Originally posted by: whjohnson

I can understand the conundrum with the 32A mcbs and the 2.5 radials being a problem, but this?

Again, the MCB and cable combination is overated but not unsafe - overcurrent protection and additional protection are in place locally and upstream


What is wrong with the 1.5mm/6A mcb combination?


Nothing - I didn't say there was -

The MCB and cable combination is over rated - what's the CCC of 1.5mm2 cable - wouldn't 1.0mm2 on a 6A MCB have more than taken care of it

With a 13A fuse in circuit upstream, what's the point of a 1.5mm2 conductor capable of carrying 17A

The lighting is effectively controlled by an upstream RCD which is providing additional protection (but probably an issue with coordination)

Does that clarify my comment ?

Regards

OMS

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Failure is always an option
 06 December 2012 11:10 AM
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OMS

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Edit: Who is the longest standing member/contributor to this forum who is still active on here? I'm thinking GB at the moment.


GB, Andy Jewsbury, Paul Skyrme and Sparkingchip I think

The rest of us are but yuffs in comparison

OMS

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Failure is always an option
 06 December 2012 03:55 PM
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Legh

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The rest of us are but yuffs in comparison


What on earth is a YUFF ?

legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 06 December 2012 04:07 PM
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ebee

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Young Undesirable Flammable Farts.

Actually it is Welsh for Youths

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 06 December 2012 04:21 PM
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OMS

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LoL - the youth of today, Ebee - we were never like that at that age (or so we like to think)

Once you start to sound like your Dad, it's game over unless you start to misbehave again -

Regards

OMS

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Failure is always an option
 07 December 2012 01:32 AM
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Legh

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Well, nothing is new, is it?
We always referred them as: 'ABF' which of course one would have to watch out for the blow back The seventies equivalent to the 'SBC'....

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 07 December 2012 01:38 AM
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OMS

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Nope - nothing is new Legh - same s11t - different day

Regards

OMS

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Failure is always an option
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