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Table 12. Benchmark D

omestic Hot Water Event Characte (three-bedroom house)

ristics and Constraints

Characteristics

Si

Ser

Bath

CW

DW

Sink

Shower

0.62

7.81

0.67

3.52

Exponential

Log-Normal

1.14

2.25

0.61

0.68

Normal

Normal

Characteristics Average Duration (min) Standard Deviation Duration (min) Probability Distribution for Duration Average Flow Rate (gpm)* Standard Deviation Flow Rate (gpm)* Probability Distribution for Flow Rate

Average Event Volume (gal)* Average Daily Volume (gal/day)* Average Daily Events (events/day) Annual Events (events/year) Maximum Time Between Events in Cluster (min) Average Time Between Events in Cluster (min) Average Events per Cluster Number of Clusters per Year Maximum Time Between Events in Load (min) Maximum Time Between Loads in Cluster (min) Number of Loads per Cluster Average Number of Events per Load Average Time Between Events in Load (min) Average Time Between Loads in Cluster (min) Probability Distribution for Cluster Size

Fraction of events at primary fixture (kitchen sink, master bath shower/tub) Fraction of events at secondary fixture (master bath sink, second shower/tub)

0.76 25 32.9 12007 15 1.93 1.90 6319

Discrete 0.70

0.10

16.73 28 1.7 611 60 30.5 1.24 493

Discrete 0.75

0.25

Bath 5.65 2.09

Normal 4.40 1.17 Normal

23.45 7 0.3 109 60

1.00 109

Discrete 0.75

0.25

CW 3.05 1.62

Discrete 2.20 0.62 Normal

6.95 15 2.2 788

1.96 402 30 240 1.40 1.40 5.0 74.3 Discrete

1.00

DW 1.53 0.41 Log-Normal 1.39 0.20 Normal 2.13 5 2.4 858 60 9.8 4.89 176

Discrete 1.00

Fraction of events at 3rd fixture Fraction of events at 4th fixture

0.10 0.10

  • *

    Hot + cold water combined for mixed temperature end uses (sinks, showers, baths)

This equation is based on analysis by Burch and Christensen (2007) of NREL using data for multiple locations, as compiled by Abrams and Shedd (1996), FSEC (Parker 2002), and Sandia National Laboratories (Kolb 2003). The offset, ratio, and lag factors were determined by fitting the available data. The climate-specific ratio and lag factors are consistent with water pipes being buried deeper in colder climates.

In order for the constant terms in the ratio and lag factors to be representative of an average climate, the data fitting was done relative to a nominal Tamb,avg = 44°F. The lag is relative to

ambient air temperature, and Tamb,minimum

is assumed to occur in mid-January (day# = 15). The

choices for these nominal values are not critical, because although different assumptions would change the constant terms in the ratio and lag factors, the coefficients would also change, so the prediction of Tmains values would be unchanged. For models that use average monthly mains temperature, day# in Equation 5 shall be calculated using Equation 6.

Equation 6: Where:

day# = 30 × month# - 15 ,

month# = month of the year (1–12)

20

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