V-III Refrigerant Charge Calculator
This article explains how to calculate the total refrigerant charge for a V-III VRF system using up to three outdoor units.
- Total refrigerant charge = A + B + C
- A = Total factory charge of all connected outdoor units
- B = Total outdoor-unit additional charge shown by the calculator
- C = Additional refrigerant for total liquid pipe length
- 1/4 in. pipe: 0.021 kg/m
- 3/8 in. pipe: 0.058 kg/m
- 1/2 in. pipe: 0.114 kg/m
- 5/8 in. pipe: 0.178 kg/m
- 3/4 in. pipe: 0.268 kg/m
Calculation Structure
| Section | Description |
|---|---|
| A | Combined factory refrigerant charge for Outdoor 1 (Master), Outdoor 2 (Slave 1) and Outdoor 3 (Slave 2), where applicable |
| B | Combined additional charge associated with the selected outdoor unit models |
| C | Additional refrigerant charge calculated from the total applicable liquid pipe lengths |
Total Refrigerant Charge (kg) = A + B + C
Step 1 - Select the Outdoor Units
Select the applicable outdoor unit models in the calculator:
- Outdoor 1 - Master
- Outdoor 2 - Slave 1, where fitted
- Outdoor 3 - Slave 2, where fitted
The calculator provides the factory charge and any model-based additional charge for each selected outdoor unit.
Step 2 - Calculate Section A
Add the factory charge for all selected outdoor units.
If only one or two outdoor units are installed, unused outdoor unit positions remain at zero.
Step 3 - Calculate Section B
Add the additional charge values shown by the calculator for each selected outdoor unit.
Step 4 - Enter Additional Pipe Lengths
Enter the total applicable pipe length in metres for each liquid pipe size.
| Pipe Size | Additional Charge Rate | Calculation |
|---|---|---|
| 1/4 in. | 0.021 kg/m | Length (m) x 0.021 |
| 3/8 in. | 0.058 kg/m | Length (m) x 0.058 |
| 1/2 in. | 0.114 kg/m | Length (m) x 0.114 |
| 5/8 in. | 0.178 kg/m | Length (m) x 0.178 |
| 3/4 in. | 0.268 kg/m | Length (m) x 0.268 |
Add the calculated charge for all pipe sizes together. This becomes Section C.
Step 5 - Calculate Total Refrigerant Charge
Worked Example
The following example demonstrates the calculation method only.
- Combined factory charge (A): 20.00 kg
- Combined outdoor-unit additional charge (B): 1.50 kg
- 1/4 in. pipe: 20 m
- 3/8 in. pipe: 30 m
- 1/2 in. pipe: 15 m
- 5/8 in. pipe: 10 m
- 3/4 in. pipe: 5 m
Pipe charge:
- 20 x 0.021 = 0.42 kg
- 30 x 0.058 = 1.74 kg
- 15 x 0.114 = 1.71 kg
- 10 x 0.178 = 1.78 kg
- 5 x 0.268 = 1.34 kg
Total pipe charge (C):
0.42 + 1.74 + 1.71 + 1.78 + 1.34 = 6.99 kg
Total system refrigerant charge:
20.00 + 1.50 + 6.99 = 28.49 kg
Maximum System Charge
| Outdoor Unit Configuration | Maximum System Charge |
|---|---|
| 1 Outdoor Unit | 31.5 kg |
| 2 Outdoor Units | 63 kg |
| 3 Outdoor Units | 94.5 kg |
Technician Checklist
- Select the correct Master and Slave outdoor unit models.
- Confirm the factory charge for each outdoor unit.
- Add the factory charges to calculate Section A.
- Add the calculator's outdoor-unit additional charges to calculate Section B.
- Measure the applicable 1/4, 3/8, 1/2, 5/8 and 3/4 in. pipe lengths.
- Calculate the pipe charge for each size and add them together to calculate Section C.
- Calculate the total system charge using A + B + C.
- Confirm the result is below the applicable maximum system charge.
- Record the final refrigerant charge on the commissioning documentation.