Steps to ensure proper installation of monitoring and metering equipment

Following best practices for proper field device installation will help avoid performance issues and help designers realize the true return on investment (ROI). See four steps to ensure proper installation of monitoring and metering equipment and instrumentation, including proper grounding and shielding.

By Rick Schear December 5, 2016

While investments in electronic monitoring and metering systems are made within complex industrial environments, and connections seem to be correct, problems still exist.

Some devices function perfectly, others do not function at all, while some perform erratically or occasionally send error messages. The majority of problems seem to occur within sensitive control or power transmission assemblies.

Often, a lack of attention has been given to the installation details of monitoring and metering device wiring during design and installation. Some of these important wiring issues include incorrect wire selection or installation, improper instrumentation grounding, and inadequate electromagnetic protection for wire and terminations. 

Four steps to proper monitoring and metering equipment installation

The following are best practices to ensure proper function of monitoring and metering equipment:

1. Ensure adherence to manufacturer recommendations. 

Manufacturers will most likely provide extensive recommendations for the design, installation, and maintenance of power and communications wiring used in field bus products. This information typically spans INCOM [Industrial Communications network from Cutler-Hammer, acquired by Eaton], RS-485, and Ethernet physical layers. Adherence to these recommendations is vital to ensure robust and reliable communications.

Network segments installed according to manufacturer recommendations will provide flexibility, simplicity, and noise immunity. Failure to follow recommendations often will result in sub-optimal system performance. For example, to minimize data corruption, it is not advised to run communications wiring in a power tray common with high-frequency loads, such as adjustable frequency drives or soft starters.

Proper grounding is also an important aspect of field device installation. Most instrumentation systems have two grounds including the electrical or power ground and the instrument ground. It’s important to realize that these two grounding systems have different purposes.

The shield should be continuous across a network segment and connected to the building’s electrical system grounding electrode conductor. The 2017 National Electric Code (NEC) provides guidance on grounding communication cables.

Cable selection also is essential for robust communications. Cable developed for RS-485 communications is recommended. Control and instrumentation cables are unacceptable for RS-485 applications.

Additionally, power distribution and automation applications require shielded cable. Most cable is available with two types of shielding, foil and braid-over foil. Either can be used, although braid-over foil is preferred. The foil covers high- radio frequency and eElectrical fast transient exposures, while the braid-over foil covers low-frequency surge events. For typical terminal block connections, the cable must support a shield drain wire.

2. Understand infrastructure challenges and environmental factors.

System capacity calculations should be performed when new systems are being developed or devices are being added to existing systems. The purpose of the calculation is to determine if the system design has the capacity to support the number and type of devices intended for use.

Problems may be unrelated to capacity. For example, most loads in modern electrical distribution systems are inductive. These loads can include motors, transformers, gaseous tube lighting ballasts, and induction furnaces. Inductive loads need a magnetic field to operate. These inductive devices can cause harmonics to be created by electronic circuits, which can create problems for connected loads.

All harmonics cause additional heat in conductors and other distribution system components. Harmonics also can cause electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, and is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.

High levels of harmonics and EMI can often result in erratic behavior of electronic equipment, including inconsistent data communication between computer equipment and field devices, which can jeopardize the effectiveness of energy monitoring and metering devices.

These issues can be traced back to incorrect wiring schemes such as installing unshielded communications cables too close to wiring carrying inductive loads. Replacing existing cable with a shielded alternative, or simply changing the proximity of communications wiring to inductive loads, can correct this problem.

However, if wiring adheres to manufacturer recommendations and data is still unreliable, it is recommended to consult with the field device manufacturer or a power quality specialist to determine if line filters and conditioners can solve issues.

3. Diligently review pre-approval documents and plans.

The potential problems outlined above can be avoided by giving adequate attention to the details of field device wiring recommendations during the design and installation phases.

It is always a best practice to closely review pre-approval documentation and plans to ensure important wiring details are met, including proper treatment of each type of instrument, correct wiring for signals, proper grounding, and meeting specifications for instrumentation wire and terminations.

As a result, possible issues can be identified and rectified prior to installation, which can save a tremendous amount of troubleshooting time and labor compared to the identification of issues after installation and commissioning.

4. Test systems before and after installation.

It is vital to use testing equipment to measure capacity, harmonics, and EMI before and after installation to streamline the field wiring process; Proactive testing can help designers identify possible obstacles and implement protective measures before a bill of materials is created. These studies also should be performed following installation to ensure wiring measures have correctly addressed identified issues.

Paying close attention to field device data during start-up, peak usage, and the ramping down of systems also easily can identify problems. EMI and harmonic levels can vary during these periods, so keeping an eye out for inconsistencies or data collection errors often can help correct the situation shortly after installation, and the field device can then function properly. If issues with data collection are identified, contacting the field device manufacturer directly for immediate troubleshooting and correction support is among other options.

Without proper installation, it is impossible to reap the benefits of metering and monitoring devices. The real-time data these devices provide, simplifies maintenance, reduces downtime, and enhances efficiency.

However, without properly functioning systems, most organizations never fully achieve the true return on investment for these devices. By following best practices for device wiring and installation, designers, installers, and plant management can achieve the full benefit of real-time data acquisition without the headaches of improperly performing equipment and the need for time-consuming troubleshooting and testing.

Rick Schear is a product manager at Eaton; edited by Emily Guenther, associate content manager, Control Engineering, CFE Media, eguenther@cfemedia.com.

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Key Concepts

  • The benefits of properly installing metering and monitoring devices
  • The challenges due to incorrect metering and monitoring device installation
  • Following device wiring best practices.

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