A 14-section interactive reference guide covering ASHRAE standards for HVAC engineering and mechanical systems design. Includes psychrometrics, cooling and heating load calculations, duct sizing, the refrigeration cycle, chiller and cooling tower selection, VRF systems, ASHRAE 62.1 ventilation requirements, and ASHRAE 90.1 energy code compliance.
Each section targets a core HVAC discipline: system types and the design process (Section 1), psychrometric properties and ASHRAE design conditions (Section 2), ASHRAE RTSM cooling load components with sensible/latent formulas (Section 3), heating load calculations and winter design conditions (Section 4), equal friction duct design and velocity limits (Section 5), air distribution CFM rules and ASHRAE 62.1 outdoor air rates (Section 6), the vapor compression refrigeration cycle and refrigerant transition (Section 7), chiller types and cooling tower approach temperature (Section 8), boilers and hot water system GPM formulas (Section 9), heat pumps and VRF diversity/piping rules (Section 10), ASHRAE 62.1 VRP ventilation calculations and MERV filtration (Section 11), DDC controls and BAS sequences (Section 12), ASHRAE 90.1 energy code system selection and fan power limits (Section 13), and a master quick-reference formula table (Section 14).
Use the Prev / Next buttons at the bottom of the reader, or press the arrow keys on your keyboard. Click the ☰ menu button in the top-right corner to open the table of contents and jump directly to any section. The gold progress bar at the top tracks your position through all 14 sections. Scroll wheel also advances slides.
This guide references ASHRAE 62.1-2022 (ventilation), ASHRAE 90.1-2022 (energy), ASHRAE 55-2023 (thermal comfort), ASHRAE 15-2022 (refrigeration safety), ASHRAE 34-2022 (refrigerant classification), ASHRAE Guideline 36-2021 (sequences of operation), ACCA Manual J (residential load calculation), and ACCA Manual D (duct design). Always verify the adopted edition with your local authority having jurisdiction (AHJ) before applying code-specific values.
The sensible heat formula Q = 1.1 × CFM × ΔT assumes standard air density at sea level (0.075 lb/ft³) and specific heat of 0.240 Btu/lb·°F — apply altitude correction factors above 2,000 ft. The GPM formula GPM = Q / (500 × ΔT) uses 500 as a constant combining water density (8.33 lb/gal) and 60 min/hr. For chilled water, always verify ΔT assumptions against actual coil selections. Duct sizing friction rates of 0.08–0.10 in.wg/100 ft apply to commercial; use 0.06–0.08 for residential per Manual D.
Standard design uses 400 CFM/ton for cooling and 350 CFM/ton for heating with a forced-air system. Supply air is typically delivered at 55–60°F for cooling (10–15°F below space temperature) and 90–120°F for heating. At 400 CFM/ton, a 5-ton system moves 2,000 CFM total.
Choose a design friction rate of 0.08–0.10 in.wg per 100 ft of duct. Using a duct calculator (Ductulator) or ASHRAE Handbook tables, size each duct section to achieve this friction rate at the required CFM. Keep main supply velocities under 900 FPM and branch ducts under 700 FPM for low-noise systems.
Per ASHRAE 62.1-2022 Table 6-1, offices require 5 CFM per person plus 0.06 CFM per square foot of floor area. For a 10-person, 2,000 sq ft office: (10 × 5) + (2,000 × 0.06) = 50 + 120 = 170 CFM minimum outdoor air.
EER (Energy Efficiency Ratio) measures efficiency at a single operating condition (95°F outdoor, 80°F/67°F indoor). SEER (Seasonal Energy Efficiency Ratio) measures efficiency over an entire cooling season across varying conditions. SEER is always higher than EER for the same unit. Minimum standards: 14 SEER (northern US), 15 SEER (southern US) as of 2023; SEER2 is the new rating method.