Part 18(a)—Electrical Systems and Controls, Part 1
By Ed Butts, PE, CPI
In July, we completed the engineering and design of water wells, groundwater pumping systems, and mechanical systems (piping and valving). Now it is time to move into the fundamentals of electrical and control/protection systems and the basics associated with this critical element of pumping systems.
Most of the pump and water systems constructed and in operation today use electrical power in some form to operate the drivers (motors) and controllers for the pumps. This column begins a five-part series that is not intended to be used as an engineering reference nor a design guide, but as an introduction explaining the basic theory and concepts of electrical and control design.
Part 1 will introduce the four groups of electrical components and provide a brief overview of electrical codes and steps to a successful electrical system. Part 2 will outline the various types of electrical power systems and voltages available in the United States and internationally as well as a review of the first two electrical system groups: line governance and management devices. Part 3 will provide an overview of groups three and four, load protection and control devices, and the most common methods used for control and protection of pumping and water systems. Part 4 will outline local and remote control and SCADA (supervisory control and data acquisition) systems shown in group four. Part 5 will wrap up the series with an overview on the various methods of instrumentation available for water systems.
Disclaimer: This disclaimer applies to this entire series on electrical system design for small and large systems as well as all other types of electrical work. As always, I remind you to use prudent care and caution and to always observe, apply, and implement any and all of the following design criteria, statements, information, recommendations, and tips to the recognized and local codes and established procedures. After all, I will not be doing you any favors if I recommend a procedure you cannot use due to some local code restriction or your possible lack of knowledge or experience.
And remember this basic tenet: Your local electrical code or inspector will always have the power to overrule, reject, or deny issuing a permit for even my best advice! In addition, I must also caution you to always perform and limit your work in electrical design and installation to only what you are authorized, knowledgeable, and qualified to perform through the proper education, experience, training, and licensing.
Finally, as my most stringent and emphatic warning, always observe the proper personal, personnel, and equipment safety procedures and never attempt to design or conduct any electrical work for which you are unlicensed, untrained, or inexperienced. Electrical energy has the potential to unleash high and dangerous voltages and currents that can release tremendous values of explosive gases and heat, leading to potential arc-flash exposures which can result in property destruction and personal injury or death. Electricity must always be respected.
Four Electrical System Groups
Electrical design for a typical pumping plant can consist of various elements. However, there are generally four distinct groups (indicated as 1, 2, 3, 4) of electrical and control components I consider within a given system. Note that although most of this discussion refers directly to the electric motors used to operate pumps, for our purposes, all electrical consuming devices or machinery will be referred to as loads.
1) Electrical System (Line) Governance: The governance realm of components comprise the equipment required to primarily receive, distribute, and protect the electrical power within the electrical system itself.
The sizing and scope of this equipment is largely dependent on the type (number of phases), voltage, and amperage rating of the electrical service or feeder, but typically includes the system’s main disconnect (fuse or circuit breaker), metering, conductors, conduit, lightning protection, and ancillary equipment such as junction boxes, terminals, and the bonding and grounding subsystem.
The proper design and installation of this group is vital for the overall efficient transmission of electrical power to the loads and as the front-line method of protection against short circuit and overload current for personnel and all downstream equipment. This group is often referred to as the service or main but can also consist of a second-tier feeder or submain.
2) Load Management Devices: The load management group includes the devices needed to further distribute and provide control of electrical power to the ultimate load. These devices are exposed directly to the line and load’s voltage and current and are therefore subject to the same voltage and ampacity rating as the load.
In their simplest versions they could be nothing more than a circuit breaker and snap switch controlling a lighting fixture, but also can be as elaborate as a motor starter or variable frequency drive.
For a pumping plant, the load management devices or the branch circuit generally consists of the load’s disconnect and short circuit protection (circuit breaker or fuses), motor controller or starter, load conductors, and overload device (where the load current is measured directly). Protection of the individual load circuit from short circuit currents through grounding and bonding is also included in this category.
3) Load Protection Devices: The load protection devices consist of the components that sense or monitor external or load operating conditions and protect the load and electrical system from any anomalies.
These conditions can vary greatly from system to system, but typically include load overload (using current transformers or thermal blocks), phase loss or unbalance, load heat sensors or thyristors, and other special devices designed to specifically protect the load or electrical system from unusual operating conditions.
4) Load Control Devices: Finally, the load control devices include all components needed to provide operational oversight and parameters to the load management system.
As opposed to the load protection devices, this group is primarily used to provide an efficient and repeatable set of operating parameters to the load. Once again, this group of devices can be as diverse and comprehensive as the designer’s imagination, but generally includes one to four separate devices that, in concert, provide the proper operating conditions for the load.
In a water system setting, the most common devices include pressure switches, level/flow/pressure sensors or transmitters, control and time delay relays, process instruments or sensors, and SCADA and control systems or switches.
Always Observe the Basics
The first, and most obvious, step in an electrical design is to always be aware of and properly apply the basics of electrical theory and code to your specific needs.
In order to properly design a water or pump system’s electrical system, as well as ensure its safety to installers, the client, and anyone who may come into contact with it, it is imperative you as the system designer fully understand all aspects of the electrical work you are involved with.
This does not necessarily mean that you need to understand the higher-level concepts of the calculus, three-phase harmonics, or high voltage electrical transformers if you are only working with single-phase power supplies and fractional horsepower motors on a day-to-day basis.
However, it does mean you must be able to effectively grasp and understand the fundamentals of these four primary elements of design: electrical theory; electrical acronyms and definitions; electrical code; and real-world application and design techniques, particularly the elements that directly apply to the safety and controlled shutdown aspects of an electrical installation.
Step 1. Understanding Electrical Theory
There is probably no other topic in water system design that is more confusing than electrical theory. Fortunately, it doesn’t have to be this way.
I have met many folks currently working in water system design or installation who are under the mistaken belief they must have complete and full knowledge of every aspect of single- and three-phase power systems in order to effectively design or work with any type and size of electrical system. This could not be further from the truth.
Although I am a practicing registered professional electrical engineer, the occasions when I need to apply higher math and complex electrical theory in actual design work for any design are infrequent. I have never needed to use them at any time for a domestic water system design in more than 40 years of practice.
Virtually every electrical design issue or problem involving a water or pumping system can be solved by knowing and using simple math (addition, subtraction, multiplication, division, fractions) or basic algebra.
With that in mind, if you believe you are already lacking, I encourage you to pursue some math refresher courses followed by a limited course of training in basic AC and DC electrical theory. Most communities have numerous sources for this level of instruction such as community colleges, night classes, trade schools, union training halls, and private instructors.
There are even various online courses that offer an excellent alternative for those who don’t have the time or desire to attend a conventional classroom setting or who simply wish to learn on their own and at their own speed.
The bottom line is if you are going to be working with electrical system design on any level, you must find a way to learn and understand electrical theory and employ it on a common-sense basis.
Typically, the following 10 topics comprise my recommendations for the minimum level of technical knowledge a water system designer should have:
- Ohm’s law (voltage, amperage, resistance, impedance) for AC and DC applications
- Basic understanding of parallel and series circuits
- Basic understanding of AC circuit nomenclature (inductance, capacitance, tuned circuits)
- Basic understanding of AC circuit power relationships (watts, power factor, horsepower)
- Basic understanding of AC motor technology
- AC motor types and principles (fundamental concepts such as volts-amps-watts-efficiency relationships; torque; terms; code; design; motor types such as splitphase, capacitor-start, capacitor-start/run, polyphase)
- Wire sizing formulas and techniques (voltage drop, inductance, code issues)
- Electrical system dynamics (short circuits, single-phase power systems, transformers)
- AC system protection concepts (fuses, circuit breakers, grounding, overloads)
- Basic three-phase power system concepts (for those working with three-phase power)
You have noted I put the word “technical” in italics. I did this to stress the technical relationships involved in electrical theory are not necessarily the same as what the local code may require. In fact, if you are involved with electrical system design long enough, you will become fascinated in just how many places where the code and logical design seem to clash. And that brings us to our next topic.
Step 2. Electrical Standards, Acronyms, and Definitions
Throughout the next several columns, we will reference several standards used for electrical design.
The first and most common is the National Electrical Code (NEC) issued by the National Fire Protection Association as NFPA Standard 70. The NEC is regarded as the governing electrical code for use in the United States, but many states or localities also add revisions and amendments to the NEC that are applicable to their area only. The NEC is updated every three years, with the most recent edition issued in 2020.
The second acronym we will commonly use is one referring to NEMA standards. NEMA represents the largest electrical trade association in the United States and is short for the National Electrical Manufacturers Association.
NEMA standards are available and recognized for numerous components and classes of electrical equipment including motors, enclosures, controls, generation, transmission, and distribution equipment.
In addition to NEMA, many electrical standards are now parallel to another group called the International Electrotechnical Commission (IEC). The use of either NEMA or IEC standards are generally recognized by most governing and inspection authorities in the United States.
Although the standards for most electrical equipment are established by NEMA or IEC, most electrical equipment must undergo a rigorous testing and certification procedure to ensure the equipment is rated for the intended application and will not represent a fire danger when used in approved environments. Most research, testing, and product certification in the United States is conducted by one or more of three agencies: Underwriters Laboratories (UL), Canadian Standards Association (CSA), or the Electrical Testing Laboratories (ETL).
Typically, if the electrical device or component complies with the applicable specifications and passes the testing procedures, the device is either listed or recognized for use. Although most states and localities recognize testing and approval from any of the three laboratories, there is no specific guarantee of this uniformity for any individual state or locality. Therefore, I caution you to fully investigate and verify whether any electrical component or system is approved for the intended use and application in your region before applying or installing it.
Step 3. Know the Applicable Codes
As someone who has worked with every version of the NEC, or more simply known as the Code, since 1974, I can tell you the only predictable part of the Code is that it is unpredictable since it is always reviewed, revised, and updated every three years.
In fact, many individuals who regularly work with the NEC will often take refresher courses or classes to remind them of the code specifics and attend update courses during the three-year NEC update period.
As of this writing, the current version of the Code is NEC-2020, which will remain in force until the 2023 edition of the NEC is issued and becomes effective.
Although different countries may offer their own version of an electrical code, the NEC has become the most universally accepted and adopted electrical code in the world and is predominantly used throughout the United States as the standard-bearer electrical code, with many states offering their own specific revisions or addendums to the basic code.
The paramount concern behind the preparation and issuance of the NEC is the use of proper design, application, and installation techniques of electrical systems to provide a safe, but not necessarily, efficient electrical installation and operating environment.
Although not intended for use as such, the NEC has been an indispensable element in electrical system design and application since 1897 even though the main sponsor of the Code, the NFPA, has repeatedly asserted the Code is not to be thought of or used as a design guide, but strictly as a safety guideline. Although the NFPA issues each version of the NEC as an advisory document, virtually all U.S. states and jurisdictions routinely adopt the Code as a legal and enforceable standard during each code cycle.
Even though the Code is not formally recognized as a design guide, it is difficult to not look upon the Code as a minimum design guidebook. After all, most of the information that is contained within it is specifically related to the safe design of an electrical system—what more would a designer want?
As is the case with electrical theory, information contained within the Code provides critical knowledge and information for any system designer, while other information in it is relatively unimportant and mundane for most day-to-day work.
A section with information that is important to know is contained in Article 100–Definitions. To be totally effective, a designer must be aware of the specific definitions and their applications used throughout the NEC, especially since a simple misunderstanding between terms can mean and cause real trouble with an inspector or electrician.
For example, many people often confuse the terms “feeder” and “branch circuit” as they are defined in the Code or even mistakenly think they mean the same thing. Simply stated, the feeder constitutes the conductors between the service equipment (i.e., the main panel) and the branch circuit device. The branch circuit refers to the conductors between the final overcurrent device protecting the branch circuit (i.e., the branch circuit fuse or circuit breaker) and the destination or load.
The NEC addresses each type separately and each has its own specific requirements. Refer to Figure 1 for the NEC nomenclature and defined terms for each type of circuit. Proper grounding and bonding of an electrical system is a critical task for a successful and safe installation. Figure 2 details the typical grounding and bonding requirements needed for a single-phase submersible residential pump installation.
The NEC is formatted into an introduction, nine chapters with individual explanatory sections referred to as articles within each chapter, annexes, and an index. There are approximately 125 articles, and each one refers to a specific subject.
Parts are designated by roman numerals (Part I, Part II, etc.). Sections are identified using capitalized numbers and the actual NEC rule is contained within the section. A Code section may be broken down further by using numbers in parentheses. For example, the specific section that addresses supplemental grounding electrodes in an electrical installation is in Section 250.53(D)(2). This is shown for a motor circuit in Figure 3.
Tables often need to be consulted during design and are identified. For example, Table 310.16, a commonly used table, displays the maximum ampacity of conductors. Exceptions are always shown in italics as an alternate to a specific rule. There are two types of exceptions. One is mandatory while the other is regarded as permissible. When a rule has several exceptions, the ones that are mandatory are listed before those
that are permissible.
Fine Print Notes are intended for use solely as explanatory information and not as actual Code. Unless otherwise stated, these should be simply regarded as Code-sanctioned recommendations or suggestions, and not as mandated requirements.
The articles in Table 1 above are listed in their respective order within the NEC, and in my judgement are most representative of the articles a water system designer must display a working knowledge of, or at the very least, have the ability to locate, research, and verify.
Although each article is important in its own way, the articles with the most overall importance related to pumping and water systems are: Articles 110, 220, 240, 250, and 430. In fact, to ensure a safe installation, a full working understanding and knowledge of Article 250 on grounding and bonding and Article 430 on motors and motor controllers are paramount.
An electrical system must be effectively and completely grounded and bonded to ensure safety to the individuals who must work with or around the system every day, and motors and their controllers must be properly sized and selected to drive the load and protect the motor. Whenever working with electrical systems, an adequate knowledge of the applicable
and current electrical code is essential.
In most regions, the NEC is used as the primary code, with various states and jurisdictions implementing their separate amendments, addendums, and revisions. Individuals are advised to purchase the current version of the Code in its entirety along with any local or state revisions or addendums and learn it to gain a full understanding of the requirements and limitations before setting out to do any electrical design or installation. Generally, the total cost is less than $150. The NEC articles in Table 1 are those that are generally most important for water systems-related work.
Step 4. Reading Electrical Schematics and Plans
Being able to read and understand electrical drawings and schematics is an important element of working with electrical systems. Basically, reading a schematic and plan is just a matter of recognizing the symbols and observing how they connect.
The most common symbols for water pumping applications are shown in Figure 4, with an example for a motor control and protection circuit shown in Figure 5.
Electrical circuits are usually indicated to route from one point to another. In most cases, this generally assumes the circuit originates at the source of power and runs to the powered device. This is referred to as power coming from the source or origin and running to the destination. The complete circuit in slang terms is often called the home run or a circuit that goes directly from the fixture to the circuit breaker or fuse panel.
While understanding and being able to read electrical symbols is important, the most critical aspect of reading electrical schematics is applying them to a specific installation. Electrical control circuits are generally shown in full detail with the phase (line) and return conductors (i.e., the neutral in 120-volt circuits and second phase line in 230-volt circuits) shown throughout the drawing.
Power circuits, on the other hand, are often shown in a unique style called a one-line power diagram. A one-line power diagram is most often used for simplicity on three-phase circuits where all three phases are identical in their origin and destination, and therefore do not require that all three legs need to be shown. One-line power diagrams are frequently used for motor control centers, motor circuits, and three-phase power distribution and transmission.
An example of a one-line power diagram for a 40 hp, 460- volt, three-phase motor is shown in Figure 6a, with a description of the circuit components in Figure 6b.
This wraps up this first installment on electrical systems for water well applications. The next installment will feature an overview of the many devices used for load control and protection, along with examples of each.
Until then, keep them pumping!
Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 40 years of experience in the water well business, specializing in engineering and business management. He can be reached at firstname.lastname@example.org.