65% HVAC Load Reduction at ArcBest

About ArcBest

ArcBest^SM is a multibillion-dollar logistics company delivering integrated solutions primarily under the ArcBest brand. Their offerings include less-than-truckload services via the ABF Freight^® network, ground expedited solutions through Panther Premium Logistics^®, household moving under the U-Pack^® brand and vehicle maintenance and repair from FleetNet America^®. From Fortune 100 companies to small businesses, customers trust and rely on ArcBest for their transportation and logistics needs.

With a relentless focus on meeting their customers’ needs and unique access to guaranteed transportation capacity, Arcbest creates solutions to even the most complex supply chain challenges. They are focused on providing the best customer experience possible with seamless access to a broad suite of logistics capabilities, including truckload, LTL, ocean and air, ground expedite, managed transportation and warehousing.

Their over 13,000 employees deliver knowledge, expertise and a can-do attitude with every shipment and supply chain solution, residential move and vehicle repair. Headquartered in Fort Smith, Arkansas, ArcBest has significantly expanded their total service offerings to include both asset-based and asset-light solutions to meet any customer need.

No matter the job, ArcBest finds a way.

The Challenge

Originally designed to support an occupancy level of 850 people, the corporate headquarters has grown to now have 1,085 people plus visitors. Ten percent of the people work at night, requiring 24/7 conditioning of air. The increase in occupancy drove a need to introduce more outside air to maintain air quality. All of this outside air had to be conditioned, increasing electrical energy costs. In addition, the extra outside air caused draftiness on cold winter days, and during the summer the extra outside air flow through the air handlers resulted in some parts of the building getting too cool.

I previously got calls from people that they were cold during the summer, which was a direct result of having to introduce so much chilled air into the building to meet the appropriate CO₂ levels. Likewise, they felt drafts during the winter due to all the outside air that was being used to ventilate the building. When the HLR modules are running, our people are more comfortable.”

Richard Rieske
Director of Corporate Facilities at ArcBest

The Building

The Corporate Headquarters Building is in Fort Smith, Arkansas, a warm and humid city in the Southeastern United States. The 190,000 ft² building (see Figure 1) has five floors of office space separated into two wings (east and west primary zones). Two staircases connect all building floors.

The building has a central core (bathrooms, coffee rooms) and a peripheral open office plan. There is a computer room on the 1 st floor and executive offices and conference rooms at the southern side of the 4 th and 5 th floors.

Each wing is served by a dedicated air handling unit (AHU). Building return air is an open plenum suspended ceiling type while air is ducted to line diffusers. Building pressurization is regulated on each floor by return air mounted exhaust fans.

At the start of the project, the building’s central plant on the ground floor had two packaged hermetic centrifugal liquid single-speed chillers (375 tons each). On warm days, the second 375-ton chiller was required, but now with the enVerid HLR ® modules they typically only need a single chiller as the peak HVAC cooling capacity has been reduced by about 273 tons.

All outside air intake for the HVAC system is demand control ventilation (DCV) dependent (controlled by space CO₂ sensors). The outside air damper is actuated based on an averaged CO₂ value on a per floor section basis. Each floor has about ten CO₂sensors strategically distributed throughout the floor. CO₂ sensors residing in the eastern section on each floor were averaged separately from those in the western section. CO₂ set point is observed by the BMS to actuate outside air damper position.

“Running a second chiller significantly increased our energy utility costs” per Tom Daigle, Manager of Building Systems at ArcBest. “By using the enVerid HLR modules, we are not conditioning as much outside air and we are projected to save $63,709 annually.

We are reducing approximately 273 tons of HVAC cooling capacity.”

Tom Daigle
Manager of Building Systems, ArcBest

The building has a Carrier iVu Building Management System (BMS) running BACnet over MSTP which can optionally be integrated with enVerid’s HLR BACnet to control the outside air (OA) damper. The following registers are available in the system:

• Outside air temperature and relative humidity [°F, %]
• AHU VFD [%]
• Return air exhaust fan VFD [%]
• CO₂ values [ppm] per sensor and averaged values
• Cooling coil valve position [%]
• Supply air temperature and set point [F]
• Mixed air temperature [F]
• Supply/return water temperature [F]
• OA Damper position [%]
• Object mapping

The Project

The kickoff began with a site survey by the enVerid team of the building mechanical layout, an Indoor Air Quality (IAQ) assessment and identification of potential locations for integrating the HLR 1000E systems. The number of HLR modules needed and the resulting outside air reduction were calculated according to ASHRAE Standard 62.1 Indoor Air Quality Procedure (IAQP) for a typical office building.

The site survey assessed the spaces that are cooled and heated (including stairways and closeted spaces), and documented the existing hydronic systems, power meters and all DCV, VAV and AHU interactions in the building, including dampers, sensors and exhaust systems.

The survey measured and planned for the positioning and installation of the HLR modules, ensuring that they would fit and could be easily moved into position. In this phase, the team also checked for wireless connectivity options and suggested connection points to the BMS.

Lastly, the team took snapshot baseline measurements of CO₂ , energy use and other air quality indicators. This information was shared with the facilities management team.

The Central Plant Mechanical Room (see figure 3) on the first-floor houses two AHUs: one which conditions the western side of the first floor and the other that conditions the computer UPS room – which is isolated and separated from the office space. The computer room was not included in the HLR retrofit as the outside air intake is fixed at a low level. The Eastern Mechanical Room contains the AHU that conditions the eastern side of the first floor.

Inside the mechanical rooms each AHU has their supply air (SA), return air (RA), and outside air (OA) ducted. Each mechanical room has an outdoor air inlet ducted from a louver on the mechanical room north-east exposure. A return air exhaust fan (separated from the return air duct with a gravity damper) is connected to a louver on the mechanical room north-west exposure.

In the installation phase the enVerid project team selected and supervised electrical and mechanical subcontractors with the customer’s approval. 10 HLR modules, installed in each of the building’s mechanical rooms, will cover all spaces within the building. A slip-stream of return air from AHU is ducted through the HLR module to be cleaned. Outside air used for regeneration and regeneration exhaust from the HLR are ducted to the louvered outside air in each mechanical room. Figure 5 shows an example of adsorption (A, B) and regeneration paths (C, D). Figure 6 shows a schematic of HLR module by-pass connection to the AHU.

Additionally, the enVerid project team continues to work with ArcBest’s Facilities Management post-installation to optimize energy, IAQ and environmental comfort. ArcBest data continues to be captured for the National Renewable Energy Laboratory (NREL), to provide documented consumption information to the US Department of Energy.

Energy and Air Quality Measurements

Using HLR Technology, ArcBest could take advantage of ASHRAE 62.1 Indoor Air Quality Procedure (IAQP) and use 65% less outside air compared to using the ASHRAE 62.1 Ventilation Rate Procedure (VRP). As a result, the annual energy savings for heating and cooling are calculated to be $63,709.

For indoor air quality (IAQ), contaminant concentrations were measured prior to the HLR operation, then again after the HLR module had been installed and running for at least one week. Indoor air quality monitoring was performed per US Environmental Protection Agency (EPA) standards and the results were analyzed and certified by an independent lab (PRISM Analytical Technologies).

This investigation included environmental and indoor air quality sampling of temperature, relative humidity, carbon dioxide (CO 2 ), full scan of speciated (separated by species) volatile organic compounds (VOC) and total VOC, aldehydes (e.g., formaldehyde), and particulate matter with aerodynamic size of less than 2.5 μm (PM 2.5 ). These include all the contaminants of concern found in office buildings. The investigation included sampling throughout the building at 10 different locations for CO₂ , and two different locations for VOCs. Instruments used were calibrated before each use and functioned within the limits of performance specifications appropriate for pollutants measured in indoor environments.

The Impact

273 tons Peak HVAC Load Reduction

The HLR reduced peak HVAC load by 273 tons, which corresponds to a 36% decrease in total HVAC load. On warm days, ArcBest’s second 375-ton chiller was required, but now with the enVerid HLR modules they typically only need a single chiller. This savings impacts the “demand charges” on ArcBest’s utility bill, which in many locations, has a major impact on the overall cost of electricity. In addition, when ArcBest replaces the HVAC equipment in the future, the peak capacity required will be 36% less, providing significant savings in capital expense.

Energy Savings of $63,709 per Year

Based on sensible and latent energy calculations, the energy savings for reducing outside air by 26,640 CFM equates to $63,709 annually using a standard energy model as applied to Fort Smith, AR, outside temperature and relative humidity data downloaded hourly from 2009 to 2013 (see figure 7).

Water Savings of $11,535 per Year

ArcBest was also able to conserve on cooling tower water but a separate water meter wasn’t available so this information was not included in the overall project savings. However, based on standard calculations, ArcBest is saving 2.175 million gallons of water and saving $11,535 in water and wastewater charges.

Earned a One-Time Energy Rebate of $66,900

The local electric utility, Oklahoma Gas & Electric, offers rebates for energy efficiency projects. The rebate of $6,690 per HLR module, funded a substantial portion of the deployment

Maintained Indoor Air Quality

CO 2 levels vary throughout the day but are maintained at levels below 1,000 ppm see (Figure 8).

VOC measurements included TVOC and a full scan of speciated (separated by species) VOCs, identified by the USGBC as VOC contaminants of concern. The results, shown in Figures 9 and 10 below demonstrate the air scrubbing effectiveness of the HLR Technology.

Mixtures of Concern (MOC), introduced as part of ASHRAE Standard 62.1-2016 IAQP, are two or more hazardous substances that have similar toxicological effect on the same target organ or system. Their combined effect should be considered additive as exposure to low concentrations of MOC may cause adverse effects to human health 1 . Figure 11 shows the identified MOC and the organ-impact related characteristics of each COC.

To show compliance, the ratio of the measured concentration of each contaminant to its exposure limit is determined, and the sum of these ratios for each MOC group should not be greater than one. The result of these calculations is shown in the bottom row of Figure 11. The calculated values of each of the mixtures is below 1, therefore, it meets the limit of the MOC.

DCV System No Longer Necessary

By incorporating HLR modules and using IAQP to manage how much outside air is used for ventilation, ArcBest no longer needs to rely on its demand control ventilation (DCV) system. Using IAQP, HLR modules enable reduction in outside air, a feature not available with DCV, because it provides IAQ management for all contaminants, not just people-related contaminants. Consequently, ArcBest is using the HLR modules to control outside air dampers, thereby bypassing the DCV system. Additionally, by using the HLR and IAQP, ArcBest is now managing ventilation based on all COC instead of just CO₂ .

Additional Savings:

• Filters: A 65% reduction in outside air can extend the lifetime of the outside
  air filters by 2-4x and lessen the impact of coarse, fine and ultrafine particles
• Reduced Corrosion: A reduction in outdoor air intake provides several
  secondary benefits that include extending the useful life of the existing
  mechanical equipment and ductwork

enVerid’s people are Class A, top-notch and the HLR system works as advertised.”

Tom Daigle
Manager of Building Systems, ArcBest

Conclusion

ArcBest℠ is a logistics company with creative problem solvers who have The Skill and The Will^® to deliver integrated logistics solutions. At ArcBest, We’ll Find a Way to deliver knowledge, expertise and a can-do attitude with every shipment and supply chain solution, household move or vehicle repair.

The ArcBest headquarters building in Fort Smith, AR, was designed to support an occupancy level of 850 people which had grown to 1,085 plus visitors. The increase in occupancy drove the need for increased outside air ventilation, resulting in an increase in energy consumption and challenges in maintaining air temperature comfort throughout the building.

Results: Reduced HVAC capacity, Improved Energy Efficiency and Indoor Air Quality (IAQ)

• 273 tons reduction in HVAC cooling peak load
• $63,709 energy cost savings annually
• $11,535 in water and wastewater savings
• $66,900 utility rebate
• Extended particulate filter life
• All COC and MOC are maintained at a healthy level
• Eliminated overhead of DCV system
• Better indoor air comfort
• 65% average reduction in outside air needed (IAQP using HLR vs. VRP)