Manual J vs Rule of Thumb: When to Use Each
Manual J is a room-by-room load calculation; rules of thumb estimate tonnage from square footage. How each works, why oversizing hurts, and when each is appropriate.
What Size Heat Pump Do I Need? A Guide for Cold Climates
Size a heat pump for both cooling and heating with balance-point analysis for cold climates, climate zone factors, and when to add backup heat.
Furnace Sizing Guide: What Size Furnace for My House?
Find the right furnace BTU for your home by climate zone and insulation with AFUE adjustment, worked examples, and why oversizing is the most common mistake.
HVAC Delta T: Normal Range and What a Bad Reading Means
What Delta T (temperature split) means for AC and furnaces, the normal ranges, how to measure it, and what high or low readings tell you about a system.
Superheat vs Subcooling: A Field Guide for HVAC Techs
What superheat and subcooling mean, how to measure each, normal target ranges for TXV and fixed-orifice systems, and what readings tell you about refrigerant charge.