As building owners fight to control operating costs, they often turn their attention away from maintenance in an effort to pinch pennies. Or, they underpay for their maintenance program and attempt to “fix” problems by adding additional heating or cooling rather than trying to discover why systems aren’t performing optimally. By stepping over dollars to pick up dimes, they’ve created a culture of deferred maintenance.
The only winning solution when maintenance is underperformed is retrocommissioning.
Retrocommissioning evaluates a building’s current operation and compares it to how the building should operate. This sometimes means going back to the original design criteria for the conditioned space, but often times buildings are no longer serving the same purpose for which they were originally intended.
Retrocommissioning can allow an owner to reduce the utility cost for running the mechanical systems in a building, improve comfort conditions in the space, extend the life of the mechanical systems, and reduce downtime. Some specific needs that building owners can immediate identify include temperature complaints, excessive noise from units cycling on and off too frequently, building pressurization issues, and uncontrolled energy costs. Often, low cost or no cost improvements can be identified.
Value of Setback Schedules
Some of the problems we at Brewer-Garrett have uncovered in retrocommissioning include systems that are running 24/7 that should be on a night setback schedule. Originally, the building’s energy management system had a schedule, but during one particularly cold winter, the building hadn’t heated up enough by the time it was occupied, so the building maintenance staff “temporarily” put the HVAC system in manual and just let it run. Two years later, the “temporary” fix was still in place.
We’ve also found a similar problem with a digital control system at a local university. When the system shut off for night setback, an out of calibration discharge air static pressure sensor sent back a value of less than 4 mA, which caused the energy management system to rule the point as unreliable. As a result, when the system was called to run, the energy management system had the fan locked out due to the unreliable point. Rather than identifying the problem and fixing the sensor, improper troubleshooting caused the building maintenance team to override the fan to run 24/7.
Guide to Optimum Building Performance
One of the greatest benefits of retrocommissioning comes in the form of a complete guide and report on how the building is supposed to run. The documentation serves to provide operational procedures for all tested building systems. This becomes an invaluable tool when training new maintenance personnel, or when reviewing the operation of a system that’s not frequently inspected.
In addition, retrocommissioning provides more consistent environmental and operational performance, and improves building sustainability. At another commercial building, our retrocommissioning process discovered that all the chilled water valves on the building’s air handling units were 100% open, and the fans and secondary pumps were running at 100%. However, the primary chilled water pump had failed, and the backup could only deliver 10% of the design flow. As a result, the facility management team had the entire building running 24/7 because it could never recover from night setback.
Adding Up the Savings
Energy savings realized through retrocommissioning can range from significant to outstanding. We’ve seen 5% to 35% reductions in energy usage in before-and-after scenarios.
We’re also seeing the emergence of data harvesting as a way to move retrocommissioning into more of a continuous commissioning process. Ten years ago, the cost of automation systems and associated memory was at a premium. Today, it’s much more cost effective. Data from thousands of terminal boxes can be gathered in 15 minute increments 24 hours/day. The flow from a VAV box can be compared to the amount of CO2 in the space, temperature in the space, and the status of an occupancy sensor. Using a database program such as SQL or Oracle, the voluminous amounts of data can be quickly evaluated and alarms produced when what’s measured begins trending away from the norm.
Retrocommissioning can also provide improved comfort in buildings that were hastily designed and constructed. Buildings that were constructed in the last three years provide some of the best opportunities for retrocommissioning, as indicated by occupants’ comfort complaints. With today’s plan-and-spec construction process rushing to turn the building over to an owner, commission of a mechanical system can sometimes be reduced to, “throw the switch and if it doesn’t smoke, it’s good to go.”
The Brewer-Garrett Company was recently called to consult at an office building that was only two years old. The owner said the perimeter offices were always cold, however, the installing contractor and their controls contractor couldn’t find a problem. The variable air volume (VAV) boxes were moving and the electric reheat coils were operational. After the warranty period, we were asked to look at the system and design a second system to provide heat in the space.
Before we redesigned the system, we retrocommissioned what they had, and found the building automation system was never programmed properly. The VAV boxes were set up as cooling only, and the heating coil would never come on. The good news: we saved them the cost of installing another mechanical system they didn’t need, and the affected offices are comfortable in the winter. The bad news: their cost of energy will go up, now that the heating system is working as it should.
The biggest opportunities for retrocommissioning includes buildings that were never commissioned, buildings that were commissioned improperly, or buildings that have had a significant change in use.
To be successful in retrocommissioning, a contractor needs to have systems experts that understand how all the intricate components and subsystems of a mechanical system work together to provide HVAC. There’s also a need for engineering resources to determine how the systems should be operating most efficiently.
Lastly, you must have a competent service department to fulfill repairs uncovered during the retrocommissioning process. Without a service department team in place, the retrocommissioning report will collect dust on a shelf, with other energy audits and efficiency reports, which outline the needs of the building, but provide no resources to affect the repairs.
The building owner and in-house maintenance staff must be actively involved in the process and promote change to the status quo.
Greg McDonald is service general manager for The Brewer-Garrett Company, Cleveland, OH. Brewer-Garrett specializes in energy services, HVAC services, Design/Build, integrated facility services, and building commissioning. For additional information, visit Brewer-Garrett.com.