HVAC & Electrical Engineering Guides
37 free, in-depth engineering guides covering HVAC system design (heating/cooling load, duct sizing, pipe flow, pump head, radiator sizing, boiler sizing) and electrical calculations (Ohm's Law, wire sizing, voltage drop, NEC compliance, and more).
HVAC Design Guides
Heating Load Guide
ASHRAE, GB 50736, and SHASE-S 101 standards. Key parameters, formulas, and common mistakes for accurate heat loss estimation.
Cooling Load Guide
Unit-index method, orientation/insulation/window corrections per ASHRAE, GB 50736, and SHASE-S 101.
Duct Sizing Guide
ASHRAE/SMACNA, GB 50736, and SHASE-S 010 velocity standards. Calculate duct dimensions from airflow and velocity targets.
Pipe Flow Guide
Continuity equations, velocity guidelines, and common design mistakes for HVAC water and steam systems.
Pump Head Guide
Total dynamic head calculation: Darcy-Weisbach friction loss, local losses, static head, pump power, NPSH, and FAQs.
Radiator Sizing Guide
EN 442 and GB/T 13754 standards. ΔT correction formula, radiator output matching, and real-world installation tips.
Pipe Insulation Guide
Heat loss calculation, condensation prevention, material comparison (fiberglass, mineral wool, foam, calcium silicate), and common design mistakes.
Boiler Sizing Guide
Heat loss calculation, efficiency correction, altitude derating, fuel types, and common sizing mistakes for residential and commercial applications.
Expansion Tank Sizing Guide
Acceptance factor, fluid type effects, tank type comparison (bladder vs open), and common mistakes for closed and open HVAC systems.
HVAC Unit Converter Guide
Conversion factors for power, air flow, pressure, temperature, and efficiency units. Common mistakes and practical engineering applications.
Electrical Design Guides
Ohm's Law Guide
Voltage, current, resistance, and power. DC circuits, NEC/IEC standards, and real-world examples.
Electrical Power Guide
Real/reactive/apparent power, power factor, single and three-phase systems.
Watts to Amps Guide
DC, single-phase, three-phase systems. Power factor effects on current draw.
Amps to Watts Guide
Circuit types, voltage effects, and practical wiring applications.
Voltage Drop Guide
NEC 210.19 compliance, single-phase and three-phase circuits, conductor sizing for branch circuits and feeders.
Wire Size Guide
NEC 310.16 ampacity tables, voltage drop limits, copper vs aluminum, temperature derating factors.
Wire Ampacity Guide
NEC Table 310.16, temperature correction, bundle derating, and insulation type selection.
Circuit Breaker Sizing Guide
NEC 240, 125% continuous load rule, motor protection, AIC ratings, and coordination.
Motor Current Guide
NEC 430 FLA tables, starting current, service factor, and overload protection sizing.
Conduit Fill Guide
NEC Chapter 9 tables, fill percentage limits, jam ratio, and practical installation guidelines.
Box Fill Guide
NEC 314.16 conductor count, device deduction, clamp fill, and grounding conductor rules.
Electrical Load Guide
NEC Article 220 demand factors, residential and commercial load calculation methods.
Transformer Guide
kVA sizing, voltage ratio, single and three-phase connections, impedance and efficiency.
Power Factor Correction Guide
Capacitor sizing, kVAR calculation, energy savings analysis, and harmonic considerations.
Energy Consumption Guide
kWh calculation, electricity tariffs, appliance ratings, and standby power analysis.
Electricity Cost Guide
Rate structures, peak/off-peak pricing, cost per kWh by region, and energy-saving strategies.
Solar Panel Guide
System sizing, panel count estimation, payback period calculation, and efficiency factors.
Resistance Guide
Series and parallel circuits, resistor color codes, temperature effects, and tolerance analysis.
Voltage Divider Guide
2 and 3-resistor dividers, loaded vs unloaded circuits, and precision considerations.
RC Time Constant Guide
τ=RC, charge/discharge curves, 5τ rule, and timing applications in filter and delay circuits.
Capacitor Code Guide
3-digit code decoding, pF/nF/μF conversion, tolerance codes, and ceramic vs electrolytic types.
HP to kW Guide
Mechanical vs electrical HP, metric HP, and efficiency adjustment for motor sizing.
Lumen Guide
Illuminance standards by room type, LED vs incandescent efficiency, and lighting design basics.
AWG to mm² Guide
American Wire Gauge to metric conversion, conductor properties, and cross-reference tables.
Insulation Resistance Guide
Megger testing, minimum values per IEEE 43, temperature correction, and pass/fail criteria.
Conduit Offset Bend Guide
Offset formulas, shrink calculation, bend marks, and EMT/rigid conduit techniques.
Electrical Quote Guide
Material takeoff, labor estimation, overhead markup, profit margin, and professional quoting templates.