HVAC Techs, Start with the building envelope
The proper procedural sequence duty of a tech in this age of the reduction of energy usage is to first, reduce the heat-gain heat-loss of a building.
Then one can reduce equipment size & make an optimal match to the ductwork system.
http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html
http://www.udarrell.com/sizing_ac_duct.htm
- udarrell