goodman ckl-18-1

[metal malone]

2 units side by side one a goodman ckl-18-1. The other goodman ckl-18-1-b . The 18-1 nameplate states charge to 53 oz. R22. The 18-1 b nameplate states to charge to 72 oz R22. Units look identical. Both units cooling exact square footage. Same size air handler. Whats the difference between the two

[bigtime]

The b needs 19 oz more refrigerent.

[metal malone]

Thanks bigtime. I counted that up and still had one toe left. But I am wondering why

[cjpwalker]

Probably a new revision. Check the dates on the serial numbers - 10 seer vs 13 maybe? Is there another row of coils on the 'b' unit?

19, huh? Fortunately men can count to 21. That's why we're better at blackjack than women.

[metal malone]

Thank you CJP. My apologies for posting on the welcome thread. Good day everyone

[V12tech]

A new split system's condensing unit has enough refrigerant to accommodate up to a 30 ft line set typically, only after this point is it required to add additional amounts per additional line set and size etc. Some units have more coil surface area and will have a condensing temperature closer to ambient than a same BTU condensing unit with a smaller coil surface area, hence efficiency rating.
A fixed metering device is a more critically charged unit as opposed to a modulating one such as a TXV valve that will have a receiver and can handle
being overcharged a bit better than the fixed type that are dependent on the ambient temperature/pressure relationship of the unit and it's refrigerant used, For example:
Under design conditions of 95F outdoors and 80F indoors and 50% humidity,..

A normal efficiency R22 condensing unit will condense around ambient plus 30F , So 95F ambient plus 30F = 125F
convert that 125F to pressure for R22 and you have 279#.

A more efficient condensing unit with a large coil surface area might hold 8 lbs or R 22 and condense at ambient plus 25F !!

Now for the indoors the TXV type will sense the suction lines temperature trying to maintain a 10F superheat about 1 foot after the evap coil, but no more than about 20F or so to the compressor if possible, as this is what cols the compressor besides the oil.
A 80 F room will require a 40F evap coil to provide a Delta T (temp differential) of 20F for a 60F supply grille air temp.
This is all design conditions and is ball park for the tecnicians with partially charged units