HVAC Renovations: VRF Systems

Whether you’re the facility maintenance manager, a system specialist, or an up-and-coming crew member looking to show your worth, you know how important it is to run an efficient facility. You also know that heating and cooling account for the most significant expenses at any commercial facility. So, what if we told you that we could improve efficiency in your HVAC system while also reducing the hefty expenses that come with it? With a Variable Refrigerant Flow HVAC system, you can do just that.

Discover how you can improve efficiency in your #HVAC system while also reducing the hefty expenses that come with a #VariableRefrigerantFlow (VRF) in @RasMech’s latest blog: Click To Tweet

What’s Different About This System?

Like most other systems, VRF HVAC units consist of an outside unit and inside fans. The difference, however, is that a VRF HVAC system uses refrigerant to push cooled or heated air throughout a series of small air handlers. This allows for each handler to control the amount of hot or cold air entering into an area. Unlike other options, VRF systems can produce 30% to 40% energy savings, which is significant when 50% of a building’s energy usage comes from its HVAC system. VRF systems are essentially a ductless system that distributes refrigerant to different zones through refrigerant piping.

VRF system operation

When it comes to VRF systems, they tend to be a nontraditional HVAC systems choice, in comparison with conventional ducted systems circulating the air or chilled-water throughout the building. The term VRF translates to the ability of the system to vary and control the refrigerant flow through multiple evaporator coils to provide individual temperature control in various mechanical comfort zones.

By using direct expansion (DX) throughout the system as part of the basic refrigeration cycle, VRF systems will transfer the heat from the room directly to evaporator coils located within the space that’s being conditioned. The heat-transfer carrier, in this case, is the refrigerant, which delivers heating and cooling to various zones with less energy as compared with air or water.

Each VRF system acts as a multi-split system – connecting multiple indoor units with one centralized outdoor condensing unit assembly while providing simultaneous heating and cooling and heat recovery in various zones as follows:

  • The VRF heat pump system provides heating and cooling for all indoor units during a specific time
  • The VRF’s provide cooling and heating which doesn’t occur at the same time
  • Heat-recovery systems provide simultaneous cooling and heating as well as heat recovery, resulted in transferred energy from cooling zones to heating zones of the building.

All of the above features can be accomplished by using VRF-enhanced technology: 

  • Variable-speed and capacity-modulated inverter duty compressors
  • Outdoor fans with variable frequency drive motors
  • Indoor units with electronically commutated motors (ECM).

Ready to Make the Switch?

Many large companies are making the switch to sustainable practices. Commercial facilities are no exception. The efficiency of a VRF HVAC system is considered to be of added value in many sustainable programs and certifications, such as LEED®.

Whether you’re designing a new facility or changing out the unit at your current place, a VRF system is a great way to save space in a commercial building. These units often don’t require air ducts to deliver air throughout the facility. The evaporators can be installed within the ceiling or wall-mounted.

A noteworthy feature of a VRF HVAC is the ability to control the temperature of each area. Rooms with outside facing walls may need more warm air during the winter, and cool air during the summer than those in the center of the building. By controlling how much heat or warmth is distributed by each handler, you can ensure that all occupants are comfortable.

[Need help implementing climate control strategies to reduce stress and energy consumption on your HVAC? Read: Climate Control Strategies to Reduce HVAC Stress.

Is VRF the RIGHT solution for your building? If you check off any of these… It’s time to make the switch: 

  • Your building requires some areas to be colder while others to be warmer
  • Your building has or needs quick temperature changes
  • You need a low-cost HVAC solution
  • Your building was designed to have a ductless system
#VRFhvac units have arguably the best control over the airflow in each space of a facility which leads to overall facility efficiencies and cost reduction. Find out more benefits with @RasMech: Click To Tweet

With a typical central HVAC system, you lose all forms for heating or cooling when you need to work on the unit. During the blazing hot summer or the frigid winter months, lacking a system that will maintain the temperature of a large facility quickly becomes noticeable. A single degree drop in the winter or rise in the summer can drastically decrease occupant comfort. Plus, when the unit is back up and running, you will face an increase in utility costs to get the facility back to the norm. Since a Variable Refrigerant Flow HVAC system contains a series of air handlers, technicians can work on one handler at a time while leaving other units operable. This reduction in downtime is both comfortable and cost-efficient.

The advantages of a Variable Refrigerant Flow HVAC system include:

  • Increased energy efficiency and energy savings. This can average about 20-30%  energy savings relative to variable air volume systems with reheat and constant air volume systems with gas heat.
  • Develops efficient part-load performance due to inverter-duty variable-speed compressors modulating the capacity from 10-100%.
  • Holds efficient zoning control from simultaneous cooling and heating with heat recovery.
  • Reduces ductwork and duct losses that can be confined to the ventilation air system (approximately 20% of the conventional HVAC system).

A modern VRF system can provide technicians some major advantages, such as zoning, individual temperature control, minimized ductwork, excluding the need for secondary fluids (chilled-water or hot-water distribution), and associated costs. All of this technology consists of a single outdoor condensing unit, multiple indoor units serving various zones, refrigerant piping with branch selectors, and associated controls.

Many VRF systems will require an R-410A refrigerant for the heat-transfer fluid and the working fluid. This allows the system to achieve a high energy-efficiency ratio (EER) of 15 to 20, while developing an integrated energy-efficiency ratio (IEER) of 17 to 25. VRFs are 20-30% more efficient than conventional HVAC systems due to its ability to utilize a partial load operation, speed modulation, zoning capabilities, and heat-recovery technology.

From the benefits above, you’ve probably gathered that a VRF HVAC system is incredibly efficient. These units have arguably the best control over the airflow in each space of a facility which leads to overall facility efficiencies and cost reduction – two things that every maintenance man or woman works hard to achieve at their facility.

Variable Refrigerant Flow HVAC System: FAQ 

Q: How does it provide simultaneous heating and cooling?

A: VRF can simultaneously heat and cool a building by absorbing residual heat when cooling one zone and redirecting it to another zone, resulting in less energy waste and more productivity.

Q: Can a VRF only be used in commercial buildings?

A: No, it can be used in both residential and commercial. VRF systems can be scaled to meet the climate control needs of a small single-family residence all the way to commercial, high-rise buildings.

Q: Are VRF systems difficult to install?

A: Not at all! VRF equipment weighs much less than ducted equipment which happens to make it easier to install, especially for those with limited space.

Stay Compliant with Codes and Standards

If you’re thinking about renovating your VRF system, it’s essential that you’re implementing the most current codes and standards. All VRF systems must comply with ASHRAE Standard 15 (packaged with Standard 34): Safety Standard for Refrigeration Systems and Designation and Classification of Refrigerants. This adheres to refrigerant capacities and possible leakage for systems that serve small rooms, and could cause oxygen depletion.

Earlier, we mentioned that all VRF systems use the refrigerant R-410A. The safety classification of R-410A in ASHRAE Standard 34 is classified in group A1: nontoxic and nonflammable refrigerant with zero ozone-depletion potential. Due to the ability of oxygen depletion, ASHRAE Standard 34-2013 Addendum L has established the maximum refrigerant concentration limit (RCL) of 26 lbs/1,000 ft3 of room volume for occupied spaces.

According to Standard 15, a VRF system is classified as a direct system/high-probability system where a refrigerant leak can potentially enter into the occupied space.

ASHRAE Standard 15 requirements should be applied to all VRF system designs in the following steps :

  • Determine the occupancy classification for the rooms
  • Calculate room volume
  • Determine the amount of refrigerant in the system including the outdoor unit, indoor units, and associated piping
  • Verify that the room is not too small using the following formula:

Minimum allowed floor area (sq ft) = Total system refrigerant charge (lbs) x 1,000 RCL (lbs/1,000 ft3) x ceiling height (ft)

Whether you’re convinced a Variable Refrigerant Flow HVAC system is the right choice for your facility or you have questions on how to make the most out of your current system, don’t hesitate to reach out to your single-source provider, Rasmussen Mechanical Services, to discuss any of your HVAC needs.

This article was originally published on March 13, 2019. It was updated on September 24, 2019. 

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