I have read that a low refrigerant charge in a refrigeration system can cause the system's evaporator to ice up. I happen to have a dehumidifier which is exhibiting this symptom. I do not expect to be able to repair the dehumidifier but, as something of an HVAC enthusiast, I am curious as to why and how this happens.
I am not by any means an HVAC technician, although I would like to understand refrigeration systems better than I do now.
I have a dehumidifier here which is definitely not suffering from a dirty evaporator coil or restricted airflow over the evaporator coil. It is currently operating in a room in which the temperature is 76 degrees Fahrenheit and the relative humidity is 58%. Nevertheless, the bottom part of the evaporator ices up after only a few minutes of operation:
Picture of Iced Evaporator
Of all the explanations I have read for why a dehumidifier's evaporator might ice over, only the "it has a slow refrigerant leak and hence a low charge" explanation seems to apply. But I don't understand why a low refrigerant charge would result in a portion of the evaporator becoming excessively cold, and I hope someone might be able to explain it to me.
For what it's worth, this dehumidifier was purchased in or around 2004, and I believe (but am not 100% sure) that it uses R-134a refrigerant.
Again, I'm not looking to repair the unit. Rather, I only want to learn more about how these refrigeration systems work and what might be causing this to happen.