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PF OLSEN service supplier


To meet current building compliance in New Zealand, Renegade Electrics was tasked with designing and implementing a system for safely switching on/off 64 newly installed air conditioning units and 8 ventilation fans in the main HQ building's four wings during fire alarm activation. This building automation solution aimed to restrict passive airflow to prevent fueling/spreading fires.

Building Automation

PLC controlled HVAC panels installed.

Zelio PLC Relay controlling HVAC for building automation and control.


We quickly identified that it would also be possible to automate/isolate  the HVAC equipment (Heating/Ventilation/Air Conditioning) to maximize energy savings and equipment longevity for out of hours non use. Four PLC controlled contactor panels were designed, assembled and installed adjacent to each of the HVAC panels  and individually networked back over the local ethernet network to a master HMI user interface. A single fire alarm trigger input or alarm panel armed/disarmed input to the master controller will subsequently cycle off/on all four of the HVAC controllers via the local ethernet communication network  to meet  the customers requirements. Additional temperature monitoring and control was implemented into each HVAC controller enclosure to ensure no risk of fire/equipment damage should prolonged usage occur.

PLC  HVAC panel displaying current state


We utilized four Schneider Zelio SR3B101BD PLC modules  with Modbus network cards to provide the automation and communication of the HVAC contactors. 

As building automation specialists, we leveraged the Ethernet networking capabilities of these controllers for a seamless installation process, eliminating the need for extensive cabling. Utilizing Modbus TCP/IP communication protocol and enabling port forwarding, we ensured remote access over the World Wide Web, facilitating efficient and cost-effective control solutions.

We utilized a Schneider HMISTU-655 HMI (Human Machine Interface) to enable end user control, monitoring and trending for on/off times and enclosure temperatures. The end user or technician can access and interact with this information either  locally on  the site panel or remotely  off-site  via a smart phone or tablet.

Smart phone HMI screen for control and monitoring of PLC automation equipment.

HMI panel displaying partial way through HVAC  cycle  (Green is On - Orange is Off)

Temperature trending on a smart phone HMI screen for building HVAC equipment monitoring and control.

HMI panel displaying enclosure temperatures.

Zelio Smart Relay PLC controller for HVAC temperature control and monitoring.


Temperature protective control is implemented to ensure each enclosure does not overheat. A thermistor constantly monitors internal temperatures and will cycle of the stages of  for that individual controller if the temperature reaches in excess of 40oC. The controller will remain off until the temperature is within range, and then cycle the stages back on.  The HMI is programmed to show logging trends, events and alarms. Panel over temperature  conditions are an unlikely scenario as the enclosure has panel ventilation and the trending clearly  demonstrated a consistent temperature range between 22oC - 37oC.

PLC  HVAC panel displaying enclosure temperature.

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