volts500 wrote:

"Tony Hwang" wrote in message
news:sywnb.206443$pl3.17868@pd7tw3no...


Doug Miller wrote:


In article C4bnb.197307$pl3.160437@pd7tw3no, Tony Hwang

wrote:

Doug Miller wrote:



In article Wl3nb.194451$9l5.193936@pd7tw2no, Tony Hwang



wrote:


Tom Horne wrote:



As long as the lamps are incandescent the wattage of the
lamps can be used as the VA of the lamps.


VA is not equal to Watts. Reason? Power factor, Cosine Phi.
As far as math is concerned.


As far as a purely resistive load such as an incandescent lamp is

concerned,

they are indeed equal.


Hi,
Since you used word PURELY, even the filament of incandescent bulb has
inductance, how could it be pure R without X? I still stick my gun on
my statement. Watts is not equal to VA, better give some margin.
Tony


OK, why don't you do the math, and tell us how much difference there is
between watts and volt-amperes for, say, a 60-watt incandescent light

bulb?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Hi,
Also wiring has inductance. If I install 15A circuit, I'd let it carry
~13A and have peace in mind. Are you going to give full load in your
case then?
Tony



Tony, your argument holds about as much water as a tiny piece of pork (fat)
in a can of "Pork" and Beans.......interesting how the pork is always listed
_first_.

The reason why the NEC limits a continuously loaded lighting circuit
(defined by the NEC as a circuit expected to remain on for 3 or more hours)
to 80% (that's 12 amps for a 15 amp circuit) is because the circuit breaker
will start to nuisance trip when left on for an extended period of time if
the full 15 amps is applied continuously, _not_ some ridiculous argument
about the minuscule amount of inductance in an incandescent lamp.

Hi,
15A breaker won't trip at 15A. Depending on what kinds, it has to be
over 15A. The delay time is different. Just like fuses, fast blow vs.
slow blow. Like 15A fuse does not blow at 15A. Hardly any electrical
load is pure resistance. They're mostly inductive load. Never saw a
phase correcting capacitor banks in commercial buildings? Inductance
causes surge when power is turend on. Tell me one pure resistive load in
any utility grid.
In non-DC circuit we talk about impedance(combination of resistance and
reactance; sum of inductive and capacitive reactance)
As an example, again I emphasize example, not real figures,
a 60W light bulb has 6 Ohm resistance and 1 micro Henry reactance.
Impedance at 60Hz is root of 6+(2 x Pi x 60 x 1/1000,000). Definitely
more tahn 6 Ohms.
This thread is closed for me.
Tony