R410A (classified as A1, non-flammable) and R32 (classified as A2L, low flammability) differ considerably in terms of their properties, meaning that direct retrofit using R32 is a cause for serious concern. 

FETA has noted that a number of points must be considered:

• Refrigerant manufacturers have clearly stated that A2L refrigerants are not suitable for retrofit.
• A system that was originally designed for R410A will not have taken into account the safety factors required when using an A2L refrigerant and could create a significant safety hazard. Systems designed for use with R32 have different pressure switch regimes, altered inverter profiles, and specially designed heat exchangers.
• Charging an existing system with R32 would leave the system non-compliant with the refrigerant safety standard EN378, leading to the possibility of forming a flammable atmosphere in a leakage situation.
• Such a refrigerant change would be strictly against the system manufacturer’s instructions, and would render any relevant warranty invalid. It would also mean that the system would no longer be compliant with its original CE marking or the Pressure Equipment Directive specifications, and could have insurance implications.
• R32 has a higher compressor discharge temperature than R410A, and will increase wear on the compressor, reducing its life significantly.
• Should any problem arise from a system change such as this, any liability would rest entirely with the person who carried out the change.

It is not good practice to charge a system with a refrigerant for which it was not originally designed, and it is strongly discouraged.