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Fire Apparatus Electrical System Choices: Time to Think About Them

Bruce Nalesnik, KME Chassis Product Manager

For many years, the purchase of a piece of fire apparatus did not involve consideration of the actual electrical system being provided. A hardwired point-to-point system was the standard, with each manufacturer providing variations of this method according to their designs and tendencies. But over the past several years, a clear-cut choice has evolved as to which type of system to select—staying with the older traditional type hardwired design or selecting the newer multiplex systems available today. This article will present some of the features and benefits of a multiplex system, which should be considered in the selection of an electrical system for your future apparatus. 

What is Multiplexing?
Multiplexing is the transmission of multiple signals or messages on a single network, enabling a constant flow of information along a single cable, using input and output modules. The automotive industry has been using this technology for quite a few years now. Some commercial truck manufacturers have made multiplexing standard, and others are striving to integrate this technology into their product lineups.

Multiplex systems allow for a single network of communication between vital electrical components, along with reduced wiring and connections.

So, why should multiplexing be a preferred choice for fire apparatus today? 

  • Fewer Wires: As simple as it sounds, one of the more impressive aspects of multiplexing is the plain fact that up to 40 percent fewer wires can be achieved in a fully integrated multiplex fire apparatus. Today’s fire apparatus have more electronic components on them than ever before, resulting in increasingly complicated electrical system build-ups. With a hardwire system, these challenges are magnified. The use of a multiplex system eliminates the need for large bulky wire harnesses that require crimping, splicing, and tracking to diagnose and fix an issue. Multiplex systems send multiple signals along one line which can be monitored by the operator.

    As fire apparatus have evolved, harnessing and wiring demands have increased as well.

    A fully multiplexed apparatus features significantly less wiring providing for a much cleaner installation and easier maintenance and troubleshooting in the field.
  • Less Downtime Means More Uptime: More than ever, keeping your apparatus up and running is paramount. With fewer wires, fewer connections, and greater life expectancy of components, multiplexing decreases the likelihood of an electrical problem resulting in the dreaded “out of service” status. And when an issue does arise, a sophisticated onboard diagnostic system is provided for quick and easy troubleshooting. With strategic placement of remote power modules, the need to trace a wire from front to back or any significant length is eliminated. If additional support is needed, certain multiplex systems provide remote diagnostic capabilities as well as remote programming.
  • Versatility and Flexibility: Taking full advantage of multiplexing technology offers the end user a wide variety of options and capabilities. If multiplex switching is used, these switches are fully programmable according to the fire departments requests. Switching function changes can easily be done if needed during production as well as in the field, with remote reprogramming also available.

Another significant offering in multiplex technology is the use of screens for all major electronic functions. These screens offer multiple functions including, but not limited to:

  • Chassis Information Center 
  • Seat Occupant Display
  • Remote Mirror Controls 
  • HVAC Controls With Climate Control
  • Emergency Light Switching
  • GPS Integration
  • Multiple Video Inputs
  • Onboard Diagnostics
  • Climate Control

Utilizing this screen technology can also provide substantial space savings inside the cab, and allow for future integration of technologies such as Wi-Fi and Telematics.

An example of vital fire apparatus functions that can be consolidated into an UltraView or Vista IV Display.

With the complexity of today’s apparatus, this type of switch arrangement often leads to running out of adequate space to install other electrical components.

A cab with dual multiplex screens provides for a clean ergonomic environment and allows for proper installation of all electrical components. 

What’s on the Horizon?
As electronic technology advances, having the most modern electrical system as your base will allow you to add features as they become available. Wi-Fi capabilities are expanding to fire apparatus, allowing operators to tap into hot spots while out of the station while also allowing in-station monitoring as well. 

Telematics, already being widely integrated into the truck fleet industry, will start to find its way into fire apparatus as well, and is currently being offered as an integral option in some multiplex systems. Telematics offers in-use truck tracking and monitoring of a truck’s performance and condition, allowing early detection of potential issues, discerning if they are minor or major in scope, and addressing them before they do become major issues affecting the apparatus’s ability to respond and stay in service.

Consider Choices
There are electrical system choices available today that merit consideration during the apparatus procurement process. There is a clear “Y” in the road on this issue: the traditional hardwire system or the newer generation multiplex system. Each fire department has its own unique requirements and expectations as to the electrical functions on their apparatus. With the newer generation of firefighter now starting to take on more of the decision making process, the technological advancements and opportunities with multiplex systems seem to be having an effect as more and more apparatus are being specified with these systems.


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