Hi everybody,
My team and I are working on a CI project (office floor) where the tenant has installed occupancy sensors for up to 75% of connected lighting load. In that sense, I would appreciate if someone would tell me if that means that we get the 15% reduction in lighting power as shown in Table G3.2. (Yes, the office floor is less than 5000 ft2) If not, how much reduction in lighting power do we get? and how do we perform such calculation?
In other words, what is the correlation among the amount of sensors that are in place and the percentage of reduction in lighting power?
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
734 thumbs up
November 19, 2012 - 12:06 pm
This is a confusing Table and never made much sense so I've generally ignored it.
I take the Table as only applicable to lighting that does not require automatic shutoff elsewhere in the Standard. If the lights are in a building less than 5,000 sf then you can claim the 15% reduction for adding occupancy sensors. And this is referring to the total building's floor area, not just one tenant. Only claim the savings for the 75% of the lighting load that you have controlled by occ sensor. The number of sensors doesn't matter, just the watts of lighting controlled by those sensors.
(connected lighting load) * (75% controlled by occ sensor) * (15% per Table G3.2) = reduced wattage bonus.
Alex AC
6 thumbs up
November 19, 2012 - 5:06 pm
Thank you for your quick reply, Bill. Sorry for the confusing wording. Watts of lighting controlled is what I meant to say by "amount of sensors". So, I see. Given that this is a CI project and the scope of work of the tenant is only within a single floor, then we CAN NOT refer to Table G3.2 to claim any reduction on lighting power by the sensors, right?
Aside from that, I´ve started to document our "Total lighting load for the project space" (Option C) as required by the EA Credit 1.2 form found on LEEDonline and I´m having a bit of a problem determining the "Task lighting that is not exempt per ASHRAE 90.1 2007 Section 9.2.2.3". Could you expand on this, please?
Lastly, I´ve seen the phrase "automatic control device" quite a few times across Section 9 of Standard 90.1. Is this an equivalent term for a sensor/controller when it comes to reducing lighting power? what do they mean by automatic?
Thanks again!
Bill Swanson
Sr. Electrical EngineerIntegrated Design Solutions
LEEDuser Expert
734 thumbs up
November 20, 2012 - 10:20 am
There are lots of terms that are confusing until you use it all the time. "Baseline" used to really confuse me, why not just say Code maximum? So yes, "automatic control device" is a sensor, timer, relay panel, or any other non-manual thing that can turn lights on and off. Something other than a simple on/off wall switch. They don't want to rely on people having to remember to turn off the lights when they leave. The phrase has a definition at the beginning of 90.1 that is vauge but says this same thing.
My opinion is that Table G3.2 is only applicable to lights that don't need automatic shutoff. But that's my opinion and I know others disagree. Don't you love Code language?
Section 9.2.2.3 has a list of 16 types of lighting that is exempt and doesn't need to be counted with the total wattage for interior lighting. There have been many projects that would ignore office task lighting because it was being supplied with the office furniture and not by the electrician. Maybe the interior designer hasn't even picked the task lighting yet when the energy model is being done. ASHRAE 90.1 says that ALL interior lighting (excluding those listed in 9.2.2.3) must be counted in the total. This line in the LEEDonline form is a reminder to count the task lighting when you're totaling your interior lighting wattage.