Geothermal Loop Sizing Guide
A geothermal loop connects a heat pump to steady earth temperature. The loop must move enough heat without excessive pumping cost. A small loop may freeze, overheat, or lose capacity. A large loop costs more than needed. This calculator gives a planning estimate before detailed design.
What the calculator checks
The tool starts with the building load. You can enter tons, kilowatts, or BTU per hour. It then adjusts the load for heating or cooling operation. Cooling usually rejects compressor heat into the ground. Heating usually extracts less heat than the delivered output, because the compressor also adds heat.
Loop type changes the starting length. Vertical bore fields often need fewer surface feet. Horizontal trenches need more land. Slinky loops pack pipe into shorter trenches. Pond loops need suitable water depth and stable water levels.
Why soil data matters
Thermal conductivity controls how quickly heat spreads through soil or rock. Dry soil moves heat slowly. Wet sand, clay, and rock often perform better. When conductivity is low, the calculator increases loop length. When the value is high, required length falls. Use local test data when available.
Design safety
The safety margin adds extra loop length. It helps cover uncertain soil, future load growth, pipe fouling, grout quality, and weather swings. Larger margins are useful during early planning. Final designs should use accepted software, local codes, and professional review.
Flow and pressure
The flow estimate uses gallons per minute per ton. Proper flow helps the heat pump meet rated performance. The pressure result is only an approximate pipe friction check. Real systems include headers, fittings, valves, antifreeze, and manifolds. These parts can raise pump head.
Using the result
Review the total loop length first. Then check bore count, trench length, fluid volume, and flow. Compare several loop types if land is limited. Save the CSV for project notes. Download the PDF for sharing. Treat the output as a feasibility estimate, not a stamped engineering design.
For best accuracy, measure real design loads first. Guessing from floor area can oversize the field. Check drilling access, trench depth, pipe spacing, and local permits. Also review antifreeze rules. Some regions restrict fluid types or discharge methods before ordering final materials.