AFCI as first device in circuit

[smallfish]

Why is it that an afci receptacle if installed in a branch circuit, needs to be installed as the first outlet of the circuit and that the raceway from electrical panel to first outlet must be metallic?
(See 2008 National Electrical Code, Section 210.12 (B) Exception 1.)

Is it simply to protect the supply conductors to this device so that it is more certain to provide protection when needed?

Thanks

 

[Sierrasparky]

It was quite obvious to me that the AFCI is a manufacture driven product. It's inception was at the beginning to prevent fires from damaged wires or devices plugged in.

Now if the home run to the first device is run in metalic then what is the real risk if a nail is driven into the conduit. Nothing ,

with the AFCI device at the first outlet then anything plugged in will be protected.

 

[david]

Why is it that an afci receptacle if installed in a branch circuit, needs to be installed as the first outlet of the circuit and that the raceway from electrical panel to first outlet must be metallic?
(See 2008 National Electrical Code, Section 210.12 (B) Exception 1.)

Is it simply to protect the supply conductors to this device so that it is more certain to provide protection when needed?

Thanks

The idea is to give mechanical protection of the wiring method used in the form of a metallic wiring method until arc fault protection takes over at the first device.