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Frequently Asked Questions

What is VRF?

VRF is short for “Variable Refrigerant Flow”. It is a type of direct expansion (DX) multi-split system that incorporates a variable capacity compressor with a network of multiple indoor fan coil units. A VRF system increases efficiency by providing cooling or heating only to the individual zones where conditioning is required. Most VRF systems also employ a stand-alone controls and communications network.

How is a VRF system different from a conventional system?

A conventional system usually operates at a fixed speed. On days where the full capacity is not required, the system will turn off and on to maintain the space temperature. These systems will also have a single indoor unit connected to a network of ducts. A fan distributes air through the ducts and brings return air back to the central system. This is less efficient than a VRF system because it can only heat or cool the entire system; there can only be one set point. Also, the fan and duct losses of a conventional system can add an additional 30% to the total energy consumption.

What is a Heat Recovery or Simultaneous VRF system?

A heat recovery VRF system has the ability to cool one room (pull heat from one room) and distribute heat to another room. By doing this, the efficiency of the system is improved. While this is effective for some applications, there are also additional material and installation expenses associated with Heat Recovery. For many applications, the energy savings does not justify the additional installation costs. Instead, by using proper zoning and system design, a Heat Pump VRF system can be designed to provide comfort for all occupants.

How is the efficiency of VRF rated?

Prior to January 1, 2010, VRF systems were rated using the Integrated Part-Load Value (IPLV). This is the same method used to calculate part-load efficiency of chillers. However, after January 1, 2010, ASHRAE 1230 defined IEER as the standard rating for VRF systems.

How is IEER Calculated?

The IEER rating requires that the unit efficiency be determined at 100%, 75%, 50% and 25% load (net capacity). These efficiency values are then weighted based on real world conditions with each efficiency given a weighted value using the following equation:

IEER = (0.020 · EER@100%) + (0.617 · EER@75%) + (0.238 · EER@50%) + (0.125 · EER@25%)

Because if improved part-load performance of VRF systems, IEER values should always be better than full load value of the system.

How is it possible for a VRF system to produce better part-load efficiency?

When a VRF system is operating at part-load capacity, the heat transfer across the indoor and outdoor coil is significantly improved. For example, if a 20 ton VRF system were operating at 50%, it would be delivering the performance of a 10 ton system. However, this “10 Ton System” would have the coil surface area of a 20 ton system. This drastically improves the efficiency of this system

What is the Heating Seasonal Performance Factor (HSPF)?

HSPF is the total heating output of a heat pump, including supplementary electric heat, necessary to achieve building heating requirements during its normal annual usage period. This is calculated by dividing heating by the total electric power consumed during the same period.

Does a VRF system require Traps and Sight Glasses?

Because of efficient oil management, a VRF system does not require any traps or sight glasses. Instead, most of the oil is collected in the oil separator, located immediately after the compressor. For the small amount of oil that makes its way into the system, a VRF system will go into “oil recovery” mode. During oil recovery, the compressor ramps up and pushes any lingering oil back to the accumulator where it can be returned to the compressor.

Can I deliver greater than 10 tons from a 10 ton system?

This is a common misconception. A VRF system often allows for a greater connected capacity than the condensing unit. This is beneficial for applications where there are multiple zones which have a large total capacity, but where every room will not call for heating/cooling at the same time. A VRF system can shift the load to the occupied rooms based on changes in demands. However, this system will never be able to provide more than the maximum total capacity of the outdoor unit.

Do VRF Systems qualify for LEED points?

Yes! Depending on the features which are installed, a VRF system can qualify for up to 40 LEED points.

Is VRF expensive?

A VRF system uses a combination of advanced electronics and precision mechanical components to deliver the highest efficiency possible.  As such, the initial cost for a VRF system tends to be more than most conventional systems. However, when you take into consideration the quality of the system, ease of installation and the reduced energy consumption (which represents 80% of the lifecycle cost of the equipment), a VRF system is almost always the most economical option.

 




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