TheMGPremium
join:2007-09-04
Canada
kudos:1 Reviews:
 ·TekSavvy DSL
| reply to nunya
Re: X10 Appliance Module: Window A/C??? said by nunya:Yeah, considering an incandescent load is purely resistive (for all intents and purposes). Actually, there might yet be some logic behind that spec.
Incandescent bulbs have a very high inrush current when first turned on, which that X10 device may not be able to handle beyond 15A of inrush current. Something like that anyways. |
|
| said by TheMG:said by nunya:Yeah, considering an incandescent load is purely resistive (for all intents and purposes). Actually, there might yet be some logic behind that spec. Incandescent bulbs have a very high inrush current when first turned on, which that X10 device may not be able to handle beyond 15A of inrush current. Something like that anyways. Bingo, incandescent bulbs have HUGE inrush current, because the resistance of the filament is proportional to it's temperature. So when it comes on, it's cold and low resistance, and draws a surge of current till it gets hot.
I just checked the resistance of a 100 Watt incandescent bulb; it's 10 ohms, and 10 ohms at 120 volts is 120/10= 12 Amps! Surprising how much of a jolt those bulbs take to start up eh? It's an extremely short spike of current before the filament gets hot, but it still needs to be considered, especially with devices that use solid state electronic switches. |
|
bemis
join:2008-07-18
Reading, MA Reviews:
 ·Comcast
 ·Verizon FiOS
·Verizon Online DSL
| said by Raphion:I just checked the resistance of a 100 Watt incandescent bulb; it's 10 ohms, and 10 ohms at 120 volts is 120/10= 12 Amps! Surprising how much of a jolt those bulbs take to start up eh? It's an extremely short spike of current before the filament gets hot, but it still needs to be considered, especially with devices that use solid state electronic switches. I wish I had paid more attention in school... because what you said does not seem right.
It does not take 12A to start a 100W light bulb..... does it?
My living room has 5 100W bulbs on a single switch, so does that mean it draws 60A when I flip the switch to on?
I suppose it might be believable if the current draw is nearly instantaneous and so it occurs so quickly that there is no time for the fuses/circuit breakers to blow or the wiring to heat up... |
|
|
|
Reviews:
·AT&T U-Verse
| said by bemis:I wish I had paid more attention in school... because what you said does not seem right. It does not take 12A to start a 100W light bulb..... does it? My living room has 5 100W bulbs on a single switch, so does that mean it draws 60A when I flip the switch to on? I suppose it might be believable if the current draw is nearly instantaneous and so it occurs so quickly that there is no time for the fuses/circuit breakers to blow or the wiring to heat up... Yes, the instant start current can be very high, but it's only for a fraction of a second. It could be up to ~17A/bulb (on the peak of the sine wave) if the resistance of the filament is 10ohm when cold. But it only lasts for a very, very short time. Even if it starts with the 17*5=85A, 8ms later it will be 0...
Haven't you noticed that bulbs tend to burn when you switch them on? |
|
| reply to Raphion
Incandescent bulbs ??? Are they still legal ??? Aren't they a MAJOR contributor to Global Warming ? Every time someone turns on an incandescent bulb, it probably kills a Polar Bear.
Sorry, I just couldn't resist. Won't be able to get my tongue out of my cheek for a week.  |
|
