Our 3 yr. old geothermal 1 ton attic system occasionally shuts off. Each time we are told various reasons cause the shut down. The most recent shut down was caused by low refrigerant levels, we needed 2 lbs. added. We noticed our most recent maintenance agreement was ironically changed from the prior 2 agreements to omit, yes you guessed it,2 lbs. refrigerant added if needed. So we had to pay for the refrigerant. Now I am wondering what comes next. If we need refrigerant there must be a leak? Or does it somehow evaporate in the system over time? Our geo system is still under warranty. I want to approach the business that installed our system but thought I could use more information before hand. Any thoughts on this? Is it common? Is this toxic?