Originally posted by RoBoTeq Turtle; once again I will try to explain that you are misreading the piston chart.
Take for instance the CKL30-1 condensing unit. The chart lists different capacity coils and what piston to use with each of these coils. Here is how you should be reading this chart;
"IF" you are using a 24,000 BTU coil, it will have a .059 piston in it. You must "change the .059 piston "to" a .065 piston in that coil. (note 3: purchase piston kit from distributor)
"IF" you are using a 29,000 Btu coil, it will have a .059 piston in it. You must change this .059 piston "to" a .065 piston. (note 4: the required .065 piston comes with the indoor coil)
"IF" you are using a 30,000 Btu coil, it will have a .065 piston already installed in it, so there is no need to change the piston.
"IF" you are using a 31,000 through 36,000 Btu coil, they will have .068 to .071 pistons in them respectively. YOU MUST CHANGE THE EXISTING PISTON IN ANY OF THESE COILS TO A .065 PISTON.
"IF" you are using a 42,000 to 49,000 Btu coil, they will have .078 to .082 pistons in them, respectively, and MUST BE CHANGED TO A .068 piston.
The .065 piston is required with all coils from 24,000 Btu nominal capacity to 36,000 Btu nominal capacity with a slightly large piston needed if you want to go even larger with the indoor coil.
There is no "range" of pistons allowed. There is one specific sized piston for each specific coil and the .065 piston is the standard piston for this unit.
This is turtle.
I can see where your explaining the goodman evaperator coil and a goodman condenser coil. You can use the exact Goodman flow rater kit of as you say a .065 kit # 17898-65. Now this is not true at all for your going to install a trane 3 ton evaperator coil on the furnace and then have the 2.5 ton condenser on it.
Now explain to me where in the goodman or Trane Piston chart do they state that there is a exact piston to be used for this match up of a 3 ton Trane evporator coil / and a Goodman 2.5 ton condenser. Now before you answer you may go back and see what the O.P. piston size was being used and worked very well. if i remember it was a .070 something size.
Now here is one to just look at about a Carrier size piston in their equipment match up which does sometime come close to Trane piston sizes.
Ever carrier piston size used in the old to new models of 2.5 ton condnsers and coils are as of 1995 was .063 to a .076 on different models. I would never try to tell you what size a piston and evaperator coil piston size i would use on a 2.5 ton goodman condenser for it to be exactly right. I could only guess or pick from the range. Now with not knowing the exact size piston to use, i would use your guess of a .065 for it being in the ranges of the units. there is nothing exact when mismatching the coils and condensers.