Basically you must be sure that the compressor is 18 thousand the same as the previous one, now the next thing to consider is the physical space. that fit or fit the outlet and inlet, the pipe diameter is not as critical if they are both 18 will handle a similar flow (I speak of equipment that uses the same refrigerant) important point because depending on this will be the oil to use see to the tables or technical sheet, the rotary capacitor usually uses 20uf and the 20uf piston. In the case of the capillary it is similar although valve is more efficient (but more expensive than capillary) and I recommend you monitor the nominal current value because the piston ones consume more current (you will pay more light) and check the wiring for weak points, something else Remember to make a good sweep, greetings I hope it serves you,