Hi guys,
This question has been nagging at me for a while. What's the difference between 115v and 120v lamps, and how should I figure out which to buy?
I've always been under the impression it didn't matter much and have always bought 115v if given the option.
Thanks all!
Your math is correct, as far as it goes. Some other formulas that come into play:Someone double check my math and correct me if I'm wrong: ...
lumens/LUMENS = (VOLTS/volts)^3.4
life/LIFE = (VOLTS/volts)^13 (I.e., reduce the volts to 90% and the life increases by 393%!)
EFFICIENCY/efficiency = (VOLTS/volts)^1.9
watts/WATTS = (volts/VOLTS)^1.6 (not 'squared' as you would get with a fixed resistance)
coltemp/COLTEMP = (volts/VOLTS)^0.42
See the note to "watts/WATTS = (volts/VOLTS)^1.6": "(not 'squared' as you would get with a fixed resistance)" Further, lumen is more indicative of output than watt.... So, if you run a 120v lamp at 115v, the 25.05 Ohms of resistance would cut the output of a 575w lamp to 527w (W=V^2/R)
Likewise if you run a 115v lamp at 120v, the 23 Ohms of resistance would boost the output to 626w. ...
See http://www.controlbooth.com/forums/question-day/9282-acceptable-put-4x-s4s-dimmer.html .... Which is why I don't like using four S4 units on a circuit, if they have 115v lamps installed.. (4x626=2504w) ...
STEVETERRY says it's okay, therefore it's okay.Guys, what you are missing here is that a dimmer rated for 120V nominal does not deliver 120V at the outlet. You have the drop across the SCR, the choke, and the cable run to the outlet. That is precisely why a 575W HPL lamp is rated at 115V--so that you can get the expected lumen output and color temperature despite those voltage drops.
So, 4x575W 115V lamps on a 120V 20A dimmer rated for continuous full loading is just fine--as long as you don't exceed 115V at the outlet. And that would be hard to do without a line voltage higher than 120V.
Depends on how you define "ok." Using a 120V long-life lamp on a circuit that only supplies 115V will certainly last longer than a 115V long-life on a 115V circuit, but may not be "ok" to designers, except those who like their output dim and yellow.So, If "long lamp life to save money" is the primary issue, I'm ok using ...
From what I read here... Sure, but wouldn't a designer prefer ever-so-slightly dimmer lamps, than ones that aren't working at all? OK for me means working fixtures. Can most designers really tell if a dimmer is at 96% instead of full? Would Mom notice the difference watching her kid on stage for the first time? I'd guess poor alignment would affect things more than 4% of voltage difference, and 5 year old faded Roscolux causing more of a color difference than an ever-so-slightly color temperature difference? No?
(I'll measure out of curiosity, and would be interested in comparing the two side by side.) Your data on lamp life differences is great, thanks.
Your dimmers may or may not allow regulation, but be aware they can only lower, not boost, voltage.
From what I read here... Sure, but wouldn't a designer prefer ever-so-slightly dimmer lamps, than ones that aren't working at all? OK for me means working fixtures. Can most designers really tell if a dimmer is at 96% instead of full? Would Mom notice the difference watching her kid on stage for the first time? I'd guess poor alignment would affect things more than 4% of voltage difference, and 5 year old faded Roscolux causing more of a color difference than an ever-so-slightly color temperature difference? No?
(I'll measure out of curiosity, and would be interested in comparing the two side by side.) Your data on lamp life differences is great, thanks.
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