25yr old unit. Open loop. So this all started about a year and a half ago. We noticed the bill was quite a bit higher than it should be. So after pulling out the multimeter and Doing some testing I noticed the start capacitor was toast(holding my breath and fingers crossed) I replaced it but the compressor was seized(was run low on refrigerant). Oh well. So I began my long quest to resolve the issue. After many hours on the phone only one contractor would take the job. So we replaced the compressor and it was unsuccessful. I'm a little rough of recollection but I replaced all the water lines to and from the unit and added a balancing valve and temperature probes. Well doing that I discovered refrigerant in the water lines(leak in the coaxil). At this point I'm realizing I have some issues. So trying to resolve this quickly( this is already 6 to 8 weeks into no heat in minus 30 degrees Celsius.) I opt to replace the coaxial,the reversing valve, and the expansion valve. So basically we replaced everything but the heat exchanger in the ducting. They made multiple trips over the next 2 to 4 weeks. All the refrigerant lines were freezing up and the coil was icing over. So we replaced the expansion valve. Still to no avail the system kept freezing up. So the owner came out and opened the valve as wide open as it would go and added more refrigerant for the 3rd time it seemed to run ok.( not great but it ran with out turning to a brick of ice) and now just over a year later I noticed it sounded just a little off. So I checked it and it was more frozen than it as ever. I don't believe this to be an airflow problem(cleaned the system twice ). It ran just fine without icing for many years until "they fixed it". Just my opinion it is due to lack of professionalism and knowledge. Not knowing how to size a systems components properly or the charge needed(possibly combined with a small leak..?). ANY help of advice would be appreciated.