Reducing Wiring and Infrastructure with Smart Junction Boxes

Emerson's Kyle Lednicky


Emerson's Alan Harris


Wired instrumentation requires infrastructure such as junction boxes, cables and cable trays. In a 2018 Emerson Exchange presentation, Reduce Junction Box, Cable, & Tray Costs by Utilizing the New Emerson Appleton PlexPower Fiber Panels, Emerson’s Kyle Lednicky, Alan Harris and an Engineering Contractor (EPC) shared this innovation.

Kyle opened discussing the PlexPower panel that has been available and in use for many years for electrical distribution for power, lighting, and motor control applications. Traditional panels used in hazardous locations are heavy, cast aluminum with many bolts, making for costly installation and maintenance. With PlexPower, the electrical circuit breakers are rated for Class I, Division 2 at the component or breaker level, allowing for more flexibility and easier installation.

The new PlexPower fiber panel released this summer, uses the existing component level technology combined with a fiber patch panel inside one stainless box. Project costs are reduced by moving power and fiber distribution into the field and connected to Smart Junction Boxes. Power/Data/Control in a reduced number of cables can feed the PlexPower Fiber panels.

The EPC engineer shared a case study where they used DeltaV electronic marshalling (DeltaV CHARMS). They were designed to be located in junction boxes out in the field with the processing equipment.

Configured to Order (CTO) junction boxes were specified with home run cables between the systems and junction boxes. Marshalling cabinets were eliminated and the junction boxes fanned the wiring out to the instruments. Field circuit panels were used to distribute power.

An analysis was performed between a conventional project and the one with CHARMS and distributed power with 2200+ I/O. The traditional design required 195 home run cables and the remote I/O required 16 cables. Terminations were reduced from over 23,000 down to 2,100. Marshalling cabinets were eliminated as were some rack rooms. Cable tray was reduced from qty. of four 24″ cable trays to one 12″ cable tray. Documentation was dramatically reduced as well. The project added fan out cable, fiber optic cable and terminations, but the reductions in the other areas dwarfed these additions.

Alan next came up to speak about the hybrid cables used to connect PlexPower Fiber Panels to the Smart junction boxes. In conjunction with Belden, Emerson is using a composite style hybrid cable including both power and fiber combined in one cable. The cable runs out to redundant PlexPower hubs. These panels distribute power and communications via the fiber. Many accessories can be added including smart lighting, gas detection, CCTVs, RFID access points, WiFi, etc.

The savings come from eliminating I/O and marshalling panels and reducing the size of buildings needed to house them. Also, all the associated costs from installation improves costs and schedules.

Alan shared a story of a manufacturer who decided to use smart junction boxes later in the project after the cable tray had already been designed and installed. The result was very empty cable trays and extra costs that could have been avoided with an earlier decision in the project.

Learn more about the line of PlexPower products on Emerson.com.