How is 3 ton condenser and 5 ton coil different than 5 ton 2 stage on low stage?

[shellboy]

Reading all replies to earlier thread regarding a 5 ton coil with a 3 ton condenser, I was wondering how much different that is when compared to a 5 ton coil with a 5 ton 2-stage condenser? Amana/Goodman rate their low stage as 65% of high stage, which theoretically would be 3.25 ton and 5 ton condenser- both stages using a 5 ton coil.

[SBKold]

In the field it's more like 75-80%

[shellboy]

In the field it's more like 75-80%

What about the brands that have two compressors (Trane?) and operate at 50% and 100%, or 2.5 tons and 5 tons, with a 5 ton coil?

[SBKold]

What about the brands that have two compressors (Trane?) and operate at 50% and 100%, or 2.5 tons and 5 tons, with a 5 ton coil?

Yes the coil will adjust via the thermal expansion valve and airflow will drop according to compressor technology. Then proper sizing and ductwork are key to deliver longer more efficient run times in low stage.

[shellboy]

Yes the coil will adjust via the thermal expansion valve and airflow will drop according to compressor technology. Then proper sizing and ductwork are key to deliver longer more efficient run times in low stage.

So given the coil/condenser size mismatch in low stage, should the low stage operate at something less than 400 CFM/ton? Should high stage operate at 400 CFM/ton or more? Does a newer 5 ton compressor really have 5 ton capability (60,000BTUs)?

[beenthere]

So given the coil/condenser size mismatch in low stage, should the low stage operate at something less than 400 CFM/ton? Should high stage operate at 400 CFM/ton or more? Does a newer 5 ton compressor really have 5 ton capability (60,000BTUs)?

CFM should be based on the indoor RH.

At 105°F condensing temp they do.