Understand the Guidelines for Additional R-454B RefrigerantUpdated 11 days ago

Introduction

This article provides guidelines for selecting the appropriate additional charge of R-454B refrigerant according to the piping length. In addition, the article provides formulas for calculating the additional charge of refrigerant. 

Note: The only mode approved for verifying the system charging is in Forced Cooling mode. The outdoor temperature must be between 68-113°F (20-45°C), while the indoor temperature must be between 68-89°F (20-32°C). 

Additional Refrigerant Guidelines

Weigh-In Method

Use the weigh-in method during the initial installation or when replacing a system charge. In addition, use this method when power is not available or operating conditions are not in optimal range. 

The factory charge in the outdoor unit is sufficient for 25 feet (7.62 m) of standard size interconnecting liquid line. An additional 0.54 oz/ft of R-454B refrigerant is needed when the length of the lineset is more than 25 feet (7.62 m). 

Note: Subcooling (Cooling mode) is the only recommended charging method when the outdoor ambient temperature is between 68-113°F (20-45°C) and the indoor ambient temperature is between 68-89°F (20-32°C). For more information, see this article. 

New Installations

Calculate the additional charge for linesets greater than 25 feet (7.62 m). 

1. Total length of line (m/ft) = (a)
2. Standard line setup = 25 ft (7.62 m) (b)
3. (a) - (b) = (c)
4. Refrigerant multiplier = 50g/m (0.54 oz/ft) (d)
5. Additional refrigerant quantity (c*d) = (e) - Note: If the lineset is less than (25 ft / 7.62 m), (e) = 0

Sealed-System Repairs

Calculate the total system charge. 

1. Total length of line (m/ft) = (a)
2. Standard line setup = 25 ft (7.62 m) (b)
3. (a) - (b) = (c)
4. Refrigerant multiplier = 50g/m (0.54 oz/ft) (d)
5. Additional refrigerant quantity (c*d) = (e) - Note: If the lineset is less than (25 ft / 7.62 m), (e) = 0
6. Factory filling quantity (nameplate) = (f) 
7. Total system charge (e + f) =