1. What is Hydronic Flow Rate?

The hydronic flow rate is the volume of water required to transfer heat through a hydronic (water-based) heating or cooling system. It's a critical parameter for proper system design and pump selection.

2. How Does the Calculator Work?

The calculator uses the hydronic flow rate equation:

Where:

• 500 — Constant that accounts for the specific heat of water (1 BTU/lb-°F) and the weight of water (8.33 lb/gal)
• Heat Load — Total heating or cooling requirement in BTU per hour
• ΔT — Temperature difference between supply and return water

Explanation: The equation calculates how many gallons per minute (GPM) of water flow are needed to transfer the specified heat load given the system's temperature difference.

3. Importance of Flow Rate Calculation

Details: Proper flow rate calculation ensures adequate heat transfer, prevents undersizing or oversizing of pumps, and helps maintain system efficiency and comfort.

4. Using the Calculator

Tips: Enter heat load in BTU/h and temperature difference in °F. Typical ΔT values are 20°F for heating and 10°F for cooling systems, but always verify with system specifications.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for residential systems?
A: For a 100,000 BTU/h boiler with 20°F ΔT: ~10 GPM. For a 3-ton (36,000 BTU/h) chiller with 10°F ΔT: ~7.2 GPM.

Q2: How does ΔT affect flow rate?
A: Higher ΔT means lower required flow rate. Doubling ΔT halves the required flow rate, reducing pump size and energy use.

Q3: What if my system uses glycol?
A: Glycol solutions require flow rate adjustments (typically 10-20% higher) due to different specific heat and viscosity properties.

Q4: How do I account for multiple zones?
A: Calculate flow rate for each zone separately, then sum for the main pump. Consider diversity factors for simultaneous operation.

Q5: What about head pressure?
A: This calculator determines flow rate only. You'll need additional calculations for head pressure to properly select a pump.