Helium has the molecular weight of 4. This makes the helium molecule smaller next to Hydrogen. Because of the smaller molecular weight it can able to escape from small leaks pretty easily compared to refrigerant. Therefore Helium is used in leak detection. Helium has the other advantage of inertness.

On and after Jan 1^st ,2015 HCFC refrigerants are banned for new systems. Use of HCFCs are allowed for existing systems

Higher Ozone Depletion Potential of CFCs attributes to stability of CFCs in lower atmosphere. Presence of Hydrogen in the HCFC refrigerant compound reduces its stability and are less likely reaching stratosphere where 90% ozone layer present

Presence of Hydrogen in HFC refrigerant compound makes it unstable at lower levels of atmosphere

High Pressure Gauge – Red
Low Pressure Gauge – Blue

Nitrogen constitute of about 78% of air we breathe. It is colorless, odourless, non flammable, stable and non inert gas. Dry Nitrogen is used as leak detection gas and purging gas in HVAC system

Boiling point of the refrigeration liquid depends on the surrounding pressure. Liquids vaporize when the molecules are apart and faster. As pressure increases, an external force is applied on the refrigerant molecules to be close to each other. Therefore boiling point of the liquid increase with increase in pressure

In Condenser refrigerant changes phase from gas to liquid after expansion. This liquid refrigerant reaches evaporator and absorbs heat (eg: from room) to change from low pressure liquid to low pressure vapor

Refrigerant gas in condenser rejects the latent heat of vaporization thus converting from gas to liquid

Bubble point temperature is which the refrigerant just start to evaporate and Dew point is one where the last refrigerant evaporate

Ideal Refrigerant should have low boiling point. Refrigerant liquid should vaporize at the evaporator to cause cooling. Higher the boiling point the compressor should able to create too much vacuum for refrigerant to evaporate.  Low specific heat & high latent heat increases the refrigeration effect for kg of refrigerant.

Lower the molecular weight of the refrigerant compound, easier the refrigerant to escape from the small leak as the size of the molecules are small