1. What is the Recirculation Pump Sizing Formula?

The recirculation pump sizing formula calculates the required flow rate (in gallons per minute) based on the heat load and temperature difference in the system. This is essential for proper hydronic system design.

2. How Does the Calculator Work?

The calculator uses the flow rate formula:

Where:

• 500 — Constant that accounts for the weight of water (8.33 lb/gal) × 60 min/hour × specific heat (1 BTU/lb-°F)
• Heat Load — Total heat to be moved by the system (BTU/hour)
• ΔT — Temperature difference between supply and return (°F)

Explanation: The formula balances heat transfer requirements with the water's thermal properties to determine the necessary flow rate.

3. Importance of Proper Pump Sizing

Details: Correct pump sizing ensures efficient system operation, prevents energy waste, and maintains proper heat distribution throughout the system.

4. Using the Calculator

Tips: Enter heat load in BTU/hour and temperature difference in °F. Typical ΔT values range from 10°F to 20°F for most hydronic systems.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical ΔT for residential systems?
A: Most residential systems use 20°F ΔT, while radiant floor systems often use 10-15°F ΔT.

Q2: How do I determine my system's heat load?
A: Heat load should be calculated by a professional based on building heat loss calculations or equipment specifications.

Q3: What if my system uses glycol?
A: Glycol solutions require flow rate adjustments - typically 10-20% higher flow rates than water-only systems.

Q4: How does pipe size affect pump sizing?
A: While this calculator gives flow rate, pipe size affects head pressure which is needed for complete pump selection.

Q5: What's the 500 constant in the formula?
A: It's derived from water's properties: 8.33 lb/gal × 60 min/hour × 1 BTU/lb-°F = ~500.