Is it normal for a geothermal system to make a lot of noise when it comes on, and also dim the lights in a house? Note that it isn't always "loud" when it comes on, and the lights don't always dim - I would guess its really loud 5% of the time, and just "vibrates" the unit all the other times. We had a geothermal system installed two years ago in our house. I believe that it is a 4 ton unit with a two stage system and around 400 feet of underground loop. We have had two compressors replaced. The compressors had sheared the mounting bolts each time. The contractor replaced a control module the last time that the compressor was changed, and mentioned that this should take care of the problem. At first the unit was very quiet when it came on, similar to what we experienced when the unit was first installed. Since that time, it has been getting louder when it comes on. It is quiet when it runs, its just the noise it makes when it comes on. I am concerned about the life of the system. Also, if it is drawing an excessive amount of current, it may be negating any energy/cost savings. I am getting ready to have the HVAC contractor come and take a look at the system again. I wanted a "second independent opinion" before doing that, from someone that has experience w/ other geothermal systems. Also, the first stage of our system rarely comes on, even when the thermostat is just one degree below the temperature setting - is this normal? Maybe I am being "overly concerned" knowing the history of this system. The contractor had refused to replace the unit up to this point.