The following overview offers a quick reference to key considerations with some of the most efficient technologies. As with lighting, trial installations are a good idea; so is working with manufacturers and distributors.
Getting the most from Hvac controls
Honeywell Pressure Sensor
Because a building's carrying out can be dramatically improved by installing and fully using Hvac controls, it is needful to understand and correctly use those controls. The place to start is with a close look at what is as a matter of fact transpiring in your building, 24 hours a day, seven days a week.
What is happening with each piece of equipment? On holidays? Weekends? As the seasons change, do your operations change? It is important to understand where and how vigor is being consumed in order to identify where waste is occurring and where improvements can be implemented. Then it is imperative to ask, "What exactly do I want these controls to do?"
Energy administration systems (Ems) are designed to run personel pieces of tool more efficiently and to permit integration of equipment, improving carrying out of the system. In a typical Ems, sensors monitor parameters such as air and water temperatures, pressures, humidity levels, flow rates, and power consumption. From those carrying out points, electrical and mechanical tool run times and setpoints are controlled.
Seven-day scheduling provides hour-to-hour and day-to-day operate of Hvac and lighting systems and can inventory for holidays and seasonal changes. As the name implies, night temperature setback allows for less cooling in summer and less heating in winter while unoccupied hours.
Optimal start/stop enables the entire principles to look ahead several hours and, relative to current conditions, make decisions about how to proceed; this allows the principles to ramp up slowly, avoiding morning ask spikes or unnecessary run times.
Peak electrical ask can be controlled by sequencing fans and pumps to start up one by one rather than all at once and by shutting off pieces of Hvac tool for short periods (up to 30 minutes), which should only minimally sway space temperature. Economizers sacrifice cooling costs by taking benefit of cool outdoor air. Supply-air temperature-reset can preclude excessive reheat and help sacrifice chiller load.
An Ems can contribute an abundance of data about construction performance, but someone has to outline out what they want the Ems to do and then give it directions. Calibrating controls, testing and balancing are key to any well-maintained Hvac system, but are especially needful to optimize operate efforts.
Variable speed drives and energy-efficient motors
Variable speed drives (Vsds) are nearly all the time recommended as a reliable and cost-effective upgrade.
Vsds are profitable where tool is oversized or often operates at part-load conditions. Savings of up to 70 percent can be achieved by installing Vsds on fan motors operating at part-load conditions. They may be applied to compressor or pump motors and are generally used in changeable air volume (Vav) systems. They are also cost efficient in water-side applications. Backward-inclined and airfoiled fans are the best Vsd candidates.
Air-handler configurations controlled by changeable inlet vanes or outlet dampers squander vigor at part-load conditions. Using throttle valves to sacrifice flow for smaller pumping loads is also inefficient. The efficiency of motors begins to drop off steeply when they run at less than 75 percent of full load; they can consume over twice as much power as the load requires. Vsds operate electronically and continually adjust motor speed to match load.
The power to run the Vsd is proportional to the cube of the speed (or flow), which is why this technology is so efficient. If the speed is reduced by just 10 percent, a 27 percent drop in power consumption should result. A Vsd pilot study performed by Epa found that Vsd retrofits realized an annual median vigor savings of 52 percent, an median ask savings of 27 percent and a 2.5-year easy payback.
Perform harmonic, power factor, electric load, and torsional analyses before selecting a Vsd. Though harmonic and power factor problems are not common in Vsd applications, Vsds should generally be adequate with integral harmonic filters (or a three-phase Ac line reactor) and internal power factor correction capacitors (or a single capacitor on the Vsds' main power line). In general, this tool is not thorough and must be specified.
Improved create and good materials enhance the carrying out of energy-efficient motors, which use 3 to 8 percent less vigor than thorough motors; units with efficiencies of 95 percent are available.
To achieve maximum savings, the motor must also be properly matched with its load, expanding run time at peak efficiency. Motors operate best when running at 75 to 100 percent of their fully rated load; motors routinely operating below 60 percent of rated capacity are prime candidates for retrofit. For motors whose loads fluctuate, Vsds should also be considered.
Smaller, more efficient motors are integral to a principles downsizing stratagem; downsizing a 75 horsepower thorough motor to a 40 horsepower energy-efficient model will consequent in vigor savings of 15 percent.
Some energy-efficient motors have less "slip" than standard-efficiency motors, causing energy-efficient motors to run at slightly higher speeds; reconsider a larger pulley to compensate for the higher speed and to maximize vigor savings. Installing a new pulley or adjusting the existing one can also be an alternative to a Vsd when the cost for the Vsd is prohibitive or the load has been reduced.
Improving fan principles performance
A common way to enhance the efficiency of the air distribution principles is to change constant air volume (Cav) systems to Vav. One authority on vigor issues, E-Source, reports that "typical (Vav) air flow requirements are only about 60 percent of full Cav flow."
Vavs acknowledge to load requirements by varying the volume of the air straight through a aggregate of pressure controls and dampers rather than by varying the air's temperature. Agreeing to the air pressure, fan power and volume of conditioned air are reduced, thus expanding vigor efficiency. Of course, it is crucial to declare indoor air quality (Iaq) when altering air handling systems.
To maximize savings, Vav components such as Vsds, variable-pitch fan blades, diffusers, mixers, and Vav boxes must be operating properly; just zoning is also required to achieve Vav optimization.
E-Source recommends inspecting the following Vav retrofit procedures:
• perfect load discount measures and think the maximum and minimum air flow requirements,
• measure existing fan performance; explore duct principles for possible improvements,
• stage fans that are in parallel configurations,
• commission the principles thoroughly,
• optimize static pressure setpoint and implement reset control, and
• possibly take off return air fans.
Energy-efficient and properly sized motors are also recommended along with just operate strategies. Installing a self-contained, thermally powered gismo to each diffuser can add greater operate to Vav systems by controlling personel spaces, rather than entire zones, and eliminate the need for Vav boxes. Such a gismo also offers Vav-style capabilities to Cav systems.
Vav retrofit costs and paybacks can vary widely. Facility problems related to fan control, reduced contribute air distribution, location of pressure sensors and their reliability, in expanding to deficient design, can diminish a Vav retrofit's performance. Because Vav boxes are relatively costly and one is required for each zone, it is generally not cost efficient to partition the space into many zones. just zone designation -- Agreeing to occupancy, internal loads and solar gain -- will maximize efficiency, increase comfort and sacrifice reheat.
When reheat cannot be eliminated, reconsider these steps to minimize it: ensuring thermostat calibration; expanding contribute air temperatures while the cooling season; and monitoring reheat year round and possibly employing reheat only while winter months. Where reheat is used primarily to operate humidity, a desiccant wheel or a heat pipe might be considered.
Downsizing existing Vav fan systems is a relatively low-cost way to save vigor when loads have been reduced or when the air distribution principles was oversized to begin with. The following are means to downsize fans or airflow requirements:
• sacrifice static pressure setpoint to meet actual temperature and airflow requirements.
• Rightsize motors and upgrade to energy-efficient models; setup larger pulleys.
• Replace the existing fan pulley with a larger one; that will sacrifice the fan's power requirements by reducing its speed.
• Make sure the fan's speed corresponds to the load. Reducing a fan's speed by 20 percent reduces its vigor consumption by roughly 50 percent.
There are several ways to conclude if Vav fan systems are oversized. If a motor's measured amperage is 25 percent less than its nameplate rating, it is oversized. If a fan's inlet vanes or outlet dampers are terminated more than 20 percent, it is oversized. If the static pressure reading is less than the static pressure setpoint when inlets or dampers are open and Vav boxes open 100 percent, as on a hot summer day, the principles is oversized. Again, be sure to reconsider Iaq requirements when downsizing air handling systems.
Chillers and thermal storage
No one wants to replace a perfectly good chiller just because of the Cfc phaseout. But once load-reducing efficiency upgrades have been completed, it may as a matter of fact be profitable to replace an oversized chiller. That's especially true given rising prices and tightening supplies of Cfc refrigerants.
Oversized units 10 years or older are good candidates for replacement. A high-efficiency chiller reduces vigor costs throughout its lifetime; first costs are reduced because the exchange chiller is smaller than the old one. Depending on the old unit's efficiency and load, a high-efficiency chiller's vigor consumption can be.15 to.30 kW/ton less, decreasing vigor consumption by as much as 85 percent if combined with downsizing.
An alternative to exchange is to retrofit chillers to adapt a new refrigerant and to match reduced loads. That may involve orifice plate replacement, impeller exchange and possibly compressor replacement, depending on the chiller's specifics.
Retrofitting may entail gasket and seal exchange and motor rewinding. Depending on the refrigerant and the way the retrofit is performed, the chiller may lose either efficiency or capacity. To conclude either exchange or retrofit is a good option, reconsider both first and life-cycle costs.
Retubing the condenser and evaporator yields large vigor savings but either it makes sense, given its high cost, depends on the health of the chiller. Water-cooled condensers are generally more efficient than air-cooled units. Because condenser water flows straight through an open loop, it is susceptible to fouling. Scale build-up will inhibit heat exchange efficiency; maintenance is therefore required to keep the surfaces clean.
Absorption chillers are an alternative to centrifugal models. Absorption chillers cost up to 0 per ton more than vapor compression chillers like centrifugal units, but can be profitable in areas of high electrical ask charges or where steam or gas is available, depending on the local utility rate structures. Using a aggregate of the two chiller types can sacrifice electrical ask charges.
Thermal vigor storage (Tes) uses accepted chiller tool to yield conditioned water or ice (or occasionally someone else phase-change material) in off-peak periods. Water is withdrawn from storage while the day or at peak hours and circulated straight through the cooling system.
Tes systems can be incorporated into new and existing systems and can contribute partial load leveling or full load shifting. Tes helps decrease operating and maintenance costs; in some cases, a smaller chiller can be specified. Some systems contribute lower contribute air and water temperatures, so air and water flow requirements can be cut.
Water-side improvements
Fill material, size and fan configurations sway cooling tower efficiency. Cellular fill (aka film packing) increases efficiency over other fill types. Oversizing the tower to allow for closer coming to ambient wetbulb temperature can enhance its efficiency. Generously sizing the tower and expanding its share of the chiller load can make economic sense because a cooling tower's first cost and vigor use per ton are less than a chiller's.
At part-load conditions, applying a Vsd to the fan (or pump) will enhance the tower's efficiency. Systems with Vsds and several fans are more efficient when all tower cells are operating at reduced speed as opposed to one or two cells at full speed.
Because cooling towers contain large heat exchange surfaces, fouling -- scale or slime build-up -- can be a problem. The efficiency of improperly treated systems can be improved with efficient water treatment. High-efficiency towers are available; induced-draft types are more popular and efficient than forced-draft towers. carrying out can also be improved by expanding cooling outside area.
In original pumping systems, flow is generally constant volume; a throttle valve reduces flow at part-load conditions, inhibiting efficiency.
Installing Vsds on secondary pumps in changeable flow systems, rightsizing pumps and motors to meet load requirements, and upgrading single loop systems to primary/secondary loop configurations can increase the carrying out and reliability of pumping systems. In upgrading chilled water pumps, it is important to meet maximum and minimum flow rates straight through the chiller.
Other cooling options
Desiccants are dehumidification materials which can be integrated into Hvac systems to sacrifice cooling loads and increase chiller efficiency while improving indoor air quality and comfort. Formerly found only in niche and market applications, desiccant cooling is extending throughout market markets.
Desiccants make sense when the cost to regenerate them is low compared to the cost to dehumidify below dewpoint and can sacrifice Hvac vigor and peak ask by more than 50 percent in some cases.
Evaporative coolers contribute one of the most prudent and efficient means of cooling, using up to 75 percent less vigor than vapor-compression systems. Though first cost is typically higher, paybacks for volatile coolers range between six months and five years. Though volatile coolers are particularly prevalent in the arid West and Southwest, they can assistance most U.S. Climates. E-Source states that, in aggregate with volatile cooling, desiccant cooling can eliminate refrigerative air conditioning in many climates.
Hybrid systems that concentrate volatile cooling with accepted Hvac technologies offer supplementary opportunities. To enhance carrying out reconsider lower air velocity; good fill materials; higher fan, pump and motor efficiencies, including Vsds; good belts or direct drive; improved housing; improved controls; and duct sealing. Allowable maintenance is key to energy-efficiency.
Packaged air-conditioning units are typically found in structure or construction zones where the cooling load is less than 75 tons. Running these units at part load can severely sacrifice efficiency. They are generally not as efficient as chiller systems but can be upgraded and rightsized when replaced. Existing systems can be improved by using higher efficiency compressors, larger condensers and evaporators, and Vsds, though life expectancies of 10 to 12 years for these technologies may mean that retrofits are not cost-effective.
Heat pumps are among the most energy-efficient heating and cooling technologies available today. Low operating costs, increased reliability and long life expectancies enhance their viability. They function best in moderate climates and Allowable sizing is critical.
Multi-unit configurations can assistance larger loads and contribute zoning; large, modernized central units contribution capacities of up to 1000 horsepower or 750 kilowatts are gaining popularity. Air-to-air type heat pumps are the most common because of low up-front costs; ground contribute heat pumps are the most efficient but tend to have higher first costs.
Boiler upgrades
Especially in colder climates, improved boiler carrying out -- with improved fuel and airflow controls over a range of load conditions and increased heat exchange outside areas -- can lead substantially to vigor savings. Smaller units arranged in modular systems increase efficiency up to 85 percent while small units replacing those with open-loop condensing systems shoot combustion efficiency up to 95 percent.
Boiler retrofits, combined with improved maintenance measures, can also increase efficiency -- up to 90 percent. New burners, baffle inserts, combustion controls, warm-weather controls, economizers, blowdown heat saving and condensate return conversions contribute increased efficiency opportunities. A smaller "summer" boiler might be a good option when a boiler is required year round though at reduced capacities in warmer conditions. The much smaller summer boiler is sized for reduced loads; the main boiler is shut down.
Hvac upgrades can contribute large economic benefits, enhance occupant comfort and principles reliability, and sacrifice operating costs. But to maximize benefits and minimize capital investment, load-reducing measures, such as lighting upgrades, should precede Hvac principles upgrades.
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