VRV/VRF System Pipe Sizing

Course Title:

VRF / VRV System Design and Pipe Sizing (Daikin)

Module 1 – Introduction

• VRF (Variable Refrigerant Flow) definition

• VRV (Variable Refrigerant Volume) definition

• Terminology difference (VRV patented by Daikin)

• Applications & benefits

• One outdoor can connect >60 indoor units

Module 2 – Components & Refrigerants

• Compressors:

  • Digital Scroll Compressor

  • Inverter Scroll Compressor

• Refrigerants: R-410A, R-407C, R-32, R-454B

• VFD (Variable Frequency Drive) operation

  • Power frequency relation to compressor speed

Module 3 – System Types

• Cooling Only VRF

  • Variable speed scroll compressor

  • Electronic Expansion Valve (EEV)

• Heat Pump VRF

  • Cooling or heating (not simultaneous)

  • Uses 4-way Reversion Valve & NRV

• Heat Recovery VRF

  • 3-pipe system

  • Cooling & heating simultaneously

Module 4 – Capacity & Piping Limits

• Capacity range: 3 TR to 42 TR (10 kW to 150 kW)

• Max piping length (Daikin example):

  • 150 m same level

  • 50 m ODU above IDU

  • 40 m ODU below IDU

• Daikin pipe sizing conditions:

  • Max total length = 1000 m

  • Max equivalent length = 190 m

  • Max 13 m branch to last ODU

  • Max 90 m from first indoor branch to farthest IDU

  • Max level difference ODU–IDU = 90 m

  • Max level difference IDUs = 30 m

  • Max level difference ODUs = 5 m

Module 5 – Diversity Factor

• Concept in VRF design

• Not all IDUs run at full load simultaneously

• Example: 20 HP total indoor load with 15 HP ODU

Module 6 – Design Process (Daikin Example)

1. Collect project requirements – building survey

2. Perform heat load calculation (E-20 Excel, HAP)

3. Select indoor units (IDUs)

4. Select outdoor unit (ODU)

5. Design refrigerant piping layout in AutoCAD

6. Perform pipe sizing (manual or software)

Module 7 – Pipe Sizing Basics

• Purpose:

  • Ensure correct refrigerant flow

  • Avoid oil return issues

  • Maintain performance & efficiency

• Pipes: liquid, gas (suction), discharge (heat recovery)

• Refnet joints/Y-branch connectors

• Pipe sizing rules:

  • Size increases after each branch

  • Different for horizontal/vertical

  • Long run adjustments (>40 m) require 1-step larger pipe

Module 8 – Manual Pipe Sizing Steps (Daikin)

1. Verify pipe conditions

2. Find CI of indoor units & update on Refnet

3. Size pipe between Refnet & IDU (Table 5)

4. Size pipe from ODU to first Refnet (Table 9 or 10)

5. Size pipe between Refnet to Refnet (Table 6 or 7)

6. Select outdoor branch kit (Table 4)

7. First Refnet from branch kit (Table 3)

8. All other Refnet updates (Table 2)

Module 9 – Common Issues from Wrong Pipe Sizing

• Poor cooling/heating

• Oil return failure → compressor damage

• Refrigerant pressure drop → efficiency loss

• System alarms/trips