Operations & Maintenance

Boilers are a critical component of many HVAC systems in large buildings. There are three main boiler types—fire-tube boilers, water-tube boilers, and electric boilers—and there is a fair amount of variation across products. However, there are several best practices regardless of boiler type or its specifications. ​​​ 

The National Board of Boiler and Pressure Vessel Inspectors lists the following as “General Requirements for a Safe and Efficient Boiler Room”:   

1. Keep the boiler room clean and clear of all unnecessary items. The boiler room should not be considered an all-purpose storage area. The burner requires proper air circulation in order to prevent incomplete fuel combustion. Use boiler operating log sheets, maintenance records, and the production of carbon monoxide. The boiler room is for the boiler! 

2. Ensure that all personnel who operate or maintain the boiler room are properly trained on all equipment, controls, safety devices, and up-to-date operating procedures. 

3. Before start-up, ensure that the boiler room is free of all potentially dangerous situations, like flammable materials, mechanical, or physical damage to the boiler or related equipment. Clear intakes and exhaust vents; check for deterioration and possible leaks. 

4. Ensure a thorough inspection by a properly qualified inspector. 

5. After any extensive repair or new installation of equipment, make sure a qualified boiler inspector re-inspects the entire system. 

6. Monitor all new equipment closely until safety and efficiency are demonstrated. 

7. Use boiler operating log sheets, maintenance records, and manufacturer’s recommendations to establish a preventive maintenance schedule based on operating conditions, past maintenance, repair, and replacement that were performed on the equipment. 

8. Establish a checklist for proper startup and shutdown of boilers and all related equipment according to manufacturer’s recommendations. 

9. Observe equipment extensively before allowing an automating operation system to be used with minimal supervision. 

10. Establish a periodic preventive maintenance and safety program that follows manufacturer’s recommendations 

Additional measures to optimize the safety, operations, and efficiency of a property’s boilers may be specific to the equipment and/or the building’s CMMS programming. However, as the Federal Energy Management Program (FEMP) notes, fire-side and water-side maintenance procedures are extremely low-cost ways to promote efficiency and optimization and “should be part of the Operations and Maintenance Program of the building.” FEMP describes fire-side and water-side maintenance for boilers as follows: 

Fire-side Cleaning and Maintenance Program. Fire-side cleaning consists of manually cleaning the particulates that accumulate on the fire side of the boiler. Reducing the residue on the fire side of the boiler increases the amount of heat that gets absorbed into the water, and helps maintain proper emissions from the boiler. Some particulate accumulation is normal for continuously operating boilers, but excessive fire side residue can be an indication of failed internal components that are expelling unburned fuel into the combustion chamber, causing excess sooting. Excess sooting can also be the result of incomplete combustion due to inadequate excess air.  

Water-side Cleaning and Maintenance Program. Hot water boilers are usually closed loop systems; therefore, the boiler water is treated before it enters the boiler and piping, and does not require any additional chemicals or daily water treatment tests. Steam boilers on the other hand, lose steam due to a variety of circumstances and therefore require additional water to maintain consistent water levels. Boiler water-side maintenance for steam boilers consists of maintaining “soft water” for the feed-water and eliminating as much dissolved oxygen as possible. The first requires daily chemical monitoring and treatment of the feed-water. The presence of “hard-water” can create a “scale” buildup on the pipes. Once built up, the scale acts as an insulator and inhibits heat transfer into the boiler water. This creates excess heat in the combustion chamber that gets vented with the exhaust gases rather than absorbing into the process water. 

The EPA has also published several “rules of thumb” for boiler efficiency improvements. They are listed below: 

Boiler Rule 1. Effective boiler load management techniques, such as operating on high fire settings or installing smaller boilers, can save over 7% of a typical facility’s total energy use with an average simple payback of less than 2 years. 

Boiler Rule 2. Load management measures, including optimal matching of boiler size and boiler load, can save as much as 50% of a boiler’s fuel use. 

Boiler Rule 3. An upgraded boiler maintenance program including optimizing air-to-fuel ratio, burner maintenance, and tube cleaning, can save about 2% of a facility’s total energy use with an average simply payback of 5 months. 

Boiler Rule 4. A comprehensive tune-up with precision testing equipment to detect and correct excess air losses, smoking, unburned fuel losses, sooting, and high stack temperatures can result in boiler fuel savings of 2% to 20%. 

Boiler Rule 5. A 3% decrease in flue gas O2 typically produces boiler fuel savings of 2%. 

Boiler Rule 6. Every 40°F reduction in net stack temperature (outlet temperature minus inlet combustion air temperature is estimated to save 1% to 2% of a boiler’s fuel use.) 

Boiler Rule 7. Removing a 1/32 inch deposit on boiler heat transfer surfaces can decrease a boiler’s fuel use by 2%; removal of a 1/8 inch deposit can decrease boiler fuel use by over 8%. 

Boiler Rule 8. For every 11°F that the entering feedwater temperature is increased, the boiler’s fuel use is reduced by 1%

Steam systems were the pinnacle of value and efficacy in their heyday, and many buildings in the state and region still use steam for a variety of purposes. The single most impactful thing that building operators can do to maintain the performance of their existing steam systems is to do regular preventative maintenance and replacement of their steam traps.​​ Buildings in the state and region still use steam for a variety of purposes. The single most impactful thing that building operators can do to maintain the performance of their existing steam systems is to do regular preventative and replacement of their steam traps.​​

The three major categories of steam traps are 1) mechanical, 2) thermostatic, and 3) thermodynamic. In addition, some steam traps combine characteristics of more than one of these basic categories. 

The Federal Energy Management Program (FEMP) published a list of “General Requirements for Safe and Efficient Operation of Steam Traps.” They are listed below: 

1. Every operating area should have a program to routinely check steam traps for proper operation. Testing frequency depends on local experiences but should at least occur yearly. 

2. All traps should be numbered and locations mapped for easier testing and record-keeping. Trap supply and return lines should be noted to simplify isolation and repair. 

3. Maintenance and operational personnel should be adequately trained in trap testing techniques. Where ultrasonic testing is needed, specially trained personnel should be used. 

4. High maintenance priority should be given to the repair or maintenance of failed traps. Attention to such a timely maintenance procedure can reduce failures to 3% to 5% or less. A failed open trap can mean steam losses of 50 to 100 lb/hr. 

5. All traps in closed systems should have atmospheric vents so that trap operation can be visually checked. If trap headers are not equipped with these, they should be modified. 

6. Proper trap design should be selected for each specific application. Inverted bucket traps may be preferred over thermostatic and thermodynamic-type traps for certain applications. 

7. It is important to be able to observe the discharge from traps through the header. Although several different techniques can be used, the most foolproof method for testing traps is observation. 

8. Without proper training, ultrasonic, acoustical, and pyrometric test methods can lead to erroneous conclusions. Traps should be properly sized for the expected condensate load. Improper sizing can cause steam losses, freezing, and mechanical failures. 

9. Condensate collection systems should be properly designed to minimize frozen and/or premature trap failures. Condensate piping should be sized to accommodate 10% of the traps failing to open. 

Once a luxury few could afford, cooling systems are now the norm in buildings throughout the region. Smaller buildings will use packaged air conditioning units or window units, while larger buildings will employ chilled water distribution through air handlers or radiant panels to deliver thermal comfort. Regular monitoring and preventative maintenance of the chillers and their associated cooling towers (in water-cooled systems) is critical to extending life and delivering efficiency. Note that the maintenance procedures for chillers also forms a good practice for any sort of heat pump technology.​​ a good practice for any sort of heat pump technology.​​ ​​​ 

There are three types of chillers: mechanical chillers, absorption chillers, and electric centrifugal chillers. The U.S. Department of Energy offers the following best practices for maximizing chiller efficiency: 

• Raise chilled water temperature – The energy input required for any liquid chiller (mechanical compression or absorption) increases as the temperature lift between the evaporator and the condenser increases. Raising the chilled water temperature will cause a corresponding increase in the evaporator temperature and thus, decrease the required temperature lift.  

• Reduce condenser water temperature – The effect of reducing condenser water temperature is very similar to that of raising the chilled water temperature, namely reducing the temperature lift that must be supplied by the chiller.  

• Reducing scale or fouling – The heat transfer surfaces in chillers tends to collect various mineral and sludge deposits from the water that is circulated through them. Any buildup insulates the tubes in the heat exchanger causing a decrease in heat exchanger efficiency and thus, requiring a large temperature difference between the water and the refrigerant. 

• Purge air from condenser – Air trapped in the condenser causes an increased pressure at the compressor discharge. This results in increased compressor horsepower. The result has the same effect as scale buildup in the condenser. 

• Maintain adequate condenser water flow – Most chillers include a filter in the condenser water line to remove material picked up in the cooling tower. Blockage in this filter at higher loads will cause an increase in condenser refrigerant temperature due to poor heat transfer. 

• Reducing auxiliary power requirements – The total energy cost of producing chilled water is not limited to the cost of operating the chiller itself. Cooling tower fans, condenser water circulating pumps, and chilled water circulating pumps must also be included. Reduce these requirements as much as possible.

• Use variable speed drive on centrifugal chillers – Centrifugal chillers are typically driven by fixed speed electric motors. Practical capacity reduction may be achieved with speed reductions, which in turn requires a combination of speed control and prerotation vanes. 

• Compressor changeouts – In many installations, energy saving measures have reduced demand to the point that existing chillers are tremendously oversized, forcing the chiller to operate at greatly reduced loads even during peak demand times. This causes a number of problems including surging and poor efficiency. Replacing the compressor and motor drive to more closely match the observed load can alleviate these problems.  

• Use free cooling – Cooling is often required even when outside temperatures drop below the minimum condenser water temperature. If outside air temperature is low enough, the chiller should be shut off and outside air used. If cooling cannot be done with outside air, a chiller bypass can be used to produce chilled water without the use of a chiller.  

• Operate chillers at peak efficiency – Plants having two or more chillers can save energy by load management such that each chiller is operated to obtain combined peak efficiency. An example of this is the use of a combination of reciprocating and centrifugal compressor chillers.  

• Heat recovery systems – Heat recovery systems extract heat from the chilled liquid and reject some of that heat, plus the energy of compression, to warm water circuit for reheat and cooling.

• Use absorption chilling for peak shaving – In installations where the electricity demand curve is dominated by the demand for chilled water, absorption chillers can be used to reduce the overall electricity demand.  

• Replace absorption chillers with electric drive centrifugals – Typical absorption chillers require approximately 1.6 Btu of thermal energy delivered to the chiller to remove 1 Btu of energy from the chilled water. Modern electric drive centrifugal chillers require only 0.2 Btu of electrical energy to remove 1 Btu of energy from the chilled water (0.7 kw/ton).  

• Thermal storage – The storage of ice for later use is an increasing attractive option since cooling is required virtually year-round in many large buildings across the country. Because of utility demand charges, it is more economical to provide the cooling source during non-air conditioning periods and tap it when air conditioning is needed, especially peak periods.​ In addition, thermal storage for usage in heat pump applications is becoming more commercially available. ​ 

Cooling Towers 

There are two types cooling towers: open or direct cooling towers and closed or indirect cooling towers. DOE lists the following “general requirements for safe and efficient cooling towers”: 

1. Safe access around the cooling tower, including all points where inspection and maintenance activities occur.

2. Fall protection around inspection and maintenance surfaces, such as the top of the cooling tower.

3. Lockout of fan motor and circulating pumps during inspection and maintenance.  

4. Protection of workers from exposure to biological and chemical hazards within the cooling water system. 

5. Cooling tower location must prevent cooling tower discharge air from entering the fresh air intake ducts of any building. 

6. When starting the tower, inspect and remove any accumulated debris.

7. Balance waterflow following the tower manufacturer’s procedure to ensure even distribution of hot water to all areas of the fill. Poorly distributed water can lead to air bypass through the fill and loss of tower performance.

8. Follow your water treating company’s recommendations regarding chemical addition during startup and continued operation of the cooling system. Galvanized steel cooling towers require special passivation procedures during the first weeks of operation to prevent “white rust.”  

9. Before starting the fan motor, check the tightness and alignment of drive belts, tightness of mechanical holddown bolts, oil level in gear reducer drive systems, and alignment of couplings. Rotate the fan by hand and ensure that blades clear all points of the fan shroud.  

10. The motor control system is designed to start and stop the fan to maintain return cold water temperature. The fan motor must start and stop no more frequently than four to five times per hour to prevent motor overheating.

11. Blowdown water rate from the cooling tower should be adjusted to maintain between two to four concentrations of dissolved solids. 

Additionally, DOE outlines the following “operations and maintenance opportunities” with chillers: 

• From an operational perspective, the blowdown losses represent the most significant water conservation opportunity. To maximize efficiency potential, calculate and understand your “cycles of concentration.” Check the ratio of conductivity of blowdown and make-up water. Work with your cooling tower water treatment specialist to maximize the cycles of concentration. Many systems operate at 2 to 4 cycles of concentration, while 6 cycles or more may be possible. Increasing your cycles from 3 to 6 will reduce cooling tower make-up water by 20 percent, and cooling tower blowdown by 50 percent. The actual number of cycles you can carry will depend on your make-up water quality, and cooling tower water treatment regimen. Depending on your make-up water, treatment programs may include corrosion and scaling inhibitors, along with biological fouling inhibitors.

• Install a conductivity controller to automatically control your blowdown. Working with your water treatment specialist, determine the maximum cycles of concentration you can safely achieve, and the resulting conductivity (typically measured as microSiemens per centimeter, uS/cm). A conductivity controller can continuously measure the conductivity of the cooling tower water and discharge water only when the conductivity set point is exceeded. 

• Install flow meters on make-up and blowdown lines. Check the ratio of make-up flow to blowdown flow. Then check the ratio of conductivity of blowdown water and the make-up water (you can use a handheld conductivity meter if your tower is not equipped with permanent meters). These ratios should match your target cycles of concentration. If both ratios are not about the same, check the tower for leaks or other unauthorized draw-off. If you are not maintaining target cycles of concentration, check system components, including conductivity controller, make-up water fill valve, and blowdown valve.

• Read conductivity and flow meters regularly to quickly identify problems. Keep a log of makeup and blowdown quantities, conductivity, and cycles of concentration. Monitor trends to spot deterioration in performance.  

• Consider using acid treatment such as sulfuric, hydrochloric, or ascorbic acid, where appropriate. When added to recirculating water, acid can improve the efficiency of a cooling system by controlling the scale buildup potential from mineral deposits. Acid treatment lowers the pH of the water, and is effective in converting a portion of the alkalinity (bicarbonate and carbonate), a primary constituent of scale formation, into more readily soluble forms. Make sure that workers are fully trained in the proper handling of acids. Also note that acid overdoses can severely damage a cooling system. The use a timer or continuous pH monitoring via instrumentation should be employed. Additionally, it is important to add acid at a point where the flow of water promotes rapid mixing and distribution. Be aware that lowering pH may mean you may have to add a corrosion inhibitor. 

• Select your water treatment vendor with care. Tell vendors that water efficiency is a high priority and ask them to estimate the quantities and costs of treatment chemicals, volumes of blowdown water and the expected cycles of concentration ratio. Keep in mind that some vendors may be reluctant to improve water efficiency because it means the facility will purchase fewer chemicals. In some cases, saving on chemicals can outweigh the savings on water costs. Vendors should be selected based on “cost to treat 1,000 gallons make-up water” and highest “recommended system water cycle of concentration.” 

Thermal comfort in buildings comes from moving either air or water around the building affecting the temperature of the space. Radiant systems employ terminal units with few to no moving parts, so the guide focuses on the air-handling systems. Proper maintenance of all the moving parts associated with these systems can make or break not just the energy efficiency of the building, but the thermal comfort and human health of the occupants as these systems also provide the ventilation air that is critical to indoor air quality.​​ ​​ 

The components of most air handling systems include fans, ductwork, damper assemblies, heating and cooling coils (or elements), and associated sensors. Most air handling systems fall into one of two categories: constant air volume and variable air volume.  

Additionally, the control of air handling systems is generally handled by the CMMS. However, there are additional measures to consider beyond system controls to achieve maximum efficiency. Several options are listed below: 

• Filters. Air filters play a critical role in maintaining indoor air quality and protecting the downstream components of the system from dirt that reduces equipment efficiency. In the worst case, dirty filters can result in supply air bypassing the filter and depositing dirt on the heating/cooling coils rather than on the filter. This results in dirty coils, poor heat transfer, and general inefficiency. In addition to the efficiency penalty, cleaning a dirty coil is far more difficult and labor intensive than replacing filters. As a rule, sites should routinely change filters based on either the pressure drop across the filter, calendar scheduling, or visual inspection. Scheduled intervals should be between one and six months, depending on the dirt loading from indoor and outdoor air. Measuring the pressure drop across the filter is the most reliable way to assess filter condition. In facilities with regular and predictable dirt loading, measuring the pressure drop across the filter can be used to establish the proper filter-changing interval; thereafter, filter changes can be routinely scheduled. Refer to manufacturer’s data for the recommendations of pressure drop across specific filters. 

• Coil Cleaning. Hot water and chilled water coils in HVAC systems tend to accumulate dirt and debris, similar to HVAC filters. As dirt and debris accumulates, it inhibits the heat transferred from the working fluid to the air stream, thus reducing the efficiency of the HVAC system. Much like HVAC filters, the scheduled intervals between cleanings are a function of the dirt loading across the coil and is primarily a function of how much dirt is in the ambient air and what has bypassed the filter. Based on the site’s periodic inspections, the given facility should develop appropriate cleaning schedules for all of the hot water and chilled water coils.  

• Damper Operation. There are a number of potential faults HVAC dampers may be subject to. These include dampers stuck open or closed, dampers manually positioned (i.e., mechanically fixed in a position using wire, boards, etc.), dampers with missing vanes, or dampers operating with poor seals.  

Fans 

ASHRAE defines a fan as follows: “[An] air pump that creates a pressure difference and causes airflow. The impeller does the work on the air, imparting to it both static and kinetic energy, varying proportion depending on the fan type.” 

Fans are often an afterthought in terms of efficiency, but they can play a key role. The United Nations Environmental Programme (UNEP) provides “Fan System Operational-Efficiency Considerations.” They are outlined below: 

• Use smooth, well-rounded air inlet cones for fan air intake

• Avoid poor flow distribution at the fan inlet

• Minimize fan inlet and outlet obstructions

• Clean screens, filters and fan blades regularly 

• Minimize fan speed 

• Use low slip or flat belts for power transmission

• Check belt tension regularly

• Use variable speed drives for large variable fan loads

•  Use energy-efficient motors for continuous or near continuous operation 

• Eliminate leaks in ductwork 

• Minimize bends in ductwork

• Turn fans and blowers off when not needed

• Reduce the fan speed by pulley diameter modifications in case of oversized motors

• Adopt inlet guide vanes in place of discharge damper control

• Reduce transmission losses by using energy-efficient flat belts or cogged raw-edged V-belts instead of conventional V-belt systems

• Ensure proper alignment between drive and driven system

• Ensure proper power supply quality to the motor drive

• Regularly check for vibration trend to predict any incipient failures like bearing damage

Pumps 

There are numerous pumps throughout a building system with a variety of names dependent upon their function. However, there are two major groups of pumps: dynamic pumps and positive displacement pumps.  

Pumps are another overlooked, but critical part, of maximizing efficiency. DOE states, “Pumps frequently are asked to operate far off their best efficiency point, or are perched atop unstable base-plates, or are run under moderate to severe misalignment conditions, or, having been lubricated at the factory, are not given another drop of lubricant until the bearings seize and vibrate to the point where bolts come loose. When the unit finally stops pumping, new parts are thrown on the machine and the deterioration process starts all over again, with no conjecture as to why the failure occurred. 

Proper maintenance is vital to achieving top pump efficiency expected life. Additionally, because pumps are a vital part of many HVAC and process applications, their efficiency directly affects the efficiency of other system components. For example, an improperly sized pump can impact critical flow rates to equipment whose efficiency is based on these flow rates–a chiller is a good example of this.” 

The Federal Energy Management Program offers the following “Large Horsepower (25 horsepower and above) Pump Efficiency Survey.” It is listed below.

Actions are given in decreasing potential for efficiency improvement:  

• Excessive pump maintenance – this is often associated with one of the following:

•     Oversized pumps that are heavily throttled.

•     Pumps in cavitation.

•     Badly worn pumps.

•     Pumps that are misapplied for the present operation.

• Any pump system with large flow or pressure variations. When normal flows or pressures are less than 75% of their maximum, energy is probably being wasted from excessive throttling, large bypass flows, or operation of unneeded pumps.

• Bypassed flow, either from a control system or deadhead protection orifices, is wasted energy.

• Throttled control valves. The pressure drop across a control valve represents wasted energy, that is proportional to the pressure drop and flow.

• Fixed throttle operation. Pumps throttled at a constant head and flow indicate excess capacity.

• Noisy pumps or valves. A noisy pump generally indicates cavitation from heavy throttling or excess flow. Noisy control valves or bypass valves usually mean a higher pressure drop with a corresponding high energy loss.

• A multiple pump system. Energy is commonly lost from bypassing excess capacity, running unneeded pumps, maintaining excess pressure, or having as large flow increment between pumps.

• Changes from design conditions. Changes in plant operating conditions (expansions, shutdowns, etc.) can cause pumps that were previously well applied to operate at reduced efficiency.

• A low-flow, high-pressure user. Such users may require operation of the entire system at high pressure.

• Pumps with known overcapacity. Overcapacity wastes energy because more flow is pumped at a higher pressure than required. 

Lighting systems continue to improve with a focus on energy efficiency, but also continue to be a source of wasted energy. Lighting advancements, both in terms of equipment and controls, seem to be on a continual path toward increased efficiency, so this is an area where retrofitting and recommissioning happens (and should happen) on a regular basis. The savings from relatively low-cost changes in lighting are almost always worth it.  

An obvious area for change is in lightbulbs and other lighting equipment. This is an area for constant review and upgrades as the savings of such a change often quickly pays for itself.

A property’s CMMS may play a significant role in lighting controls and will likely have a series of toggles to meet the building’s needs. However, regardless of whether the CMMS is involved, property owners and managers should look toward lighting controls that keep tenants satisfied while minimizing energy usage.  

DOE indicates a “proactive, planned maintenance program” for lighting systems can maximize operational efficiency and minimize the need for constant changes in lightbulbs, etc. The agency lists the following components of a proactive approach for lighting system maintenance15:  

• Cleaning of lamps, luminaries, and room surfaces at regular intervals

• Group relamping on a scheduled basis of all luminaires in an area, with spot relamping in between. One cleaning can be performed in conjunction with relamping 

• Inspection and repair of lighting equipment at regular intervals

• Inspection and re-calibration of lighting controls at regular intervals

• Re-evaluation of lighting system and potential upgrades. An upgrade may replace a group relamping cycle. 

​​Since the invention of the thermostat in the 19th century, building owners and users have been trying to use sensors and controls to improve air flow, increase efficiency, and improve building operations. In spite of a variety of barriers, the Internet of Things has increased development of systems and controls for building operations in recent years. ​All current paths to a decarbonized future flow through the concept of grid-enabled efficient buildings (often shortened to GEB) which require smart building controls throughout the energy consuming systems to effectively deliver both energy use and carbon emission reductions.​​ 

As DOE’s Office of Energy Efficiency and Renewable Energy reports in its “Innovations in Sensors and Controls for Building Energy Management” publication:

Subsequent development of wireless and network communication, open communication protocols, digital equipment operation, and cloud-based systems have been enabled through advancements in computing and allowed for embedding additional intelligence into control systems, including integration across loads and remote operation. A wide array of sensors (e.g., temperature, airflow, daylight levels) can now be used to monitor operating conditions. These measurements are then processed by device controllers to initiate the appropriate action (e.g., adjust temperature, airflow, light) through the corresponding actuators (e.g., dampers). 

The report explains commercial buildings have lagged behind other sectors in adopting automation in facility systems and controls for a variety of legitimate reasons. However, the Office of Energy Efficiency and Renewable Energy indicates the use of building automation systems is increasing and will continue to increase for the foreseeable future: 

Within the buildings sector, sensors and meters monitor and detect changes in variables affecting occupant comfort, as well as building performance and equipment operations such as energy and power consumption; temperature; light; occupancy and vacancy; indoor air quality and gas concentration levels (e.g., humidity, carbon dioxide, carbon monoxide, and volatile organic compounds); air, water, and other liquid flow and leakages (e.g., refrigerants). According to Navigant Research (2016), the market for advanced sensors in intelligent buildings was $1.2 billion in 2016 and is expected to double to $3.2 billion in 2025. Building controls, consisting of algorithms and computer logic, respond to input(s) from monitoring technologies to change environmental or operating conditions of building equipment loads or systems (e.g., lighting, windows and shading, ventilation) through a combination of controller devices and actuators. Overall, a control system consists of sensor packages with transducers to measure changes to the variable of interest, controllers to receive communication about these changes from the transducers and calculate the appropriate response, and actuators to transmit the output signal from the controllers to initiate changes in the controlled devices. Control systems with multiple devices and loads that need to be coordinated can consist of different configurations or architectures. Specifically, they can either operate with a single centralized controller or with smaller distributed nodes that coordinate across neighboring devices and that react autonomously to detected changes in their local environment. 

The variation of systems and building types and uses of these automated systems renders a detailed discussion of each of their component parts not terribly helpful in the context of this document. However, it is important to be aware of each of the components of modernized building automation systems. The Office of Energy Efficiency and Renewable Energy identifies them as follows: 

• Sensor networks

• Network communications

• Occupancy sensing

• Metering

• Fault detection and diagnostics

• Building energy modeling

• Control architectures 

• Interoperability

Building automation systems (BAS) are clearly becoming a critical part of building operations and will help drive efficiency efforts going forward. DOE expects significant energy savings as a result of the increased adoption and improvement of BAS.