[RE-wrenches] NEC 690.11 - Arc Fault Protection Provision Questions ?

[Ryan J LeBlanc]

Wrenches,

NEC 2011, 690.11 says, "PV Systems with DC source Circuits, DC output
Circuits, or both, on or penetrating a building...at over 80V... Shall be
protected by a listed (DC) arc fault circuit interrupter, PV type, or other
system components listed to provide equivalent protection." and then it goes
on to say what the arc fault should do.  

 My questions are:

1) What does "on" mean?  

On the roof? attached to the wall?  Say the array is in a field, with
combiner boxes having PV output circuits run underground and stubbed up into
the bottom of a DC disconnect mounted to the side of a house.  The conduit
is strapped to the side of the house on it way up to the bottom of the
disconnect switch.  Is this "on" the building?

2) What is a "building"?

Is it a dwelling, small and large commercial buildings?  How about an
enclosed MW in a box solution in the middle of a MW power plant, is that a
building?  I like for example that in the 600V max limitation that it
specifies 1 or 2 family dwellings, leaving small & large commercial
buildings opportunity to have 1000V systems.

Any clarification from Bill Brooks, Matt Lafferty, David Brearly, or the
host of other awesome PV Guru's on the list is extremely appreciated.

~Ryan L