Earthing inside a submain panel from main swa incomer

[davesparks]

I was referring to GN8 Appendix B (page 161)

Which is completely useless with regards the question, that only tells you the CSA of the steel armour and compares it to the requirements of table 54.7
It doesn't tell you hat size the cpc needs to be

 

[Guest 004]

Thanks Dave, you have just made me remember why I have not used this forum for a long time.

 

[i=p/u]

Use a 95mm Earth or scratch paint with 2p/screwdriver an use none

 

[Guest 004]

Thank you i=p/u
As the supply is 150, I will probably use a 70mm, but as previously said the ohmic value between the points is 0.01, which suggests to me no 'tail' required. Then you have regulations to contend with. What I was trying to assertain is whether I could use a 35mm as the ohmic value was so low anyway. End of the day whatever I use to 'comply with regs' will just be a cosmetic price of cable, and just a complete waste of time and materials. That said a tail needs (and will) be installed.

 

[davesparks]

How did you arrive at the value of 70mm

Just because the resistance is 0.01 ohms it does not mean it will handle the fault current safely.
You could measure the resistance of a short piece of 1.0mm T&E and get the same result, but it sure as hell won't cope with the fault current

 

[Guest 004]

^ take a day off Dave, and go and read some books.

 

[Leesparkykent]

^ take a day off Dave, and go and read some books.

Why don't you calculate the minimum required csa (not that you have to use the minimum) or use the Table in the BYB? Or you could just take a guess which you seem to be doing.

 

[davesparks]

^ take a day off Dave, and go and read some books.

What's the problem?
I am trying to help you see why getting a low reading is not necessarily proof that you have a suitable path for the fault current.

If I was being unhelpful I'd have pointed out that your use of the term 'ohmic value' is somewhat wrong

 

[Guest 004]

OK guys n girls, first take a look at the table posted below

https://www.dropbox.com/s/820yq4v3l2zj1m8/swa_armour.pdf?dl=0

You can clearly see that a thermoplastic swa (FP600) of 150mm does not require a supplymentary earth.

Now with this FP600 Terminated directly onto the panel, and not through a gland plate, to me this termination is sound, and can handle any fault current. The R1R2 of the cable is 0.01 ohms back to the supply, tested at the gland. This same value is obtained from the earthing terminal inside the panel.

Hope this makes things clear.

 

[davesparks]

OK guys n girls, first take a look at the table posted below

https://www.dropbox.com/s/820yq4v3l2zj1m8/swa_armour.pdf?dl=0

You can clearly see that a thermoplastic swa (FP600) of 150mm does not require a supplymentary earth.

Now with this FP600 Terminated directly onto the panel, and not through a gland plate, to me this termination is sound, and can handle any fault current. The R1R2 of the cable is 0.01 ohms back to the supply, tested at the gland. This same value is obtained from the earthing terminal inside the panel.

Hope this makes things clear.

A table on a page title DIY isn't going to carry much sway with anyone!
Plus that is not for the type of cable that you have, FP600 is a different spec to standard PVC SWA and so you need to get the CSA of the armour from the manufacturer.
But then nobody has questioned the suitability of the armour as a cpc, I think we all know that there are very few situations where an additional cpc is required.

If you are confident that the termination is suitable for the fault current then why did you ask the question in the first place?

If you have a good solid connection from the gland to bare metal then yes it may well be good enough, but a simple low current resistance test won't confirm this.
You are presumably dealing with a significant PFC on a cable that size and so I would have thought a little bit of belt and braces wouldn't hurt to ensure that fault currents will be handled safely.

 

[Guest 004]

What you getting so angry about

 

[Guest 004]

I ask a question, and all you want to is belittle with your inadequate knowledge.

 

[Guest 004]

Makes me understand even more so, that this forum was set up by a non sparks, and with house bashes trying to mod it. Pathetic

 

[Guest 004]

I'm out, ban me if you want, going back to the proper forums.

 

[Leesparkykent]

Why you getting so upset? You've had useful reply's to your OP you just seem to be ignoring them or taking them out of context. Simply you have to size it using the adiabatic equation or use the table in the BYB. Are you incapable of performing a simple calculation or something as you seem to be trying to avoid it?

 

[davesparks]

I'm not angry at all, I have tried to explain things as best I can.
I don't think I have tried to belittle you at all have I?
You came here and asked a question, which has been answered a few times over, we have variously tried to explain why the answers we have given are what they are, yet you just seem to be taking offence at the fact they aren't what you appear to want the answer to be.

What 'proper forum' are you referring to?

 

[Guest 004]

Really?? Obviously the Adiabetic returned a value a 0, that is why a NON supplymentary was not installed. Why are you so insistent on this? The equation is not hard hard to follow anyway?

 

[davesparks]

Really?? Obviously the Adiabetic returned a value a 0, that is why a NON supplymentary was not installed. Why are you so insistent on this? The equation is not hard hard to follow anyway?

Could you possibly help those of us with inadequate knowledge out by helping us understand what you meant by a supplementary? It's not a term which appears in the regs other than supplementary bonding?

The adiabatic equation used in bs7671 cannot return a value of 0 for any real-world figures.
The reason for people being insistent on it is that it is the method of sizing a cpc which gives the most economical size.

 

[Leesparkykent]

Really?? Obviously the Adiabetic returned a value a 0, that is why a NON supplymentary was not installed. Why are you so insistent on this? The equation is not hard hard to follow anyway?

What do you mean by that's the reason a 'NON supplementary' was not installed as you put it? If you mean by running in a separate earthing conductor along side of the cable then obviously the designer has obtained the necessary information from the manufacturer and found the armour to be adequate....How ever your question wasn't that was it? Your question was about taking a fly lead from the banjo to the earthing terminal in the enclosure.

 

[davesparks]

In the time it has taken this thread to develop you could have found an offcut of the SWA to use to make the link to the earth bar couldn't you?