saving energy on lighting question

[Eznot2cme]

I have a question on trying to save energy on floresent lighting. We have 4 foot 2 lamp floresent lights in our stairways. We have refitted the lights with T-8 lamps and electronic ballast. One lamp is on our emergincy generator in case if the power goes out. We were told to take one lamp out thats not on the generator circuit so that now we only have one lamp burning to save energy.My question is since we refitted everything over to electronic and T-8 bulbs, are we really saveing any energy to justify only having one lamp burning?
Thanks

 

[hurk27]

if you have "one lamp on the emg. circuit, then this means you have two single bulb ballast in each fixture.

well it does pull less energy but with the ballast still hooked up it is also still using energy, and the fact that most electronic ballast don't like not having a load for a long time and will burn up, so I would at least disconnect the unused ballast.

 

[broadgage]

Presuming that we talking about two single ballasts in each fixture, one on grid only, and one normaly on grid, but generator backed up, then removing one lamp will save 50% energy.

If the ballast is still connected to the line then it will consume some power, but probably less than one watt.
As posted above, leaving the ballast without a lamp long term might cause failure, though I have never known it.
To be certain either dissconect the ballast as suggested above, or turn off the breaker supplying these lamps.

 

[cosmos]

Seperate issue - if you have only one lamp, will the stairs be in complete darkness when it burns out?

 

[Eznot2cme]

I agree with you totaly. To me with the lights just on the emg circuit if that light goes out it will not have any light therefor to me it is also a safty issue with no back up light.My main question though was without the safty factor of having 2 lamps and since the fixture in upgraded to T-8 bulbs along with new eltronic ballast , would it actually justify the cost savings if any.Now I will say this is a 6 story building with 3 stairwells so we are talking more than one fixture.

 

[iMuse97]

As a quick estimate: .035 kW lamp (one T8) would burn for 30 hours to use 1 kilowatt-hour, at whatever rate you have, times how many lamps you've got.

 

[K2X]

If it's instant start electronic, the label should show that it is rated for one lamp or two and it should give you the amp draw for one lamp or two. If it's a rapid start e ballast than it takes two lamps for either lamp to burn. Instant start is parallel wired to the lamps and rapid starts are series wired.

Ok i just went and got an advanced instant start 2 lamp vel-2p32-sc 277 e ballast. The label says for one f32t8 the draw is .15 amps. For two f32t8 the draw is .21 amps. I think most of the brands would show about the same spread.

 

[iMuse97]

Acc. to K2X I'm off by .028kW. The second lamp only draws a few more amperes and so the additional watts to power the second lamp (in kW) is .007kW approx. Multiply this times approx. 143hours to use your first kWh. You can burn that lamp continuously for six days before you spend your first ten cents.

 

[GeorgeB]

Acc. to K2X I'm off by .028kW. The second lamp only draws a few more amperes and so the additional watts to power the second lamp (in kW) is .007kW approx. Multiply this times approx. 143hours to use your first kWh. You can burn that lamp continuously for six days before you spend your first ten cents.

Remember that power is volts*amps*POWER FACTOR. These electronic switching devices do not usually have a PF even close to 1 at partial load ... and may not at full load. I've seen some numbers somewhere, but don't recall where.

 

[kid_stevens]

Presuming that we talking about two single ballasts in each fixture, one on grid only, and one normaly on grid, but generator backed up, then removing one lamp will save 50% energy.

If the ballast is still connected to the line then it will consume some power, but probably less than one watt.
As posted above, leaving the ballast without a lamp long term might cause failure, though I have never known it.
To be certain either dissconect the ballast as suggested above, or turn off the breaker supplying these lamps.

I have replaced many T12 Magnetic ballasts because of one bad or missing bulb causing a failure but in 9 years of T8 Electronic installations I have never had a single ballast failure from a missing or bad bulb even after a year of no bulb installed.

 

[tom baker]

Put in a motion sensor.

 

[catchtwentytwo]

Put in a motion sensor.

I've found that motion detectors used with T-8 fixtures, dramatically shorten lamp life if they cycle on/off often. Has anyone else noticed that?

 

[ultramegabob]

I've found that motion detectors used with T-8 fixtures, dramatically shorten lamp life if they cycle on/off often. Has anyone else noticed that?

I havent really noticed needing to replace lamps any more often, maybe it is the motion sensor you are using.

 

[catchtwentytwo]

I havent really noticed needing to replace lamps any more often, maybe it is the motion sensor you are using.

We were using Watt Stoppers (relay type) in a 26,00 sq/ft computer room and suspected their 30 minute maximum on cycle coupled with in & out traffic contributed to the premature burn outs.

 

[K2X]

We were using Watt Stoppers (relay type) in a 26,00 sq/ft computer room and suspected their 30 minute maximum on cycle coupled with in & out traffic contributed to the premature burn outs.

I think it is well documented that instant start e ballasts have a very high start voltage which shortens lamp life. Usually you can see blackened ends on these lamps within a week. Rapid start e ballast preheat the cathods and have a lower starting voltage and longer lamp life and might be a better choice for occupancey sensors. But, rapid starts might have some other features that you don't like. For one, being series wired to the lamps, all the lamps have to be in place and operating for any of the lamps to burn .

 

[raberding]

I think the proper ballast choice for use with occ sensors is "Programmed Start"

 

[hurk27]

I have not had a problem with bulbs using the 25khz driven electronic ballast yet, I have used the watt stopper, and the leviton round ceiling mount with the remote power unit, I did have a call on one where the OCC was the type that dimmed just before it turned off the lights, changed it out and had no problem since, but short cycling magnetic ballast has always been known to shorten lamp life, so we avoid them when we can.

 

[dbuckley]

I've found that motion detectors used with T-8 fixtures, dramatically shorten lamp life if they cycle on/off often.

My memory tells me that fluoro tubes are good for a number of starts and just over 6000 is pinging away there. So if you have a short dwell time on the motion sensors in a well used area you could get through a lot of starts a day, and thus the tubes will last a lot less time than if they were left on.

I'm sure I've seen a formula that optimises for cost in tems of starts versus electricity $/KWh.