Two years ago, I was invited to visit the Atlanta corporate campus of Assurant, Inc. to discuss their Energy Star score – it was too low and they wanted to do something about it. The twelve story office building was burdened by a chiller plant that was all original construction. Chillers, pumps, and cooling towers were well-maintained, but after more than 27 years of service, they were showing their age and not performing at the level they once did. This initial meeting unofficially began design efforts that have resulted in the recent completion of a $5.7 million upgrade to the HVAC and Electrical systems, a construction project that already has proven itself with lower electrical bills that bring a smile to Tony Ring, Manager of Maintenance Operations for Assurant.
5 key upgrades to produce energy savings:
The first place we suggest improving HVAC system performance is with the terminal units located above the ceilings. These units adjust the volume and temperature of supply air being delivered to the space. For Assurant, we added 38 terminal units to the 267,000 square foot facility and more importantly, installed new controllers on all terminal units. The replacement of the old pneumatic actuators with new DDC controllers allows much greater modulation of the air handling units thereby providing a trifecta of energy savings: reduced fan horsepower, less electric reheat, and lower chilled water flow to the cooling coils.
Replacement of the air handling units was added to the project after the chiller plant design was well underway. The addition resulted in a boost for energy savings. By replacing the old air handling unit chilled water coils designed for 12°F delta-T with new coils designed for a delta-T of 16 °F, the peak pumping flow rate was reduced by 25%.
A project completed several years prior to this one eliminated incandescent lighting from the building. We implemented a sophisticated lighting control system with over 550 occupancy sensors and time schedules. The late night exterior view of the building went from “lit up like a Christmas tree” to “darker than black”. The occupancy sensors are also tied to the HVAC system for added flexibility and savings.
New source equipment for the cooling system, selected with efficiency and value in mind, provide an HVAC infrastructure that solidifies the energy savings plan. Chillers boasting an efficiency of 0.51 kW/ton at full load and 0.325 IPLV (at AHRI standard rating conditions) and cooling towers at 85 gpm/hp are much better than energy code minimums. Variable frequency drives are included on all motors.
All new and existing HVAC equipment is controlled by an open-protocol DDC system with energy monitoring to allow Assurant personnel to measure and track electrical usage.
I heard a story from Tony last month where he mentioned a phone call he recently received from Georgia Power. The representative noticed that Assurant’s electrical demand was significantly lower in May and June of 2015 compared to the same months last year. Georgia Power wanted to know if anything has changed at the facility this past year to justify the reduction. “Why yes”, Tony responded…with a little smile.
Author: Steven C. Severini, PE, CEM