Am I being a snob, or is this actually dangerous

[Inteificio]

On a distribution board last week in a farm house, I saw 2 core 4mm SWA with the sheath terminated by having a couple of strands in a terminal block.

A photo would save a thousand words, but I found out on that day that my camera phone is not waterproof =-(

The other sparky on site said it is fine if the Zs is in, which I accepted at the time.

Then I got thinking, the Zs will make sure the fuse trips, but how can you guarantee conductor safety while the fuse is tripping?
We had a similar issue in our factory where a spark proved that a distribution circuit would blow in 4s, within the limit. However I pointed out the wires would be melting the insulation after 1s.

I can do the calcs to prove how hot that conductor will get, but that is not sparky level maths and I know the guy who installed it won't be able to do that.

So my question is:

When is it ever safe to terminate only a couple of strands of the armouring on SWA when it is being used as the CPC.

This is quite important as I am going to be politely confronting the guy, and I don't want to risk causing offence if I am wrong. I will be the first to admit domestic is not my speciality.

 

[trev]

So my question is:

When is it ever safe to terminate only a couple of strands of the armouring on SWA when it is being used as the CPC.

.

Never, just do it right imho

 

[Sparky_Ben]

was it not made off using and appropriate gland?
either way i would say it is defiantely not acceptable

 

[Guest112]

code 2

 

[Inteificio]

literally two strands of the SWA were in a terminal block, a separate wire went from the other side of the terminal block to the earth bar.

 

[Guest112]

adiabatic equasion?

 

[Engineer54]

First off, ....All SWA ends should always be terminated with an appropriate sized gland, that encompasses ALL of the SWA strands!! The CSA of the SWA of an armoured cable enabling it to comply as a CPC is based on all the strands, not just a couple of them. The very fact that this SWA hasn't been glanded off, shows the lack of professionalism shown to this installation. Geezus, even a spring clamp with a braided earthing conductor would have been better than what your describing.

There is no way i can see this unconventional cable termination complying with any regulations within BS7671... Full stop!!!

 

[Inteificio]

adiabatic equasion?

That would be my way to go, calculating heat loss to the surrounding would be a pain in the arse and not increase the accuracy to any great extent.

My method would be calculating the peak current flow, then calculating the resistance of those two strands, the power dissipated in the two strands. Using the specific heat capacity of steel, we could then work out the rate of temperature increase. Work out the disconnection time and therefore the end temp of the steel wire.

Not exactly rocket science, but in turn quite a few competent sparkies would struggle with that.

The reason I have not done the maths, is to me it is beside the point. That steel might only get to 120 degs, but the fact is I know the sparky who fitted it will not have done the maths and I want to know how he demonstrated it was safe!

 

[Silly Sausage]

On a distribution board ............

Haha...Unbelievable!
I'd be interested in seeing the last PIR for that install.

 

[Engineer54]

That would be my way to go, calculating heat loss to the surrounding would be a pain in the arse and not increase the accuracy to any great extent.

My method would be calculating the peak current flow, then calculating the resistance of those two strands, the power dissipated in the two strands. Using the specific heat capacity of steel, we could then work out the rate of temperature increase. Work out the disconnection time and therefore the end temp of the steel wire.

Not exactly rocket science, but in turn quite a few competent sparkies would struggle with that.

The reason I have not done the maths, is to me it is beside the point. That steel might only get to 120 degs, but the fact is I know the sparky who fitted it will not have done the maths and I want to know how he demonstrated it was safe!

He can't, the very connection method is non-compliant, so i don't really know why your even bothering to justify or not with calculations. The termination of this SWA cable needs correcting, ...it's as simple as that!! You can't justify the present method by calculation or by any other means...

 

[Inteificio]

Documentation is not yet completed as job not finished. It is actually at my parents house as they are having some work done.

I popped up for Christmas and had a look while I was there, some of his work I quite liked, but this was my main concern.

It does kind of shock me, even taking in to account that this sparky knew that I was an electrical engineer and was probably going to have a nosey at his work, he still did this.

That is what made me doubt myself and double check, he knew that I would look at his work, surely he would be on best behaviour?

When my NIC man came to look at my stuff I spent twice as long making sure it looked extra nice!


The other main fault he did made me laugh, there is no power to two sockets on a ring. There was some boarding leaning up against them, so my money is he forgot to second fix them as he didn't see them behind the board. To me that isn't as dangerous, just funny.

 

[1shortcircuit]

I saw 2 core 4mm SWA with the sheath terminated by having a couple of strands in a terminal block.

Glands serve a purpose as you are fully aware. First question I would need to ask is what was supporting the weight of the SWA if a gland was not in use? I would not be happy with this if it was an installation I was working on but that's easy to say sat from behind my laptop screen in the comfort of my front room

I'd dread to think what else you may find if you had the opportunity to look more closely.

Shame about your phone, a picture would have been great:thumbsup

 

[Inteificio]

He can't, the very connection method is non-compliant, so i don't really know why your even bothering to justify or not with calculations. The termination of this SWA cable needs correcting, ...it's as simple as that!! You can't justify the present method by calculation or by any other means...

To me that is a grey area. BS7671 is non-statutory, as long as I can demonstrate something is safe, then I am fine with it.

A lot of the stuff I deal with is very high temp, BS7671 doesn't cover what I do, so I always rationalise along the lines of, In the event of a fire can I stand up in front of a court room and explain without any doubt what I did was safe and why.

I didn't do the maths, just explained my method in case there was any interest. The reason I didn't do the math is that he can't; therefore he could not use that as defence. I wanted to know what he would say to the judge if there was a fire at my parents house.

 

[Engineer54]

Documentation is not yet completed as job not finished. It is actually at my parents house as they are having some work done.

I popped up for Christmas and had a look while I was there, some of his work I quite liked, but this was my main concern.

It does kind of shock me, even taking in to account that this sparky knew that I was an electrical engineer and was probably going to have a nosey at his work, he still did this.

That is what made me doubt myself and double check, he knew that I would look at his work, surely he would be on best behaviour?

When my NIC man came to look at my stuff I spent twice as long making sure it looked extra nice!


The other main fault he did made me laugh, there is no power to two sockets on a ring. There was some boarding leaning up against them, so my money is he forgot to second fix them as he didn't see them behind the board. To me that isn't as dangerous, just funny.

More to the point, ...What are you going to do about this SWA termination?? Are you actually going to let it stand??

 

[Inteificio]

First question I would need to ask is what was supporting the weight of the SWA if a gland was not in use?

lol - I completely missed that....

Good point, the wire is floating free in the board, vertically coming through the base of the box. The only things holding it up are it's own rigidity and those two wires.

Can't believe I overlooked something so obvious.



As to what I should do, I bowed to the experience of my friend (FAR my superior in electrical knowledge).

I am writing down all the relevant problems and waiting until the work is signed off, and seeing what is still there.

My friend has done a lot of inspections, and the most common line he got was "that is just a temporary fix until the parts arrive".

Never call a sparky on something if they can wiggle their way out, sparkies are cunning and will always have a good excuse.

However it is hard to explain how a job they have signed off and certified is in breach of regs.


So basically, wait until he has finished and signed off the job.
Check to see if he has fixed all the issues.

If he has not, then confront him directly and ask him to rationalise his decisions, then see what my parents want to do.


You never know, he might have everything perfect when I go back; however I bloody doubt it. If you can see ANY copper on a main board I build, I feel like I have ****ed up. I could have traded the amount of copper showing on his for a small holiday!