On Dec 18, 1:20*am, Winston wrote:
nesesu wrote:
On Dec 17, 1:40 pm, *wrote:
klem kedidelhopper wrote:
Our area suffers from frequent blackouts,
(...)
In addition to the insights by other posters, if you
have standard U.S. 'split phase' service, please
consider an indicator for each half - phase.
Consider using two 4 W 'night lights'. *They won't
be fooled by electrical noise on the line, as the
neon lights might.
So L1 to neutral gets a lamp and L2 to neutral gets
another lamp. *The reason I mention this is that
the last three 'brownouts' in my area were characterized
by the total loss of L1 and very low voltage from
L2 to neutral.
--Winston
Winston, one of the main concerns that Lenny rightly had was
connecting to the entrance wires AHEAD of the main breakers. Your
average modern branch breaker is rated for 20,000A interrupting and
the main breaker for probably 50,000A. One cannot safely stick a 1/4A
3AG pigtail fuse off the mains to ptotect against a fault in your
'night lights'!
I can see how it might be a difficulty WRT the NEC.
I imagine they forbid *any* kind of load 'north'
of the branch circuits.
But looked at from a sheer electrical engineering
standpoint, I don't understand why fuses off of
L1 and L2 should not be adequate protection for
these indicators, even connected right to the
input horn. Theoretically speaking, of course.
The power company uses inductive coupled sensors
far 'north' of the consumer's branch circuits.
Perhaps it is legal, moral and correct to use
inductive sensing in a residential power
situation as mentioned upthread?
http://www.selinc.com/FCI/FaultIndicatorsandSensors/
Some years ago I assisted in wiring a friends new house and for the
electric heat in the crawl space, we installed a neon indicator in a
box in the utility/laundry room to show when the crawl space heaters
were powered. I ordered a neon panel indicator rated for 240V and
double checked it's markings along with the carton *information to be
assured it was for 240V. It was connected across the 240V 30A supply
to those heaters and the breaker switched on. Ka-boom !! Fortunately
the breaker panel was not in that room since it was showered by shards
of the Bakelite box cover and fragments of the neon bulb and holder
plus there were nice black marks radiating on the wall around the box.
A replacement indicator [same type] worked fine for years.
That is weird!
--Winston
Except for the fact that the fuses and lamps would have to be "moused"
into the panel before the main breaker in some sort of safe way, I
guess from a theoretical point of view it would seem like a workable
safe plan. However in looking at it from a strictly pragmatic point of
view I guess that I must consider the litigious society we all
unfortunately live in as well. There is always the possibility of an
insurance inspector seeing that modification on a disconnect after a
fire.
Even if the fire was caused by something totally unrelated to the
modification everyone knows that the last thing most insurance
companies will come across with is a check. And since this
modification, however technically feasible and safe would be a
violation of the NEC, subsequently a case could still be made for
noncompliance and therefore, no money. I hate to have to think this
way but I guess we all should. The inductive, or capacitive approach
would totally eliminate that factor from the equation.
I do have one question though Neil about the experiment that you
initially suggested. I can understand how wrapping the one foot length
of #22 wire around the piece of cable which simulates my entrance
cable would capacitively/inductively, or both couple the AC to the NE2
lamp, however in actual practice I won't be able to wrap just one
conductor of the entrance cable outside of the panel as they're both
together in a jacket. I would think if I were to wrap both, every time
I'd cross the pair, the second wrap would be out of phase with the
first and the net induction into my "probe" would be zero. I could get
into the panel and without making a direct electrical connection wrap
just one or both of the mains, (if I do an indicator for each phase),
and perhaps that's what you had in mind? Or am I looking at this
incorrectly? Lenny