Freon 407C is a zero ozone depletion blend of HFC refrigerants Freon 32, Freon 125, and Freon 134a. It closely matches the properties of Freon 22 and is used in many air conditioning applications. They include: New residential and other unitary air conditioning, non-fl ooded evaporator chillers. With few modifi cations, Freon 407C can be used in the same equipment designed for use with Freon 22. Retrofi t of existing Freon 22 systems. However, Freon 407C should not be used as a direct, “drop-in” replacement. Also, you should not use Freon 407C in equipment that uses a fl ooded evaporator because of the zeotropic behavior within the system. Since Freon 407C is a zeotropic blend, it helps to understand terms like bubble point, dew point, fractionation, and glide. Bubble point, or saturated liquid temperature, is the temperature at which Freon 407C (at constant pressure) begins to evaporate. Or in other words, the temperature where the fi rst bubble of vapor appears in liquid Freon 407C. Bubble point is equivalent to boiling point for single component refrigerants. Dew point, or saturated vapor temperature, is the temperature where condensation begins (at constant pressure). Or, think of dew point as the temperature at which the last droplet of liquid evaporates and saturated gas exists. It corresponds to the condensation point of a single conponent refrigerant.
Bubble point and dew point are used to describe the behavior of zeotropic blends in an evaporator and condenser. Boiling point is not used because the blend’s temperature changes as it evaporates or condenses. Fractionation describes how a refrigerant blend like Freon 407C changes from a liquid to a vapor or vice versa. Since the components of Freon 407C evaporate (or condense) at diff erent rates in the evaporator (or condenser), the blend’s composition constantly changes between the bubble point (-46.12°F/-43.4°C) and dew point (-33.16°F/-36.2°C at one atm). Once the temperature exceeds the dew point, Freon 407C is in a superheated vapor state. Glide describes the diff erence in temperature between the evaporator outlet and inlet due to fractionation. Glide can vary, depending on the state of the liquid refrigerant at either end of the evaporator (or condenser) or on pressure losses. At most common system pressures, Freon 407C has a temperature glide of 9 to 12 degrees F.