Preview Mode Links will not work in preview mode

HVAC School - For Techs, By Techs

Jun 25, 2020

Jordan Cummings is back to discuss some of the most important points in the proper installation of VRF and VRV systems. We especially cover piping best practices.

When it comes to piping, the biggest concerns on VRF and VRV systems are making sure the piping can handle the refrigerant velocity and ensuring proper oil return. Most VRF systems use PVE oil, but you still want to be cognizant of oil type, as not all manufacturers use PVE. You must consider fittings, length, and elevation changes when you pipe a VRF or VRV system.

In our suction line, we want minimal pressure drop because too much suction drop reduces the mass flow rate through the compressor. You also need to think about avoiding too much of a pressure drop on the dual pressure line when it sends refrigerant to the compressor.

You want your piping to be below the connections on the outdoor unit. The piping should be pitched up towards the unit when the outdoor unit is elevated on a stand. Of course, you'll also want to be mindful of where you place the outdoor units; the units should avoid the elements and be mindful of any awnings above.

VRF/VRV systems come together at a variety of joints, including REFNETs and wyes (multi-chassis kits). Indoor units use REFNETs, which are basically engineered, balanced wyes. Outdoor units use typical wyes. Positioning these joints also makes a huge difference when it comes to proper feeding.

Jordan and Bryan also discuss:

  • Pipe sizing with software
  • Dual pressure line
  • PVE vs. POE oil
  • Miscibility and oil carry
  • Air-cooled vs. water-cooled condensers
  • Condensate drains and trapping
  • Reduced pumping/flow on water-cooled condensers
  • External static pressure
  • Alarms
  • Piping limitations
  • Cross piping on the branch selector box
  • Expansion valve staying shut
  • Pipe expansion
  • 550 PSI, 24-hour pressure test
  • Testing as you go

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.