Planning Ways to Save<br>5-Year HVAC Planning Programs Yield Big Benefits
By Robert Schneider, M.E.
Tim Baker, M.E.
Steve Chase
TES Engineering
Proper operation of HVAC equipment is vital to the comfort and profitability of retail facilities. The approach to managing it, however, is frequently reactive and misses various opportunities to economize.
In a reactive scenario, complaints to management trigger a search for the poorly operating unit. Because of the risk of imminent failure and a six to ten week lead time for delivery, there is no time to investigate new, more energy–efficient alternatives, so the same unit or component is ordered. Likewise, contractors are hired quickly, with little or no scope definition and effectively without competitive bidding.
Most facilities' management is more vigilant, but the oversight usually is performed by generalists who lack HVAC expertise or by service/contracting companies who may have a potential conflict of interest in recommending whether a unit can be nursed along, needs major repair, or should be replaced. The tendency is still to make like-for-like replacements, and budgets typically are based on historical annual average repair costs or the proposal from the outside service firm.
Engineering guidance
In contrast, professional engineers are ethically and legally obligated to assess conditions and to provide technically appropriate recommendations. This provides a level of trust in the information presented that is not available from other sources.
The engineering recommendations can be tailored to the desire of the facility owner—including the desire to minimize expenditures. Even on a shoestring budget, looking at managing HVAC systems from a programmatic basis will enable operations directors to evaluate information and make wise decisions.
A five-year planned program that is executed by professional engineers assesses the facility's existing conditions and presents recommendations for the projected repairs or replacement of HVAC units.
Technical improvements
When replacing HVAC equipment that is 20 to 30 years old, technical advancements make a big difference in determining appropriate size. Not only are today's units more energy efficient, but engineered evaluations based on computer modeling are much more accurate than previous hand calculations or selection of size based on commonly accepted "rules of thumb."
An enclosed retail mall in the Northeast had 22 common area air cooled rooftop HVAC units and 16 tenant air cooled VAV rooftop units—all of which had been installed in 1992. A 5-year plan was developed to prioritize and generate design drawings for their replacement, as all were nearing the end of their useful life.
Field evaluation determined that the units were in decent condition, but several tenants had cooling complaints in various areas of the mall. Load calculations showed that most of the existing units were oversized in the common areas but undersized in the tenant spaces. Correcting the sizing of the units would be crucial not only for improved comfort, but also for proper operation of the units and extension of equipment life.
The analysis of replacement sequencing considered many factors, including deficiency of cooling, location, difficulty of replacement, size, installation cost, maintenance records, and personal experience of the mall maintenance personnel. The recommendation called for replacing the most undersized tenant units in the first year, followed by the rest of the units in years two through five as shown in Table 1 and Figure 1. By properly sizing the replacement units instead of performing like-for-like change-outs, estimated net energy savings for the mall totaled $73,020 annually.
Figure 1 Location and schedule of HVAC units to be replaced in the mall's 5-year plan.
Table 1 Five-year plan common and tenant RTU summary for a Northeastern mall.
Upgrades, budgeting, and dampers
A five-year plan for a Southern California mall made recommendations for required maintenance and efficiency upgrades. Priorities were based on addressing a food court odor issue and working within the mall's $100,000 annual budget. In addition, the field inspection and discussions with maintenance personnel revealed the need to replace chilled water piping throughout the system. An estimate was provided with the recommendation to perform the work in phases as budget allowed and to minimize disruption.
Table 2 lists the various projects and costs, as well as energy savings and payback periods where applicable. Aggregate annual energy savings were estimated at $70,900. Field investigations showed that outside air dampers and return air dampers did not function on 10 air handling units serving the mall common area and on all of the fan coils serving the food court seating and toilet areas. This was a major cause of the odor problems, as the food court exhaust fans were starved for make up air. Codes require a minimum CFM of outside air per person, which also made the bulk of the damper replacements or repairs a first-year priority.
The recommendation also called for upgrading the old pneumatic actuators to integrated economizers with humidistats and electronic controls. If the outside air were cooler and of less humidity than the mall return air, the economizers would modulate open, allowing lower- temperature air to enter the air handling unit. This would require less chilled water to meet the mall set point and reduce energy costs by $17,300 annually.
There is a common misconception that bringing outside air into a facility is an energy waste, and malfunctioning dampers are often just bolted shut when they falter. In fact, utilizing cool outside air—even if only during the morning and evening hours—offers the opportunity for energy-saving free cooling.
Tower replacements
Even in a must-replace situation, opting for an engineering solution vs. a like-for-like replacement pays off. A New England mall needed to replace its cooling towers due to the potential for failure. The load calculations and tower design optimization yielded savings of $52,000 on equipment cost avoidance and power and structural upgrade avoidance. Additional engineering improvements to the system produced $4,000 in equipment savings as well as annual savings of $30,900 in power and water costs over the existing operation.
Evaluate utility rebates
Working with utility companies to gain rebates for retail facilities is another aspect of a planned HVAC program. However, sometimes analysis shows the rebate isn't worth the investment.
Another New England mall needed to replace nine tenant VAV units, and the local utility offered a rebate to replace the air cooled units with evaporative cooled ones. The engineering analysis studied capacity needs and compared installation and operating costs of new high efficiency air cooled units vs. evaporative cooled ones. Even with the rebate, the owner's investment would be $1,089,900 for evaporative cooled units, compared to $1,053,000 for the alternative. Compared to existing equipment, the evaporative cooled units would save $71,700 annually through KWh and KWd reduction vs. $49,400 for the high efficiency air cooled units. However, the evaporative cooled units would incur an additional $23,600 in annual water and maintenance costs. Thus the high efficiency air cooled units would provide $1,300 more in annual operation savings. This information showed that the utility's rebate and proposal to replace the old air cooled units with evaporative cooled ones was not the right choice for the mall.
Consider skylights
A mall in the Southeast was planning to replace 16-year-old HVAC rooftop units, and had a long-term problem with cooling the large open food court area. Load calculations showed that the existing five 20-ton units were 35 tons short of the needed cooling capacity. The recommendation was to increase the size of the replacement units to 25 tons each, which was the maximum that could be supported by the existing electrical service, structure supports, and duct work. Tinting was added to a 2,820 sq. ft. portion of the skylights to reduce the cooling load in the food court by approximately 10 tons, thus avoiding costs of major upgrades to the system and higher annual costs of increased electrical service. Even though the new units were larger, their improved efficiency yielded annual power savings of $3,000. Redirecting air with adjustable diffusers and relocating the temperature sensor also enhanced comfort in the food court.
Bottom line benefits
Taking a planned approach to managing HVAC expenditures can reduce operating costs through energy efficiencies, extended equipment life, and utility rebates. And it can transform costs from being a hit to the bottom line to qualifying as capital expenditures.
The Internal Revenue Service views isolated repair costs—such as repairing a single compressor—as expenses in the year made, which reduce net profit. Planned capital expenditures are depreciated over time in much smaller annual amounts. Also, they are not included in the calculation of Earnings Before Interest, Taxes, Depreciation, and Amortization (EBITA), which is an indicator of profitability that is watched by investors. It is important to review such decisions with a professional financial counselor.
Additional areas of savings
As previously discussed, reducing the size of HVAC units is a fertile area—a 20% size reduction typically yields a 30% energy savings. But careful consideration of installation issues is fruitful as well. Planning replacement of units to minimize crane lifts can save tens of thousands of dollars and minimizes disruption at the facility. The use of helicopters has been restricted since 9/11, and some equipment weights preclude their use.
Competitive bidding on equipment and contractors produces significant savings. Installation can cost twice the amount spent on equipment, so it's important to have accurate design drawings and expert evaluation of the bids to select the properly qualified contractor with the best bid, not simply the lowest price.
Sometimes, custom units—which are more expensive—can minimize installation and total costs of the project, for example, to fit a large VAV unit on existing rooftop curbing. And occasionally, fundamental mistakes are uncovered, as in the case of a Southwestern mall that had tried to solve cooling problems for 15 years before a thorough engineering investigation discovered that design requirements provided to tenants to perform their own installations were mismatched to the base building HVAC system.
Many of these opportunities to capture savings can be materialized if a planned approach to HVAC is used. Planning provides the time element required for proper engineering evaluation.