Retrofitting VRF Systems

VRF systems have recently begun capturing a growing market share. In many new hotels, VRF has become the ultimate HVAC system given its efficiency, comparable cost to other HVAC systems, and the reduced footprint requirement compared to chilled/hot water systems. However, no system is perfect and the VRF is no exception. VRFs do not easily integrate to existing automation systems. Moreover, the VRF OEM controls may not be compliant with the increasingly stringent energy efficiency codes, such as IECC 2018, and Title 24 (California).

Retrofitting VRF thermostats requires a good understanding of each manufacturer’s capabilities to choose the best option available. The first step is to ascertain the model number and brand of each indoor unit to establish compatibility requirements. One must also establish what type of VRF system was installed – heat-pump or heat-recovery. Controlling a heat-recovery system using Verdant thermostats is easier than controlling a VRF heat pump because the system can respond to heating and cooling commands simultaneously. Simultaneous heating and cooling commands from the heat-pump indoor units may produce unexpected results and comfort issues.

Heat recovery systems pose no problems for the Verdant system. With heat pump systems, other parameters should be considered. If the heat pump system is installed in a climate zone dominated by heat such as ASHRAE Zones 1A and 2A, the Verdant system will perform well provided that the differential for switching from cooling to heating is set to at least Δ7degF. For other ASHRAE climate regions such as zone 3,4 and 5, heat pump systems paired with Verdant thermostats will not perform adequately and may cause comfort issues.

Once these details have been ascertained, please consult Verdant to determine the best option for your project. Depending on the manufacturer and the compatibility analysis, Verdant has two architectures.

For LG and Mitsubishi VRFs, Verdant has a direct connection to the indoor unit like a native LG or Mitsubishi thermostat would. For other manufacturers, a protocol converter is necessary to communicate with indoor units using Modbus. With this approach, key control functionalities of the VRF are preserved such as room temperature and setpoint communication between the thermostat and the indoor unit.