HVAC System Load Calculation

HVAC Load Equation:

\[ \text{Total Load (BTU/h)} = \text{Conduction} + \text{Infiltration} + \text{Ventilation} + \text{Internal Gains} \]

Conduction Load:

BTU/h

Infiltration Load:

BTU/h

Ventilation Load:

BTU/h

Internal Gains:

BTU/h

Total HVAC Load:

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1. What is HVAC System Load Calculation?

HVAC load calculation determines the heating and cooling capacity needed for a building. It considers heat transfer through walls (conduction), air leakage (infiltration), required fresh air (ventilation), and heat from occupants and equipment (internal gains).

2. How Does the Calculator Work?

The calculator uses the basic HVAC load equation:

\[ \text{Total Load} = \text{Conduction} + \text{Infiltration} + \text{ventilation} + \text{Internal Gains} \]

Where:

Conduction — Heat transfer through walls, roof, windows (BTU/h)
Infiltration — Heat loss/gain from air leakage (BTU/h)
Ventilation — Heat load from required fresh air (BTU/h)
Internal Gains — Heat from people, lights, equipment (BTU/h)

Explanation: The equation sums all heat sources to determine the total heating or cooling capacity needed.

3. Importance of Load Calculation

Details: Proper load calculation ensures HVAC systems are correctly sized - neither undersized (inadequate comfort) nor oversized (short cycling, poor humidity control, higher costs).

4. Using the Calculator

Tips: Enter each component load in BTU/h. For detailed calculations, use Manual J or other professional methods to determine individual components.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between heating and cooling load calculations?
A: While similar, cooling loads consider solar gain and latent heat (humidity) more significantly than heating loads.

Q2: How accurate is this simplified calculation?
A: This provides a basic estimate. Professional Manual J calculations consider hundreds of factors for precise sizing.

Q3: What are typical BTU/h requirements per square foot?
A: Roughly 20-30 BTU/h per sq.ft. for cooling in moderate climates, but varies greatly with insulation, climate, and other factors.

Q4: Why not just oversize the HVAC system?
A: Oversizing leads to short cycling, poor humidity control, higher energy costs, and reduced equipment lifespan.

Q5: How often should load calculations be updated?
A: Whenever making significant building modifications (insulation, windows, additions) or every 10-15 years as standards change.