Below is a post written by Bruce Longino, head of Engineering at Mingledorff’s.  The virtues of ductless HVAC systems have been touted recently, and especially those of VRFZ (Variable Refrigerant Flow Zoning).  Here, Bruce elaborates on these systems, and how they can benefit in design.      

“Why are Variable Refrigerant Flow Zoning [VRFZ] Systems so popular?”

by W. Bruce Longino, P.E., LEED AP

Worldwide, Variable Refrigerant Flow Zoning systems have been the dominate design templates for commercial HVAC systems. For some reason, this has not been the case in the United States of America.

Fortunately, this trend is shifting in the States, as there’s been a huge movement toward VRFZ as a common method of design. There are many reasons for this shift, particularly in the New Construction and the Retrofit & Replacement market segments. Perhaps the most significant influence in these sectors is the incredible variety of air handling equipment.

New Construction

If an Architect is aware of the advantages of the VRFZ system, he/she can save building costs. First, because the duct size is generally much smaller than that of standard systems, the building can be shortened due to reduced required plenum height. Secondly, there is no longer a need for Mechanical Rooms.

Furthermore, VRFZ systems are as efficient as water cooled systems, but without the cost of water treatment, not to mention the cost of the water itself. Inverter Driven Compressors, diversity, and heat reclaim allow such efficiencies.

To elaborate, as the load decreases, the Inverter Drive Compressor reduces speed. This increases efficiency because the compressor- at, say 50% RPM- is using less than half of the full load energy, yet the condenser and evaporator service areas are still 100%. With the compressor able to match the load requirements, it no longer needs to cycle on and off. This consistency allows more effective humidity control.

In most cases, the VRFZ systems operate with a significant amount of diversity. The combined tonnage of the fan coils may be as much as 50% more than the outdoor heat pump. Additionally, the number of indoor fan coils-per-outdoor heat pump can be as many as fifty. With multiple fan coils serving multiple exposures, as well as varying levels of human load, this system can simulaneously operate in a variety of ways.

Heat reclaim occurs when some zones are cooling while others are heating. When this occurs, the VRFZ system uses the heat removed by zones in cooling to provide that heat where needed elsewhere.

In addition to all these advantages of the VRFZ, the indoor and outdoor units are very quiet. A thirty ton VRFZ outdoor heat pump can make less noise than a builder grade three ton heat pump. The indoor fan coils operate as low as 22 dB(A).

VRFZ systems are also available with Direct Digital Controls, so the Owner can monitor the HVAC system in his/her building. As these controls come standard with the systems, there is no additional cost associated.

Here’s the bottom line in New Construction: a building designed with VRFZ systems can be cost-competitive with more traditional systems. Once the building owner factors in all the additional benefits (without additional up-front cost), VRFZ can be a very attractive and beneficial solution.

Retrofit & Replacement

In the Retrofit & Replacement market, all the benefits of the New Construction installation are realized, but this is just the beginning.

The refrigerant lines for a VRFZ system can be routed into an existing house or commercial building through three-inch-diameter holes. Often in the case of more traditional retrofits, major demolition would have to occur to do this.

Another big advantage of the VRFZ system is that it can be installed without the removal of the existing system. Then, when the VRFZ system installation is complete, it can be activated and the existing system can then be abandoned in place.  In addition, the outdoor heat pumps are modular. They can be seperated for easy maneuvering (i.e. brought up in a freight elevator), then later assembled together to operate as single outdoor units.

I hope this article has helped to highlight the significant advantages of the Variable Refrigerant Flow Zoning System. There are a lot of opportunities out there to design and install them.  Keep an eye out!  If you have any further questions on VRFZ, feel free to contact me at blongino@mingledorffs.com.