4 FM quick reads on HVAC
1. Understanding the Importance of Water Treatment
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is the importance of effective water treatment for HVAC systems.
From boilers to cooling towers, many HVAC systems depend on water to transfer heat. But constant exposure to water can cause problems for the system if steps aren’t taken to prevent them. For example, if scale builds up on heat transfer surfaces, energy efficiency is reduced. Corrosion can shorten the life of a system and possibly put operators at risk. And without proper treatment, micro-organisms can thrive in the water, including the bacteria that causes Legionnaire’s disease.
As important as it is, water treatment is easy to overlook. For one thing, the benefits are hidden from view, as are the potential harms. Another obstacle is the specialized terminology: clarification, demineralization, dearation, softening – and that’s just for boilers.
Whether the water treatment program is handled in-house or contracted out, the facility executive should ensure that the program has been designed to meet the specific needs of the system at hand – needs that vary from building to building. Making that effort pays off. A properly designed water treatment program can aid the energy performance of the system, keep equipment operating longer, further reducing life cycle costs, and help protect the health and safety of operating staff and building occupants.
2. Proper Maintenance Will Improve Air Distribution Efficiency
One way to improve the efficiency of the air distribution system is to make sure that components are operating properly, says the U.S. Environmental Protection Agency’s Energy Star program. For example, when systems have pneumatic controls, the thermostats require recalibration on a regular basis – typically once or twice a year. That sort of preventive maintenance is a better strategy than waiting for complaints from occupants who are too hot or too cold.
Zone dampers are another potential trouble spot. Facility staff should regularly inspect the damper, linkage, and actuator for to ensure they’re operating properly. In systems in older buildings haven’t been carefully maintained, there’s a good chance of having some zone dampers frozen in one position. Tackling that problem can be an expensive and lengthy process, especially in big buildings. Consider allocating a portion of the annual maintenance budget for this purpose to address a certain quantity or percentage of zones. For example, in a 100,000-square-foot, 10-story office building with 150 VAV zones, the maintenance budget might include time and money to evaluate 50 VAV zones per year.
Steps like these can not only reduce energy use, but also improve occupant comfort.
3. Evaluate How the BAS Will Connect With Other Systems
A building automation system does not exist in a vacuum. When deciding whether to install a new building automation system, it’s important to look at other building systems as well. For example, to take full advantage of the building automation system, the system will have to connect to HVAC systems. So check the controls on HVAC systems to ensure that they have the capabilities needed.
As with any powerful software system, it is essential to consider how information will be provided to a building automation system. Many facilities already have some form of building automation system. If that’s true, the facility executive will have to determine how useful maintenance and operation information will be transferred from the old system to the new one. In the best case, it will be possible to import the data automatically from the old system. Talk to the building automation system vendor to determine if it’s feasible to do that. The other route is manual data entry.
4. When Sizing HVAC Systems, Focus on Proper Margin for Safety
When the HVAC system is being designed, one important decision is how big equipment needs to be. Peak demand on very cold and very hot days is one important consideration. And flexibility for change in use of a space may be another element in the decision.
Of course, there’s a price to be paid for extra capacity, and it’s not just the higher first cost of larger units. Operating expenses are likely to rise for equipment operating at part load. What’s more, larger units may very well be noisier. Properly sized units, by contrast, will likely run better, be more energy efficient and have fewer maintenance problems.
Clearly it’s important not to oversize units. But there’s evidence that does happen in some cases. One possible source of trouble is industry rules of thumb for determining occupancy when occupancy isn’t known. Those rules of thumb may lead to an overestimation of loads. Another potential problem is building in too large a margin for so-called design days, when temperatures are at their highest and lowest, so that designers have a cushion — just in case.
For facility executives, the way to avoid oversizing is to work closely with the design team to ensure that the system can handle the loads it will be facing, with an appropriate margin for safety — but not an excessive margin.
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