I am designing a new HVAC system for a historic hotel. They currently have individual split A/C units for each room. Each AHU is a floor console, with the condensing unit on the roof. The hotel is 4 stories tall with 32 rooms. The refridgerant lines are running in the walls, floor, and ceilings in unknown locations. I wanted to locate them to save on demolition and disturbance. I had somebody out there today with a thermal camera ($10,000 unit), but in this historic building the walls are very thick with multiple wythes of brick, and we couldn't see most of the lines very clear at all. The liquid line is uninsulated, and it felt pretty warm at the unit, but it wasn't being picked up on the thermal camera. Then we tried a tone generator, and found that some of the line sets went down below to the celing space below, and we just couldn't follow the lines with much success. They tell me they have a more powerful "wand" which will be able to find the signal better through thick walls and more distance. I am hoping there will be some good insight from you all on a better solution. Right now I am thinking that we will need to cut several access doors in the ceilings and visually identify where the pipes drop down in the walls so that we can use the tone generator and wand with better success. This is a very high end and historic hotel, and I hate to do that. I really need to find these pipes because I will use some of them with a new Mitsubishi S-Series. Please advise if you have recommendations on finding refrigerant lines behind walls, ceilings, and floors.