Do refrigerant blends components separate if there is a leak?


 

The simple answer is no. The individual components of a blend do not separate out of a blend, but you may get composition shift, in some circumstances.

 

Azeotropic mixtures behave like pure substances and do not separate with the composition of the liquid being the same as in the vapour.

 

The situation with zeotropic mixtures, requires more explanation if there is a leak.

 

Blends composing of fluids of similar properties where they have a very small temperature glide have only a very small difference in the component composition between the liquid and the vapour phases. In the case of a leak, simply topping up will usually keep the blend within the component specification. i.e. R-404A, R-410A.

A blend with a greater difference (for example R-407C) can see a small composition shift if a system has a leak. Usually fixing the leak quickly can prevent any significant change and can be topped up keeping the blend within specification. A more prolonged gradual leak may lead to an increased risk of composition shift and depending on the type of leak and its location in the system may affect the composition of the fluid left in the system.

 

To try and establish any significant shift in composition, simply measure the pressure/temperature ratio and this will show if the mixture has changed from its initial proportions. Acceptable pressure difference is P< 0.3 to 0.5bmax.

 

When a blend leaks, all components of the blend will leak, but in some circumstances the composition of the leaking blend will have slightly more of the lower boiling components. However, it should be noted that no individual component leaks on its own.