RTU versus PLC

To determine the difference between RTU and PLC with the current implemented technology somehow become very difficult due to the used technology on both of the terms as well as the available features already become similar.
Initially, the RTU is refer to a controller (more common as Single Board panel mounted) that be placed remotely (therefore it is absolutely facilitate with serial communication feature), and just perform data acquisition (conversion of electrical signal to digital data) without any high-level programming capability.
While PLC (modular / rack-mounted), is more dedicated to a process control to perform standalone automatic control (therefore it is absolutely facilitate with highlevel programming capability, such as Ladder Logic and/or Sequential Text Command), and the communication capability is just optional.
Currently both of the RTU and PLC has communication port(s), support multi-protocols Modbus, DNP, IEC 60870-5, etc), has 'programmable' capability (IEC 61131-3), and Modular.
By now, most of the major brand PLCs (AB, Siemens, Modicon, GE Fanuc, etc.) support for multi-protocols, either it through their native communication module/port and/or through a third party communication module provider (such as ProSoft for AB PLC).
Therefore, personally, I would just call both of it as 'Controller' and determine it as : 1. General Purpose Controller 2. Specific Application Controller - IED, in electrical area, such as Bay Controller, Power Monitor, Protection Relay, etc. - in oil & gas area, such as Batch Controller, Flow Computer/Controller, Pump Controller, etc. 3. Integrated Controller/Sensor
- Fieldbus Instrument, Smart Fire & Gas Detector, etc.
Communication Interface
In general, any Controller with communication port shall be able to be connected to any data telecommunication infrastructure, either it direct wire, fiber optic, microwave, power line carrier, dedicated/leased line, etc. Telecommunication infrastructure shall be transparent to the data, therefore we just need to assure that the physical interface between the PLC and Data Telecommunication infrastructure is same, and you will get the data in the other site is similar as what you sent.

HVAC SYSTEM

Commercial and public buildings have been the targets of terrorist attacks in the United States and abroad. Terrorists have used high explosives to destroy or damage the World Trade Center, the Pentagon, and the Alfred P. Murrah Building; U.S. embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya; and the Khobar Towers in Saudi Arabia.1 In October 2001, terrorists sent biological weapons, Bacillus anthracis spores, through the U.S. mail to news media companies and to U.S. Congressional offices. Workers in the former Brentwood Post Office (renamed the Curseen-Morris Processing and Distribution Center); the Trenton, New Jersey, regional mail processing center in Hamilton Township; the Hart Senate Office Building; the American Media Inc. (AMI) Building; and Rockefeller Center were exposed to infectious spores when contaminated letters were processed or opened. Following these exposures, 22 people became ill, 5 of whom died.2 More than 30,000 people are estimated to have received antibiotics as a result of possible exposure to anthrax spores.3 Hundreds of millions of dollars were spent in decontamination and restoration of the attacked buildings and on hardening security in U.S. postal facilities and mailrooms in high-profile buildings throughout the country. The prospect of biological attacks is a growing strategic threat.4,5 Covert aerosol attacks inside a building are of particular concern.6 Given the fact that many Americans spend a great deal of their lives in commercial buildings, it is worth examining whether practical actions can be taken to reduce risk to commercial building inhabitants from an aerosolized biological attack. To this end, the Center for Biosecurity of the University of Pittsburgh Medical Center (UPMC) convened a Working Group to determine what steps should be recommended to reduce the risk of exposure of building occupants after an aerosol release of a biological weapon. The Working Group was composed of subject matter experts in air filtration, building ventilation and pressurization, air conditioning and air distribution, biosecurity, building design and operation, building decontamination and restoration, economics, medicine, public health, and public policy. The Working Group focused on functions of the heating, ventilation, and air conditioning (HVAC) systems in commercial or public buildings that could reduce the risk of exposure to biological aerosols following biological attacks.
This Working Group report provides practical recommendations intended to reduce the risk of building inhabitants to biological hazards. These recommendations are focused primarily on the use of currently available technologies whose applications would be neither prohibitively expensive nor require major renovations or retrofit. The report also includes a brief overview of HVAC systems for those not trained in the science, design, construction, or operation of HVAC systems. This Working Group report draws extensively on the findings and judgments made in a number of important reviews and guidance documents.7–12
Working Group Method Working Group members from the Center for Biosecurity compiled and reviewed evidence and recommendations from (a) literature published from January 1966 to June 2005; (b) guidance documents written by professional engineering societies and/or government agencies on reduction of building vulnerability to terrorism and on improvement of indoor air quality; and (c) reports and interviews with experts on building security and indoor air quality. Based on this review, core concepts and principles were drafted. The Working Group was convened on June 13–14, 2005, to discuss and critique the initial draft of the concepts and principles. Following this meeting, a report was drafted that incorporated the Working Group’s oral and written suggestions. This draft was circulated to the Working Group for critique in October 2005. The Working Group’s critiques of this draft were incorporated into a second draft, which was circulated in December 2005. The final report incorporates the critiques of the Working Group. All named authors of this report are in accord with the recommendations. Some Working Group members participated as ex officio members; those members have no position on the recommendations. Working Group Presumptions For the purposes of the recommendations in this document, the Working Group agreed to presume the following: Improvements in the performance of HVAC systems that reduce occupant exposure to airborne particles in the range of 1–3 microns in diameter could potentially reduce exposure not only to weaponized infectious agents (the size range of Bacillus anthracis spores) but also to naturally occurring infectious agents and allergens of similar size.6,13 In the future promising new and evolving technologies, such as ultraviolet germicidal irradiation and electronic filtration, might be definitively shown to play an important role in reducing risk to building occupants from deleterious agents in indoor air. However, these technologies have yet to be independently evaluated using standardized methods. The absence of such data does not mean the technologies are ineffective; it means that there was no consensus in the Working Group on their performance characteristics, and, therefore, no recommendations about these technologies were made. New standards are being developed for many classes of devices. The Working Group could support their use in reducing the risk posed by bio-aerosols if their performance characteristics are documented by standardized methods. Aerosolized infectious particles fall out of suspension and settle on work surfaces, furniture, and floors; these particles also can stick to clothing and skin and present a risk from contact exposure. This type of risk would not necessarily be ameliorated by improved HVAC system functions. HVAC System Overview: Current Operations, Possible Changes HVAC systems are integral components of most commercial and public buildings.14 HVAC systems are intended to provide for the health, comfort, and safety of occupants by maintaining thermal and air quality conditions that are acceptable to the occupants15,16 through energy-efficient and cost-effective methods during normal conditions17 and, to the extent possible, to be responsive to hazardous exposures during extraordinary conditions.11 In principle, all HVAC systems have similar characteristics, but, in practice, they vary from a simple system serving a single thermostatic zone with a single air-handling unit to complex systems comprised of many air-handling units serving hundreds of thermostatic zones controlled by centralized energy management, lifesafety, and security systems. Furthermore, in some commercial and public buildings (e.g., hospitals), the HVAC systems must have the capability to remain operational in critical areas during emergency conditions. Buildings can be commissioned to ensure that building systems, including the HVAC system, are designed to function—and actually do function—according to specifications that address the preparedness and responsiveness requirements of the facility, including those of biological attacks. Building commissioning and re-commissioning are processes conducted by a team of experts and include design review, installation, performance testing, and balancing of systems according to intended design and applicable standards and codes.18 Well-commissioned buildings have efficient ventilation, pressurization, conditioning, and filtration functions. Air leakage into and out of buildings is low. These improved functions result in better-performing HVAC systems; the quality of indoor air improves, and operating costs are reduced (8–20%).18 Unfortunately, many buildings are neither commissioned nor re-commissioned. The design of an HVAC system is influenced by many factors, including but not limited to: the function, size, and configuration of the building; the selection of building materials and furnishings; construction methods; the budgets for HVAC capital equipment, maintenance, and operation; the air-quality requirements based on occupancy and use of the building; and the outside environment. Together, these factors determine the rates at which heat, water, and air contaminants have to be removed from the occupied spaces. Building renovations may change the initially designed airflow patterns and air supply route(s). The performance of an HVAC system is evaluated by two criteria: system capacity (i.e., size) and system control (i.e., regulation of rate changes). System capacity is determined by the HVAC system’s ability to provide sufficient heating, cooling, humidification, dehumidification, air dilution, and air cleaning to maintain the desired indoor conditions at design-specified ambient (i.e., likely peak environmental) conditions. System control is determined by the HVAC system’s ability to regulate the rates of these functions to maintain the desired indoor conditions during all ambient conditions.19 A typical HVAC system has three basic components, as shown in Figure 1.14 These components are: (a) outdoor air intake and air exhaust ducts and controls; (b) airhandling units (a system of fans, heating and cooling coils, air filters, controls, etc.); and (c) an air distribution system (air ducts, diffusers, and controls; return and exhaust air collectors; grilles and registers; return and exhaust air ducts and plenums).
HVAC systems perform multiple interdependent functions, including heating, humidification, cooling, dehumidification, ventilation, pressurization, and filtration/ cleaning. In most systems, several of these functions are performed simultaneously. These functions affect the occupants’ exposure to airborne contaminants, including aerosolized infectious agents. In the context of protection from biological attacks, HVAC systems can simultaneously perform three interdependent functions—ventilation, pressurization, and filtration—while providing the required temperature and humidity control. The Working Group considered each function to determine what changes to each might reduce the risks posed by biological attacks. The Working Group focused primarily on changes that might be made using currently available technologies.
Ventilation Ventilation is the process of supplying air to or removing air from a space to reduce contaminant levels and to optimize humidity and temperature of the air within the space.16 For commercial and public office buildings, ventilation is usually achieved by exhausting some of the return air (recaptured indoor air) to the outside environment, replacing it with outdoor air, and mixing the outdoor air with the portion of return air that is being recirculated. After this mixture is filtered, it is conditioned (i.e., heated or cooled, humidified or dehumidified), and delivered to the occupied space as supply air (Figure 1). Improvements in three aspects of supply air might reduce the indoor concentrations of particles (including infectious particles that would be released during an attack): (a) the rate of air exchange (delivery of supply air and exhaust of return air); (b) the airtightness of the return air system; and (c) the effectiveness of the filtration and air cleaning processes (described later). Rate of Air Exchange There are two types of air exchange rates in HVAC systems: the supply air exchange rate, which is primarily determined by the thermal loads in the spaces, and the outdoor air exchange rate, which is primarily determined by the floor area and maximum number of occupants. Both of these air exchange rates are important for ventilation control. If the particulate concentration in the outdoor air is lower than in the indoor air, higher outdoor air exchange rates reduce the indoor particle concentrations by exhausting more of the particle-laden return air and diluting the recirculated return air with cleaner outdoor air. Thus, the indoor particle concentrations are decreased by exhausting and by diluting the return air; this process is referred to as dilution ventilation.6 Dilution ventilation requires that the system have the capacity for conditioning increased amounts of the outdoor air. Use of higher exchange rates to maximize the effect of dilution ventilation has advantages and disadvantages. Control strategies for protecting against external and internal releases of biological agents are different. If the particle concentration in the outdoor air is less than the indoor air, a high rate of air exchange will reduce the concentrations of indoor particles. In this case, as the quantity of outdoor air intake is increased, more energy is needed to condition the outdoor air. These processes increase operating costs. If the outdoor concentration of particles (if the aerosol attack involved external releases of biological agents) is higher than indoor concentrations, an increase in outdoor air exchange rate will increase the particles in the supply air. Dilution ventilation will not offer protection against external releases unless special filtration and air cleaning at the outdoor air intake is employed (shown in Figure 1).20 HVAC systems typically vary supply air exchange rates to control temperature and outdoor air exchange rates based on outdoor air temperature, or to reduce carbon dioxide concentratiion (see Figure 1). In principle, some HVAC systems may be able to control the rates of outdoor and supply air exchange and perform dilution ventilation specifically in response to increased concentrations of indoor air particles. Detection of increases in indoor and/or outdoor particle concentrations requires the use of devices that measure particle concentration in the air and a control system that could either adjust air exchange rates accordingly or generate a warning signal to indicate the need for manual adjustment.11,21 Particle counters are commercially available and are used to measure particle counts in industrial clean rooms. Furthermore, particle counters can be gated so that when the concentration of indoor and/or outdoor air particles in a particular size range increases beyond a certain point, signals can be sent to control devices to modify air exchange rates in zones in which particulate concentrations have increased. Particle counters can measure the concentration of particles of a given size (1–3-micron range) but are not specific for biological material. However, application of particle counters in commercial and public buildings is not widespread, and published literature on performance characteristics in typical commercial settings is limited. Therefore, use of these devices in conjunction with dilution ventilation is not recommended at this time. The Return Air System The return air system removes a portion of the supply air from the occupied zones and returns this air to the airhandling units for exhaust or recirculation (Figure 1). One of two methods is used to return air to the HVAC system: the ducted return or the plenum return (the plenum is the space between the finished ceiling and the floor slab above). Ducted returns collect air from each room or zone using return air devices in the ceiling or walls of the occupied spaces that are directly connected by ductwork to the air-handling unit (Figure 2A). The plenum return collects air from several rooms or zones through return air devices that empty into the negatively pressurized plenum. The air collected in the plenum is then returned to the air-handling unit by ductwork or structural conduits (Figure 2B). The effectiveness of the return air system plays a key role in indoor air quality since the HVAC system can only exhaust, filter, or condition indoor air that is returned to the handling unit. Regardless of whether the HVAC system has a ducted return or a plenum return, increasing the seal integrity of the return air system and air-handling units (Figure 1) will help to ensure that more air is returned to and reconditioned by the air-handling unit. This can be accomplished by improving the seam seals, recaulking and replacing failed gaskets, and sealing unlined structural conduits. Because return plenums draw air from openings into building cavities, return plenums are more difficult to seal than ducted returns.

Energy Analytics Solution

Berikut salah satu applikasi yang digunakan oleh salah satu brand diterapkan dalam SCADA.....ada yang ingin menambahkan,,, dari oleh karna waktu yg tersedia sangat krg pada lain waktu akan saya tambahkan lebih rinci...

Control Respon (2)

Proportional Control
A proportional control response produces an analog or variable output change in proportion to a varying input. In this control response, there is a linear relationship between the input and the output. A setpoint, throttling range and action typically define this relationship. In a proportional control response, there is a unique value of the measured variable that corresponds to full travel of the controlled device and a unique value that corresponds to zero travel on the controlled device. The change in the measured variable that causes the controlled device to move from fully closed to fully open is called the throttling range. It is within this range that the control loop will control, assuming that the system has the capacity to meet the requirements.

The action dictates the slope of the control response. In a direct acting proportional control response, the output will rise with an increase in the measured variable. In a reverse acting response, the output will decrease as the measured variable increases. The setpoint is an instruction to the control loop and corresponds to a specified value of the controlled device, usually half-travel. An example is shown in Figure 5.

In a proportional control system, the value of the measured variable at any given moment is called the control point. Offset is defined as the difference between the control point and the desired condition. One way to reduce offset is to reduce throttling range. Reducing the throttling range too far will lead to instability. The more quickly the sensor “feels” the effect of the control response, the larger the throttling range has to be to produce stable control.

Proportional plus Integral (PI) Control
PI control involves the measurement of the offset or “error” over time. This error is integrated and a final adjustment is made to the output signal from the proportional part of this model. This type of control response will use the control loop to reduce the offset to zero. A well set-up PI control loop will operate in a narrow band close to the setpoint. It will not operate over the entire throttling range (Figure 6).

PI control loops do not perform well when setpoints are dynamic, where sudden load changes occur or if the throttling range is small.

Proportional plus Integral plus Derivative (PID) Control
PID control adds a predictive element to the control response. In addition to the proportional and integral calculation, the derivative or slope of the control response will be computed. This calculation will have the effect of dampening a control response that is returning to setpoint so quickly that it will “overshoot” the setpoint.

PID is a precision process control response and is not always required for HVAC applications. The routine application of PID control to every control loop is labor intensive and its application should be selective.

Definition of Direct Digital Control (DDC)

DDC control consists of microprocessor-based controllers with the control logic performed by software. Analog-to-Digital (A/D) converters transform analog values into digital signals that a microprocessor can use. Analog sensors can be resistance, voltage or current generators. Most systems distribute the software to remote controllers to eliminate the need for continuous communication capability (stand-alone). The computer is primarily used to monitor the status of the energy management system, store back-up copies of the programs and record alarming and trending functions. Complex strategies and energy management functions are readily available at the lowest level in the system architecture. If pneumatic actuation is required, it is accomplished with electronic to pneumatic transducers. Calibration of sensors is mathematical; consequently the total man-hours for calibration are greatly reduced. The central diagnostic capabilities are a significant asset. Software and programming are constantly improving, becoming increasingly user-friendly with each update.

Benefits of DDC

The benefits of direct digital control over past control technologies (pneumatic or distributed electronic) is that it improves the control effectiveness and increases the control efficiency. The three main direct benefits of DDC are improved effectiveness, improved operation efficiency and increased energy efficiency.

Improved Effectiveness
DDC provides more effective control of HVAC systems by providing the potential for more accurately sensed data. Electronic sensors for measuring the common HVAC parameters of temperature, humidity and pressure are inherently more accurate than their pneumatic predecessors. Since the logic of a control loop is now included in the software, this logic can be readily changed. In this sense, DDC is far more flexible in changing reset schedules, setpoints and the overall control logic. Users are apt to apply more complex strategies, implement energy saving features and optimize their system performance since there is less cost associated with these changes than there would be when the logic is distributed to individual components. This of course assumes the user possesses the knowledge to make the changes.

DDC systems, by their very nature can integrate more easily into other computer-based systems. DDC systems can integrate into fire control systems, access/security control systems, lighting control systems and maintenance management systems.

Improved Operational Efficiency
Operational improvements show the greatest opportunity for efficiency improvements in direct digital controls. The alarming capabilities are strong and most systems have the ability to route alarms to various locations on a given network. The trending capabilities allow a diagnostic technician or engineer to troubleshoot system and control problems. They also allow the data to be visualized in various formats. These data can also be stored and analyzed for trends in equipment’s performance over time.

Run-times of various equipment can be monitored and alarms/messages can be generated when a lead/lag changeover occurs or if it is time to conduct routine maintenance.

The off-site access/communication capability allows an owner/operator to access their system remotely. Multiple parties can also be involved in troubleshooting a problem. The control vendor, design engineer and commissioning authority can use these features to more efficiently diagnose and visualize problems.

Increased Energy Efficiency
There are many energy-efficient control strategies employed in pneumatic logic that can be easily duplicated in DDC logic. Due to the addition of more complex mathmatical functions (easily obtained in software), there are many additional energy-efficient routines that can be used with DDC.

Strategies such as demand monitoring and limiting can be more easily implemented with DDC systems. The overall demand to a facility can be monitored and controlled by resetting various system setpoints based on different demand levels. If a DDC system is installed at the zone level, this could be accomplished by decreasing the requirement for cooling on a zone-by-zone basis.

By storing trends, energy consumption patterns can be monitored. Equipment can also be centrally scheduled “on” or “off” in applications where schedules frequently change.
 

Control Response

  

Two-Position Control
Two-position control compares the value of an analog or variable input with instructions and generates a digital (two-position) output. The instructions involve the definition of an upper and lower limit. The output changes its value as the input crosses these limit values. There are no standards for defining these limits. The most common terminology used is setpoint and differential. The setpoint indicates the point where the output “pulls-in,” “energizes” or is “true.” The output changes back or “drops-out” after the input value crosses through the value equal to the difference between the setpoint and the differential.

Two-position control can be used for simple control loops (temperature control) or limit control (freezestats, outside air temperature limits). The analog value can be any measured variable including temperature, relative humidity, pressure, current and liquid levels.

Time can also be the input to a two-position control response. This control response functions like a time clock with pins. The output “pulls-in” when the time is in the defined “on” time and drops out during the defined “off” time.

Figure 3, shows an example of two-position control in a home heating system, where the thermostat is set to energize the heating system when the space temperature falls below 70° F and turn off when the temperature rises to 72° F in the space. This is an example of a setpoint of 70° F with a two-degree differential.

Floating Control
Floating control is a control response that produces two possible digital outputs based on a change in a variable input. One output increases the signal to the controlled device, while the other output decreases the signal to the controlled device. This control response also involves an upper and lower limit with the output changing as the variable input crosses these limits. Again, there are no standards for defining these limits, but the terms setpoint and deadband are common. The setpoint sets a midpoint and the deadband sets the difference between the upper and lower limits.

When the measured variable is within the deadband or neutral zone, neither output is energized and the controlled device does not change - it stays in its last position. For this control response to be stable, the sensor must sense the effect of the controlled device movement very rapidly. Floating control does not function well where there is significant thermodynamic lag in the control loop. Fast airside control loops respond well to floating control. An example of floating controls is shown in Figure 4.

 

Zelio Smart PLC

Zelio Control

Description Zelio adalah sebuah smart relay, dalam applikasi zelio dapat menggunakan program LADDER dan FBD jadi sangat mudah dan tergantung selera dari programmer yang ingin membuatnya, zelio jg disertai simulasi program untuk program LADDER dan FBD so, fungsi ini masih ditambah lagi dengan download dan upload dari zelio ke pc/laptop or sebaliknya untuk keperluan backup program selanjutnya, dengan harga yang cukup ekonomis dan mudah diterapkan siapapun bisa menghemat baudget utk membuat PLC.

Tujuan diciptakannya Smart Relay :

1. Untuk menggantikan logika dan pengerjaan sirkit kontrol relay yang merupakan instalasi langsung.

2. Dengan smart relay rangkaian kontrol cukup dibuat secara software.

3. Smart Relay dirancang untuk instalasi dan perawatan oleh teknisi elektrik industri yang tidak harus mempunyai skill elektronika tinggi.

Keunggulan Smart Relay :   

1. Sangat mudah untuk diimplementasikan dan waktu implementasi proyek lebih cepat.

2. Bersifat fleksibel dan sangat handal.

3. Mudah dalam modifikasi (dengan software).

4. Lebih ekonomis daripada PLC untuk aplikasi yang sederhana.

5. Memerlukan waktu training lebih pendek.

Zelio

1. Zelio adalah Smart Relay yang dibuat oleh Schneider Telemecanique.

2. Tersedia dalam 2 model : Model Compact dan Model Modular.

3. Jika diperlukan dapat ditambahkan modul I/O tambahan (expansion I/O modules) , baik I/O diskrit maupun I/O analog.

4. Beberapa option lain juga dapat ditambahkan (Modul komunikasi MODBUS dan Memory).

Keunggulan Smart Relay Zelio :

1. Tersedianya modul komunikasi MODBUS sehingga Zelio dapat menjadi slave PLC dalam suatu jaringan PLC.

2. Terdapat fasilitas Fast Counter (hingga 1KHz).

3. Dapat diprogram dengan menggunakan Ladder dan FBD.

4. Terdapat 16 buah Timer (11 macam), 16 buah Counter, 8 Buah blok fungsi Clock setiap blok fungsi memiliki 4 kanal), automatic summer/winter time switching, 16 buah analog comparator.

5. Dapat ditambahkan 1 modul I/O tambahan.

Pemilihan Smart Relay

1. Pemilihan Smart Relay diturunkan dari kebutuhan aplikasi.

2. Perhatikan batasan kemampuan Smart Relay.

3. Inventarisasi jenis sinyal/tegangan yang ditangani (analog/digital, AC/DC).

Batasan Kemampuan

1. Jumlah dan jenis input.

2. Jumlah dan jenis output

3. Jumlah memory yang tersedia. Zelio dapat diprogram hingga 120 Row (1 Row terdiri dari 5 kontak dan 1 koil).

4. Cara/teknik pemrograman (Ladder Diagram atau FBD).

Keterangan :

1. Jika aplikasi yang akan dibuat memiliki jumlah I/O <= 20 (12 Input dan 8 output) maka gunakanlah Zelio Compact. Dan jika jumlah I/O nya lebih dari 20 gunakanlah Zelio Modular (Zelio Modular Max I/Onya = 40 I/O).

2. Pemilihan tegangan (12 Vdc, 24Vdc, 24 Vac dan 100-240 Vac) tergantung pada jenis tegangan sensor-sensor dan aktuator-aktuator yang akan digunakan.

The HVAC Commissioning Process

Developing new skills can be an intimidating and difficult undertaking.

Very often we are our own worst enemies by making things that we are not familiar with more difficult than they actually are. Getting started and prioritizing important issues may well represent the largest hurdle on the path to broadening our talents.

With practice and experience, procedures become second nature. This has been our experience with the art of HVAC commissioning. Sometimes it is perplexing to hear questions from colleagues about the commissioning process that seem self evident to us. Herein lies the dilemma of teaching effectively; on the one hand good teachers know their subject matter intuitively, but at the same time they must communicate the basics clearly, and without assumptions. So let us see if together we can debunk some of the mystery surrounding the HVAC commissioning process.

The Foundations of Commissioning

HVAC commissioning is a specialty. As it turns out, many of the qualities, skills, talents, and experiences of test and balance professionals prepare them uniquely for the HVAC commissioning agent role. Unlike engineers and builders who spend months and years on individual projects, TAB personnel witness a varied and broad range of construction and design applications, including common problems both in installation and coordination. Combining these hard-earned skills with a consistent commissioning methodology forms the basis for an effective HVAC commissioning practice.

So what is the commissioning process? Neophytes may hold the belief that design engineering credentials or years of construction installation experience are necessary as a foundation for developing a commissioning process. While these are also effective avenues from which to approach commissioning, they are not mandatory – there's more than one way to skin a cat. The point is that commissioning is not designing or building the project. Commissioning is proactive verification of compatibility between construction activities and design intent. You don't have to understand the entire chemical composition of chocolate to determine whether or not the cake is chocolate flavored.

However, you do have to know what chocolate tastes like in order to taste it. Similarly, to commission effectively you must have the ability and experience to read the drawings and specifications – particularly control sequences – in order to render commissioning services.

TAB professionals do this every day on every project. Two vehicles form the foundation of the commissioning process. These are the commissioning team and the commissioning plan. No matter the delivery mechanism of commissioning services – whether it be independent, contractor, or design professional driven – successful commissioning contains these two elements. No single individual has the ability to ferret out every design and construction problem on a project. Selecting and motivating a commissioning team and supplying a clear commissioning plan in the spirit of cooperation and partnering can overcome the

shortfalls of individual people. That's it: commissioning team + commissioning plan = commissioning process!

The Team and the Plan
The HVAC commissioning team is defined in the AABC HVAC Commissioning Guideline :

• Owner

• End-user

• Architect

• Mechanical engineer

• Electrical engineer

• Commissioning agency

• General contractor (or construction manager)

• Mechanical contractor

• Electrical contractor

• Controls contractor

• Sheet metal contractor

• TAB agency

• Owner's O&M staff

Depending on project specifics, additions or subtractions from this list may be required. For example a manufacturer/ vendor may need to be on the commissioning team, or the owner and the end-user may be the same party. Now what about the commissioning plan? The commissioning plan starts with the request for proposal (RFP) response. In other words when a commissioning agency develops the scope on a project to price services, this becomes the basis of the commissioning plan. From this point forward the commissioning scope morphs into a commissioning plan that continues to evolve throughout the course of design, construction, acceptance and warranty period and beyond (as in continuous commissioning).

After developing the commissioning scope and marrying it with project-specific equipment and systems, obtaining project schedules and timelines becomes a necessity to price the project. One needs to know the number of phases and the completion date to estimate meetings, manpower commitments and sequences of commissioning activities. Breaking down the scope elements and combining them with timeline information results in a quotation and a crude commissioning plan.

From the perspective of a TAB firm, it is obvious that when quoting TAB services on a project employing commissioning, details of the commissioning plan must be made available to assess the required TAB involvement for accurate pricing. Even if a commissioning plan is not issued (and technically it should be before contractors are asked to prepare bids) a scope of commissioning services most likely exists from which to evaluate the TAB commitment.

A common fallacy is that HVAC commissioning involves extensive TAB involvement. In reality, most HVAC commissioning utilizes the TAB report as a tool for evaluating system performance, while requiring only a marginal amount of TAB verification on the order of selecting 10 percent of documented TAB data – a condition typically found in TAB specifications even when commissioning is not formally incorporated as a separate project trade. The heavy lifting on HVAC commissioned projects comes from the controls contractor, who must manipulatesystems to accommodate testing. The remainder of this article will present an HVAC commissioning scope of work and HVAC commissioning fee breakdown that lead to effective pricing and further development into an actual commissioning plan. In future articles we will demonstrate the "fleshing out" of this

scope into a more detailed and procedural commissioning plan. We will further explore the pre-design, design.

construction, acceptance, and post-acceptance phases and add the details needed to describe start-up, systems verifications checks, functional performance tests and O&M training.

Sample Commissioning Scope of Work:
1. Introduction

A. Commissioning Process

1) The purpose of the commissioning (Cx) process is to ensure that the building owner receives a functional, timely product that conforms to the Design Intent Document, and provides an accurate accounting of any deviations that do not meet those requirements.

B. Design Intent Document

1) The Design Intent Document (DID) represents a composite of design drawings, project specifications, submittals, change orders and industry standards which describe the HVAC systems of this facility.

References to design intent will be taken from these contract documents. The DID is an evolving manuscript maintained by the design professional to track and incorporate design alterations which occur throughout the construction process. Any industry

standards used for this project will be specifically noted when referenced.

C. Commissioning Team

1) The Commissioning Team (CT) shall consist of key parties involved in design, construction and testing of this facility. It is necessary for each agency to appoint team members that will have long-term commitments to this project. Switching team members during the project will reduce the ability of the CT to provide continuity and acceptable results to the building owner. Team members must maintain an ongoing supervisory position on this project. One team member shall be provided by each of the parties listed below:

(a) Engineering Services (ES)

(b) Design Engineer (DE)

(c) General Contractor (GC)

(d) Mechanical Contractor (MC)

(e) Controls Contractor (CC)

(f) Test and Balance Contractor (TABC)
(g) Electrical Contractor (EC)
(h) Commissioning Agent (CA)

2. Commissioning Process
A. Design Review

1) The Design Intent Document (DID) represents a composite of design drawings, project specifications, submittals, change orders, and industry standards which describe the HVAC systems of this facility. References to design intent will be taken from these contract documents. These documents will be reviewed with special attention to adherence of selected equipment to design intent, optimization of performance, accessibility, TAB provisions, and O&M considerations.

B. Kick-Off Meeting

1) A kick-off meeting will be scheduled early in the construction process. The meeting will primarily focus on scheduling issues and reviewing each commissioning team member's responsibilities. Members of the CT will be expected to attend this meeting.

C. Commissioning Meetings

1) Commissioning meetings will be held in conjunction with progress meetings as necessary. The CA will be on site for the Cx meetings. Commissioning meetings will be used to address any problems that alter the design intent or hinder the commissioning process. These meetings provide an open forum for exchange of ideas between contractors, vendors, designers, users and owners.

D. Resolution Tracking Forms (RTF)

1) Resolution tracking is a method employed by the CA to monitor and record problems, their causes, and solutions. The use of these lists prevents problems uncovered during commissioning from being forgotten, and expedites their resolution. The use of RTF's helps ensure that problems or questions will be resolved in a timely manner.

E. System Verification Checklists (SVC) / Manufacturer's Checklists

1) The CA will review the SVC for each piece of equipment prior to start-up. Equipment will be released for start-up only after these checklists have been completed by the installing contractor and reviewed by the CA.

2) The equipment manufacturers' checklists must also be reviewed by the CA prior to start-up. These lists must be completed by the installing contractor, and reviewed by the CA before start-up can commence.

F. Start-up

1) CT members involved in installation, fabrication, manufacture, control, or design of equipment are required to be present at the time of start-up. A factory-authorized technician will be on site to start equipment when required by the specifications. This

will minimize delays in bringing equipment on line & expedite acceptable functional performance in accordance with the DID.

G. Controls / TAB Monitoring

1) Close monitoring of the Control Contractor's progress will promote efficient coordination of the TAB work. The CC will be expected to submit point by point checklists verifying that his work has been completed and all systems are ready for TAB work

and Functional Performance Testing. Programming and graphics will be surveyed by the CA for completeness and conformance with the DID and the owner's scheduling requirements.

2) TAB work will be monitored so that any problems that prevent or hinder proper air and water balance can be addressed and corrected with minimal delays. By addressing these problems as quickly as possible, we can ensure that functional performance testing and owner training will take place on schedule.

H. Functional Performance Tests (FPT)

1) The functional performance tests shall include all HVAC and related equipment.

(a) AHUs will be tested in designed operating modes. Proper operation will be verified at minimum OA, maximum OA, automatic control, and other modes, if necessary, to achieve DID conformance.

(b) VAVs will be tested at minimum and maximum airflow setpoints, and under automatic control. Intermediate settings will be tested as necessary.

(c) Exhaust fans will be tested for conformance to DID.

(d) Hot water pumps will be tested at under relevant operating conditions.

(e) Hot water coils will be tested under relevant operating conditions.

(f) Temperature control devices will be tested at maximum heating and maximum cooling conditions, and under automatic control. Intermediate settings will be tested as necessary to achieve DID conformance.

(g) HVAC systems will be tested to ensure that the building as an integrated system operates properly.

I. Building Turn-Over / Owner Orientation / User Training

1) The CA will assist contractors prepare, coordinate and review operation and maintenance (O&M) manuals, working closely with each contractor to achieve specificity and completeness.

2) The CA will review as-built drawings, working closely with each contractor to achieve specificity and completeness.

3) The CA will coordinate and facilitate owner orientation and user training in conjunction with specified allotted hours for each applicable contractor and subcontractor in order to deliver to the owner/user adequate training and information needed to properly operate and maintain the HVAC systems. The commissioning agent will make himself available for questions and problems the owner/user encounters during the initial occupancy of the facility. We recommend contacting the CA with post construction difficulties in order to efficiently direct problems to the appropriate contractors.

4) The CA will assist the owner/user with warranty issues.

5) The CA will coordinate and facilitate off-season testing, calibrating, and servicing as specified in the contract documents.

3. Conclusion

A. HVAC Commissioning aspires to provide the owner with an added level of confidence that the design object tives set forth for this facility integrate features commensurate with the best interests of the university's plans as set forth in DID. An unbiased commissioning team approach augments the efforts of the design and construction teams to deliver a facility that meets the owner's HVAC Engineering Standards and Performance Specifications, as well as usage requirements.

Sample HVAC Commissioning Scope Breakdown

1. Design Review The Design Intent Document (DID) represents a composite of design drawings, project specifications, submittals, change orders, and industry standards which describe the HVAC systems of this project. References to design intent

will be taken from these contract documents. These documents will be reviewed with special attention to adherence of selected equipment to design intent, optimization of performance, accessibility, TAB provisions, and O&M considerations.

2. System Verification Checklists (SVC)

[CA] will write SVC's based on the DID. These checklists will be created for HVAC systems and subsystems. This includes, but is not limited to, Air Handling Units, Variable Air Volume Boxes, Unit/Cabinet Heaters, Perimeter Heating, Exhaust Fans, HVAC Pumps, and Boilers. Draft copies will be submitted to the DE and the Contractors for review and comments prior to placement on the job site. These SVCs will be bound in a three-ring binder and placed on the job site for use by the installing

contractors. No system will be started until the appropriate SVC's have been completed.

3. Functional Performance Tests (FPT)

[CA] will write FPT's based on the DID. These tests will be created for HVAC systems and subsystems. This includes, but is not limited to, Air Handling Units, Variable Air Volume Boxes, Unit/Cabinet Heaters, Perimeter Heating, Exhaust Fans, HVAC Pumps, and Boilers.

4. Manufacturer's Pre-Start Checklists / Start-Up

Procedures

The manufacturers pre-start checklists and start-up procedures will be supplied by the installing contractors to [CA]. These lists will be included in the thee-ring binder along with the SVC's for use by the installing contractor.

5. Preliminary TAB Review

The preliminary TAB report set-up will be reviewed prior to HVAC equipment start-up, in order to ensure that the final TAB report format and content is acceptable.

6. HVAC Equipment Start-Up

Start-up of major HVAC systems will be witnessed by [CA]. The appropriate contractors and/or manufacturer's representative will be required on site to perform start-up. No system will be started until the appropriate SVC's have been completed. No system will be started until the Manufacturer's checklists have been completed. Start-up will be performed according to the Manufacturer's recommended procedures. [CA] will visit the site to review completeness of installation in conjunction with progress meetings prior to starting HVAC equipment.

7. TAB Review

A pencil copy of the TAB report will be reviewed prior to submission of the final TAB report. A written review will be submitted to the TAB contractor and to the DE for their comments. An acceptable TAB report will be required before Functional Performance Testing can be carried out. [CA] will visit the site during the TAB process in order to assist TABC and CC in the effective completion of their scope of work.

8. Functional Performance Testing

Each major system will be tested. A random sample of each subsystem will be tested. This will be coordinated and witnessed by an [CA] representative and the owner's maintenance staff. Witnessing the FPTs will constitute part of the O&M Training. No FPTs will be performed until the system and related subsystems have been started, the TAB work has been completed, and the TAB report has been submitted and reviewed.

9. Building Turn-Over / O&M Training

Owner training will be coordinated through [CA]. The training will be provided by the installing contractor, or manufacturer's representative, and witnessed by [CA]. This training should include both classroom training and hands-on operational training. The owner may choose to video tape this training for future use. [CA] will visit the site during the Turn-Over and Training period to ensure that any on-going HVAC related problems are being addressed and corrected in a timely and efficient manner.

Conclusion

Please note that our fee is based on the assumption that [CA] will not make regular site visits or attend progress meetings until substantial amounts of HVAC equipment have been installed. It should also be noted that the installing contractor will be responsible for completion of the SVCs and the Manufacturer's Pre-Start checklists. We would also request that progress meeting minutes be forwarded for our records. Two meetings are implicitly included in the above pricing. One "Commissioning Kick- Off Meeting" would be provided to acquaint the contractors with the HVAC Commissioning process and their role in that process. One additional meeting would be provided just prior to start-up to review the process and procedures. Our pricing includes time for Start-up and Functional Performance Testing for a single-phase project.

Sample HVAC Commissioning Fee Breakdown:

1. Design Review .

2. System Verification Checklists (SVC) .

3. Functional Performance Tests (FPT) .

4. Manufacturer's Pre-Start Checklists / Start-up Procedures .

5. Preliminary TAB Review .

6. HVAC Equipment Start-Up .

7. TAB Review .

8. Functional Performance Testing .

9. Building Turn-Over / O&M Training .

10. Meetings & Site Reviews .

11. Resolution Tracking Forms (RTF) .

Total Commissioning Cost .

[Note: items 10 & 11 can be incorporated into items 1 thru 9, above, or itemized separately – cost breakdowns should be developed to suit business practices.]

AUTOMATION GLOSSARY

A

A/C – Air Conditioning

ACH – Air Changes Per Hour

Actuator – A device used to operate a damper or control valve.

AE – Architectural and Engineering; or Architect and Engineer

AFD – Adjustable-Frequency Drive

AHU – Air-Handling Unit, It can be a whole unit including the blower, heating and cooling elements, filter racks or chamber, dampers, humidifier, and other central equipment in direct contact with the airflow. This does not include the ductwork through the building.

Algorithm – A calculation method that produces a control output by operating on an error signal or a time series of error signals.

Analog – Continuously variable (e.g., a faucet controlling water from off to full flow).

ASD – Adjustable-Speed Drive

ASHRAE – American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc.

ATC – Automatic Temperature Control

Automatic control system – A system that reacts to a change or imbalance in the variable it controls by adjusting other variables to restore the system to the desired balance.

B

Baffle – An orifice placed inside the duct to adjust the duct size to the damper size.

BAS – Building Automation System

BHP – Boiler Horsepower; also, Brake Horsepower

BMS – Building Management System

C

CAD – Computer-Aided Design

CBAS – Computrols Building Automation System

CFM – Cubic Feet per Minute

CHW – Chilled Water

CMMS – Computerized Maintenance Management System

CO2 – Carbon Dioxide

Compensation control – A process of automatically adjusting the setpoint of a given controller to compensate for changes in a second measured variable (e.g., outdoor air temperature). For example, the hot deck setpoint is normally reset upward as the outdoor air temperature decreases. Also called "reset control".

Controller – A device that senses changes in the controlled variable (or receives input from a remote sensor) and derives the proper correction output. Most controls are automatic but have user-inputs such as temperature set points, e.g., a thermostat. Controls may be analog or digital, or a combination.

Control agent – The medium in which the manipulated variable exists. In a steam heating system, the control agent is the steam and the manipulated variable is the flow of the steam.

Controlled medium – The medium in which the controlled variable exists. In a space temperature control system, the controlled variable is the space temperature and the controlled medium is the air within the space.

Control point – The actual value of the controlled variable (setpoint plus or minus offset).

Controlled Variable – The quantity or condition that is measured and controlled.

COP – Coefficient Of Performance

Corrective action – Control action that results in a change of the manipulated variable. Initiated when the controlled variable deviates from setpoint.

Cycle – One complete execution of a repeatable process. In basic heating operation, a cycle comprises one on period and one off period in a two-position control system.

Cycling – A periodic change in the controlled variable from one value to another. Out-of-control analog cycling is called "hunting". Too frequent on-off cycling is called "short cycling". Short cycling can harm electric motors, fans, and compressors.

Cycling rate – The number of cycles completed per time unit, typically cycles per hour for a heating or cooling system. The inverse of the length of the period of the cycle.

D

D-B – Design-Build

Damper – A hydraulic or mechanical device used to regulate airflow in an HVAC system.

Damper seal – Features used to restrict the leakage of a damper.

Damper system – The damper plus it's related components (e.g., duct work, diffusers, coils, and mixing boxes)

DB – Drybulb

DDC – Direct Digital Controls. See also Digital and Digital control.

Deadband – A range of the controlled variable in which no corrective action is taken by the controlled system and no energy is used. See also "zero energy band".

Deviation – The difference between the setpoint and the value of the controlled variable at any moment. Also called "offset".

Digital – A series of on and off pulses arranged to convey information. Morse code is an early example. Processors (computers) operate using digital language.

Digital control – A control loop in which a microprocessor based controller directly controls equipment based on sensor inputs and setpoint parameters. The programmed control sequence determines the output to the equipment.

DOAS – Dedicated Outdoor Air System

DOE – U.S. Department of Energy

Drive Blade – A damper blade that is driven directly by an actuator, a linkage, an axle, or a jackshaft connected to the drive blade in an adjacent damper section.

Droop – A sustained deviation between the control point and the setpoint in a two-position control system caused by a change in the heating or cooling load.

DX – Direct Expansion

E

Electric control – A control circuit that operates on line or low voltage and uses a mechanical means, such as a temperature-sensitive bimetal or bellows, to perform control functions, such as actuating a switch or positioning a potentiometer. The controller signal usually operates or positions an electric actuator or may switch an electrical load directly or through a relay.

Electronic control – A control circuit that operates on low voltage and uses solid-state components to amplify input signals and perform control functions, such as operating a relay or providing an output signal to position an actuator. The controller usually furnishes fixed control routines based on the logic of the solidstate components.

EMS – Energy Management System

Enhanced proportional-integral-derivative (EPID) control – A control algorithm that enhances the standard PID algorithm by allowing the designer to enter a startup output value and error ramp duration in addition to the gains and setpoints. These additional parameters are configured so that at startup the PID output varies smoothly to the control point with negligible overshoot or undershoot.

EPA – U.S. Environmental Protection Agency

F

Final control element – A device such as a valve or damper that acts to change the value of the manipulated variable. Positioned by an actuator.

Fire Damper – A thermally actuated damper arranged to automatically restrict the passage of fire and/or heat at a point where an opening violates the integrity of a fire partition or floor.

FPM – Feet Per Minute

G

GPM – Gallons Per Minute

H

HEPA – High-Efficiency Particulate Air

HTML – Hypertext Markup Language

HTTP – Hypertext Transfer Protocol

Hunting – See Cycling

HWR – Hot Water Return

HWS – Hot Water Supply

I

IAQ – Indoor Air Quality

Ideal Damper System – A system with a linear relationship between the percent open damper position and the percent of full airflow

IS – Information Systems

IT – Information Technology

L

Lag – A delay in the effect of a changed condition at one point in the system, or some other condition to which it is related. Also, the delay in response of the sensing element of a control due to the time required for the sensing element to sense a change in the sensed variable.

Leakage – The amount of air passing through a damper with a given pressure drop and a given torque holding the damper closed.

LEED™ – Leadership in Energy and Environmental Design, a designation by the U.S. Green Building Council

Load – In a heating or cooling system, the heat transfer that the system will be called upon to provide. Also, the work that the system must perform.

M

Manipulated variable – The quantity or condition regulated by the automatic control system to cause the desired change in the controlled variable.

MEC – Mechanical, Electrical, Communication

MEP – Mechanical, Electrical, Plumbing

Measured variable – A variable that is measured and may be controlled (e.g., discharge air is measured and controlled, outdoor air is only measured).

Microprocessor-based control – A control circuit that operates on low voltage and uses a microprocessor to perform logic and control functions, such as operating a relay or providing an output signal to position an actuator. Electronic devices are primarily used as sensors. The controller often furnishes flexible DDC and energy management control routines.

Modulating – An action that adjusts by minute increments and decrements.

O

O&M – Operations and Maintenance

OA – Outside Air

OEM – Original Equipment Manufacturer

Offset – A sustained deviation between the control point and the setpoint of a proportional control system under stable operating conditions.

On/off control – A simple two-position control system in which the device being controlled is either full on or full off with no intermediate operating positions available. Also called "two-position control".

Opposed Blade Damper – A damper constructed so adjacent blades rotate opposite to each other.

P

Parallel Blade Damper – A damper constructed so each blade rotates in the same direction.

PID – Proportional, Integral, Derivative

PM – Preventive Maintenance

Pneumatic control – A control circuit that operates on air pressure and uses a mechanical means, such as a temperature-sensitive bimetal or bellows, to perform control functions, such as actuating a nozzle and flapper or a switching relay. The controller output usually operates or positions a pneumatic actuator, although relays and switches are often in the circuit.

PPM – Parts Per Million

Process – A general term that describes a change in a measurable variable (e.g., the mixing of return and outdoor air streams in a mixed-air control loop and heat transfer between cold water and hot air in a cooling coil). Usually considered separately from the sensing element, control element, and controller.

Proportional band – In a proportional controller, the control point range through which the controlled variable must pass to move the final control element through its full operating range. Expressed in percent of primary sensor span. Commonly used equivalents are "throttling range" and "modulating range", usually expressed in a quantity of engineering units (degrees of temperature).

Proportional control – A control algorithm or method in which the final control element moves to a position proportional to the deviation of the value of the controlled variable from the setpoint.

Proportional-Integral (PI) control – A control algorithm that combines the proportional (proportional response) and integral (reset response) control algorithms. Reset response tends to correct the offset resulting from proportional control. Also called "proportional-plus reset" or "two-mode" control.

Proportional-Integral-Derivative (PID) control – A control algorithm that enhances the PI control algorithm by adding a component that is proportional to the rate of change (derivative) of the deviation of the controlled variable. Compensates for system dynamics and allows faster control response. Also called "threemode" or "rate-reset" control.

R

RFP – Request For Proposal

RFS – Request For Submittal

RH – Relative Humidity

RO – Reverse Osmosis

ROI – Return On Investment

Reset Control – See Compensation control.

RTD – Resistance Temperature Detector

S

SCFM – Standard Cubic Feet per Minute

Sensing element – A device or component that measures the value of a variable.

Setpoint – The value at which the controller is set (e.g., the desired room temperature set on a thermostat). The desired control point.

Short cycling – See Cycling.

Smoke Damper – A damper arranged to control passage of smoke through an opening or a duct.

Step control – Control method in which a multiple-switch assembly sequentially switches equipment (e.g., electric heat, multiple chillers) as the controller input varies through the proportional band. Step controllers may be actuator driven, electronic, or directly activated by the sensed medium (e.g., pressure, temperature).

T

TAB – Testing And Balancing

TES – Thermal Energy Storage

Throttling range – In a proportional controller, the control point range through which the controlled variable must pass to move the final control element through its full operating range. Expressed in values of the controlled variable (e.g., degrees Fahrenheit, percent relative humidity, pounds per square inch). Also called "proportional band". In a proportional room thermostat, the temperature change required to drive the manipulated variable from full off to full on.

Time constant – The time required for a dynamic component, such as a sensor, or a control system to reach 63.2 percent of the total response to an instantaneous (or "step") change to its input. Typically used to judge the responsiveness of the component or system.

Two-position control – See on/off control.

U

UL – Underwriter’s Laboratory

UV – Ultraviolet

V

VAV – Variable-Air Volume

VFD – Variable-Frequency Drive

VSD – Variable-Speed Drive

X

XML – Extensible Markup Language

W

WAN – Wide Area Network

WB – Wetbulb

WC – Water Column

WG – Water Gauge

Z

Zero energy band – An energy conservation technique that allows temperatures to float between selected settings, thereby preventing the consumption of heating or cooling energy while the temperature is in this range.

Zoning – The practice of dividing a building into sections for heating and cooling control so that one controller is sufficient to determine the heating and cooling