I have a Trane XE1000 heat pump (fixed Orifice). The previous owner change the indoor air-handler however, never changed the heat pump and condenser coil. Before selling the house he replaced the compressor on the unit as well. For the last 2 years we've been having to re-charge the system with R-22. Almost every year we lose about 2lbs of refrigerant and when we switch it on to A/C the indoor coil freezes up. The last two technicians indicated that the leak is likely at the coil because there is heavy corrosion on the base of the coil where it makes contact with the pan.
Both technicians tried to do a leak test using a "sniffer" but couldn't find anything. I bought a sniffer and spent hours around the compressor and evap coil and it never went off. I even tried soap water around the connections on the evap coil but got nothing.
Due to money, I was planning to replace the evap coil and recharge the system with R-22a. I took measurements of the Evap coil and I see a few coils on this site *.*/viewcatego ... *
that seem to fit OK,with some modification made. to the cabinet panel. I have brazed before and have an idea on the procedure of "pumping down" and cutting out the old evaporator coil. However I have several questions.
1. How do I find the tonnage of the old coil. It's a XE1000 which indicates it should be around 3.5 to 4 tons. But when I look in the specs it list different coil sizes that can go on this unit. When I took the panel off there is no more model numbers to indicate what the coil model was to indicate size.... When I buy a new coil do I have to be exact in the size or is it OK for it to be slightly larger. The coil is a fixed Orifice.
2. When I remove the old coil will it have some leftover oil inside? Also will I have to replace that oil?
3. Are there any online guides regarding recharging a R-22a, I understand you use much less. Also do you have to calculate superheat/supercool. Since this is a fixed orifice should it be easier?