4  FM quick reads on HVAC

1. How to Make the Repair-or-Replace Decision


Managers facing repair-or-replace decisions for pumps must take into account both in-house maintenance capabilities and company policy. Some managers opt to repair as long as the pump casing remains in good condition, which can be decades. Technicians simply replace rotating or worn parts as needed, and if the in-house maintenance shop has cutoff machines, drills, lathes, milling machines and shapers, technicians can make many of the needed parts.

One alternative approach is to follow the policy that optimum service life occurs when cumulative maintenance labor and material costs equal a pump's replacement cost. Managers can use a formula to calculate a pump's optimum service life in hours and can compare optimum hours to actual operating hours.

An hour meter or service-hours recorder attached to the pump can help accurately determine actual hours. The service recorder is the best option because it accumulates operating hours and sorts them into idling hours and hours under load — valuable data for evaluating the effectiveness of the pump design. When actual hours exceed optimum hours, the unit is replaced.

Company financial policy also affects the repair-or-replace decision. Managers must expense parts for rebuilding in the year purchased, but they can capitalize and depreciate replacement pumps over several years. With either option, managers need to watch for upgrade possibilities to newer, more energy-efficient designs, such as VFDs to replace throttling valves. Upgrading the design of a pump or drive can help defray the upfront costs through energy and reliability savings.


2.  HVAC: Why Things Go Wrong

What happens when the engineers leave and move onto the next project? Simple: Things start to "drift."

There are a few simple explanations for drift. First, the complex controls used in new installations are reliant on sensors. Sensor technology has improved in the last five years; however, these devices still require periodic recalibration and replacement. Secondly, people, both occupants and operators, are not machines. People have minds of their own and are not inclined to mold themselves into the prescribed behavior dictated in the design conditions and sequences of operation. We say that "passive buildings require active occupants" to achieve outstanding performance. But, in most commercial buildings, the opposite logic is employed. Occupants and facility managers alike want buildings to actively control themselves, so that occupants can go about their business with little or no attention paid to the building systems.

Even when the components are complex, the HVAC system control logic should not be. If facility staff, in response to a building occupant complaint or a change in tenancy, cannot quickly find a simple or temporary adjustment to the system, they will be forced to override the controls and deviate from the intended, and presumably optimal, sequence of operations.

Some of the problems that routinely occur include: permanent temperature resets that may result in simultaneous heating and cooling or poor refrigeration performance, system static pressure increases to overcome isolated air distribution issues, automatic start/stop overrides, manual locking of outside air dampers, disabling energy conservation control features, non-functioning sensors, previously unknown control device and valve failure and improper installation of components.

The good news is, there are a few things facility managers can do to reveal operational deficiencies as well as to enhance performance, to varying degrees. Measures to optimize HVAC systems include energy audits and commissioning. Indeed, from a simple audit to retro- and ongoing commissioning, reexamining the building's HVAC systems is the first step to optimizing efficiency.

3.  Replacing HVAC Equipment Before It Fails Pays Off

Today's tip from Building Operating Management: Replacing HVAC equipment before it fails can pay off.

While upgrading HVAC equipment is never an easy process, it's certainly easier to do it before something breaks. Nike found this out the hard way.

"We had a reactive plan in place when it came to replacing HVAC equipment, due to budget restrictions, and would only replace the units after they had failed and had no more life left in them to be salvaged," says Kirk Beaudoin, territory facilities manager, North American retail operations, Nike. "After a few difficult summers, where multiple units had failed, causing major discomfort and lost sales as consumers left complaining of the temperatures, leaders asked what we could do to avoid these issues in the future."

The result was a program that allows Beaudoin and his staff to replace rooftop units at the stores before they fail. It also allows them to replace all of the units — usually five — at once.

"It allows us to bring the whole store up to our new equipment brand standards, with greater energy efficiency, r410a refrigerants, and makes connectivity with our EMS easier," he says. "As the fleet is slowly replaced/upgraded, we'll have to revisit the replacement plan, as the equipment 'should' be in greater shape, and last longer, so replacing them one off as needed will likely make more fiscal sense, as we can squeeze more life out of each unit."

If you're looking into upgrading your HVAC system because equipment is reaching the end of its life or because the building needs better service, it can be an easier sell than simply looking to become more energy efficient.

"Are you trying to solve a problem? Or are you trying to make it more efficient?" says Clayton Ulrich, senior vice president, engineering services, Hines. "It's clearly very hard to justify what we would loosely call an HVAC upgrade in an existing building if there isn't a problem."

This has been a Building Operating Management Tip of the Day.

4.  Be Aware Of Factors That Cause HVAC Performance To Slip Over Time

Today's tip from Building Operating Managementcomes from David P. Callan and Kyle Hendricks of Environmental Systems Design: Be aware of factors that cause HVAC performance to slip over time.

Over time, building performance drifts out of tolerance from the original design intent. When tenant occupancy changes, equipment wears and temporary set point adjustments aren't restored, a building will perform very different operationally than it did at move-in. For these reasons, even a fairly new building that was commissioned and aligned with design intent before occupancy, may not be meeting its owner's operational expectations.

There are a few simple explanations for drift. First, the complex controls used in new installations are reliant on sensors. Sensor technology has improved in the last five years; however, these devices still require periodic recalibration and replacement. Secondly, people, both occupants and operators, are not machines. People have minds of their own and are not inclined to mold themselves into the prescribed behavior dictate in the design conditions and sequences of operation. We say that "passive buildings require active occupants" to achieve outstanding performance. But, in most commercial buildings, the opposite logic is employed. Occupants and facility managers alike want buildings to actively control themselves, so that occupants can go about their business with little or no attention paid to the building systems.

Even when the components of the system are complex, the control logic should not be. If facility staff, in response to a building occupant complaint or a change in tenancy, cannot quickly find a simple or temporary adjustment to the system, they will be forced to override the controls and deviate from the intended, and presumably optimal, sequence of operations. Considering that building occupants are customers, and the customer is always right, this happens frequently.

Some of the problems that routinely occur include: permanent temperature resets that may result in simultaneous heating and cooling or poor refrigeration performance, system static pressure increases to overcome isolated air distribution issues, automatic start/stop overrides, manual locking of outside air dampers, disabling energy conservation control features, non-functioning sensors, previously unknown control device and valve failure and improper installation of components.

For more on this topic, click here.

This has been a Building Operating Management Tip of the Day. Thanks for listening.


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