The picture here is the nameplate to a split system air conditioning system. This label states that this 2 Ton outdoor air conditioner requires 3 pounds and 14 ounces of R22 refrigerant. This does not mean that the system only requires 3 pounds and 14 ounces of Freon. Most manufacturers put enough Freon into the outdoor unit to compensate for up to 15 feet of line set. This does not include that amount of Freon required for longer line sets and does not include the amount of Freon required for the evaporator coil.
You can safety assume that this 2 Ton air conditioner system contains approximately 6 pounds of Freon total in a normal 25 foot line set installation with a matching coil. Add 2 pounds to the outdoor unit specification will cover most units. This is not the way to charge the unit with Freon, just give you a best guess as to the maximum amount of Freon that the system will take.
The higher the efficiency of your 2 Ton air conditioning system the more Freon on average that it will contain than less efficient products in the same product line. The reason for this is that a 2 Ton air conditioner at 20 SEER will have more coils for the Freon to travel through to dissipate the heat the Freon contains. More coil space equals greater efficiency, but also equals more room for the Freon to fill. So a 2 Ton 13 SEER air conditioner will contain less Freon than a 20 SEER 2 Ton air conditioner.
The reason take your 2 Ton air conditioner will have less Freon in it than an identical 2 Ton model which is a heat pump is that the heat pump contains a couple of extra controls. It has a reversing valve and a receiver or accumulator. The reversing valve merely changes the flow of the Freon, but adds refrigerant space to the 2 Ton heat pump. The accumulator or receiver will be installed in the 2 Ton outdoor unit and operates to prevent liquid slugging of the compressor during the heat mode. This will add a considerable amount of refrigerant space depending upon the size of the accumulator.
The shorter the line set the better your 2 Ton air conditioner will work and less amount of Freon your 2 Ton system will use. In the picture of the Freon chart we can see the effect of line set sizing and length on the amount of Freon that a system uses. A typical line set size for a 2 Ton air conditioner is ¾” and we can see that in R22 Freon systems we will need to add 0.62 ounces of Freon for each foot of line set over 15 feet. A fifty foot line set will cause you 2 Ton air conditioner to use an additional 1 pound 5.7 ounces. If we are using R410a or Puron (same thing) we add 0.51 ounces per foot and we come up with an additional amount of Freon of 1 pound and 1.85 ounces.
The 2 Ton outdoor condensing unit contains a refrigerant charge equal to 15 feet of line set and a matching 2 Ton evaporator coil. The manufacturer of the air conditioning system will allow a smaller evaporator coil by one size and a larger evaporator coil by 2 sizes. The smaller coil is for use in very humid parts of the country and will allow the 2 Ton evaporator coil to be colder and remove more moisture from the air. The large coil will increase cooling of the air and increase the SEER and EER of the system. In our climate here in Southern California we want the larger coil. This does mean that additional refrigerant will be required. Unfortunately there are no charts that I have been able to find to tell me how much Freon to add. It is only a few ounces though.
A 2 Ton air conditioning system’s Freon charge will be affect by the heat exchange rate of the indoor evaporator coil and the outdoor evaporator. The higher the humidity the more heat is transferred and the charge of the Freon will be slightly different. The thermostatic expansion will throttle back this Freon or let more pass through the evaporator as the temperature and humidity decreases and increases. This adding and subtracting of Freon according the temperature is much more prevalent in the older fixed orifice systems (10 SEER and older).
Older systems require more Freon. The efficiency gains in the newer equipment have them performing much better with much less Freon. A few years back I came across a 4 Ton system from Comfortmaker that required a minimum of 18 pounds on the label. That is an incredible amount of Freon for a single residential system.