how much power can be safely drawn from two household outlets?

Give this a shot, navigate down to, and through, the electricity stuff.

The wall receptacle is probably rated

Are 20A breakers and 20A wiring that prevalent? Most panelboards I see (North of the USA) are chock full of 15A breakers.

Tungsten Lamps (incandescent) do indeed experience large inrush currents when turned on cold. Perhaps the inrush current is indeed on the order of 30 A. but it is just for a fraction of a second and should not affect wire size or overcurrent protection. The instant the filament heats up, the resistance increases dramatically and the current returns to normal.

Interestingly enough, it does effect the switch. That's why switches for incandescent lights must be T-Rated (T for Tungsten). It means the contacts are rated to handle big sparks (inrush currents). It also partly depends on a random event, the instantaneous time that the contacts are closed. If this occurs during a 0 crossing of the AC voltage, there will be no spark. If it occurs at the peak voltage, you might get a damn big spark.

Doesn't everyone have a switch in their house that sometime makes an audible and visible spark? And sometimes not.... The above paragraph explains why.

Beachcomber

"operator jay" wrote in news:Jtuoe.2568$mN.28907 @news1.mts.net:

Here in the South USA, typically 15A for lighting circuits and 20A for recepticals. (Thats the way I install them, and what I have seen in almost all the homes that I have worked in anyway.)

On Sun, 05 Jun 2005 06:11:34 GMT Anthony wrote: | "operator jay" wrote in news:Jtuoe.2568$mN.28907 | @news1.mts.net: | |> Are 20A breakers and 20A wiring that prevalent? Most panelboards I see |> (North of the USA) are chock full of 15A breakers. |> | | Here in the South USA, typically 15A for lighting circuits and 20A for | recepticals. | (Thats the way I install them, and what I have seen in almost all the homes | that I have worked in anyway.)

I see that in lots of homes around here in WV (considered by some to be part of the south).

My plan for my future house is to just go with 20A across the board, while still keeping all lighting on separate branch circuits apart from all the receptacle branch circuits. Switched receptacles intended for table lamp use will be on the lighting circuits.

How do you get nominal 13 amps on a 300-500 watt, 120 v circuit?

which would correspond to a peak of appx. 19A.

I was looking at the 1600W case.

I've experienced this when turning lights off. It should not be inrush when switching a light off because the filament is hot. This should just be a little bit of circuit inductance, and would depend on the zero crossing of amperage, which should pretty well coincide with the zero crossing of voltage on an incandescent lighting circuit. I haven't noticed this when switching lights on. But I guess as switch contacts are getting close together, current could start to flow before they quite made contact and arc (according to your voltage crossing as above) or the contacts could bounce a tiny bit and arc. I just don't recall noticing it when turning lights ON.

I guess if you have let say 15.9 Amps on a 20 amp circuit with the lights on and you start up equipment rated at anything over 5 Amps the lights will flicker and something could act up on that circuit Like a CB Tripping ect., but chances are it's not an Internal Problem (not exclusve to His Home/Office and the Utilities should be notified of it.

Normally they can account & manage for certains loads only, and sometimes an automatic swtich gear is needed on their Undeground Distribution System to handle in rush Currents & Peak Hour Switching to a Higher Demand Factor. =AEoy

Not again ? };-)

Ans. to OP: As much as it is rated for and less, Not More.

=AE

Your not likely to notice it unless you are messing around with direct current incandescent lighting. Since direct current has a constant voltage it is much more prone to arcing. The next time you are removing an ancient switch from service look on the strap or yoke and see if you don't find a T embossed or stamped into the metal. That T is for tungsten and you will never find it on an AC only switch. It means that the switch is listed to safely close on the inrush of that load of tungsten filament lighting without being damaged when used in a DC circuit. Such circuits are still found as emergency lighting in old buildings were the emergency power consist of a drop out relay that connects a lighting only single phase panelboard to 120 wet cell batteries running in series and tapped for 120/240 volts DC.

On one job in such a structure my employer decided to use some left over battery pack emergency lighting fixtures instead of the plain vanilla Edison based exit fixtures that were specified. You can imagine what happened when the first power failure occurred and that DC voltage found it's way to all of those battery pack charging transformers that were now connected to those lines. The first in battalion chief on the fire response called for the second alarm because of all the smoke from burning emergency light fixtures.

How the heck did the DC packs start that fire Tom ? Old Damaged Lighting Equipment ? i don't see how the DC would trail back to it's charger circuit in a Power Down condition., how old were they ?

OOT; I don't like it when i hear a switch pop, fizz or make any other miniature explosion type sound other than click when you activate it., to me it is a sign of either an underrated device or a faulty one. Roy

From: snipped-for-privacy@mindspring.com (HorneTD) operator jay wrote: "Beachcomber" wrote in message news: snipped-for-privacy@news.comcast.giganews.com... Interestingly enough, it does effect the switch. =A0 That's why switches for incandescent lights must be T-Rated (T for Tungsten). =A0 It means the contacts are rated to handle big sparks (inrush currents). It also partly depends on a random event, the instantaneous time that the contacts are closed. If this occurs during a 0 crossing of the AC voltage, there will be no spark. If it occurs at the peak voltage, you might get a damn big spark. Doesn't everyone have a switch in their house that sometime makes an audible and visible spark? And sometimes not.... The above paragraph explains why. I've experienced this when turning lights off. It should not be inrush when switching a light off because the filament is hot. This should just be a little bit of circuit inductance, and would depend on the zero crossing of amperage, which should pretty well coincide with the zero crossing of voltage on an incandescent lighting circuit. I haven't noticed this when switching lights on. But I guess as switch contacts are getting close together, current could start to flow before they quite made contact and arc (according to your voltage crossing as above) or the contacts could bounce a tiny bit and arc. I just don't recall noticing it when turning lights ON. j Your not likely to notice it unless you are messing around with direct current incandescent lighting. Since direct current has a constant voltage it is much more prone to arcing. The next time you are removing an ancient switch from service look on the strap or yoke and see if you don't find a T embossed or stamped into the metal. That T is for tungsten and you will never find it on an AC only switch. It means that the switch is listed to safely close on the inrush of that load of tungsten filament lighting without being damaged when used in a DC circuit. Such circuits are still found as emergency lighting in old buildings were the emergency power consist of a drop out relay that connects a lighting only single phase panelboard to 120 wet cell batteries running in series and tapped for 120/240 volts DC. On one job in such a structure my employer decided to use some left over battery pack emergency lighting fixtures instead of the plain vanilla Edison based exit fixtures that were specified. You can imagine what happened when the first power failure occurred and that DC voltage found it's way to all of those battery pack charging transformers that were now connected to those lines. The first in battalion chief on the fire response called for the second alarm because of all the smoke from burning emergency light fixtures.

You are describing two different effects here.

The inrush is a brief high current occurs when the load is initially energized, after the contacts close. Therefore, it does not cause arcing, but it can cause some heating.

When you open the switch contacts feeding an inductive load, the inductor tries to maintain the current flow. Therefore, the voltage across the inductor rises (inductive "kick") and a sometimes significant arc occurs at the contacts. This is what arc suppressor devices such as r/c networks, reverse diodes on DC loads, etc.help to eliminate. They do not affect the inrush current, however.

Ben Miller

-- Benjamin D. Miller, PE B. MILLER ENGINEERING