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Hi guys got a few questions on the regs.

Do we have to bond both sides of SWA cable if we are using a core for earth. And if so would it need a banjo and fly lead when going into a metal enclosure? Also does the fly lead back to the panel/CU have to be connected to the MET?

Thank you guys
 
You don't need to bond both ends of the SWA armour provided the Zs for an internal cable short is low enough to clear in the required time (e.g. 5s for feeder, 0.4s for final circuit) so you should use the R2 for the armour in your calculation of the cable's Zs to check. Otherwise you might need the internal CPC connecting to the far end to help with that by lowering the cable armour R2.

It is always recommended to use a flying lead as (a) you can never be sure the connection to the box will remain good, and (b) in some cases (big cables!) the fault current can exceed what the sheet metal can locally handle.

I'm not sure about your last question. Normally the flying lead goes to whatever local earthing connection block is present. One presumes it has connections back to the MET that are adequate, if not other work is needed!
 
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Hi guys got a few questions on the regs.

Do we have to bond both sides of SWA cable if we are using a core for earth. And if so would it need a banjo and fly lead when going into a metal enclosure? Also does the fly lead back to the panel/CU have to be connected to the MET?

Thank you guys
Firstly it is not bonding, it's earthing. There is no requirement to connect the sheath to earth at both ends, but if only connected at one end you would need to verify Zs at the opposite end will meet disconnection time. It's easier and better practice to earth at both ends. If the metal enclosure is clean metal and is earthed elsewhere via a copper conductor there is no requirement for a banjo and flylead. Again it is good practice to provide a flylead and essential if the gland contact is not clean metal. The flylead is normally of the size required for the cpc and need not go to the MET as long as the earth path back to the MET is of the same required CSA
 
Firstly it is not bonding, it's earthing. There is no requirement to connect the sheath to earth at both ends, but if only connected at one end you would need to verify Zs at the opposite end will meet disconnection time. It's easier and better practice to earth at both ends. If the metal enclosure is clean metal and is earthed elsewhere via a copper conductor there is no requirement for a banjo and flylead. Again it is good practice to provide a flylead and essential if the gland contact is not clean metal. The flylead is normally of the size required for the cpc and need not go to the MET as long as the earth path back to the MET is of the same required CSA
You don't need to bond both ends of the SWA armour provided the Zs for an internal cable short is low enough to clear in the required time (e.g. 5s for feeder, 0.4s for final circuit) so you should use the R2 for the armour in your calculation of the cable's Zs to check. Otherwise you might need the internal CPC connecting to the far end to help with that by lowering the cable armour R2.
Thank you

It is always recommended to use a flying lead as (a) you can never be sure the connection to the box will remain good, and (b) in some cases (big cables!) the fault current can exceed with the sheet metal can handle.

I'm not sure about your last question. Normally the flying lead goes to whatever local earthing connection block is present. One presumes it has connections back to the MET that are adequate, if not other work is needed!
So it’s not bonding when the swa is not being used as the CPC? And is what you’re saying is if for example you have a few swa cables running into a panel you should connect these all together with fly leads and the cable with the biggest cpc Will give us the size of the fly lead from the banjo to the MET?
 
So it’s not bonding when the swa is not being used as the CPC? And is what you’re saying is if for example you have a few swa cables running into a panel you should connect these all together with fly leads and the cable with the biggest cpc Will give us the size of the fly lead from the banjo to the MET?

It is earthing, it is not bonding, the two are different things.

No, the flylead from the banjo does not have to connect to the MET, it can connect to the earth bar of the DB or panel etc that the SWA is connected to or the earth terminal of any piece of equipment that the SWA is connected to.

The flylead should be of the correct size for a CPC for the circuit that the SWA is connected to, if one flylead is used for multiple cables it should satisfy the requirements for using a single CPC for multiple circuits.
 

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