Keeping your world up and running.®

Lighting in the lab

How to lower electric bills

March 2013

As part of their training, members of Paul Meyers' Building Automation 101 class at the Electrical Training Institute in Indianapolis wanted to identify opportunities for decreasing energy consumption. A close-at-hand project was to perform an energy consumption survey on the lighting in the open lab area, including a proposal for a lighting upgrade based on measurable, accurate data.

Collecting the data

The apprentices took all the measurements using a Fluke 1735 Three-Phase Power Logger and analyzed the measurements using the included Fluke Power Log software.

Fluke 1735 Power Logger

Fluke 1735 Power Logger

They took the first measurement at the three-phase 480-volt Main Distribution Panel mains for a period of 168 hours, and found that the total energy consumed was 6,421.1 kWh. Their second measurement was at the three-phase 480/277 volt Lighting Panel HP-1 for a period of 168 hours. The total energy consumed was 1,578.7 kWh. This correlates to 24.59 percent of the total electricity usage contributed to lighting in the building.

Apprentices took a third measurement on circuit #17 in panel HP-1, which feeds the back high bay lights and two emergency fixtures. The total energy consumed was 262.42 kWh, correlating to 16.62 percent of the total lighting power and 4.09 percent of the total building electricity usage.

The measurement on circuit #17 indicated the 175-watt metal halide lights were on for an average of 12.6 hours per day five days a week and off on Saturdays and Sundays. This timing is probably due to the long re-strike time if the lights are shut down after a class finishes occupying the space.

Class recommendations

The class project consisted of two strategies to reduce energy consumption:

  • Reduce the lighting load
  • Reduce the time the load is present using an occupancy-based control system

The existing HID (high intensity discharge) fixtures are not appropriate for occupancy-based switching, due to long re-strike and cool down times. The class determined that three-lamp T5HO fluorescent fixtures can be substituted for the current fixtures on a one-to-one replacement utilizing existing electrical piping and circuitry. Their vision is to reduce the time of use from the existing 12.6 hours per day to 7 hours per day by installing three passive infrared occupancy sensors at the west and south entrances plus a centrally located sensor, to ensure full coverage.

Justification for investment

The calculated rate for electricity at the Electrical Training Institute is 11.35 cents per kWh. Costs for lighting the lab with the current fixtures at the current times are estimated to be $1,549.97 per year. The class estimates a savings of $837.89 per year by installing fluorescent T5HO fixtures controlled by an occupancy-based system. Estimated installation and purchasing costs add up to $2,526.35. IPL, the Indianapolis Power & Light Company, offers a rebate of $28 per fixture ($476 total), and the estimated salvage value of the old fixtures is $50 each ($850 total). This results in an expected cost of $1,200.35. These calculations indicate a return on investment in less than 1.5 years.

Equipment Price Qty Total
I5-354T5-WG-UNV-L5841-EBT1-U $137.25 17 $2333.25
AYC-CHAIN/SET-U $4.30 17 $71.10
PIR Motion Sensor $40 3 $120
SUB TOTAL     $2526.35
Fixture Rebate IPL     -$476
Fixture Salvage     -$850
TOTAL     $1200.35