SWA Fly lead

[brizospark]

what size should the fly lead from SWA earth tag to cpc bar be?

If for instance a 6mm SWA is run in should the fly lead be 6mm?

 

[brizospark]

earth tag

 

[sparkiegaz]

ive always put half the size in on every swa ive terminated,,,,or if there is a seperate cpc run with swa i take into panel through a stuffing gland up to earth bar..

 

[sparkydude]

What about when its a main panel , we have a job with the swa cables to be terminated into the galvanised steel glandplate on the top of the panel , this is already bolted to the chassis of the panel and has a 16mm bond from the top plate to the earth bar. The panel is a schneider okken . Would you take a flying earth lead from every SWA banjo to the bar in a CPC half the phase size ?? or would this just be overkill. They are using the armour as the CPC for all these outgoing circuits so best readings are needed to meet the disconnection times .

any oppionions welcomed

 

[SimpleSimon]

You could use the adiabatic equation to work it out?

 

[pblec]

supplementory bonding so regs say no more than 1/2 the smaller protective conductor (544.2.1) so it would be 4mm

 

[sparkydude]

been a while can you refresh my memory on that one simple simon

 

[philipb]

When i worked in a factory i would make off the swa as normal then run a 6mm
earth cable from the brass lockring to a earth clamp on the armour.
contractors used to say it was overkll but it maintains the earth if the
gland comes loose.

 

[Engineer54]

And how pray, did you clamp the SWA?? I don't think i'm going to like the answer to this!!!!

 

[SimpleSimon]

been a while can you refresh my memory on that one simple simon

Adiabatic equation is in the regulations. I don't know the formulae from heart and my books not at hand. But using this will determine the minimum size needed.

 

[Deleted member 9648]

supplementory bonding so regs say no more than 1/2 the smaller protective conductor (544.2.1) so it would be 4mm

How can a fly lead from an SWA be supplementary bonding?.....I'ts earthing.

 

[pblec]

is that the s = route I2t over k but is that not for protective conductors rather than supplementory bonding

 

[pblec]

whats the difference between earthing and bonding

 

[SimpleSimon]

Pblec I mean this with no dis-respect but I hope you are not undertaking this task as the main installer as you could be a little out of your depth. We are willing to help you on here but basic understanding of earthily and bonding is a must.

 

[pblec]

no disrespect i know what it is thats why i asked

main protective bonding conductor - earth wire comeing into house

main equipotential bonding - incoming services, steel etc

supplementory bonding - is additional bonding

wp says its earthing and not supplementory bonding i beleive earthing and bonding are the same thing and was hopping for him to clarify

 

[yellowvanman]

Well if you know what it is then you would know that earthing and supplementary bonding is NOT the same!

 

[SimpleSimon]

Well for staters the earth coming into your house is called your MAIN EARTHING CONDUCTOR not bonding.
And secondly wp is right what your proposing is an earth tag. Your earthing the SWA armour.
Bonding is bringing all extrenous parts to the same potential so different potentials don't exist.

 

[brucelee]

S = Isquared x T then hit square root and finally divided by K i think lol cant show exactly asdont know how to on the laptop its in the regs pg128
S = is the nominal cross sectional area of the conducter
I squared is the value in amperes of fault current of negligable impedence which can flow through the protective device , due account being taken fof the current limiting effect on the circuit impedences and the limiting capability I2t
T the operating time of the disconnecting device in seconds corresponds to the fault current I amperes
K is the factor taking into account of the resistivity ,temperature coefficient and heat capacity of the conductor material , and the apropriate initial and final temperatures

 

[pblec]

simon please its too easy check out page 167 544.1 amendment 1 2011

is supplementory bonding not connecting of conductive parts of electrical and non electrical items to prevent a dangerous voltage to prevent a dangerous voltage apearing between them under an earth fault conditions

 

[SimpleSimon]

It is and are you saying that's the job your fly lead is doing?

 

[pblec]

i beleive its exactly that and i even quoted the regulation should someone wish to dispute my statement.
the fly lead is earthing / providing supplementory or aditional bonding to the armour - just in case i didn't bury it deep enough.
them terms are quite alright i've not made any blaring errors

 

[SimpleSimon]

i beleive its exactly that and i even quoted the regulation should someone wish to dispute my statement.
the fly lead is earthing / providing supplementory or aditional bonding to the armour - just in case i didn't bury it deep enough.
them terms are quite alright i've not made any blaring errors

But what you keep failing to miss is earthing and bonding are two separate things.
Your idea is fine to provide an additional earth tag in case of failure of a decent earthing of the gland to the panel (like if someone fails to scrape off the galvanised paint).
But I would call this earthing because you are providing a back up to the steel wire earthing. Others may have a different opinion. There is no potential difference to occur between the two points because both points are already earthed.

 

[pblec]

its not a back up to the SWA earthing it is the SWA earthing and yes the proper term is bonding (but we all know the difference)

either way is my original post right or wrong

 

[pblec]

sorry just red your post am i completely stupid i've been classing the fly lead as the link from the gland nut / banjo to the earth bar.

is the fly lead something different

 

[SimpleSimon]

Wrong.
So if there was no fly lead what would happen than?

 

[SimpleSimon]

sorry just red your post am i completely stupid i've been classing the fly lead as the link from the gland nut / banjo to the earth bar.

is the fly lead something different

No your right on that part.

 

[pblec]

if the bonding wasn't connected, then theres no connection to earth for the armour.

i'd say the armourd sheath is an extraneous conected part so needs to be connected back to the earth to allow the supply to be automaticaly disconnected by the circut protective devices should a fault occur.

would you not say that?

 

[telectrix]

and heres me thinking a fly lead was so as to take my pet fly walkies.

 

[SimpleSimon]

if the bonding wasn't connected, then theres no connection to earth for the armour.

i'd say the armourd sheath is an extraneous conected part so needs to be connected back to the earth to allow the supply to be automaticaly disconnected by the circut protective devices should a fault occur.

would you not say that?

No I wouldn't.
The SWA is connected to earth via the gland which would be connected to the steel casing of the DB board which is connected to the earth bar via the way it is made. Therefore you don't need a fly lead. If your DB casing is plastic than you would use a fly leadbut this would act as an extension of the earthed steel wire. Therefore an earth.

 

[pblec]

what steel casing on the DB, its not mentioned, did you presume it was steel, id tend to think if it was steel then the question wouldn't have been asked either way the reply is still the same supplementory bonding is 1/2 protective conductor 544.2