Chapter 2: Control System Design Process
2.1. Introduction
2.2. The Dilemma
2.3. The Key Players
2.3.1. The Designer s Requirements and Challenges
2.3.2. The Contractor s Requirements and Challenges
2.3.3. The Owner s Requirements and Challenges
2.4. Tying it Together
2.4.1. System Diagram and Sequence of Operation
2.4.2. Point List
2.4.2.1. Benefits of a Points List
2.4.2.2. Typical Components
2.4.3. Specifications
2.4.3.1. Scope of Work
2.4.3.2. Component Specifications
2.4.3.3. Assembly Specifications
2.4.3.4. Operator Work Stations
2.4.3.5. Installation Requirements
2.4.4. Floor Plans
2.4.5. Standard Details
2.5. Putting These Concepts to Work
Figures
Figure 2.1 Detailed Points List
Figure 2.2 Typical Detailed Valve Schedule
Figure 2.3 Typical Performance Criteria Based Valve Schedule
Figure 2.4 Typical Detailed Damper Schedule
Figure 2.5 Control System Network with No High-level Controllers
Figure 2.6 Control System Network with High-level Controllers
Figure 2.7 Typical Installation Detail for a Specialized Application
Figure 2.8 Typical Installation Detail for Multiple Trades
Figure 2.9 Mechanical Room Drawing with Control Information
Figure 2.10 Typical Control Panel Detail
Figure 2.11 Typical Analog Input Wiring Detail
Figure 2.12 Typical specialized terminal strip installation
Also See
Tables
Table 2.1 Common Air Handling System Points Specified in Contract Documents
2.1. Introduction
This chapter provides an overview of a control system design process that has been used successfully to provide well-functioning control systems for numerous commercial, institutional, and industrial HVAC projects. While the process outlined this chapter is not the only viable method for successful control system design, it does provide a useful template that illustrates important design elements. These elements need to be addressed directly and proactively to ensure that the design intent is met. Otherwise, they will be addressed by circumstance or default with results that are far from the desired outcome. The Design Guide uses the template to focus on why and how to specify the elements it contains, thereby guiding designers who wish to modify their existing processes to reflect some or all of the template s components.
Projects with inadequate control system designs often require additional effort and capital outside of the project budget to meet design intent. Some people may argue that providing detailed specifications will add cost to the project in an industry where budgets are already tight. In this chapter, we advocate that:
The capital expended up front during design to ensure the details are adequately addressed will typically be orders of magnitude less than the capital expended subsequent to construction to correct the defects and pay for the inefficiencies that result from lack of design detail.
The costs can be controlled by standardizing the proposed methods and by directing the task to those in the best position to accomplish it.
For example, to obtain a functional economizer, someone has to size the dampers, make configuration decisions, and select actuators. Even if the damper is not properly sized, someone will have to make those decisions when it is ordered or installed. While it may take someone with experience to properly size the damper compared to simply ordering it, the time required for the engineering is minimal compared to the cost of modifying or replacing the dampers after they are installed and the operating cost penalties associated with poor performance. On some projects, the designer may be the best candidate for this role. On others, it may be the contractor. What matters is that someone is charged with the task and then held accountable for the results. With these issues in mind, we will start the chapter by examining the working environments for the parties with vested interest in a good control system design. By understanding these working environments, potential problems can be acknowledged and dealt with through a good control system design process.
2.2. The Dilemma
HVAC control systems are the central nervous system of the machine world. The most efficient, well-selected and installed mechanical equipment can be reduced to a problem-riddled, inefficient mechanical nightmare by a poor control system design. One would expect that developing the control system design and installation parameters would be a significant portion of the HVAC design process and that the design of the control system would start early in schematic design. Unfortunately, this process often does not occur, and the control system information is often added to the construction documents at the last minute. In addition, the control system design information is frequently structured in a manner that delegates much of the responsibility for the final product to the control contractor with very little project specific detail included in the contract documents. As a result, the control contractor must develop a price for a final product that is loosely defined in a competitive bidding environment. The result is often less than perfect, frustrating the designer, the contractor, and Owner with problems that can plague the project for its lifetime.
2.3. The Key Players
The key players in the dilemma described above are the HVAC designer, the control system contractor and the building owner. All three of the players have distinct but interrelated needs with regard to the design of the control system. The following sections bring the needs of each party to focus and identify the challenges that each party faces. With an understanding of these issues, the designer is in a good position to lead the efforts to ensure that a robust control system is installed that meets the needs of the owner.
2.3.1. The Designer s Requirements and Challenges
The rapidly evolving technology associated with current HVAC system design confronts designers with a multiplicity of control system requirements and challenges.
Time and Fee Restrictions The technology employed in current building systems has rapidly advanced over the past several decades. At the same time, there are shorter design windows for development of these more complex designs. The fast-paced development and construction schedules and the interdisciplinary interactions required to implement sophisticated building technologies have resulted in the need for frequent meetings between the design team leaders, which has resulted in increased overhead while fees have not increased in a corresponding manner. The net effect is a decrease in the amount of time the design team leaders can devote to project technical development work. To solve this problem, they often delegate tasks to lower level staff that have less experience from which to draw to make crucial technical decisions. Delegating tasks to the contractors via performance specifications has become a common approach for control system design. Unfortunately, competitive bidding pressures often prevent control contractors from implementing the necessary level of quality. The contract language is so vague that it can be interpreted liberally at the expense of quality and performance. With dedication to writing control system technical specifications, designers can successfully create a level playing field for bidders to provide quality controls installations. Specifications are discussed in detail in Section 2.4.3.
Time Warp: Project time frames have been compressed.
In the late 90 s a project engineer working on a hospital surgery addition project was reviewing files from the original, 1940 s vintage, surgery construction project. While reviewing these documents, he discovered that the time allowed for the original project was the same as the time allowed for the current project. Yet, the current project had far more complex issues to consider: The new surgery suite was constructed over an existing outpatient clinic that had to remain in service during construction. The newer project had more complex licensing standards and more complex HVAC, electrical, and utility systems. To top it off, all systems had to be interfaced to the existing plant while it remained in service.
Technical Expertise The rapidly evolving field of direct digital control has left many HVAC designers feeling that they lack the knowledge required to develop a detailed control system design. Tight construction schedules and fee structures leave little time or money to support the training required to stay current with the details of control system hardware, programming, and architectural issues for a wide array of manufacturers and suppliers. As a result, many designers delegate many of the details of the control design to the contractors bidding the project, believing that they do not have the time, budget, or expertise to do otherwise. While this may be true with respect to the specific technical details of any given manufacturer s system, many important parameters related to the design of the control system are actually a function of HVAC requirements the designer is (or should be) familiar with. Examples of these parameters include set points and sequencing, control point locations, and sensor accuracy.
Minimize Field Installation and Start-up Problems The HVAC designer has a vested interest in providing plans and specifications that minimize the field installation and start-up problems associated with their projects. Not only does this ensure that the intent of their design is fully realized, it also protects them from liability problems associated with systems that fail to perform to the Owner s expectations, and improves their ongoing client relationships. For HVAC systems, a good control design is key to successfully achieving the design intent of the project and efficient, reliable system operation. Designers who can develop methods that allow them to clearly and completely describe the control system requirements will be rewarded with systems that start up smoothly and operate reliably. The resulting bottom line will be happier clients, fewer field problems that rob valuable billable production time from other projects, improved client relationships that can foster repeat business and better fees, and reduced liability and exposure to litigation.
2.3.2. The Contractor s Requirements and Challenges
Control contractors operating in the current construction market find themselves faced with requirements and challenges that are directly related to those that the designer faces.
Time and Fee Restrictions The control contractor must develop a low bid for a project based on the information available on the construction documents, usually within a short bid window. The portion of the project that the control contractor bids is technically complex with contractual and physical interfaces to virtually every other contractor working on the project s mechanical and electrical systems as well as some of the architectural trades. Much of the work associated with a DDC system involves the electrical trades, and many control companies require that their sales engineers perform a detailed electrical take-off for the project or obtain competitive pricing from electricians. The sales engineer or their subcontractors have to develop an understanding of the system architecture and the location of the points relative to the physical arrangement of the equipment on the project. The technical issues associated with the system s architecture and installation requirements will generally dictate the physical requirements for installing the system. If this information is not well-developed on the contract documents, then the sales engineer will need to develop it within the constraints of the available requirements.
In most cases, while the contractor is developing their bid, the project is still in a state of flux. Last minute changes, answers to bidders questions, and additional clarifications are being added to the contract documents through addendum. Most addendums can add significant contractual and cost for the contractors, yet their scope is difficult to define since they are usually verbal in nature but describe project elements that would normally be described by drawings.
The control contractor s fee restrictions result from the fact that they are bidding for work in most cases (vs. negotiating without competition). They will not get all of the projects for which they submit a bid, so some costs associated with bidding work must be supported as overhead. Thus, there can be considerable pressure to minimize the amount of effort placed into bidding a project. This bidding environment tends to work against the sales engineer developing well-planned technical solutions to design issues that are not addressed by the contract documents, especially when faced with time pressures.
Knowing is Not Necessarily Doing in a Competitive Bidding Environment: The importance of clear and complete specifications.
Vague control system requirements in HVAC contract documents often make it difficult for those bidding to do their best job if they want to get the work. For instance, contract documents that say little about sensor requirements may leave the bidders with little choice other than to select the lowest priced sensor that meets the letter of the documents. Though the paper requirement is met, the sensor may not meet the real operating requirements. Similarly, if system architecture issues are not addressed in the contract documents, competitive bidding pressures will force the bidders to structure the system in the least costly configuration possible. In some cases, this configuration may limit system response time, programmability, and future expansion and flexibility, all of which could become significant issues.
Technical Expertise Control contractors commonly find themselves in the position of having technical expertise that they are somewhat powerless to apply. The controls contractors are most familiar with the technical details of the proper application of their control system. In addition, many manufacturers have a staff with considerable HVAC applications engineering expertise. However, if the contract documents do not provide sufficient information to allow the controls contractor to exercise their expertise, competitive pressures to be the low bidder will usually cause the control system to be optimized for price rather than performance, quality, or ease of use. Contract documents that go beyond generic requirements to provide fundamental information and address key HVAC performance issues will allow the control contractors to apply their expertise to provide a bid for a system that truly meets the designer s intent while still being competitively priced.
Minimize Field Installation and Start-up Problems Control contractors are in one of the more difficult positions during the construction and start-up phases of a project. Their submittals are customized to match the specific system configurations associated with the project and cannot be completed until the submittals for other equipment on the project are finalized. The control system installation work is also highly dependent up on the work of the other contractors since the sensors and actuators cannot be mounted until the structures on which to mount them have been constructed. Program debugging cannot begin until the systems are substantially complete and operational. In many projects, weather delays, shipping delays, and other problems cause the installation work to slip behind schedule. If the project completion date is not allowed to slip, the control contractors can find themselves caught between an inflexible project completion deadline and HVAC systems that have not been completed to the point to allow control system installation and debugging to proceed. The control contractor, like the designer, has a vested interest in minimizing installation and start-up delays in order to have adequate time to complete their installation and testing. Their benefits are similar to those realized by the Designer, including fewer warranty problems that disrupt production on other projects, improved customer relationships that can foster repeat business and better profit margins, and reduced exposure to liability.
2.3.3. The Owner s Requirements and Challenges
Many of the challenges faced by the design and construction team are reflections of the challenges faced by the Owner in developing the project.
Time and Fee Restrictions The pressure on the Owner to complete the project and meet the timeline, budget, and market cycles can be intense because the overall success or failure of the project can be tied to these factors. While an Owner may be convinced to spend above budget in one area in order to save money in other areas, this Owner may be unwilling or even powerless to spend money outside of the original project budget. Similar constraints apply to project timelines. Technical problems with dire consequences to the design and construction team, causing them to want to extend the construction timeline or seek additional funds may pale in comparison to the consequences the Owner faces if the project does not come in on time and on budget.
The Owner wishes to foster competitive bidding with a level playing field so that the HVAC system purchased represents the best value for the money while still meeting their operational needs. Systems that are bid as equivalent as a result of vague contract documents, but are not really equivalent on an operational basis can ultimately cost many times the first-cost savings in wasted energy and other operational issues. On the other hand, detailed boilerplate specifications that are not customized to the specific project may provide features that the Owner does not need, increasing first cost without providing a long-term advantage. Inappropriate application of a boilerplate can result in operational problems and inefficiencies due to improper application of systems or components
Technical Expertise Even though a sophisticated Owner might have considerable in-house expertise in control systems, the people in those positions seldom have time for more than a cursory oversight role for new construction due to the demands associated with operating the Owner s existing facility or facilities. A less sophisticated Owner or an Owner with only a few properties may not have in-house control expertise to dedicate to a new project until the project s operating staff comes on board. As a result, most Owners look to their design and construction team to attend to the details of developing and bringing online the control systems for their new facilities. Ideally, much of the facility-specific knowledge will be transferred to the Owner s staff during the training that occurs as a part of the start-up process. Contract documents that provide a clear basis for the control system design, supplemented by a good set of control drawings are an important part of the knowledge base that will be provided to the Owner for the life of the building. These documents will be the foundation upon which much of the operating staff s technical expertise for the building is developed. Thus, the benefits of a well-developed control design accrue to the Owner directly via the construction documents and indirectly via the control submittals that evolve out of these documents.
Minimize Field Installation and Start-up Problems More than anyone, the Owner has a vested interest in having a project with a minimal number of installation and start-up problems. Problems of this type can often lead to unanticipated and unavoidable delays in completion of the facility. These delays can ripple into problems gaining the necessary occupancy permits to be able to move in tenants, or delays in production or other beneficial use of the facility, all of which can have an adverse impact on the Owner s financial plan. It is not unusual for start-up and installation problems to be only partially resolved. These unresolved issues then become ongoing operational problems and inefficiencies that require expenditures from the facility s operating budget to correct or they simply plague the operators and the tenants for the life of the facility. The benefits that accrue to the Owner from a control system design process that minimizes installation and start-up problems include fewer warranty and ongoing operational problems and improved customer relationships with tenants, which can translate into long-term leases and better rates. For production facilities, minimizing installation and start-up problems causes fewer disruptions to the production process, which results in better profitability. In both types of facilities, minimizing these problems reduces the Owner s exposure to litigation, both in defending themselves from disgruntled tenants seeking damages as well as in seeking restitution from errant designers and contractors.
On Time, On Budget, and Too Late: Business concerns override construction schedules.
In the late 90 s, semiconductor manufacturers experienced a sudden and unexpected economic downturn. One manufacturer was completing a 250,000 square foot expansion when the downturn occurred. The facilities group was baffled when management passed up some attractive energy savings opportunities in their drive to maintain schedule, because implementing them might have delayed the start-up of production. The facilities group became painfully aware of the reason behind management s drive when the facility was closed one week prior to initiating production. Even though the plant was on time and on budget, it had missed going into production during the peak of the market cycle, and the manufacturer chose let the plant sit idle.
2.4. Tying it Together
As can be seen from the preceding section, the designer, contractor, and owner have interrelated requirements and challenges associated with a project s control system. All parties have interwoven time and financial constraints under which they all must operate. The owner initiates the project to meet some specific need, often with specific technical requirements that must be met in order to be successful. Often, these technical requirements have evolved out of operating experience on other projects. The designer must understand these needs and translate them into mechanical systems that, if properly controlled, can meet them. The contractor must interpret and implement the designer s control requirements per the design intent, thus satisfying the operational needs set out at the start of the project by the Owner. Obviously, all parties benefit from a process that provides a smooth installation and problem free start-up.
Designers can take a significant step towards ensuring that their control system needs are met by incorporating certain key elements into the control system design either by including them directly on their contract documents or by requiring that they be furnished as a part of the control system submittal package (and then verifying that they are in fact provided and well executed). These components include:
1 System Diagram and Sequence of Operation A System Diagram is a schematic drawing of the arrangement of the entire system to be controlled including all interacting components. The location of all control system inputs and outputs associated with the HVAC system should be included on this diagram. In a narrative format, the sequence of operation describes the required HVAC control process in detail including all operational and interlock requirements.
2 Benefits of a Points List Each physical point on the project as well as key virtual points should be identified on a points list. The list should include important parameters such as sensor accuracy requirements, alarm limits, and trending requirements.
3 Specifications The performance and installation requirements for the sensors, actuators, final control elements, controllers, workstations and other components that comprise the control system are detailed in the specifications. Control damper and control valve schedules are an important component of these specifications.
4 Floor Plans The location of the input and output points as well as key components like control panels, operator workstations, major cable and conduit routes, and sources of power are shown on control system floor plans.
5 Standard Details Typical installation requirements for the control system elements are provided in standard details. These details can illustrate the general design intent for the system, provide a consistent basis for estimating the control price, provide the basis for the system-specific control system design development by the control contractor, and provide guidance for the other trades involved on the project who must coordinate with the control contractor.
The specification, system diagram, and operating sequence will exist in some form on just about all projects. Other elements, such as the point list, floor plans, and installation details may not be part of the normal scope of design services and may not even show up on the contractor s submittals. However, once some experience is gained, these components are surprisingly easy to generate, especially in an office that utilizes a CAD package and word processing to automate tasks. As a result, some designers are electing to include them with their design package while others are including language to delegate them to the control contractor, thus ensuring that they are attended to. These elements generate rewards through improved communication of the design intent, better bidding, fewer start-up and operational problems, which will more than pay for any added costs that may be incurred. Return on investment is also realized through improved client relationships, improved fee structures, and reductions in the often non-billable time associated with resolving disputes and handling field problems during the construction process and warranty year. The following sections will discuss each of the six components of the control system design process listed above in greater detail.
2.4.1. System Diagram and Sequence of Operation
Successful HVAC designs hinge on the smooth, integrated interaction between the system s components and the loads served. It is not just an air handling unit; it is an air handling system made up of an air handling unit, intake system, distribution system, terminal equipment, return system, relief, and exhaust system. It is critical that the control system design reflect this systems-based perspective. It is this systems perspective that guides creation of the system diagram and the detailed sequence of operation.
The system diagram is a drawing that shows the entire system under consideration in schematic format, not just portions of the system. This method allows the user to see the entire process and visualize the potential interactions without having to flip between multiple documents. A detailed system sequence of operation or system narrative goes hand in hand with the system diagram in documenting the overall operation of the system. Many times, the sequence provided on the contract drawings and duplicated in the specification provides a good overview of how the system is intended to perform, but fails to address critical details which can make or break the success of the installed system. Well-documented system drawings also provide a useful field reference for the commissioning and operations personnel. More information and examples of the systems perspective is provided in the Functional Testing Guide for Air Handling Systems (Functional Testing Guide) in Chapter 2: Functional Testing Basics.
Most designers will find that the schematics and operating sequences typically included on their construction documents can be readily adapted to reflect the system concept, often with little effort and a great deal of benefit for an improved design process and improved installations. Often, the difficult part of this transition to the system concept is learning to write out the detailed operating narrative. This detailed narrative is just a written statement of what the designer should already know: the details of how they expect the system to function. Furthermore, the initial development effort can often be amortized over subsequent projects since many of the operating requirements for HVAC systems do not vary from project to project. This allows a designer to develop standard sequences for typical system configurations that can then be adjusted as necessary to the specific requirements of a project.
In addition to the ongoing usefulness of a well-written sequence of operation to the building operators, the sequence is essential for a smooth commissioning process. The commissioning provider must test and evaluate the system sequence based on how well it meets this detailed sequence.
No Diagram or Narrative No Drafters: One way to improving the design process.
Some consulting firms have found that the system diagram and narrative sequence of operations are such an integral part of a successful design that they are required as the starting point for any new project. Before a project engineer can request drafters and designers for a project, they must have developed a system schematic, a fairly detailed narrative describing how the system should work, and a rough estimate of the heating and cooling loads. If this process is well-executed, a significant portion of the engineering required to make the project successful is complete or will fall out of the information developed. The technique can yield preliminary equipment selections and motor loads within 10-15% of final values, as well as parameters for estimating costs and equipment room, mechanical chase, and ceiling space requirements. This type of information can also be used to coordinate and negotiate with the other project team members based on a foundation of technical information, not rules of thumb.
Similar considerations apply to the system diagram. For most design firms, a schematic rendering of their standard systems will not vary much from project to project because the schematic arrangement is fairly independent of building geometry. This means that a design firm can develop standard schematics for the systems configurations that they use repeatedly and then tailor these standards to the needs of specific projects.
The current technology automated office environment makes all of this easy to accomplish using standard word processing and computer automated design and drafting techniques. Developing a project s system configurations and operating sequences from existing standards does not remove the need for technical assessment and expertise to adapt the standards to the specific needs of a project. It does minimize the amount of time that must be spent in this process by avoiding reinventing the wheel .
2.4.2. Point List
Both the narrative sequence and the system diagram provide a basis for developing the points list. Some designers incorporate the point list into the narrative sequence, while others provide it as a table in the specifications or contract drawings or by showing the points on the system schematics. Regardless of where the point list is located, it is a good idea to show the points in the proper location on the system diagram to guide the contractors during construction.
The point list should include all physical points on the project, including hardwired interlocks. It is also a good idea to include required virtual points such as calculated flows or energy consumption. Other virtual points, such as set points and tuning parameters can also be included, but these points can usually be accommodated with less effort by the designers through a specification reference or a general note attached to the point list.
While some commissioning and O&M-related points may not directly affect the ability of the control system to function, they provide a means to ensure that the system continues to perform as intended by allowing key performance parameters to be monitored, trended and alarmed. When coupled with an ongoing commissioning plan and good training for the operating staff, monitoring points enable the design intent and design efficiency of the HVAC systems to persist over the life of the facility.
2.4.2.1. Benefits of a Points List
A point list can provide a great deal of information regarding the requirements for the control system. Detailed specifications of control and monitoring points can be beneficial to both designers and controls contractors in the following ways:
Without a points list, the determination of points is left to the contractor s interpretation of the contract documents. Often points are left out that are not necessary to execute the sequence but are useful for future sequence modifications, building control loop tuning, energy consumption analysis, and O&M troubleshooting. Adding the points later can be difficult and expensive.
By clearly stating the minimum point requirements for the project, the designer can ensure a level playing field for all control system bidders.
Requiring specific points enables the bidders to more easily obtain pricing from electrical contractors and equipment suppliers.
The point list can be used to tie together information about the point location and function on the system diagram with information about its physical location in the building. This can be especially helpful if the points are not shown on a floor plan.[1]
The point list provides a place to clarify the requirements for sensor accuracy, sensor configuration, and any other special requirements.
The points list reveals requirements of the control system architecture. The point density required in a particular location may determine the controller network configuration and the I/O requirements for the controller.
The points list can be developed early in design to provide a starting point for the control system budget.
Physical Points and Virtual Points: The value of virtual points.
Computer-based control systems employ two classes of points: physical points and virtual points. Physical points exist as hardware devices, typically sensors or actuator. They are wired to the controller I/O to allow the control program to execute the intended functions and provide information for diagnostics and troubleshooting. In contrast, virtual points exist in the controller s memory and are used to store set points, counter and timer values, perform calculations, and act as logic flags. They may also represent physical quantities such as a flow rate calculated based on a differential pressure signal or a Btu consumption calculated from a flow rate and a temperature difference. Not all virtual points are important for automatic control. However, the information provided by virtual points can be very useful to operators. It is important is that the designer ensures that the details associated with the virtual points are a part of the turn-over package provided to the Owner once the system is commissioned and functioning properly.
2.4.2.2. Typical Components
In addition to listing the minimum points requirement for the project, the point list is a convenient way to specify the requirements associated with each point, such as sensor type, accuracy, and point name. An example point list is shown in Figure 2.1. The spreadsheet used to create this figure is also provided as a starting point for developing your own point list. Providing a useful points list is critical, but there are many ways to go about doing it. Some may feel that the attached example contains too much detail, the detail should be located elsewhere, or that the contractor should provide some of the information.
The following items are suggestions for consideration when developing your point list format.
Point Name and Symbol The point name provides a consistent way to reference the point in the contract documents and correspondence. It may also be convenient to add a suffix indicating if the point is part of the base bid or an alternate where appropriate.[2] (Other point naming convention considerations are discussed in Section 3.6.1.) Some designers find it convenient to combine the point name with a drawing symbol for different point types and use this information to designate the point location on the system schematics and floor plans.[3] (See Figure 2.9 for an example of this.) Project personnel will quickly learn to interpret these codes and will appreciate the utility they bring when reading the control drawings.
Applicable Details Applicable details point the contractor or installer to drawings that further describe the point installation. A column to indicate drawing details has not been shown on the example points lists due to space constraints but is included in the template.
System and Service The full name of the point and the system that it corresponds to. For many systems, this can become the point descriptor.
Sensor Type and Accuracy A minimum level of accuracy should be specified. Requirements for sensor type and accuracy are presented by application in Section 3.3 Sensor Accuracy.
Limit and Warning Alarm Requirements See Section 3.6.4 Programmable Alarms for details about selecting alarms.
Trending Requirements See Section 3.6.6 Point Trending for more information on trending during the commissioning process and during normal operations.
Bid Level Section 3.2 Point Selection can assist designers in selecting points to include as a base bid or alternative bid level. A column to indicate bid level has not been shown on the example points lists due to space constraints but is included in the template.
Notes The notes column indicates details that will help the project personnel understand the purpose of the design requirements.
Figure 2.1 is an example of a typical point list where the designer specified the project point requirements in detail. Alternatively, the designer may specify only the points required and refer the contractor to the specification for some of the requirements. In this case, the designer may require that the control contractor provide a detailed point list as a part of the submital process.
Link to a detailed points list (Excel spreadsheet). Save this spreadsheet to use as a starting point for point lists on your projects.
Figure 2.1 Detailed Points List
Table 2.1 lists point types that are commonly found on air handling systems. Each of these categories of points should be included in the points list.
Table 2.1 Common Air Handling System Points Specified in Contract Documents
Analog Inputs
Digital Inputs
Analog Outputs
Digital Outputs
Virtual Points
System discharge temperature
Fan proof of operation
Economizer damper command
Fan Start/Stop
Set points
Mixed air temperature
Filter status
Relief damper command
Drive Enable/Disable1
Calculated flow rates
Coil leaving temperature
Humidifier proof of operation
Face and bypass damper command
Humidifier shut down
kWh consumption
Zone temperature
Preheat coil pump proof of operation
Hot water valve command
Preheat coil pump command
PID constants
Zone humidity
Selector switch status
Chilled water valve command
Duct system pressures
Override switch status
Humidifier valve command
Building and zone pressures
Low temperature limit status2
Drive speed command
Outdoor air conditions
Mixed air plenum static safety status2
Inlet vane command
Return air CO2 level
Discharge static safety status2
Valve and damper actuator positions
Return static safety status2
Direct flow rate measurement
Power status3
Power status3
Terminal zone flow rates.
