This is my first time on here. Just a matter of note my back ground was E&I Tech., so have a technical background. I have lived in a complex for 7 yrs, bought house new, with 60 houses on a geothermal system. The system is open loop & I am assuming supply & return form 2 loops supply loop & return loop, with take offs for each house & return water going into main return loop. Most houses are upwards of 12 years old. To my knowledge there have been no problems with heating until this year. We have experienced lower than normal temps. Sometimes below 0 deg C for longer periods of time. There have been problems with upwards of 15+ units. I am not sure of exact number. I have asked around & some units are keeping up fine while others do not. Some units have had problems within units themselves & others have not. In my case the HVAC Tech made a modification to my unit to take care of potential freezing conditions within unit. I hope I understood this correctly. My unit works better somewhat. Still not totally satisfied. My unit was supplying air with a temp. of 30 Deg C & then one day dropped to 20 Deg C. I had determined that the 30 Deg C is a normal temp, from over the years of checking. One resident replaced his unit with a Bosch & still has problems. I believe most units, at least mine is a Climate Master 2T unit. I did a rough calculation & came up with a size of 2.5T. I do know some others are identical. I do believe water temp, dont know what temp is, is lower than previous years as I always noticed that over water lines snow would not accumulate until larger amounts of snow had fallen. Then when you shoveled over these areas snow was always slushy. I am not sure how deep these lines are buried. Not confident they are lower than 3-4 ft. Also I am assuming water pressure will play a big part in efficiency as well. With more units calling for heat is it possible that pressure will drop below a level where system works efficiently?? I hope I have supplied enough information to have someone provide some hints as to what problems we may be experiencing. As a matter of note I live on west coast of Canada where temps are normally above freezing, & may drop for a day or 2. This year we have experienced upwards of 2 weeks below freezing.