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Refrigeration, HVAC and Building Management System products are available with a range of different communication technologies to fit the unique project needs and requirements of each project. Some communication technologies are more appropriate in different situations. We have outlined some of the basic advantages and disadvantages to each technology in this post.

Ethernet (IP)

Ethernet is one of the most widely used technologies for computer networking in the world. The most recent refinements of the standard allow for very fast speeds of up to 100Gbits per second. The most widely used Ethernet cabling (Cat5e) has a range of 100 meters and must utilise other technologies or devices for distances greater than 100 meters.

Did you know: Resource Data Management supplied and installed the first fully IP networked retail refrigeration system in 2001?

With Ethernet, it is possible to pass both power and data over the one cable which removes the need for an additional cable. Power over Ethernet (PoE) is available on a range of RDM products, reducing installation times and costs. An additional benefit to using Ethernet IP over other methods is that there is often no additional hardware required to interface with a device. Many modern laptop computers and most desktop computers have an in-built RJ45 port for Ethernet connectivity.


Similar to RS232, RS485 is a serial communication transmission standard. It can operate at a data rate of up to 10Mbits per second across distances up to 1,200m, however, speeds will always need to decrease for longer distances. RS485 is designed for a master/slave topology – one device reporting into another. As RS485 communicates at lower speeds than the likes of Ethernet it has the advantage of being more resilient to the noise present in industrial environments.

Generally, RS485 networks are limited to 32 devices on one network and under certain circumstances up to 128 devices. In comparison, IP networks can easily facilitate hundreds of devices.


RS232 is a standard for serial transmission of data (one bit sent at a time), widely used in computers and digital systems. RS232 can achieve speeds of up to 1.5Mbit per second across distances up to 20m. RS232 is a point-to-point communications method only and cannot be used to create a network of devices. While RS232 is low-cost, it has poor insulation against electrical noise and, as a consequence, may perform poorly in industrial applications of moderate distance. RDM controllers utilise RS232 as a method of communicating with another communications technology like Ethernet or RS485 but do not use it to create networks.


WiFi facilitates wireless local area network connections across various frequencies. Many WiFi enabled devices can connect to a wireless local area network via a wireless access point and then communicate with each other over WiFi and extended Ethernet networks. WiFi speeds can typically be up to 1Gbps. The range for WiFi is determined by the environment (indoors, outdoors, electrically noisy, etc.) the number of access points in a given area and the strength of the access points’ antennae.

Fibre Optics

Fibre optic networks have a long proven track record of providing data transmission backbones all around the globe. Fibre optic cables provide high reliability network connections which are not affected by electromagnetic noise and do not radiate any of the signal, making them more secure than traditional copper cabling. RDM products utilise 100Base-FX fibre optics which have a transfer rate of 100Mbits per second and a cable range of up to 2,000 meters.

Did you know: RDM were the first to introduce fibre optic networking directly at the controller level? Fibre optic communications are available on our DMTouch and TouchXL products.


USB (short for Universal Serial Bus) is an industry standard for physical connectors and communication protocols between computers and devices. USB is often used for both communication between devices and to power devices. Whilst the older USB 2.0 standard can transfer data at speeds of up to 480Mbits per second, the newer USB 3.0 specification allows for speeds up to 5Gbit per second, over ten times as fast. Typically, USB range is limited to 5 meters before it requires extension or repeater technology.

RDM Products and Communication Optimisation

Whilst communication technologies might be rated for certain speeds or distances, some RDM equipment has been tested to work to lower specifications in order to maintain effectiveness. Please consult individual product information before ordering.


Refrigeration & BMS | Posted on 11 Jul 2017


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