Section 6.1.1/Refrigerant Charge Limits
ASHRAE 15 Section 6.1 covers refrigerant quantity limits based on safety group, room volume, and occupancy type.
The quantity of refrigerant in a system is limited based on the refrigerant's safety classification (A1, A2L, A2, A3, B1, B2L, B2, B3), the volume of the smallest occupied space the refrigerant could leak into, and the occupancy type. For common A1 refrigerants (R-410A, R-134a), the refrigerant concentration limit (RCL) must not be exceeded if the entire charge leaks into the smallest connected space. For A2L refrigerants (R-32, R-454B), the lower flammability limit (LFL) fraction applies. Systems exceeding the charge limits must have the equipment located in a machinery room or outdoors.
Why this section exists
A refrigerant leak in an occupied space can displace oxygen (causing asphyxiation with large charges of A1 refrigerants), create toxic concentrations (B-class refrigerants like ammonia), or create flammable atmospheres (A2, A2L, A3 refrigerants). The charge limits ensure that even a complete system leak cannot create dangerous conditions in the occupied space. These limits are becoming more critical as the industry transitions from high-GWP A1 refrigerants to lower-GWP A2L alternatives that have mild flammability.
What plan reviewers look for
Plan reviewers check the refrigerant type and charge on the equipment schedule. They calculate the concentration if the charge leaks into the smallest connected space and compare it to the RCL or LFL from Table 4.1.1. If the charge exceeds the limit, they verify the equipment is in a machinery room or outdoors. For A2L refrigerants in new systems, they check for the additional safety requirements (leak detection, ventilation).