What would you code this as.

[Vortigern]

The point of the fuse preceding the cable is that the fault current in the cables cannot reach a point that the cables would basically melt/explode due to current. i.e. the fuse is there to protect the cable so we would expect to find the rating of the fuse before the cable supplying the next submain would be lower then the cable rating in very simple terms. There is no way of knowing that in the future someone would not increase that load. But I am thinking of a short on the cables coming from the henley box that would be the problem there.

 

[Electrics]

The 6mm cable is basically a sub main feeding the 2way CU in the out building, therefor a suitably sized s/fuse should be fitted at the supply end to protect the cable , at present its relying on the DNO fuse.

What's the difference electrically between this coming from 100a incoming fuse to RCD protection in the shed and a regular 100a supply going to RCD protection in a CU?

 

[Raptor0014]

There are some people in this forum that are jumping on the wrong bandwagon here. Maybe you should all take a deep breath and actually read the OP properly and if unsure ask me questions.

Rather than reply to every post individually I will update here.

Firstly yes I am a fully qualified, and registered with CPS, electrician. However, although qualified I lack experience as have only been fully qualified etc since Feb.

I am fully aware there are a no. of issues and I have coded them already on the certificate.

Eg,

SWA not terminated (it is glanded at the other end)
Single insulation exposed
Cables not supported
Undersized cable in relation to the OCPD (the cutout which is the query I had)
The covers for the connectors are actually just balancing (which you can't tell from the pic)
There is no earth sleeving/tape on the black insulated conductor

When I do the certificates I like to ensure I give the client as much accurate information as possible.

I was asking specifically about the size of the SWA and the fact there is no OCPD. I even stated in the OP that I had coded it as a C2. Maybe I should have been clearer but what I was getting at was my C2 code correct or did anyone think it warranted a C1?

The client mentioned it has been fine for the last 8yrs or so and I said they had been lucky then as there is nothing to stop that cable pulling 80a when it's designed at most to pull 47a if it were clipped direct.

I am acutely aware that my qualifications don't trump experience. I knew it was wrong, I had already coded it as such. What I wanted to ensure was that I was giving the client accurate information.

The one thing I will ALWAYS do if I am unsure is ask, hence my post here, even if it opens me up for potential ridicule. I'd rather be thought a fool and learn by asking a question, than keep quiet and get it wrong.

Peace, out!!

 

[freddo]

Maybe I should have been clearer but what I was getting at was my C2 code correct or did anyone think it warranted a C1?

I'd go for C2.

 

[Pretty Mouth]

There are some people in this forum that are jumping on the wrong bandwagon here. Maybe you should all take a deep breath and actually read the OP properly and if unsure ask me questions.

Rather than reply to every post individually I will update here.

Firstly yes I am a fully qualified, and registered with CPS, electrician. However, although qualified I lack experience as have only been fully qualified etc since Feb.

I am fully aware there are a no. of issues and I have coded them already on the certificate.

Eg,

SWA not terminated (it is glanded at the other end)
Single insulation exposed
Cables not supported
Undersized cable in relation to the OCPD (the cutout which is the query I had)
The covers for the connectors are actually just balancing (which you can't tell from the pic)
There is no earth sleeving/tape on the black insulated conductor

When I do the certificates I like to ensure I give the client as much accurate information as possible.

I was asking specifically about the size of the SWA and the fact there is no OCPD. I even stated in the OP that I had coded it as a C2. Maybe I should have been clearer but what I was getting at was my C2 code correct or did anyone think it warranted a C1?

The client mentioned it has been fine for the last 8yrs or so and I said they had been lucky then as there is nothing to stop that cable pulling 80a when it's designed at most to pull 47a if it were clipped direct.

I am acutely aware that my qualifications don't trump experience. I knew it was wrong, I had already coded it as such. What I wanted to ensure was that I was giving the client accurate information.

The one thing I will ALWAYS do if I am unsure is ask, hence my post here, even if it opens me up for potential ridicule. I'd rather be thought a fool and learn by asking a question, than keep quiet and get it wrong.

Peace, out!!

Fair play @Raptor0014 , hope you won't be deterred from asking in the future ?

 

[MJPD29]

Doing an inspection and came across this.

Feeds are as follows:

Cutout to Meter - 25mm
Meter to connector blocks - 25mm
Connector blocks to CU’s (2 in the house) 16mm.

So far so good as the cutout is 80A not the 100A it’s labelled as.

My query is the 6mm 3 core XPLE that’s going to an outbuilding.

At the outbuilding end is 2 way CU with a 40 RCD switch and a 16a socket & 6a light circuit.

Now I know the RCD will stop the cable ever pulling more than 40A. But as it’s wired into those connectors it has the potential to pull 80a (in theory).

I’ve coded it as a C2 as to me it’s potentially dangerous given there’s no OCPD protecting the cable from the connector until it reaches the RCD in CU in the outbuilding. It’s been there approx 8yrs according to the owner and there are no signs of thermal issues anywhere at either end. But thought I’d garner opinion from the more experienced/knowledgeable folk on here.

What would you code it as? Or would you deem it safe given the RCD at the other end?

View attachment 91498

The RCD will most definelty not stop the cable from pulling more than 40a. It offers no overload protection whatsoever. As for your coding your correct with c2.

 

[ferg]

There are some people in this forum that are jumping on the wrong bandwagon here. Maybe you should all take a deep breath and actually read the OP properly and if unsure ask me questions.

Rather than reply to every post individually I will update here.

Firstly yes I am a fully qualified, and registered with CPS, electrician. However, although qualified I lack experience as have only been fully qualified etc since Feb.

I am fully aware there are a no. of issues and I have coded them already on the certificate.

Eg,

SWA not terminated (it is glanded at the other end)
Single insulation exposed
Cables not supported
Undersized cable in relation to the OCPD (the cutout which is the query I had)
The covers for the connectors are actually just balancing (which you can't tell from the pic)
There is no earth sleeving/tape on the black insulated conductor

When I do the certificates I like to ensure I give the client as much accurate information as possible.

I was asking specifically about the size of the SWA and the fact there is no OCPD. I even stated in the OP that I had coded it as a C2. Maybe I should have been clearer but what I was getting at was my C2 code correct or did anyone think it warranted a C1?

The client mentioned it has been fine for the last 8yrs or so and I said they had been lucky then as there is nothing to stop that cable pulling 80a when it's designed at most to pull 47a if it were clipped direct.

I am acutely aware that my qualifications don't trump experience. I knew it was wrong, I had already coded it as such. What I wanted to ensure was that I was giving the client accurate information.

The one thing I will ALWAYS do if I am unsure is ask, hence my post here, even if it opens me up for potential ridicule. I'd rather be thought a fool and learn by asking a question, than keep quiet and get it wrong.

Peace, out!!

This is unfortunately the nature of internet forums sometimes.

In fairness this one is not too bad in comparison to others. The mods here made a real effort to get it that way and continue to make an effort to keep it so.

 

[Electrics]

The client mentioned it has been fine for the last 8yrs or so and I said they had been lucky then as there is nothing to stop that cable pulling 80a when it's designed at most to pull 47a if it were clipped direct.

How were they lucky? Sorry i'm confused.

Cables don't just pull 80a just because they're attached to an 80a fuse.

If he's only got lights and sockets on the end of that SWA which are also RCD/MCB protected i fail to see how it can ever pull 80a. Even if you put five hundred electric rads in the shed the shed's CU will trip long before that cable can ever pull more than 80a, surely?

Or am i getting this totally wrong?

 

[Julie.]

How were they lucky? Sorry i'm confused.

Cables don't just pull 80a just because they're attached to an 80a fuse.

If he's only got lights and sockets on the end of that SWA which are also RCD/MCB protected i fail to see how it can ever pull 80a. Even if you put five hundred electric rads in the shed the shed's CU will trip long before that cable can ever pull more than 80a, surely?

Or am i getting this totally wrong?

Because it's not just overload that an overcurrent device protects against, if there were to be a fault at the remote end of the swa then it could draw say 150A, which would take 1000 or so seconds to blow the dno fuse (~100 secs at 200A etc) this could result in the swa overheating and causing fires.

Of course it depends on the Zs at the remote end, it could have a decent fault current level and blow the dno fuse earlier. But by having the correct size fuse for the overload protection and fault protection would eliminate this.

Arguably it doesn't need overload protection, but it must have fault protection, and the dno fuse is unlikely to achieve this, there is also a dno requirement to provide one's own fuse for longer runs

 

[Electrics]

Because it's not just overload that an overcurrent device protects against, if there were to be a fault at the remote end of the swa then it could draw say 150A, which would take 1000 or so seconds to blow the dno fuse (~100 secs at 200A etc) this could result in the swa overheating and causing fires.

Of course it depends on the Zs at the remote end, it could have a decent fault current level and blow the dno fuse earlier. But by having the correct size fuse for the overload protection and fault protection would eliminate this.

Arguably it doesn't need overload protection, but it must have fault protection, and the dno fuse is unlikely to achieve this, there is also a dno requirement to provide one's own fuse for longer runs

So electrically how is this different from the tails going from 100a incomer to CU?

 

[Julie.]

So electrically how is this different from the tails going from 100a incomer to CU?

Compare the realistic Zs between an installation having a decent length of 6mm^2 and 1/2 metre of 25mm^2.

Also the 16 or 25mm^2 can take much more current than 6mm^2 before overheating the same.

 

[HappyHippyDad]

There are some people in this forum that are jumping on the wrong bandwagon here. Maybe you should all take a deep breath and actually read the OP properly and if unsure ask me questions.

Rather than reply to every post individually I will update here.

Firstly yes I am a fully qualified, and registered with CPS, electrician. However, although qualified I lack experience as have only been fully qualified etc since Feb.

I am fully aware there are a no. of issues and I have coded them already on the certificate.

Eg,

SWA not terminated (it is glanded at the other end)
Single insulation exposed
Cables not supported
Undersized cable in relation to the OCPD (the cutout which is the query I had)
The covers for the connectors are actually just balancing (which you can't tell from the pic)
There is no earth sleeving/tape on the black insulated conductor

When I do the certificates I like to ensure I give the client as much accurate information as possible.

I was asking specifically about the size of the SWA and the fact there is no OCPD. I even stated in the OP that I had coded it as a C2. Maybe I should have been clearer but what I was getting at was my C2 code correct or did anyone think it warranted a C1?

The client mentioned it has been fine for the last 8yrs or so and I said they had been lucky then as there is nothing to stop that cable pulling 80a when it's designed at most to pull 47a if it were clipped direct.

I am acutely aware that my qualifications don't trump experience. I knew it was wrong, I had already coded it as such. What I wanted to ensure was that I was giving the client accurate information.

The one thing I will ALWAYS do if I am unsure is ask, hence my post here, even if it opens me up for potential ridicule. I'd rather be thought a fool and learn by asking a question, than keep quiet and get it wrong.

Peace, out!!

Hi Raptor,

I haven't read the thread at all really as I have been up all night with raging tooth pain and at present have a bag of peas on my face.... lovely. Moving on to the point, I expect someone has mentioned it, but I think its important to emphasise it again as its a pretty major mistake and you have not mentioned it in your above post.

The RCD is 'rated' at 40A, meaning it can safely take up to 40A without getting damaged. It doesn't trip at 40A. If you have fitted an RCD before, thinking that the rating on it was overcurrent protection then you would need to go back and check it has another form of overcurrent protection if it needs it.

Keep asking ?

 

[Raptor0014]

Hi Raptor,

I haven't read the thread at all really as I have been up all night with raging tooth pain and at present have a bag of peas on my face.... lovely. Moving on to the point, I expect someone has mentioned it, but I think its important to emphasise it again as its a pretty major mistake and you have not mentioned it in your above post.

The RCD is 'rated' at 40A, meaning it can safely take up to 40A without getting damaged. It doesn't trip at 40A. If you have fitted an RCD before, thinking that the rating on it was overcurrent protection then you would need to go back and check it has another form of overcurrent protection if it needs it.

Keep asking ?

Hi Happy,

It’s not been fitted by me. I also made a mistake in my original post as it’s a RCCB in the outbuilding.

But thanks for the considered response. Hope the tooth is better.

 

[Electrics]

Compare the realistic Zs between an installation having a decent length of 6mm^2 and 1/2 metre of 25mm^2.

Also the 16 or 25mm^2 can take much more current than 6mm^2 before overheating the same.

But isn't it that the SWA isn't ever going to pull any more than the RCD/MCBs in the shed will allow?

I'm just confused as to how someone running a couple of lights and sockets off 6mm SWA has been 'lucky'?

 

[Julie.]

But isn't it that the SWA isn't ever going to pull any more than the RCD/MCBs in the shed will allow?

I'm just confused as to how someone running a couple of lights and sockets off 6mm SWA has been 'lucky'?

That's overload.

Put a nail through the cable at the far end is fault current.

All (ish) parts of an installation must have fault current protection, which must disconnect in a suitable time without causing cable damage etc.

I doubt that a 100A fuse will provide that for a 6mm^2 cable of a reasonable length

 

[telectrix]

that 6mm SWA can withstand enough overload current for long enoughto fry the 40A RCD without even getting hot.

 

[Electrics]

That's overload.

Put a nail through the cable at the far end is fault current.

All (ish) parts of an installation must have fault current protection, which must disconnect in a suitable time without causing cable damage etc.

I doubt that a 100A fuse will provide that for a 6mm^2 cable of a reasonable length

But how are you gonna damage it in normal circumstances, it's SWA.

Still a bit confused to be honest.

Is this one of those situations where it's against regs but in reality not all that dangerous?

 

[Electrics]

that 6mm SWA can withstand enough overload current for long enough to fry the 40A RCD without even getting hot.

But what i don't get is the circuits attached to the MCB's attached to the RCD won't allow it so the device pulling the amperage will become disconnected before overheating of the SWA is possible?

So SWA->RCD->MCB->DEVICE, before the SWA can overheat 'because it can potentially pull 80a' as in the OP, the MCB will disconnect, stopping whatever it is that's pulling the amps, before the SWA even gets close to overshooting its rating, no?

 

[Julie.]

Is this one of those situations where it's against regs but in reality not all that dangerous?

No, it is a real issue!

What do you mean

But how are you gonna damage it in normal circumstances, it's SWA.

No fault is normal circumstances!

It isn't normal to drive a nail into a cable - but you will find loads of instances of "I was putting up a shelf and... or I was just putting this picture up and..."

Cable damage occurs -a lot!



Are examples of swa damage.

Faults happen, you need to protect against damage to the installation in the event it happens.

 

[Electrics]

No, it is a real issue!

What do you mean

No fault is normal circumstances!

It isn't normal to drive a nail into a cable - but you will find loads of instances of "I was putting up a shelf and... or I was just putting this picture up and..."

Cable damage occurs -a lot!
View attachment 91536
View attachment 91537

Are examples of swa damage.

Faults happen, you need to protect against damage to the installation in the event it happens.

Im not saying these faults don't happen i'm asking about OP claiming the client was 'lucky' because the cable 'could pull 80a' because there's an 80a main fuse. I'm just talking about the installation as it is now not under a situation where it may develop a fault.

Isn't it only the equipment the other end that can pull 80a, which would never happen since it's lighting and sockets protected by 6 and 16 amp MCB's?