What Is a Water-Source Heat Pump (WSHP) System?
Water-source heat pumps connect each zone's heat pump to a building-wide water loop — the loop absorbs heat from zones needing cooling and delivers it to zones needing heating, with a boiler and cooling tower (or geothermal wells) balancing the loop temperature. Every zone gets independent control; the building shares energy internally. The commercial workhorse for offices, schools, hotels, and multifamily.
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How the loop works
Each WSHP (a small packaged unit per zone — closet, ceiling, or rooftop) rejects heat to the loop in cooling mode and extracts heat in heating mode. The loop floats (typically 60-90°F): when the building's net load is cooling, the cooling tower rejects the excess; when net heating, the boiler adds heat. Interior zones (always cooling) continuously heat perimeter zones (always heating) — the building's internal heat transfer is free energy. Loop heat recovery is the efficiency story.
Design considerations
The MEP engineer sizes: the loop piping (reverse-return for self-balancing), the boiler and tower (for the net block loads — smaller than the sum of zone peaks because of diversity), pump heads, and the WSHP selections per zone (capacity, efficiency, noise ratings — closet units need acoustic attention). Water treatment protects the loop (closed-loop treatment program). Controls sequence the boiler/tower staging on loop temperature.
Geothermal variant
Replace the boiler and cooling tower with a ground heat exchanger (vertical bores or horizontal loops): the earth becomes the heat source/sink — the loop runs cooler, heat-pump efficiency rises, and the fossil boiler disappears. Higher first cost (the well field), lower operating cost, and the cleanest version of the system. The geotechnical/thermal conductivity testing sizes the well field — test before committing.
The bottom line
WSHP systems share energy between zones through a building water loop — boiler/tower (or geothermal wells) balance it. Size for net block loads; treat the loop water.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.