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Tycom is a proud partner to Fluke! We had to share this article from Fluke with our clients:

Early reports from the field suggest that the new Fluke 772 and 773 Milliamp Process Clamp Meters may be game changers, breaking new ground for technicians in the HVAC controls industry. With the feature sets these meters offer, troubleshooting of the most common problems in modern control systems becomes a snap.

Common applications for these meters include communications measurement, milliamp loop sensor measurement, damper and valve actuator troubleshooting, and troubleshooting the operation of variable frequency drives (VFDs). Let’s look at some typical scenarios for each of these examples.

Communications measurement

A controls technician receives a too-hot complaint from a room on the third floor of a building on campus. A quick check of the BAS front-end computer reveals that the variable air volume (VAV) box controller is offline, not communicating. The technician grabs his new Fluke 773 and heads out to the building.

• After reaching the room, a quick check of the VAV box in the ceiling reveals that the VAV damper is in the closed position. The VAV controller normally has an LED that blinks when the controller is online. That LED is off.
• The technician quickly attaches his Fluke meter to the RS-485 Communication bus wiring terminals and measures the proper voltage, reading approximately +2.5 V dc between the three terminals, labeled +, – , and ref.
• A quick check of the wiring shows that the communications connector was not fully seated, causing a communications loss.
• After seating the connector properly, the VAV box controller comes back online, the communications LED resumes blinking, and the VAV damper begins to stroke open.
• A call is then placed to the operator in the control room and the controller is now online. The room immediately begins to cool down.

Milliamp loop sensor measurement

The foundation of each model in the 771/772/773 Milliamp Clamp series is the groundbreaking ability to troubleshoot milliamp sensors inside crowded control panels – without breaking the circuit. In this scenario, our technician notices that the static pressure inside the supply duct of a VAV system seems to be too high.

• A check of the BAS front-end computer indicates that the sensor is reading a perfect 1″ WC of static pressure.A check of the actual static pressure using an airflow meter such as the Fluke 922 indicates that the static pressure is actually 1.5″ WC. For these systems, 1′ WC is considered normal.
• The technician takes his 773 Milliamp Clamp out to the control panel and finds the wires that terminate the static pressure sensor to the controller. As in many of the control panels in this building, the wiring looks like cooked spaghetti. The small jaws of the 772/773 enable the technician to clamp the exact wires perfectly. He reads the milliamp signal and compares it to the listed range for the sensor. The sensor is 0 – 20 mA and has a range of 0 – 2″ WC. It is currently reading 15 mA. At 1″ WC it should be reading 10 mA.
• The technician uses his laptop and opens up the program in the controller. He finds that the programmer did not scale the sensor properly in the software, which caused the error.

Damper and actuator troubleshooting

Another controls technician receives a too-cold complaint from an office in the building. The system is VAV with a hot water reheat valve.

• A quick look determines that the valve is closed. She connects her laptop to the controller and uses it to commission the controller. She attempts to override the valve open, but without success.
• She disconnects the wires to the actuator from the controller and then connects to the Fluke 773. She uses the meter to send a 0 – 10 V dc signal directly to the valve actuator to make it open and close. The valve actuator then works perfectly.
• Reviewing the controller programming, the tech determines that the reheat valve was forced closed by an improperly operating interlock, which is then removed. After this, the reheat valve works properly and the space warms up.

Troubleshooting VFDs.

During a spell of hot weather, all the occupants of a building complain that it is too hot.

• The chilled water pump system uses a VFD, but its operating pressure is too low.
• The controller sends a milliamp signal to the drive to command it to the correct frequency to obtain the correct system pressure. A tech disconnects the system controller, connects the Fluke 773 directly to the terminal block of the VFD, and generates a milliamp signal to the drive to increase the speed. Despite generating a 100% signal to the drive, it never comes up to speed.
• A check of the recorded fault statuses of the drive indicates that a circuit board has failed. The manufacturer is contacted and the faulty board replaced, at which time the drive operates correctly again and the chilled water system returns to the correct pressure.

In these common scenarios, the Fluke 772 and 773 meters are already proving themselves in the wide range of troubleshooting situations encountered in today’s buildings. Every controls technician will want one in their tool bag.

Tycom is a proud partner to Fluke! We had to share this article to our clients with a few changes to relate to South Africa’s situation:

Globally & very definitely South Africa, solar installations (also known as photovoltaic or PV installations) are continuing to multiply rapidly, driven by compelling economics for utility-scale solar generation and efforts to decarbonize the grid (and our continuing load shedding). As solar distribution systems and loads become larger and more complex, the possibilities of transient overvoltages increase — and the implications for safety become more important than ever.

When you’re taking measurements on solar installations, these transients are invisible and largely unavoidable hazards, which means that your protection depends on the safety margins already built into your tools. That’s where the Measurement Category Rating comes in: it’s designed to tell the user which types of electrical installations the measurement device may safely make measurements in.

A voltage rating alone, however, won’t tell you how well a handheld tool was designed to survive high transient impulses — its category rating also must fit the environment you’re working on.

What to know about overvoltage category ratings

Standards that define measurement category ratings are all about safety. Safety standards for measurement equipment are set by the International Electrotechnical Commission (IEC) to ensure that the instrument and operator are never the weak link in the system — and subsequently the location of failure — if a voltage transient occurs. The measurement categories are defined below.

^{IEC 61010 measurement categories apply to test equipment for <3000 V mains measurements and correspond to the overvoltage category definitions and transient protection defined for mains installations from IEC 60664.}
The division of a power distribution system into categories is based on the fact that a dangerous high-energy transient, such as a lightning strike or switching transient, will be attenuated or dampened as it travels through the impedance (ac resistance) of the system. The higher the category, the larger the prospective fault current available and the higher the voltage transients can be — peaking as high as 10,000 V for mains being measured at CAT III < 1500 V.

Solar installations are Category III environments

IEC 61730-1 defines PV modules as permanently wired electrical installations (Category III), not point-of-use electrical outlets (Category II).

^{Overvoltage categories in a photovoltaic installation connected to the utility energy grid}
In addition to being tested to an actual overvoltage transient value, handheld measurement tools are required to have a minimum insulation level — a combination of solid insulation, clearance, and creepage — between internal components and circuit nodes to meet the category rating. Insulation protects internal circuits against fire/arc fault and the operator against electric shock. The higher the working voltage and measurement category rating, the greater the insulation required.

Within a category, a higher voltage rating denotes a higher transient withstand rating. For example, a CAT III 1500 V meter is resistant to much higher energy transients, and therefore offers superior protection compared to one rated CAT III 1000 V.

Solar installation voltage is increasing

Overvoltage category III 1500 V systems are becoming the new normal in solar, delivering cost savings and efficiency gains to facility owners. Each inverter can process more energy, more panels can be connected in series to make longer strings, which requires fewer wires and inverters.

For safety and accuracy, making measurements in an overvoltage category III environment requires CAT III rated tools.

The Fluke 393 FC Solar Clamp Meter is the only CAT III 1500 V/CAT IV 600 V TRMS Clamp Meter which meets the insulation requirements for CAT III environments like solar installations and measures up to 1500 V dc.

The dielectric tests for a CAT III 1000 V current clamp is 8000 V pk/7000 V rms. For CAT III 1500 V, it’s 10000 V pk/9700 V rms.

^{The Fluke 393 FC CAT III 1500 V TRMS Clamp Meter is the world’s only CAT III rated clamp meter adequately rated for use in 1500 V PV installations.}
When choosing measurement tools for PV panels, it’s worth considering the worst-case scenario of the job. First, choose a meter rated for the highest category you could be working in. Then, look for a voltage rating that matches your needs. Choosing the right CAT rated tool for your environment helps you and your team make reliable measurements while reducing risk.

The 393 FC meets the safety requirements for test equipment (IEC 61010-2-032) corresponding to the overvoltage category level of the PV array electrical installation (IEC 61730-1). It offers safe and accurate voltage measurement up to 1500 V dc in solar and battery applications, with features that help make the job easier:

• 25% thinner jaw (compared to Fluke 37x meters) makes it easier and faster to take measurements in tight and overcrowded spaces
• IP 54 protection for dusty and rainy outdoor conditions
• Fluke Connect™ gathers and stores data in the cloud for access anywhere
• Includes CAT III 1500 V insulated test leads
• Carries the Fluke promise of proven safety, ruggedness, and reliability

Why use a CAT III rated tool in solar installations? It comes down to safety: yours. Don’t entrust your protection (or your team’s) to any tool that’s not adequately rated for the job.