4  FM quick reads on HVAC

1. Specifying Effective Portable Cooling Equipment

I'm Steve Schuster, associate editor of Maintenance Solutions magazine. Today's topic is Specifying Effective Portable Cooling Equipment.

Institutional and commercial facilities are full of technology that produces important benefits, from energy savings and sustainability to productivity and efficiency. Few products, however, have made the transition from occasional stopgap to permanent must-have as rapidly as portable cooling units.

Facilities of all kinds have come to rely on computer servers and information technology (IT) equipment for their core operations. One result of this evolution is that cooling units maintenance and engineering managers once specified primarily to provide emergency cooling have become permanent units that provide cooling in server rooms. Given the complexity of the cooling challenge in such spaces, managers might consider working closely with the manufacturer or distributor to specify the most appropriate unit.

Questions to consider when specifying cooling equipment —

Does the unit have auto restart in case of a power outage?
What is the operating range of the unit?
What kind of application support is offered by the manufacturer or distributor?
Does the seller offer rental units in case a warranty issue arises or the heat load increases, requiring more cooling?

Underfloor Air Distribution Can Benefit High Performance Buildings

Today's tip from Building Operating Management comes from Jeffrey L. Heiken of KlingStubbins. Underfloor air distribution systems can offer benefits to high performance HVAC designs.

Underfloor air distribution enhances building operation and energy efficiency. Underfloor air distribution systems supply air from the floor level, putting the cooling source in closer proximity to cooling need. With conventional overhead air delivery systems, the conditioning air is typically forced from the ceiling level down to the occupant and equipment. In a cooling mode, the air must travel through a mass of hotter air that has naturally risen to the ceiling. As it falls, the cooler conditioned air mixes with hotter air, reducing the performance of the HVAC system.

Underfloor air distribution systems invite the hot air to rise, displacing it upward to the ceiling levels for return. The occupied lower 7 feet is conditioned; above that level, elevated temperatures are not sensed by occupants or equipment. The pressurized plenum of the underfloor space serves as a supply air distribution system. It is a low static pressure delivery system. The economic benefit of reducing fan static pressure requirements comes in fan energy savings.

On a high rise project in Raleigh, North Carolina, an energy model was used to evaluate elements of a high performance HVAC system. The building was a 305,000 square foot public safety building for police and fire operations. One element considered was an underfloor air distribution system. The raised flooring in this application enhanced space utilization flexibility and was a value added element the owners desired for office space.

The model for this project showed a 13.4 percent decrease in fan energy use with the underfloor system.

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

Demand Control Ventilation Systems Can Save Energy, Achieve Occupant Satisfaction

Today's tip from Building Operating Management comes from Angela Cremeans and R. Stephen Spinazzola of RTKL: In facilities with wide swings in occupancy, demand ventilation systems — which strike a balance between occupant satisfaction, energy efficiency and cost savings — are worth a close look.

Demand ventilation systems — also known as dedicated outdoor air systems — are 100 percent outdoor air systems that include filtration along with heating and cooling coils. Normally, demand ventilation systems have some sort of heat recovery and are variable in volume, modulating down to 25 to 50 percent air flow. The systems provide humidity control for the entire building because they dehumidify outside air down to as little as 30 percent humidity, allowing the base building system to be dedicated strictly to cooling, not dehumidification.

Recent development of economical and accurate carbon dioxide sensors makes it feasible to use them as an integral part of a demand ventilation system. Model codes now allow the amount of outdoor air to be reduced below a constant 15 CFM per person.

Of course, there are issues that should be evaluated when deciding to proceed with a demand ventilation system.

The first question is whether local code allows outside air levels to be reduced. If the answer is no, determine whether the code official is willing to look at alternative schemes as part of a comprehensive design solution.

Depending on the base mechanical system, there may be some added first costs to implement a demand ventilation system. A demand ventilation system requires a parallel duct system to get outside air to individual spaces. The biggest savings in operating costs are in conference rooms and other assembly-type spaces.

Demand ventilation should not be considered unless the facility manager plans to do a full commissioning of mechanical systems prior to occupancy. Commissioning will ensure systems are performing as intended. Also, care should be taken to make sure the air balance is designed so that the minimum outside air doesn't drop below what is required to maintain positive building pressure.

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

With HVAC Upgrades, Look Beyond Like-Kind Replacement

Today's tip from Building Operating Management magazine: When replacing elements of the HVAC system, evaluate whether to replace units with a like kind or not.

Say you're replacing a chiller. Because chillers can easily last 30 years or more, the odds are good that the needs of the building and its occupants have changed since it was installed. In that case, it probably isn't a good idea to replace units with like kind.

For one thing, chillers with older technology are not as energy efficient as units made today. What's more, you might find out that the size of the existing unit may not meet the needs of current and future occupants. There's also the question of how much redundancy you have and need. Questions like those are why bringing in an outside engineer, while an added expense, is probably a good idea.

The result of not replacing in kind can be significant. Two Shell Plaza in Houston was formerly outfitted with four 500-ton chillers. As a result of an upgrade by Hines, two of those chillers remain, but only in a backup role. The cooling is now provided by a pair of 680-ton chillers with variable frequency drives. That approach not only allows for more efficiency, but also gives more flexibility when it comes to providing cool air during off-peak hours when only a limited number of tenants need it. Changes like that can only come about if a project is properly evaluated beforehand and the building's use is carefully examined.

In some cases it might be preferable to replace with similar units. Kirk Beaudoin, territory facilities manager, North American retail operations, Nike, says that tracking service calls, breakdowns and temperature complaints helps his company identify problems that would prevent the organization from being able to replace old units with similar new units. "Our assumption is that our stores were properly designed when built. So unless we have identified ongoing comfort issues that are related to sizing of equipment, or if there have been any modifications to the store which would require a review of the systems, we generally replace with the same tonnage," he says.

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


HVAC , cooling equipment , sustainability , green building , cooling technology

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