Energey conservation with T8 fluorescents

[ControlThis]

I don't have too much experience in dealing with fluorescent lighting. I'm in an industrial facility with a few hundred 8 foot T8 fixtures. We're looking to save money by turning lights off in areas that don't need as much light. Can we achieve this just by pulling bulbs, or does that part of the circuit really need to be disconnected? What are the losses by having the ballast powered up with no bulbs? How about a ballast that runs two bulbs with only one bulb installed? Some areas we want to pull every other bulb leaving some ballasts half loaded. Is this bad? Any input would be appreciated.
Thank You!

 

[davidbeach]

It depends. Some ballasts have the lamps (not bulbs, bulbs are something planted in the garden) in series and others have the lamps in parallel. Remove one lamp from a series ballast and the other will go out as well. Some ballasts have much higher losses with a missing lamp than other ballasts.

 

[itsmoked]

It would be better to un-wire every other fixture than to pull lamps.

Are these spaces exposed to daylight?

Can you use occupancy sensors?

If you pull lamps or otherwise turn them off permanently and someone falls down the stairs, even if they''re drunk, a lawyer would have a field day, as someone originally decided the fixtures where needed and, possibly, they were approved by an inspector,(reaffirming the need).

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ControlThis]

Not much daylight is available.
We are using a bunch of occupancy sensors. Problem is that we just had a major recontruction of how the production floor is set-up, so now there's too much lighting in some areas and not enough in others. Good suggestion though on the liability consideration. Thank you!
I did contact the manufacturer of the ballast and found that there is a no-load loss of 12 watts on this particular ballast. 151 watts with two lamps and 92 watts with one lamp. Knowing this, when you do energy consumption calcs, I'm assuming you use the wattage of the ballast and not the 86W that is printed on the lamp itself?

 

[EEJaime]

There are different consequences for delamping fixtures which depend mostly on what type of ballasts are present. Older magnetic ballasts had a more difficult time running a parttial load and would often have a much reduced output from the remaining lamp, thereby reducing the illumination levels even further than intended. Ballast life also suffered, I am not positive about the technical reason why, just know it occurred. They also often dusplayed a random color shift in the light output of the remaining lamp as well which would make a space appear absolutely horribly illuminated.

You do not save much in the way of energy consumption by de-lamping and in many cases the energy use goes up as the ballast factor suffers with partial loading as Davidbeach stated.

If you can disconnect either one ballast in a multiple ballasted fixture and provide even illumination at a lower footcandle level, that would be the optimal as long as you kept the levels to a safe minimum. If the fixtures have but one ballast, then disconnecting every second or third fixture in a regular pattern, while making sure all exit paths, work areas and safety hazards were still properly illuminated would save some energy.

You did not state what kind of spaces these were, but you mentioned an "industrial facility". You should be careful as Keith stated because as a norm, we design industrial spaces with minimal illumination as it is in general use areas, so removing a single fixture in a specific area may leave that area below a safe lighting level. And there are scary things that hang in the shadows, they've been to law school.

 

[itsmoked]

when you do energy consumption calcs, I'm assuming you use the wattage of the ballast and not the 86W that is printed on the lamp itself?

Yes the total energy consumed, not just the lamp.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

As a suggestion, see if you can get a sales rep from a fixture vendor to do a quick evaluation. It's been a long time but my first exposure to lighting levels was when an occupational safety inspector wrote up one of our customers under the factories act for inadequate lighting levels in a workplace. Our lighting calculations and suggested fixtures were supplied by a trusted sales rep.
Following this, our company had me trained trained in lighting calcs as they applied to the factories act.
Someone familiar with your local codes may be willing to walk through your plant and suggest which areas are over lighted and which are under lighted. You may then decide to hire the person to do a complete lighting plan to bring your building back into compliance with your local codes.
Remember that even if an injury is not related to lighting levels and an OSHA inspector comes on site and notes that some lighting levels are below standard, you may be in trouble.
We had an instance where an installation initially met the local code with an added maintenance factor but over time with NO maintenance the lighting levels dropped below the levels specified in the local factories act. An inspector did a spot check. the result was a write up and a fine. We were in changing lamps and cleaning glass ware shortly afterwards.
Hope this helps.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ControlThis]

Thanks for all the input!
We will be having a lighting vendor in anyways because we are considering LED lighting in some areas. I will surely ask that they make recomendations based on legal issues and proper lighting levels.