Refrigerant R744 Charge Factor
WARNING: This page is about a different car, the 2022 Volkswagen ID.4 and 2021 Volkswagen ID.4. However, it is still accessible from the selected car via links, so may be relevant.
- When filling compressed-gas cylinders (return cylinders, recycling cylinders etc.) the applicable regulations, technical regulations and laws must be observed.
- Overfilling of compressed-gas cylinders (return cylinders, recycling cylinders etc.) must always be avoided. Overfilled compressed-gas cylinders do not have a sufficient gas cushion to accommodate the liquid expansion caused by the effects of heat. There is a danger of rupture.
- To ensure safety, only use compressed-gas cylinders fitted with a safety valve.
- A canister must have space for vapor as well as liquid. As the temperature rises, the liquid expands. The space filled with vapor decreases. At a certain point, there will only be liquid in the canister. Beyond this, even a slight increase in temperature causes a large amount of pressure to build up in the canister as the liquid attempts to continue expanding despite the absence of the necessary space. The forces that result are strong enough to rupture the cylinder. To prevent a cylinder from being overfilled, the regulations regarding compressed gases specify how many kilograms of refrigerant may be added to a cylinder per liter of internal volume. The product of multiplying this charge factor by the internal volume of the cylinder is the permissible capacity. The figure for refrigerant R744 used in motor vehicles is 0.74 kg (1.63 lbs)/liter.
- A certain density for refrigerant R744 in the refrigerant circuit is specified by the vehicle manufacturer in order to operate the A/C system. The density specifies how many kilograms of refrigerant R744 per m3 of available internal refrigerant circuit volume are added. The capacity for refrigerant R744 was calculated for a particular available internal refrigerant circuit volume. The available internal volume is approximately 250 g (8.8 oz)/Liter.
- If the density is exceeded, the static pressure in the refrigerant circuit increases sharply and the pressure relief valve activates (at a density of 400 kg (881.85 lbs)/m3 [or 0.4 kg (0.88 lbs)/Liter], for example, the static pressure will already start to increase to 144 bar (2, 088.55 psi) at an ambient temperature of 80 °C (176 °F)). Refer to REFRIGERANT VAPOR PRESSURE TABLE .