Fuses are sacrificial devices that help protect costlier components in an electrical system from the damaging effects of overcurrent. (They can also help make control systems UL- and NEC-compliant.) To be sure, there are many other solutions for protecting electrical gear from overcurrent, including circuit breakers and protective relays. Information from Cumming, GA-based AutomationDirect (automationdirect.com), though, lists 10 reasons why end users also should consider fusing.
— Jane Alexander, Managing Editor
Overcurrent protective devices that have tripped are often reset without first investigating the cause of the fault. Electromechanical devices may not have the reserve capacity to open safely when a second or third fault occurs. When a fuse opens, it’s replaced with a new fuse, meaning the protection level is not degraded by previous faults.
Fuses typically are the most cost-effective means of providing overcurrent protection. This is especially true where high fault currents exist or where small components, such as control transformers or DC power supplies, need protection.
Fuses have no moving parts to wear out or become contaminated by dust or oil.
North American standards
Tri-National Standards specify fuse performance and the maximum allowable fuse Ip and I²t let-through values. Peak let-through current (Ip) and I²t are two measures of the degree of current limitation that is provided by a fuse.
The high current-limiting action of a fuse minimizes or eliminates component damage.
Overcurrent-protective devices, with low-interrupting ratings, are often rendered obsolete by service upgrades or increases in available fault current. Updated NEC and UL standards are fueling the need to install potentially expensive system upgrades to non-fused systems.
Fuses can be easily coordinated to provide selectivity under overload and short-circuit conditions.
Fuses do not require periodic recalibration. That is not the case with some electromechanical overcurrent-protective devices.
As a fuse ages, the speed of response will not slow down or change. A fuse’s ability to provide protection will not be adversely affected by the passage of time. MT
Fuses consist of a low-resistance metal or wire that is used to close a circuit. When too much current flows through the low-resistance element of the fuse, the element melts and breaks the circuit. This keeps the excessive current from continuing down the circuit to more expensive equipment.
A Q & A with Danita Knox, GE Energy Connections.
When’s the best time to upgrade a power system? According to Danita Knox of GE Energy Connections, Atlanta, it can vary. Consider the following situations as ideal opportunities:
- if a facility had or is planning a significant expansion that might affect overall power-system loading
- if a recent arc-flash study revealed significant incident levels or danger of exposure for electrical workers or operators
- if personnel are having difficulty locating replacement and spare parts for the site’s electrical system
- if plant personnel desire better monitoring of the overall power system.
Once the decision has been made to move forward on an upgrade, what’s next? We asked Knox for some insight into what facilities can do to make these projects go smoothly.
MT: What trends in power-system upgrades are you seeing among older installations?
Knox: One trend involves customers replacing older electromechanical relays, meters, and trip units with newer digital “smart” equivalents. This provides a single, multi-function device that incorporates communications (local and network), event logging, and monitoring (graphical screens and remotely using web tools). Critical applications include upgrading to smart switchgear offerings that feature built-in monitoring, diagnostics, redundancy, and remote-control capabilities.
Facilities are also adding devices to their power systems that help locate workers further away from the equipment they operate. This is done, in some cases, by adding remote racking devices to existing breakers or using robot-type devices to operate equipment from a safe distance. We’re seeing more sites updating old fused devices, such as a load interrupter switch, with faster-operating vacuum breakers and relay equivalents that reduce arc-flash incident levels.
Finally, with limited budgets for large capital projects in many plants, it’s essential for them to find ways to extend the life of their existing equipment. To that end, facilities are often looking at retrofit options.
MT: What tips do you have for sites that are embarking on a power system upgrade?
Knox: Ideally, it helps to start with a comprehensive arc-flash study. This can provide remediation suggestions on how to reduce arc-flash exposure levels and improve personnel and equipment safety. To begin an arc flash study, an operation needs an accurate schematic or diagram of the facility. Plant personnel familiar with the electrical system can usually collect the information needed to build this diagram. An accurate schematic also provides critical information that can be a great tool to develop safe and proper LOTO (lock-out/tag-out) practices.
With a thorough arc-flash study, plant operators can then evaluate multiple options that help define steps to start upgrading a power system. Upgrade projects can be prioritized into smaller projects, depending on employee exposure, process needs, available outage periods and budget constraints.
MT: To get management buy-in, what’s the best way to estimate the return on investment (ROI) and benefits of an upgrade?
Knox: Often the need to upgrade is based on some failure or electrical incident that has caused downtime, equipment damage, or, worst-case scenario, employee injury.
When you look at the cost associated with downtime and/or injury, it’s fairly easy to calculate ROI if the project is done in a phased approach. Some trip unit, relay, and breaker upgrades can be done under the threshold of a maintenance budget.
MT: Are there any budget-friendly ways to upgrade a legacy system?
Knox: Yes, there are. It’s important to look at upgrade options that solve the most problems with minimal disruption to plant operations and equipment.
Consider, for example, if a single upstream breaker/relay combination in the facility can reduce arc-flash exposure for downstream feeder breakers without upgrading each breaker. Does the site have unused spare breakers that can be rotated out with a local service shop for upgrades that can later be installed during a short outage?
If a plant is updating old relays and meters, it should get new doors with new components prewired. This allows a shorter outage while equipment is being replaced. Also, “replacing the guts” in the existing compartment in a field outage can help reduce upgrade costs, assuming the new equipment has been pre-determined to fit the compartment and it can be easily wired. MT
Danita Knox is senior product manager for Power Delivery Services within GE Energy Connections, headquartered in Atlanta.
Steps to a Successful Power-System Upgrade
According to GE’s Danita Knox, as a site prepares for a power-system upgrade, it’s important to identify and select a reputable vendor that’s experienced, trained, and knowledgeable in designing this type of complex project. A power-system upgrade includes these steps:
- Budgeting for hardware, software, and labor.
- Development of a project schedule and careful outage planning for the upgrade.
- Design of the system and procurement of all components prior to the outage.
- Labor and logistics planning for the outage to ensure that work is completed on time.
- Testing of all critical components prior to the outage.
- Failure mode and effects analysis to plan for challenges during the outage and prepare solutions or workarounds.
- Site safety and work policy that includes LOTO (lock-out/tag-out) training and documentation.
“During the upgrade,” Knox said, “an experienced project manager with a background in power systems is indispensable. Many facilities operate continuously with infrequent planned outages. Careful planning and execution is required to maximize work and re-energize systems in a timely manner.”
Knox advises creating a detailed schedule and work procedures early on, including planning types of labor and required skill-sets and procuring all materials well in advance. “Regarding procurement,” she cautioned, “be careful to consider smaller items, such as personal protective equipment and installation components. If these small details are missed in outage planning, they can create schedule slippage, safety risks, or technical errors while limiting the amount of work accomplished.”
Two Schneider Electric facility engineers share their tips for ensuring the safety, efficiency and reliability of a site’s electrical system.
By Jane Alexander, Managing Editor
The infrastructure of a typical commercial or industrial facility is a complex network of electrical, electronic, process and control, automation and building-management systems. Some facilities include critical power and cooling systems as part of that infrastructure. And when something goes wrong, there’s typically one go-to person. Whether his/her title is facility engineer (as used in this article), manager or director, this individual has a full plate. For example, following is a partial list of job responsibilities listed in a recent online job posting for a Lead Facility Engineer:
- Ensure adherence to safety policies and procedures
- Monitor buildings, grounds and equipment for safety and functionality
- Maintain data center systems
- Perform routine maintenance tasks
- Troubleshoot, evaluate and recommend system upgrades
- Order parts for maintenance and repairs
- Request proposals for work that is to be outsourced
- Supervise shift personnel; support training initiatives
- Oversee maintenance reporting activities
- Supervise and audit contractors
- Ensure accurate and timely completion of work order requests
- Serve as on-call facility manager, as needed
As Facility Engineers for Schneider Electric with more than 20 years of combined service, Kirk Morton and Keith Smith perform many of the functions listed above. Morton is responsible for the daily operations of a 100,000-sq.-ft. office building with 400+ employees, while Smith oversees operations at one of Schneider Electric’s manufacturing facilities. While many of their day-to-day tasks are similar, Smith’s industrial facility naturally has more systems and requirements to address than Morton’s office building. These include compressed air systems, crane and hoist inspections and load tests, processed water/wastewater treatment and site storm- water prevention plans.
Morton and Smith also are responsible for outsourcing various services, for managing outsourced/contracted employees, and for ensuring contractors follow safety standards in place at the worksite (facility managers, not contractors, retain ultimate responsibility for plant safety). While the traditional reason for outsourcing is to enable an organization to focus on its core competency, there can be others, as reflected in the following four models:
- The company needs contractors to help meet operational/productivity requirements.
- Contractors with a specific skill set are needed to perform specific tasks.
- A company uses contractors for projects.
- A company uses contractors to act as consultants, i.e., Managed Services.
Reliable power is paramount
Morton and Smith agree that a reliable power system is at the heart of safe and efficient operations. Per Schneider Electric requirements for all of its locations, both have implemented preventive maintenance programs at their individual sites. Their programs follow the recommendations of NFPA 70B and requirements of NFPA 70E:
A well-administered Electrical Preventive Maintenance program: reduces accidents, saves lives and minimizes costly breakdowns and unplanned outages. Impending troubles can be identified, and solutions applied, before they become major problems requiring more expensive, time-consuming solutions.
Source: NFPA 70B-2013 Ed., Section 4.2.1
When it comes to their sites’ respective electrical infrastructures, Morton and Smith may deal with different systems, but their overall focus is on reliability. “We really don’t have any issues in our commercial office space,” says Morton. “The meters and monitoring equipment are our own and very reliable, as is our switchboard. In addition, we have a reliable back-up source for our data room.”
Smith’s manufacturing operation doesn’t have issues with its electrical systems either, thanks to its robust generator and battery backup capable of providing redundant power. Still, he emphasizes, any maintenance and repair activities must be scheduled and performed to accommodate work schedules. “And departmental workloads must be considered.”
Unfortunately, some facility personnel may not be knowledgeable or adequately trained in the specific equipment or power distribution systems that comprise the electrical infrastructure at their sites. With regard to preventive maintenance of an operation’s electrical system, special skills and knowledge are required, which is why this work is often outsourced. Based on their own responsibilities with regard to electrical work, Morton and Smith offer the following tips for other facility managers:
Due to the increasing complexity and interconnectivity of today’s electrical systems, few companies have the in-house experience to service all of a facility’s electrical components. Facility management needs to ensure that electrical workers are qualified, as defined by OSHA and NFPA 70E, to work on the specific equipment that is to be maintained. This applies to in-house staff, as well as third-party contractors. Fundamental require-
- A complete understanding of equipment, the required work scope and electrical hazards present.
- Proper use of personal protective equipment (PPE), tools, shielding and test equipment as well as precautionary techniques.
- Discipline and decision-making skills to determine risk and ability to maintain a safe work environment.
For maintenance and testing activities, an in-depth interview of potential electrical service providers is suggested, and applicable references should be obtained. Ask questions up front relative to Field Personnel Competency Training to determine product knowledge. Morton and Smith say it’s important to learn about the service provider’s safety training program. As noted, the company that outsources the work is responsible for workplace safety, whether the maintenance worker is an employee or a contractor.
2. Outsourcing electrical work
Morton and Smith point out that if a site elects to outsource its electrical work, its facility engineer(s) still have several crucial responsibilities:
Facility engineers should obtain and maintain all of the operations and maintenance manuals that accompanied the original electrical equipment. If any have been discarded, misplaced or lost, the original equipment manufacturer (or their representative) should be contacted and replacement copies requested. These documents are often available online and can be searched by the manufacturer’s name and electrical equipment identification.
Facility engineers must be clear regarding the specific equipment they desire to have cleaned, inspected, maintained, serviced and tested, as well as be clear regarding each piece of electrical equipment that is to be removed from service for inspection, maintenance or testing.
Before any electrical maintenance program is initiated or contracted, facility management should provide exact, detailed and up-to-date one-line diagrams of the entire electrical-power-distribution system. These records should also indicate the specific location, room number, floor or area location where each piece of electrical power distribution equipment can be found. If this documentation is not available or is out of date, the services of a licensed professional electrical engineer should be contracted and commissioned to create and maintain current electrical one-line diagrams and equipment name-plate data.
The facility’s needs for temporary electrical power must be met during a scheduled maintenance interruption. Facility engineers should ensure the availability of a temporary power source.
3. Ensuring safe, efficient, reliable electricity
Both Morton and Smith agree that having a preventive maintenance program in place helps mitigate the risk of unplanned downtime. They also recommend a battery back-up as well as back-up generator capabilities, because even with regularly scheduled preventive maintenance, all facilities will experience unplanned electrical outages from time to time. MT
Leveraging best practices in maintenance with state-of-the-art monitoring technologies and remote services will keep your UPS systems in compliance, reliable and available.
By Jane Alexander, Managing Editor
Because uninterruptible power supply (UPS) units and their batteries must function properly during unplanned outages, a compromised emergency power system can mean serious trouble. At this critical time, batteries supply power to digital control systems and emergency lube oil pumps, enabling automatic controls to do their job.
In applications like oil and gas, petrochemical and power generation, dead batteries that prolong power interruption can cause dangerous chemical-process instability, damage to equipment or, in some cases, the shutdown of a facility. Damaged equipment could take months and millions to repair, while lost power production could be more expensive and lead to fines and penalties. For example, in a recent case regarding the 2011 blackout in the southwest United States, a public power entity agreed to pay a $12 million civil penalty for its role in the outage.
According to Wally Vahlstrom, Director of Technical Services for Emerson Network Power’s Reliability Services group, a proper preventive maintenance program can help a plant avoid those types of costly incidents and, in turn, provide several added benefits.
Benefit: battery-testing compliance
Every emergency power system contains life-limited components that should be maintained according to recommendations from the Institute of Electrical and Electronics Engineers (IEEE), manufacturer specifications and as required by the North American Electric Reliability Corporation (NERC). Batteries are no exception. In the event of a power outage, a single bad cell in a battery string could compromise the entire backup system and leave a plant without protection.
While UPS battery manufacturers may market their batteries with a 10-year design life or life span, actual battery service life could be much shorter due to the external factors that cause degradation. Several effects that can shorten battery life include:
- Frequent discharge cycles
- High or improper room temperatures
- High or low charge voltage
- Excessive charge current
- Manufacturing defects
- Loose connections
- Strained battery terminals
- Poor and improper maintenance
In reality, batteries lose capacity in as little as three years. According to IEEE, the “useful life” of a UPS battery ends when it can no longer supply 80% of its rated capacity in ampere-hours. At this point, because the aging process accelerates, a battery should be replaced.
Benefit: increased battery life
Because of the many factors that can affect the useful life of a UPS battery, it is important that—as soon as it is placed into service—a battery be maintained with a program that identifies system anomalies and provides information that trends end-of-life. Through this type of maintenance program, plant owners and operators can get the most out of their investment in these critical assets.
Batteries that are beginning to fail cause an imbalance that adversely affects the life of other batteries in the string and should be removed from service. Moreover, when UPS battery replacement is needed, time is critical—especially in light of the financial impact an extended or unplanned outage can have on an organization. In a concerted effort to increase its system reliability, the public power entity cited in the above-referenced blackout expects to invest at least $20 million in battery storage facilities within its transmission operations area.
Benefit: maximized system reliability
To avoid UPS battery failure, the best practice is an approach that includes integrated battery monitoring and preventive maintenance (PM). In Emerson Network Power’s data analysis of more than 450 million operating hours for more than 24,000 strings of UPS batteries, the impact of regular preventive maintenance on reliability was clear. The analysis revealed that the mean time between failures (MTBF) for units that received two PM service visits a year is 23 times better than those that received no PM visits.
Furthermore, operations with battery monitoring systems installed at their sites had a reduced rate of outages due to bad batteries. While outages still occurred, the incidents were isolated to cases where customers were either not watching their system or did not know how to properly analyze the data provided by the monitor. This revealed the need for experts to correctly monitor the alarm data and properly maintain those systems.
Benefit: improved system availability
The ideal UPS battery maintenance program is one that uses monitoring in conjunction with remote services. Teams responsible for managing critical infrastructure are essentially able to augment their staff with a remote services solution that includes data acquisition, equipment trending, monitoring alert management, maintenance and remote diagnostics, as well as parts and service-personnel dispatch.
The latest technology, such as that used in Albér battery-monitoring products, can identify potential problems by tracking critical parameters like cell voltage, overall string voltage, current and temperature. Periodic tests of the battery’s internal resistance can also verify a battery’s operating integrity. For a UPS, technology can be embedded and allow, for example, continuous monitoring of multiple unique parameters. At defined intervals—or at the activation of a critical alarm—the monitoring device will communicate to a remote system engineer and provide alarm details, allowing immediate corrective action.
By combining monitoring with remote services, plant managers can define escalation plans that are executed upon any alarm condition. Your chosen service partner should have critical infrastructure experts available to support monitoring efforts 24/7 to improve overall system availability. MT
Wally Vahlstrom is Director of Technical Services for the Electrical Reliability Services business of Emerson Network Power. For more information, visit emersonnetworkpower.com.
Fluke Corporation has expanded the Fluke Connect system with its new Ti90 and Ti95 Infrared Cameras featuring wireless connectivity. According to the company, the Ti90 and Ti95 deliver best-in-class image quality with up to 84% better spatial resolution (of handheld industrial infrared cameras priced $1000- $2000), thus allowing technicians to conduct infrared inspections from a safer distance without compromising accuracy. Their 3.5-inch color LCD screens are up to 32% larger than competitive models and offer adjustable brightness for easy viewing in most conditions.
These new cameras come with an extensive SD memory system, including a removable 8 Gb SD memory card or 8 Gb wireless SD Card. This feature allows technicians who share cameras to simply swap SD cards at the end of their shifts instead of needing to download images onto their PC before turning the camera over to the next technician.
AutoBlend and Picture-in-Picture modes are available in the included SmartView reporting software that lets technicians easily perform analyses and image adjustments/enhancements.
About Fluke Connect
The Fluke Connect system allows maintenance technicians to wirelessly transmit measurement data from their test tools to their smart phones for secure storage on the cloud and universal team access from the field. More than 20 Fluke tools connect wirelessly with the app, including digital multimeters, infrared cameras, insulation testers, process meters and specific voltage, current and temperature models.
Fluke Connect ShareLive video call allows technicians to collaborate with others, letting them see the same images and measurements, and get approvals for repairs without leaving the field.
The Fluke Connect app can be downloaded for free from the Apple App Store and the Google Play Store.
A steel plant’s remote racking systems offer a safe alternative to manually racking circuit breakers by keeping operators outside the flash-protection boundary.
By Tim Burttram, Plant Electrical Engineer, Cascade Steel
With the threat of an arc flash incident at circuit breakers, distance can be an operator’s best friend. That’s one of the facts that led Cascade Steel to evaluate the latest offerings in remote circuit-breaker racking technology. The mill wanted a remote racking system that was quick and easy to deploy. Wasting money on a piece of equipment that electricians and maintenance personnel wouldn’t use wasn’t feasible.
Founded in 1968, Cascade Steel Rolling Mills is a state-of-the-art steel-manufacturing facility that takes recycled metal and turns it into high-quality finished steel products. Located in McMinnville, OR, the company’s electric arc furnace (EAF) mini-mill produces a wide range of hot-rolled products such as reinforcing bar (rebar), coiled reinforcing bar, wire rod, merchant bar and other specialty products (Fig. 1).
Like other industrial operations, Cascade Steel is tasked with safeguarding its workers, equipment assets and the environment. Any company that generates, transmits, distributes or uses electricity at high, medium or even low voltages has an obligation to protect its personnel from hazards such as arc flash and others that might occur in switchgear equipment.
Breaker racking issues
Arc flash hazard mitigation is at the top of every plant or mill’s electrical-system-safety list. Employers must ensure that their electrical-system workers go home at night by understanding arc flash risks and the latest technologies designed to minimize them.
The simple act of manually racking a circuit breaker, with an operator positioned in front of the device, creates an arc flash hazard. Parts break or don’t line up. Equipment malfunctions. Even with the best personal protective equipment (PPE), plant and mill workers are still going to get hurt in some way if things go badly.
At the Cascade Steel site, plant personnel recognize the NFPA70E standard as the basis for their electrical safety program. This standard requires that to work on electrical apparatus with elevated energy levels, electricians must de-energize upstream equipment to avoid the potential for an arc flash. This means opening and closing circuit breakers, and eliminating power to various areas of the melt shop or rolling mill—a potentially dangerous situation for both human and equipment assets (Fig. 2).
Why remote racking?
History has shown there is no better protection against a potentially deadly arc flash incident than a safe working distance between the operator and the switchgear. This approach has clear advantages over flash suits designed only to decrease exposure to burns; it also minimizes the risks posed by airborne projectiles often associated with arc blast fatalities.
To reduce hazards to employees, many mill sites are installing remote circuit-breaker racking systems that allow operators to safely rack breakers from a remote location. Remote racking systems offer a safe alternative to manually racking circuit breakers and reduce the requirement for service personnel to wear a full-body arc flash hazard suit for protection. Designed to remove operators from close proximity to the breaker that’s being racked, these systems permit the insertion and removal of electrical devices while the operator is outside the flash-protection boundary.
Following its evaluation of remote racking options, Cascade Steel chose the Safe-T-Rack system from Remote Solutions LLC. This system places a protective barrier of up to 150 feet between the operator and the energized breaker. It also differs substantially from common “land-based” systems that must either be moved to the breaker location on a cart or affixed to a large base with a motor-driven mast.
Some users find land-based racking systems cumbersome: They can weigh hundreds of pounds and aren’t very portable. With this type of system, the operator must properly finesse the device to the face of the work on the circuit breaker compartment, register the X/Y/Z coordinates relative to the racking points and then secure the tool. This procedure can take up to 20 minutes per breaker, and also introduces human-performance concerns. Tool-alignment problems can result in physical damage to the circuit breaker, rendering it unserviceable.
Conversely, the remote racking device that Cascade Steel chose is easily operated with switchgear elevated above the ground. It includes fail-safe mechanisms to keep personnel from misapplying it to the wrong breaker. It also includes specific attachments and software to address particular racking parameters such as torque and breaker travel. The switchgear-based racking apparatus can be mounted on the breaker itself or on the breaker-compartment door so it can be registered correctly to the racking points.
To date, Cascade Steel has installed remote racking apparatus on every rackable breaker in its mill, regardless of voltage level. The company is now working to obtain remote racking for three additional 480-volt, molded-case SPB rackable breakers.
How the system works
With a switchgear-based tool alignment philosophy, the operator uses the switchgear as a reference, aligning the remote racking apparatus only once. The device includes the exact racking point coordinates for a given circuit breaker design, and is affixed to the breaker compartment door to allow all racking tool pieces to be easily loaded or mounted. The racking point coordinates are fixed so that any time a mill worker mounts dry brackets, for example, the center point for the tool is aligned for insertion directly at the racking screw.
“Human factors” engineering also establishes a “chain of rejection” to minimize human error. This enables technicians to consistently handle racking applications on multiple breakers of various configurations (Fig. 3).
A touchscreen human-machine Interface (HMI) for “closed-door” racking also benefits mill operators. Redundant digital drives with battery backup provide fail-safe racking in the event of a power failure. Real-time breaker travel indication and user controls include an emergency stop at any time during racking, manual start/stop, and automatic retrieval and recovery of a circuit breaker.
A torque limiter for different manufacturers’ breakers found throughout the mill counts the number of turns as well as displaying real-time travel position. The system stimulates all OEM breaker interlock systems and automatically operates and monitors positive interlock.
In addition, tilt-angle monitoring allows operators to track the pitch and roll of a breaker during racking to minimize potential equipment damage. Should the device detect an out-of-level situation, it will stop the racking process. Over-torque protection is also provided for the racking motor should the shutters not open or if the breaker becomes bound in the racking process. This consistent process will extend the life of switchgear.
Some facilities make a big investment in a cart-based remote circuit-breaker racking system, only to find it goes unused. This means the operation has wasted its money and not accomplished its objective of getting workers out of the danger zone.
With a switchgear-based remote racking system, sites gain a safe, reliable and user-friendly alternative to manually racking breakers, which reduces the requirement for operators to wear a full-body arc flash hazard suit for protection. They can rack a breaker properly by its original design and insert and remove the equipment while remaining outside the flash-protection boundary (Fig.4). MT
Milwaukee Tool has expanded its Test & Measurement portfolio with two new Auto Voltage/Continuity Testers. Combining the simplicity of a traditional voltage/continuity tester with the digital read-out capabilities of higher-functionality meters, they let users accurately troubleshoot common electrical issues with ease in increasingly diverse electrical systems.
According to the manufacturer, while traditional testers only indicate broad voltage ranges that mask electrical issues like voltage drops, its new Auto Voltage/Continuity Testers deliver measurements down to the decimal, and display them on easy-to-read LCD screens. With their built-in intelligence, the devices automatically determine whether to test for voltage or continuity and also identify AC or DC Voltage, thus providing more information than a single test can supply.
Features include built-in LED work lights for low-lit areas and test-lead holders to store the probes when the job is done. Both units are compatible with common threaded carrying and mounting accessories like belt clips and magnets.
The new units will be available in August 2014.