zog
Senior Member
- Location
- Charlotte, NC
I know it takes a bunch of energy to "start" a flourecent light, is it better to leave them on or tun them off and on several times a day for energy efficency?
Flourcent lights, leave on or turn off?
- Thread starter zog
- Start date
- Status
- Location
- Massachusetts
I don't think it has to be off long to save more energy then start takes, occupancy sensors are often set in the 5 to 7 minute range.
I think the answer would depend on how many lights, etc. (question is too vague - I don't think one answer fits all conditions). I think the best energy savings means I have seen so far for flourescents was the installation of skylights and dimmable (sp?) flourescents with light sensors and dimming panel.
- Location
- Massachusetts
Lets say a running fixture draws 1 amp continuously.
Now lets say it draws 10 times that during a 1 second start up. (I doubt it is anywhere near that)
So if we leave the lamp off for a 11 seconds or more we start saving more then the start up wastes.
Of course there are other cost issues like lamp and ballast life, but I am confident turning typical fluorescent lighting saves money.
Now lets say it draws 10 times that during a 1 second start up. (I doubt it is anywhere near that)
So if we leave the lamp off for a 11 seconds or more we start saving more then the start up wastes.
Of course there are other cost issues like lamp and ballast life, but I am confident turning typical fluorescent lighting saves money.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
My thoughts are similar to Bob's.
There is a reason that someone has calculated for the setting of sensors to go off approximately 8-15 minutes.
I would say that leaving a room to get something and then coming back quickly does not show a need to turn them off. But leaving a room for more than 15 minutes in my estimation would be prudent in regards to energy savings.
There is a reason that someone has calculated for the setting of sensors to go off approximately 8-15 minutes.
I would say that leaving a room to get something and then coming back quickly does not show a need to turn them off. But leaving a room for more than 15 minutes in my estimation would be prudent in regards to energy savings.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
This is an old urban legend.
As Bob said, start up energy is measured in a time frame of secs.
I believe the default time frame setting of energy sensors has a little to do with the shortend life of lamps that occurs with each starting, and a lot more to do with the average period of 'non-movement' that a person has when sitting at a desk.
I agree. I have measured and recorded current waveforms for start up.
Fewer than 10 cycles from turn on to steady state..
zog
Senior Member
- Location
- Charlotte, NC
Good stuff guys and all makes sense, thanks.
+1, a very miniscule load, measured in milliseconds and not secs.
Here's your answer - http://kwc.org/mythbusters/2006/12/episode_69_22000_foot_fall_lig.html
Brian Oshman
Member
- Location
- Stewartsville, NJ
Turning off any lamp always saves the most energy because after all, it is not using any.
As for the delay times on occupancy sensors, it is set so that it is not inadvertently turning off while the room is being used and becoming a nuisance. No one generally sits completely still for 8 to 15 minutes at a time, they will always make some kind of movement to keep the sensor activated but set below this threshold it is more likely it will be necessary to be waving at the sensor to kick it back on.
As for the delay times on occupancy sensors, it is set so that it is not inadvertently turning off while the room is being used and becoming a nuisance. No one generally sits completely still for 8 to 15 minutes at a time, they will always make some kind of movement to keep the sensor activated but set below this threshold it is more likely it will be necessary to be waving at the sensor to kick it back on.
ItsHot
Senior Member
- Location
- A little piece of heaven!
microphonics
microphonics
Some sensors have microphonics. After a point of not detecting motion, they detect sound.
microphonics
Some sensors have microphonics. After a point of not detecting motion, they detect sound.
SmithBuilt
Senior Member
- Location
- Foothills of NC
I wouldn't use the term "any". There are high bay lights that take a while to come on and are better left on during a work period.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
HID's are dimmed, with special dimmers and motion sensors, used a lot in warehouse aisle lighting. Since the arc is not extinguished, full brightness is instantly acheived. The orange box used a giant dimmer to dim all HID's in their stores many years ago, it was controlled using a outdoor light level sensor. They discontinued the use of the dimmers though due to maintaince issues. Surges would burn out the rectifiers on the tap changing brushes leading to burn't contact surfaces at best, fires at worst.
ItsHot
Senior Member
- Location
- A little piece of heaven!
desiel
desiel
This is OT but this thread just reminded me of desiel engines! Do you leave them idling or turn them off!:smile:
desiel
This is OT but this thread just reminded me of desiel engines! Do you leave them idling or turn them off!:smile:
OT answer: with any IC engine, more than 30-60 seconds idle, turn it off (depending on the engine).
johnny watt
Member
Is it better? Is it better for whom?
I don?t have the answer but I would look at it from the owners of the lights dollar standpoint. The extra cost of purchasing, traveling, ordering and disposing of disposing of lamps is significant. Same goes for the ballasts, broken lenses and sockets from the wear and tear. The government subsidizes some of the costs but they still have an impact on the environment. For instance, pretty much all transportation ejoys extra tax dollars beyond what it brings in from the direct users.
Then you have to account for the energy cost for HVAC on top of all that.
This reminds me of hand dryers like the Xelerator touted in the WSJ. They never talk about what impact the humidity going into the air is going to have on the HVAC costs.
I don?t have the answer but I would look at it from the owners of the lights dollar standpoint. The extra cost of purchasing, traveling, ordering and disposing of disposing of lamps is significant. Same goes for the ballasts, broken lenses and sockets from the wear and tear. The government subsidizes some of the costs but they still have an impact on the environment. For instance, pretty much all transportation ejoys extra tax dollars beyond what it brings in from the direct users.
Then you have to account for the energy cost for HVAC on top of all that.
This reminds me of hand dryers like the Xelerator touted in the WSJ. They never talk about what impact the humidity going into the air is going to have on the HVAC costs.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
If it's up to me, I use a half hour as the deciding point for fluorescents.
ItsHot
Senior Member
- Location
- A little piece of heaven!
burnt lamps
burnt lamps
burnt lamps
We have talked here about shorting lamp life with frequent start ups from sensors. I have seen sensors added to restrooms by energy management guys. Restrooms have 3, 13-watt fl. lamps.One lamp remains on always,(egress). So you are shutting the other 2-13 watts on/off all day!! The energy savings???? Does not outway the lamp replacement cost?? Oh, I mentioned the other 1200,2x4 trouffers that stay on most all the time! Energy guys did not "hear" that one!!:-?
- Status