On 12/13/2013 11:37 AM, bud-- wrote:
On 12/12/2013 7:13 PM, The Daring Dufas wrote:
On 12/12/2013 5:10 PM, Pete C. wrote:

Nate Nagel wrote:

On 12/12/2013 05:49 PM, Pete C. wrote:

The Daring Dufas wrote:

On 12/12/2013 3:12 PM, Pavel314 wrote:
I recently hooked my generator into the main box, with a
lock-out device of course. If the power goes out, I'll
turn off the main switch to the street manually and flip
to generator power.

The problem is how to know when the street power is back
on, other than looking down the street to see if the
neighbors have lights on again. When I just ran extension
cords from the generator to the well, refrigerators,
etc., during an outage, when the power started up again
various lights would light up around the house as they
had been on and were still street-connected. Now,
everything is disconnected from the street.

It would be nice if there were some sort of induction
device I could clamp on the main line coming in from the
street which would light up an LED if there were power in
the line, but if there's no current actually flowing I
don't see how it would pick up the potential voltage in
the line. Is there such a thing available or will I have
to invent one?

Paul

Some utility meters have LEDs that indicate there is power. A
'non-contact' voltage tester might indicate if held next to the meter
in the right spot. I don't know of a simple method other than that I
would use to show the power is back on.



Years ago, I installed some taps for roadies to hook up
lights for the stage in a night club. To let them know that
the power was on the box at the end of the conduit, I
installed a neon pilot light for each phase. In your case,
you can get voltage sensors that can be wired to an alarm
or flashing indicator light to let you know when your main
power comes back on or just wire up a standard wall light
or an exit sign with your own panel reading "POWER". ^_^

TDD

Along those lines I installed a pair of neon indicators
mounted to a metal box cover, installed in a metal electrical
box and connected to my panel with a metal offset nipple.
They are connected to the input side of the main breaker
directly, being ~18ga wire and enclosed in metal enclosures
if something fails they are self fusing and can't start
anything on fire. I use an interlock kit for the generator
connection (Square D kit in a Square D panel).

So what happens if the #18 wire acts as a fuse? There are a few
thousand amps fault current available at the service. A fault of a
few thousand amps through #18 wire will continue an arc over a rather
long distance. And what will happen with the 'spring' in the wire -
where will the wires go when they are broken at the arc?


That sounds like a good idea, and probably what I would do were
I trying to do something like this myself, I just wonder if
it's code compliant?

Nope.


I'm not sure on that, code mostly is concerned with fire risk,
and when enclosed in all metal conduit and box the heat produced
in the mS it takes to vaporize an 18ga wire at fault currents
couldn't possibly set anything outside the enclosure on fire.

It is a rather different case. But downtown there was a maybe 8 story
building that had a fire. They tore it down to the first floor and
basement, installed a ramp, and used what was left as a parking lot.
The original service remained (208/120V), far larger than needed,
with 6 parallel sets of service wires. They cleverly stored salt for
the ramp on top of the service switchgear. The service wound up with
an arc-fault and burned down. Some of the service wires burned back
into the supply conduits. Some of them were live in the conduit. Some
wires welded to the conduit and the utility couldn't pull them out
with a comealong. (The wires were protected by "cable limiters" at
the utility transformer vault.


I always put an inline fuse holder on the power feeding the
indicators and install a 1 amp or smaller fuse.

So what happens if there is a large fault current through the fuse?
Like the wire, with high current the arc continues and the fuse and
fuse holder blow up. Fuses have a rating for available fault current.
In most applications on a branch circuit you don't think about it.
When you have high fault currents available you have to (and are
required to by the NEC).

[The fuses included in some Fluke meters are rated for high fault
currents and the meters have a "category" rating for use where there
are high available fault currents.]

Is a problem likely? Don't know. But I wouldn't connect anything to
the service wire terminals.



Also, at what voltage do the neon indicators light up? e.g.
will they glow if there's say 10V on the line?

A quick look on Digi-Key seems to indicate a 105-125VAC rating on
many indicators. I don't see a clear indication that 105VAC is
the threshold, but I expect it's not too far below that. For more
$ you could install basic panel meters, and probably inline fuses
on them, though I'd still use the indicators as well since you
can check them from a distance to see if utility power is back.


I seem to recall 90vac as the lowest voltage that will light one
of those small neon pilot lights. ^_^

TDD

NE-51 (bayonet base) and NE-2 (wire lead) are common neon pilot
lights. They trigger on at about 65V (and would be used at a higher
voltage). Neon lamps must have a series resistor which is built into
the assemblies above.


Bud, I think you may have been responding to the wrong poster but your
thoughts are welcome. ^_^

TDD