Low Cost Ways to Save Energy in HVAC System
Existing buildings present huge scope for low-cost energy-saving retrofit measures. Here are some suggestions. Analyze the energy consumption vis a vis design as only when you measure you can analyze improve and control…
- V Shridhar
Air Handling Unit
Air handling unit filter replacement once it is with black soot not only improves the indoor air quality but also saves considerable energy. Air handling units fans tend to pump more air quantity which can be adjusted to the design air quantity by changing motor pulley and belts. Of course necessary care needs to be taken to limit the fan speed within the manufacturer’s recommendation by this the fan operates to the design air quantity and saves energy.
Keep Coils Clean
In a study, HVAC systems with dirty evaporator coils and dirty condenser coils were 35-percent less efficient and 60-percent less efficient, respectively, than systems with clean coils. In addition to lowering the energy efficiency of HVAC systems, dirty evaporator coils can become a breeding ground for mold and bacteria, negatively impacting indoor-air quality.
To effectively clean condenser and evaporator coils:
• Use a wet cleaning process: Pressurized water loosens deeply embedded dirt and debris, vastly improving the cleaning process.
• Use a powerful-yet-delicate cleaning system: High-pressure equipment can damage fins, especially those on evaporator coils. Ideally, a system should deliver 125 to 200 psi of pressure and up to a half-gallon of flow per minute.
• Vacuum coils and fins: Before cleaning coils, remove dry debris with a vacuum that can reach dust and dirt in tight spaces. Other options include the use of compressed air.
• Clear blockages: Before beginning wet cleaning, make sure condensate pans and lines are free of blockages, as major damage from flooding and HVAC-system condensate can result. To remove debris prior to cleaning, consider using a wet/dry vacuum.
• Apply alkaline non-caustic cleaning foam: Use of a non-caustic cleaner helps to protect coils from corrosion.
• Apply a mold-control agent: Add a mold inhibitor that is US Environmental Protection Agency-registered and approved for use in occupied spaces to help keep coils clean and free of odor- and allergy-causing mold and mildew.
• Seek the best possible access. The closer you can get a cleaning wand to coils, the more effective the cleaning. If coils are difficult to access, consider the use of a flexible wand.
Repair Damaged or Missing Insulation
Duct and especially pipe insulation inevitably gets damaged over time. For example, workers routinely climb or step on insulated pipes. The estimates as much as 20 percent to 25 percent of insulation damaged in USA and it may be around same or more in our country
Insulation is not done with adequate care in the initial stage itself leading to large waste of energy and condensation of pipes leading to damage of false ceiling, causing molds and fungus growth.
With a damaged jacket, insulation is prone to moisture or water intrusion. Water trapped in insulation reduces insulating value, while water trapped under insulation promotes corrosion. Damaged insulation on cold systems can promote mold growth, while damaged insulation on hot systems can increase the risk of burns to people. Repairing damaged insulation can save energy and prolong pipe life.
Reset Hot/Chilled-Water Temperature
Section 18.104.22.168 of ANSI/ASHRAE/IES Standard 90.1-2013 calls for resetting chilled and hot water temperature on systems with capacity greater than 300 MBH. That strategy can save energy by increasing chiller operating efficiency and reducing unneeded dehumidification.
Beware, however, of unintended consequences. ANSI/ASHRAE/IES Standard 90.1-2013 recognizes one, stating reset of chilled water is not required when it would compromise humidity control such as in a conference room or other densely populated interior space. The standard does not, however, recognize the potential unintended consequence of increased pump energy and increased fan energy. For a given cooling coil, higher chilled-water temperature probably will translate to higher supply-air temperature and increased airflow to loads that do not vary with outdoor temperature or other reset parameter. Check that any increase in fan energy does not offset savings in chiller energy. Also, remember that with head-pressure control, air-cooled-chiller efficiency increases as outdoor temperature goes down so savings from chilled-water reset might be small.
Reset of hot water temperature often is a great idea for perimeter heating and other systems whose load varies with outdoor temperature or other identified reset parameter. It reduces heat loss through distribution piping and reduces pressure drop through control valves that stay open wider. Reset of hot water temperature is not a good idea for loads independent of the reset parameter.
Seasonal setting of the chilled water temperature i.e to higher level in winter saves the considerable chiller energy.
These are a few low cost ways to save energy in HVAC system in buildings. Some have been around since the oil embargoes of the 1970s, when the energy conservation business got initiated. As was the case then, engineers need to evaluate energy conservation opportunities and satisfy themselves that savings are achievable without compromising performance.
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