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VRF:- Variable Refrigerant Flow

 VRF:- Variable Refrigerant Flow


What is Variable Refrigerant Flow?


The term “Variable Refrigerant Flow refers to the capability of a HVAC system to control the amount of refrigerant flowing to each of the indoor units/evaporators, enabling the use of multiple evaporators of differing capacities and configurations, individualized comfort control, simultaneous heating and cooling in different zones with heat recovery from one zone to another”


Variable Refrigerant Flow (VRF) System is an engineered direct expansion (DX) multi-split system incorporating at least one variable capacity compressor distributing refrigerant through a piping network to multiple indoor fan coil units each capable of individual zone temperature control, through a zone temperature control devices and common communications network. Variable refrigerant flow implies three or more steps of control on common, inter-connecting piping.


Why do we use VRF Systems?


• Decentralized System – Zone Comfort

• Efficiency – Pay for what you use

• Flexible

• Simple to design

• Easy to install and commission

• Good value


Indoor Unit Capacity Control


• Indoor units individually controlled by LEV

• LEV has 2 functions Control the superheat across indoor unit evaporator Acts as solenoid valve to stop refrigerant flow to indoor units that are off


Smart Indoor Coil Design


• If superheat is high

the valve will open

• If Superheat is low

the valve will close


Outdoor Unit Capacity Control


• Compressor speed is controlled by

a VFD based on common

saturated suction temperature

and capacity required

• Refrigerant volume flow is directly

proportional to the compressor

speed

• Power input is directly

proportional to the cube of the

compressor speed


Different VRF Systems


• 2 Pipe System cooling only

• 2 Pipe System heat pump cooling or heating

• 3 Pipe System simultaneous cooling and

heating

• 2 Pipe System simultaneous cooling and

heating – air cooled

• 2 Pipe System simultaneous cooling and

heating – water and geothermal application


DIVERSITY


1. Time of Day

     VRF System can heat and cool simultaneously

2. Heating & Cooling

     VRF System can efficiently distribute 

cooling capacity to keep up with changing 

solar loads

3. Occupancy

      As people move throughout a building, VRF System can move energy around to maintain comfort levels within setpoint


VRF Indoor Unit Overview


• 1,2 & 4 Way Cassette

• Ducted horizontal

• Ducted

 vertical

• Ceiling Suspended

• Wall Mounted

• Floor Standing

• Water heating

   modules



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