4 FM quick reads on HVAC
1. Project Management: Chiller Challenges
The process of installing high-efficiency HVAC equipment in institutional and commercial facilities is rarely without complications, challenges or problems. One case in point is the construction of a 174,109-square-foot addition to Advocate Condell Medical Center in Libertyville, Ill., in 2011. The project included two new high-efficiency chillers, and it incorporated the installation of two new high-efficiency boilers in the existing hospital.
Successful installations often depend on the ability of maintenance and engineering managers and their staffs to troubleshoot the problems and make the needed changes quickly.
"As far as the issues with the new building, the commissioning and the involvement of the operations staff had a lot to do with minimizing the problems we had," says Joseph Buri, the medical center's manager of energy solutions.
Advocate Condell, with 281 beds, opened in 2003. The level-one trauma, acute-care facility with 745,034 total square feet sits on a 72-acre campus and is the largest health care provider in Lake County, Ill.
One goal of the 2011 addition was patient comfort.
In addition to allowing the expansion of outpatient services, Buri says, "The other piece to it was to allow the hospital to become all single-occupancy rooms." The addition featured two 600-ton centrifugal chillers, both with variable-frequency drives, which brought additional benefits to the hospital's maintenance and engineering department.
"We chose them because they matched our current chiller plant, which were centrifugal, as well, from the same manufacturer," says Buri, who was the medical center's director of facilities and construction at the time of the project. "We were looking to maintain some equipment uniformity. That was the one piece to it. We also wanted some flexibility in operations. We were looking for efficiency to be able to take advantage of the utility rebates.
"Because we went with a high-efficiency chiller, we received some rebates on the motors. So because of the higher efficiency, we received rebates of about $48,000 from the utility."
2. HVAC Policies, Procedures Can Improve Efficiency In Existing Buildings
Today's tip from Building Operating Management: HVAC policies and procedures can help improve efficiency in existing buildings.
Just as a green building can fade to gray, an ordinary building can move in the opposite direction.
Senior managers tend to "think utilities are a fixed expense," says Bill Harrison, past ASHRAE president and the CEO of Harrison Energy Partners. "Utilities are not a fixed expense." Almost any building can cut its energy use if managers pay attention, he says, because "almost invariably, a building does not operate as it should."
A study by Texas A&M's Energy Systems Laboratory concluded that a typical building can save 10 to 40 percent of its energy costs just by operating more efficiently. Buildings on the higher end of that range have severe problems to begin with, says Charles Culp, a professor in the architecture department at Texas A&M.
Obstacles to high performance, says Mike Bobker of the CUNY Institute for Urban Systems, begin with "not enough time, not enough money." But those are often just symptoms of lack of organizational commitment. "Once the organizational commitment is there, time and money are usually found," he says.
Policies and procedures can be an important way to improve efficiency. "A lot of stuff falls apart if there is not good specifications," says Lindsay Audin, president of Energywiz. He cites a university at which workers in each building were able to set the thermostat where they wanted it. Putting the acceptable setting in a manual makes it "the law."
That kind of system also makes it clear to technicians that they won't get blamed. Audin says federal buildings specify that air conditioning may not be set lower than 78 degrees, and "no matter how much people complain, it's not their decision." A manual “may take away responsibility people have not handled it well, or it may give them responsibility because they know someone has their back," Audin says.
3. Three Steps To Improve HVAC Performance: Audits, Retrocommissioning, Ongoing Commissioning
Today's tip from Building Operating Management comes from David Callan and Kyle Hendricks of Environmental Systems Design: Facility managers should consider three steps to improve HVAC performance: audits, retrocommissioning, and ongoing commissioning.
Over time, HVAC systems start to "drift" and performance declines. The good news is that there are a few things owners and facility managers can do to reveal operational deficiencies as well as to enhance performance, to varying degrees. From a simple energy audit to retro- and ongoing commissioning, reexamining the building's HVAC systems is the first step to optimizing efficiency.
ASHRAE's Level I Energy Audit is a general, walk-through energy assessment which identifies immediate options to save energy that are obvious to the naked eye, including lighting, fan operation, and other low hanging fruits. Mainly used to identify if a building should continue to the next step, this will satisfy the LEED-EBOM Energy and Atmosphere energy efficiency best management practices prerequisite.
Retrocommissioning builds on the ASHRAE Level I study. Retrocommissioning is a low-cost opportunity to save energy and optimize performance, helping a facility run the best it can with its current equipment and systems. Ideally performed every three to five years, retrocommissioning includes a review of trend data from the building and testing of the HVAC systems and their sequences of operations, including how each should be reacting to various scenarios.
Retrocommissioning will likely uncover three scenarios: space use changes that necessitate system operational changes; systems that aren't working as they're supposed to; and systems that are working as designed, but can still be optimized with new technologies and strategies. Onsite functional testing will ensure that systems are operating as the controls sequence tells them to, and a review of the trend data will identify opportunities to optimize the parameters that are working as intended. Typically, the higher the energy use of a facility, the more it will benefit from retrocommissioning. For example, a hospital or commercial building with long hours of operation and a significant HVAC load can save as much as 5 percent annually from retrocommissioning efforts.
Ongoing or monitoring-based commissioning is similar to retrocommissioning in that it reveals equipment and scenarios that aren't functioning as designed and those that can work better, but with the added benefit of doing this on an ongoing basis. Continuous monitoring of all points in the system is conducted by a team of engineers, while a weekly download of all information, either to a dashboard or through a software platform with fault diagnostics, alerts the operators when there is an opportunity to make an adjustment. Pre-programmed alerts may include an alarm when a chiller is below a certain efficiency, simultaneous heating and cooling is occurring, or a temperature gets too warm or cold.
Monitoring-based commissioning provides the opportunity to see the long-term operations and re-evaluate the building's systems on an ongoing basis, and therefore makes building optimization more robust, based on more real-time data over a longer period of time. Also, because the process is ongoing by nature, it will prevent HVAC system performance "drift" after the initial opportunities are implemented.
4. Solid Maintenance Programs keep Chillers Operating Efficiently
As chillers age, their components wear, heat transfer surfaces become fouled with scale, and breakdowns become more frequent. Solid maintenance programs that address tracking performance, conducting regular inspections, and performing all scheduled maintenance activities can extend system life while maintaining the performance of the system, but they can not completely eliminate the impact that time has on the chiller. Eventually simple wear and tear will cause maintenance costs to increase and system reliability to suffer.
To evaluate system reliability, start with a review of the chiller's operating log. Operating logs track data related to the operation of the chiller, including drive motor current and voltage, condenser water supply and return temperatures, evaporator and condenser pressures, and oil temperature and pressure. Additional information, such as the need to add oil to the system and scheduled and unscheduled maintenance activities, should be recorded in the chiller log.
Reviewing this information on a regular basis can identify trends that may be negatively impacting system performance and reliability. Are the maintenance requirements and breakdowns increasing? Is the length of time that the chiller is out of service the result of a breakdown increasing?
Another reliability factor that must be taken into consideration is the availability of replacement components. While chiller manufacturers maintain an inventory of replacement components for practically all of their models regardless of their age, it does become more difficult to get replacement components for older models. Time delays in locating and shipping these components result in longer outages for managers and building occupants.
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