conduit code questions

 I thought I remember hearing that if I run the charged wires from the PV
invertor through my attic then they need to be in metal conduit.    This
makes sense to me because the fireman etc. don't want to get shocked by
powered wires coming from the PV system when they are ripping out the
ceiling.

But this seems to imply that I also can't tie the PV invertor output into a
subpanel anywhere.    Since now all the wires coming out of that subpanel
would also need to be in conduit now.   Both coming and going wires.

So am I right that PV systems all pretty much need to be tied into the main
panel?   This would kill any chance of me installing more than one
independent system on several detached buildings I have that have power run
to them.   I was previously thinking a 2KW system now and later a bigger
system on a different roof.  Or am I missing something here as usual?

mike

  wrote:


Not that I would know the official answer, but I'm also not quite sure
what the question is. Are you suggesting that any source of high
voltage power (in the sense of greater than about 50 volts) needs to
be in metal conduit until it has passed through the single main
disconnect that serves (or would serve, in an off-grid situation) the
grid utility power? Such that an emergency worker who has shut off
what appears to be the main grid power breaker for the whole property
would not find any high voltage anywhere outside of metal conduit?

Seems reasonable from a safety standpoint, but it wasn't enforced back
when my original system went in twenty years ago. Now that I'm moving
the power system to a separate "power shed", next door to where the
generators have always lived, I'm asking myself somewhat similar
questions.

The line feeding generator power to the main breaker box in the house
is in metal where it is exposed (plastic underground) but it is not
fused at the generator end. Theory I guess being that the maximum
output of the generator could not exceed the ampacity of the
conductors. Now that it will also serve the inverter, their combined
output could exceed the capacity of the wiring to the existing main
breaker. So I suppose there should be a breaker at the power shed end,
to protect the wire. Putting a box there would also allow me to break
out power for pumps and tools without having to send it to the house
and back.

But then (here's the somewhat relevant part for your question) which
disconnect is the "main" one? Which one should have the earth ground?
And how do emergency workers who find what appears to be the main
disconnect at the house end know that there is still power in
outbuildings?

With an overhead utility feed, it would be pretty easy to figure out
where to shut off utility power to everything. With underground
utilities, even without on-site alternative power, it seems emergency
workers must just assume every building is live until they have found
a disconnect in the individual building. If the on-site power is
grid-tied, it must disable itself along with the grid disconnect. So
the only really confusing situation is non-grid-tied on-site power.

Guess I should go Google for awhile...  

Loren

 Mike Payne wrote:
...

I'm no code expert but the PV systems I've seen use conduit for all the
wiring. The conduit goes from the PV panels to a visible, lockable and
clearly marked DC disconnect and then from there to the inverter (or
charge controller). Wiring from the inverter to the panel or sub-panel
is just the same as any other AC wiring.

Anthony

 Not metal pipe though.

 ...

When professional installation companies came to quote at our house,
they both mentioned possibly putting in a subpanel for the output of
the grid-tied inverter.  I didn't think about it at the time, but it
sounded like a routine way of connection.

For the same reason that some utilities no longer even require an AC
disconnect for the inverter, I would think that a subpanel would be
ok.  If the AC mains go down, then the grid-tied inverter stops
feeding power. It seems like the faith that the fail-safe circuits in
the inverter will actually do their job has grown.

You would want to make sure that your main panel has enough capacity
to handle the PV input.  Each inverter should come in through its own
circuit breaker.  For a 2 kW system, there will probably not be any
trouble, but it's worth checking the rules, and especially later, if
you expand to another inverter.