The other week I ran across a Carrier system that had a 4ton Cond and Evap. However, the furnace was a 110k 80% furnace with a 3 ton drive...
Would that affect any performance? It seemed to have worked for the last 2 summers. Seems to be functioning okay with a 22 degree split.
As you are aware you have ~1200 CFM of airflow when you have a requirement for 1600CFM.
Many manufacturers will allow the system to operate at a minimum of 350CFM per ton which would still require 1400CFM for the 4 ton system.
What you will encounter is a low sensible capacity, high latent capacity with the possibility of a frozen coil if the airflow becomes restricted or if the system is operated at low ambient conditions.
This could also lead to compressor floodback which will eventually damage the compressor.
I am more interested in the superheat and subcooling along with indoor and outdoor conditions. The temperature drop may be high for the evaporator entering air conditions.
Need more information to make any call on the mismatch. It could be a 3 / 4 furnace. It could also be a "4 ton" condenser with 40,000 btu compressor.