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HVAC School - For Techs, By Techs

Jan 17, 2019

In today's podcast, I talk to John Oaks about his experience as a VRF tech in the field, including branch boxes and two-pipe vs. three-pipe technology. John primarily works on the troubleshooting and service side rather than the installation and programming side of the field.

Variable refrigerant flow (VRF) systems, also called VRV systems when manufactured by Daikin, are commercial HVAC systems. VRF systems work best in commercial buildings with some degree of fragmentation, like offices and medical facilities. These systems are similar to multi-zone ductless systems, but they operate on a much larger scale. VRF systems have a branch box, which acts to direct traffic between the various zones of a building and parts of the system; the branch box allows the unit to heat and cool simultaneously.

A 24v signal drives most of the controls. These controls are "daisy-chained," as VRF systems are very interconnected, and a defrost signal can have up to about 50 destinations to various components. The entire VRF installation process requires careful attention to detail, not just on the programming side.

When it comes to common issues with VRF systems, the refrigerant charge is one of the most critical problem areas. These systems mask issues with the charge, so it is difficult to find out if a system is undercharged or overcharged. In addition, you can't weigh out the charge in the same way that you would in a residential system.

John and Bryan also discuss:

  • Metering device placement
  • Industry improvements and upgrades
  • Inverter boards
  • Line set length and charge issues
  • Flares, brazing, and ZoomLock
  • Condensate removal and drainage strategies
  • Diversity of zones and efficiency
  • Two-pipe vs. three-pipe configurations
  • Cooling mode, heating mode, and mixed conditions

Learn more about Refrigeration Technologies HERE.

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