COLUMN ENGINEER'S NOTEBOOK information from the VRF control system. Filters Finally, the COVID era brought about a mass move to MERV 13 fi lters. Don't assume that every ducted VRF fan coil can use a MERV 13 fi lter, and recognize that there may be fi lter housing alterations or accessories required. Talk to your VRF rep to be sure the equipment you've scheduled can support the fi lters you specifi ed. Conclusion VRF offers the potential for very good effi ciency and good ability to account for load diversity. It can often control fan coil leaving air temperatures as well as a chilled water system, at least down to moderately low load conditions. But some things are unique to VRF. Even if every good practice is completed in the initial design, the assumption that a design is done when it leaves the consultant's offi ce is simply incorrect. The piping and distribution box portion of the project often takes a couple of iterations to get right as fi eld conditions dictate piping route changes and/or component relocation, and not all contractors understand that process. Design and redesign due to real-world conditions extends well into the VRF project's installation phase. Delays in getting software/fi rmware updates to get condensing units that were provided earlier on the same page with fan coils that came along later will typically take place at the last minute, as occupancy dates approach. The old model of having the consultant design the job and then lose contact with it from that point forward leaves a lot in the hands of the contractor, and even if commissioning agents are involved they have no way to weigh in on the situation unless they at least know how to actually measure and check some of the piping as-builts. I'd go so far as to say that a VRF commissioning effort that does not check the actual piping layout against the manufacturer's software is missing the point. Good construction projects have always required a good construction team that is together from beginning to end of a project and communicates effectively, and VRF systems have made this even more important. J A N U A RY 2 0 2 3 ashrae.org ASHRAE JOURNAL 25http://permapipe.com http://www.ashrae.org