Why does the air conditioning unit in the house freeze when you change the filter?

Answer 1

Short answer: Your system is low on refrigerant. Long answer: The only things that will cause an evaporator coil to freeze are; 1. It has a low coolant charge. 2. It has restricted air-flow. The low coolant charge causes dramatic coolant temperature changes when going through the evap. coil resulting in a colder than normal coil. The restricted airflow causes less heat transfer to the coil resulting in colder than normal coil. The coil of an HVAC unit running in AC mode should be @ or about 40 degrees... if you slow down the air crossing the coil, the "radiator" doesn't pick up as much heat as it needs to stay at that temperature, and begins to freeze the humidity that usually drains out of the housing through that PVC fitting you see comming out of it. Have an HVAC company come out and check the AC system, but be ready for some bad news... If you are noticing the system freezing up, chances are you have a refrigerant leak. (This is very bad, in that the system is a "Sealed system" nothing in, nothing out) That being the case, you will need to have it changed... the fast fix is a "re-charge". But it's just a band-aid on cancer... it will mask the symptoms, but won't fix anything. sorry. email me directly with further questions. Jack at discovertexasproperties dot com (just replace the "at" with @ and the "dot" with . )