Light bulbs

Page 3 of 4  


While what you say is true, you do know that incandescent bulbs ALSO draw a very large current surge at turn on?
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 7:01 AM, snipped-for-privacy@yahoo.com wrote:

From <http://www.digikey.com/en/articles/techzone/2012/jan/compact-fluorescent-tribulations :
"The first support call came from a customer with thirteen 23-watt CFL bulbs installed in a workspace, as replacements for 60 W incandescent bulbs. He indicated that the lights held in the ON position after only a few actuations of our control relay.
[note that 13*23W = 299W -- the equivalent of *5* 60W bulbs. Hardly anything to "worry" about!]
"We could not believe that, so we replaced the incandescents in our test rig with one CFL bulb. It was true! A relay that would run 100,000 cycles, switching asynchronously on numerous incandescent bulbs ran 10 to 100 cycles with a single CFL. Astonishing.
[asynchronously == no regard for zero-crossings of AC waveform. 1000X *fewer* relay cycles before CFL "wore out" the relay]
"So the race ensued to determine the failure cause. Relays stick closed due to high switching currents, but how can a CFL bulb that draws 23 watts suck that much current, enough to weld the contacts on a 10 amp relay, one rated for incandescent service? We set up a fixture with a current monitor to see.
[10A relay; 299W is < 3A]
"We found that some CFL bulbs draw huge inrush currents, peaking up to 17 amps, for a duration of 300 us or more!"
[half a 60Hz cycle is ~8300 us]
Watch the videos referenced in <https://electricalnews.com/photocontrol-failures-in-the-field-its-not-always-a-power-surge/ -- which essentially restates the issue more graphically.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 25 Nov 2015 08:35:47 -0700, Don Y

Interesting. I would be curious about the relay tho. A lot of "incandescent only" relays look pretty wimpy because they assume that to be purely resistive. That is one problem with "engineering". Instead of "how strong can I make it" the tendency is "how small/cheap can I get away with".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 9:21 AM, snipped-for-privacy@aol.com wrote:

Incandescent lamps only represent a "sizeable" load on startup. Once the filament gets warm, current approaches that of a purely resistive load. And, as startup can (theoretically) occur at any point in the (half) waveform, the chances of the cold filament encountering PEAK line voltage is small. E.g., if the instantaneous line voltage is 20V, then even a 10X reduction in cold resistance makes the lamp look like a *warm* lamp seeing 200V (instead of 170V that it would normally see at peak).
CFL/LED ballasts, OTOH, are *always* reactive -- rarely have power factor correction. So, that "surge" happens every (half) cycle. And, ALWAYS at the peak of the cycle (when the bridge is conducting!).
*Opening* the relay at this time usually poses the biggest risk for contact weld as current is already flowing and wants to continue to flow across the ever widening gap between the contacts. So, you draw an arc and start melting metal.

Engineering is the endless pursuit of the "least bad" solution -- acknowledging that all solutions are "bad" in some way...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 25 Nov 2015 09:44:46 -0700, Don Y

Next time I am sitting at my bench, bored, I will put a current probe on a CFL and shoot some scope pictures.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 10:25 AM, snipped-for-privacy@aol.com wrote:

Lots of folks/institutions have already done this. Your friendly neighborhood search engine will save you the headache.
Essentially, the ballast just looks like a cap sitting on the output of a bridge. So, you get all the current flowing through the bridge near the peak of the AC (voltage) waveform and none at other times (diodes being reversed biased as the cap stores a higher voltage than available on the line, at that time).
By contrast, current waveform for incandescent lamp will just look like voltage waveform scaled by some factor representative of the *hot* resistance of the filament.
The implications of CFL/LED and other highly reactive loads on power distribution can be pronounced. *Every* CFL/LED is drawing those peak loads at roughly the same (unfortunate!) time in the waveform. So, the copper wire is just acting as a heatsink for most of the time; not conducting any current!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@yahoo.com wrote:

Of course most load has reactive inductance. 2*Pi*f is inductive reactance value.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The incandescent bulbs draw a large ammount of startup current because the reistance is very low before the filiment comes up to the operating temperature. Same as with most common conductors except carbon and most simicondcuctors.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 25 Nov 2015 06:01:11 -0800 (PST), snipped-for-privacy@yahoo.com wrote:

But with a much lower rate of rize than the solid state stuff.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/24/2015 7:53 PM, Don Y wrote:

I am over wintering some plants in the room, so I need some additional light for them.

I did see some of those programmable lights, but they seemed like a bit of overkill for just adding some additional light for plants.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 9:41 AM, Muggles wrote:

If you are just putting the bulb in a typical fixture with a mechanical switch, youo should have no/few problems regardless of (practical) "size". Do note that different spectra result in different growth patterns. E.g., flowering plants tend to like the "blue-er" wavelengths.
Note that this is not the same as the "color temperature" of the bulb but, rather, specific wavelengths of light in that composite "white".

You have an understated way of describing a ~$70 purchase! :>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 10:52 AM, Don Y wrote:

hmmm I read that the "red" wavelength promoted flowering and the "blue" one was more for the foliage?

Understood...

LOL
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 10:02 AM, Muggles wrote:

since I was trying to grow anything indoors! ;-)
Nowadays, we count on the Sun to provide the optimal mix -- almost unavoidable when the things you're growing are 15+ feet tall/wide!

Getting this level of detail from an OTC product may be difficult. Unless you are specifically purchasing a "grow light"
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

When the socket limits the bulb used to 60watts, that means the socket itself and the fixture it is in, have been designed to handle a maximum of 60w of thermal load. A CFL or LED that is rated at 13.5w will be fine if it physically fits in the fixture.
--
Web based forums are like subscribing to 10 different newspapers
and having to visit 10 different news stands to pickup each one.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 7:50 AM, CRNG wrote:

That ignores the fact that there is something that turns the lamp on and off.
Do you think you could put **600** of those "60W light equivalent" lamps on a 20A circuit (2400W)?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 25 Nov 2015 08:38:10 -0700, Don Y

You could if you sequentially switched them. Turning them all on at once would turn the switch into an arc welder if it didn't trip the breaker.
I have 7 9 watt LEDs on a normal switch and you cna hear it when you turn them on..
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 2:51 PM, snipped-for-privacy@snyder.on.ca wrote:

Yup. You're essentially driving a (momentary) short as all those caps soak up charge!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Don Y wrote:

Most loads have inductive reactance. Z=2*pi*f*L
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/25/2015 8:50 AM, CRNG wrote:

Great! thanks.
--
Maggie

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
cob grow lights from cobgrowlights nice bright purple/pink. Good for your skin I heard.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.