Tools · Waterside Load

Waterside Load Calculator Hydronics

The waterside workhorse: q = 500 × GPM × ΔT ties a coil’s water flow, the temperature difference across it, and the load it’s moving. Solve in any direction — the load a measured flow and ΔT imply, the flow a scheduled load needs, or the ΔT a healthy loop should be showing.

Input

Enter ΔT as a positive difference — supply-to-return on a cooling coil, return-to-supply on heating; the math is the same either direction.

Water only. The constant bakes in water’s density and specific heat. A glycol mix lowers both — a 30 % propylene-glycol loop carries meaningfully less heat per gallon than this shortcut reports. A glycol correction row is a planned follow-up.

Output

Load (MBH) —
Tons refrigeration —

Worked example

A chilled-water coil takes 20 GPM, and the return pipe runs 12 °F warmer than the supply.

  1. The waterside equation: q = 500 × GPM × ΔT°F, in Btu/h.
  2. Plug in: q = 500 × 20 × 12 = 120,000 Btu/h = 120 MBH.
  3. In chiller language: 120 ÷ 12 = 10 tons moving through that one coil.

Flip Solve for to run it the other way: the flow a scheduled load needs at design ΔT, or the ΔT a known flow should produce — the on-the-spot check behind every low-ΔT diagnosis. A coil passing design flow at half the design ΔT is moving half the load it should; the balancing lesson walks where that goes next.

Where the 500 comes from: 8.33 lb/gal × 60 min/h × 1.0 Btu/lb·°F — water’s density and specific heat folded into one constant.

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