FWIW....PLEASE don't use propane to re-charge ANY refrigerant system, unless that system was designed and labled to be used with propane. I work with automotive refrigerants every day and aside from the fact that you can severely damage if not ruin someones multi-thousand dollar piece of equipment via contamination in the event that you have to have it serviced professionally, most refrigerants and oils DO NOT INTERMIX! They can become caustic and litterally eat away at the metals inside your unit. Use only the type of refrigerant that was originally used in the unit, and in most cases will require an HVAC or MVAC certification to purchase. These units, like home A/C units are built "sealed" and should not need service unless a leak developes. In the event that a leak has developed in your unit, charging it without repairing it will likely only lead to you wating your money on refrigerant that is simply destroying the environment. Do yourself a favor and have a certified HVAC technician take a look at it.