Greetings Everyone,
We are working in a CI project, in which, by error, the lightning contractor obtained some LED bulbs with a larger wattage than the lightning designer specified wattage. This situation lead to and increase in the project's LPD, to around 93% of the interior lightning power allowance. In order to mend this situation, the contractor proposed to change the ballast settings in order to permanently dim the luminary output to around 70%. Would this be acceptable in order to comply with the prerrequisite's LPD reduction?
ASHRAE 90.1-2007 states that one should use the maximum luminary wattage, so in principle our situation wouldn't be acceptable. On the other hand, if the ballast is permanently dimmed at 70%, the luminary will never consume more power than the one provided by the ballast, and therefore this 70% power could be considered the maximum luminary wattage.
What do you think about this situation? Any ideas?
Thanks!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 1, 2012 - 9:59 am
If the ballast settings are adjustable then what would prevent it from being adjusted again back up to the maximum setting? Not sure this is really permanent?
In this case it sounds to me like the ballast is the auxiliary referred to in 9.4.1b and the wattage is the maximum of the combination.
Luis Miguel Diazgranados
Green Factory125 thumbs up
October 1, 2012 - 1:17 pm
Thanks for the answer Marcus. The only thing that would prevent the ballasts from being adjusted once again would be the users (they don't want to readjust since they want to comply and take advantage of the energy savings), but I don't expect this to be a valid argument for ASHRAE or the reviewers. On the other hand, based on 9.1.4b, if I use a ballast that, for example, can provide a maximum of 15W to a 27W bulb, then I could consider the luminary wattage to be 15W instead of 27 W. Would you agree?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 1, 2012 - 2:03 pm
I am not a expert on LED lighting so I am not sure how a ballast rated at 15 watts can supply a 27 watt lamp. Does the ballast regulate lamp wattage? If that is possible then 9.1.4b says that the maximum wattage of the combination of the lamp and ballast should be used. So if the maximum wattage of a particular combination is 15 watts then use that.
Luis Miguel Diazgranados
Green Factory125 thumbs up
October 1, 2012 - 3:46 pm
I am also not an expert, but the lightning contractor told us this is a possibility, although the lightning intensity of the lamp will be lower. Anyhow, thanks once again for your help Marcus, we will analyze which is the best way to fix this situation.
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
734 thumbs up
October 1, 2012 - 4:50 pm
Is the lighting contractor more intersted in making a sale or in complying with 90.1?
If you try to put 27 watts of LEDs thru a 15 watt driver you will most likely burn up the driver. The driver should be sized appropriately for the LEDs being controlled by it. Drivers are often over sized a bit. (30W driver for 27W of LED) As noted it is the combination of lamp and ballast/driver that is used for peak wattage. However much the system uses when 27W of LED are installed. Maybe 28 or 29W. Most people don't know what the driver loss is so they just plug in 27W.
Marcus is correct that the peak possible must be used in the value. Programming the system to dim would not work because it could just as easily be reprogrammed. I have seen manufacturers put requested UL max wattage stickers in can lights before. Say a dimmable can light is rated for 150W A-lamp. Upon request, the manufacturer will put a sticker saying the max lamp the fixture is rated for is only 60W. Same fixture, different UL rating sticker. Then they can count that load at the reduced 60W value.
Luis Miguel Diazgranados
Green Factory125 thumbs up
October 4, 2012 - 1:22 pm
Bill, thanks for your answer. From what I gather, the contractor is trying to help the project team to find a solution to the problem we have, with at least expenses as possible. Regrettably, after a meeting with the contractor and the project owner, it looks like the only acceptable solution is to change some luminaries (and pay the extra costs) in order to comply with the 90% threshold.