1, provides NAVFACENGCOM criteria for designing, specifying, inspecting, and accepting plumbing systems for various naval shore facilities.

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MIL-HDBK-1003/1

Use the Hotel column to size central SWH systems for Bachelor Housing and Navy Lodges, due to occupant's schedules resembling those of hotel and motel occupants - the rooms are inhabited mostly between 5 PM and 7 AM."

Add "SECTION 506.3 Hot Water Mixing Equation.

Let: Qf = Fixture flow in gpm = 2.5 gpm per Public Law 102-486

Qs = Flow from SWH Storage Tank in gpm

Qc = Flow from Cold Water Supply in gpm

Tf = Temperature at fixture in degrees F = 110 F for

personnel safety

Ts = Temperature at SWH Storage Tank in degrees F, 140 F

minimum for Legionella

Tc = Temperature at Cold Water Supply in degrees F,

varies due to location and season

Mixing Equation: (Qf x Tf) = (Qs x Ts) + (Qc x Tc) Substituting Qc = Qf - Qs gives the following:

(Qf x Tf) = (Qs x Ts) + ((Qf - Qs) x Tc)

(Qf x Tf) = (Qs x Ts) + (Qf x Tc) - (Qs x Tc)

(Qf x Tf) - (Qf x Tc) = (Qs x Ts) - (Qs x Tc)

Qf x (Tf-Tc) = Qs x (Ts-Tc)

Qs = Qf x [(Tf-Tc)/(Ts-Tc)]

Substituting Qf = 2.5 gpm, Tf = 110 F, Ts = 140 F, and Tc = 50

F gives the following:

Qs = 2.5 x [(110-50)/(140-50)] Qs = 1.667 gpm

Qc = Qf-Qs = 2.5 gpm-1.667 gpm = 0.833 gpm

Check: 2.5 x 110 = (1.667 x 140) + (0.833 x 50)

275 = 233.38 + 41.65

275 = 275.03 = OK

The mixing equation may be used to evaluate the effect of variation of Tc temperatures on Qs. At Ts = 140 F, for Tc = 40 F, Qs = 1.75 gpm; and for Tc = 80 F, Qs = 1.25 gpm.