Residential DHW Flow Rates in CA Software

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Sorry to be so late to this post, but I believe you'll find the details in this white paper found on the CBECC-Res Reference Documents page. In summary, a dataset of measured DHW draws from over 700 single-family homes in California were used to develop a set of discrete DHW draw events over the annual simulations. The draw events are defined by:

• when they start
• how long they last
• what the average flow rate is over the draw event
• what DHW draw type it is (shower, sink, clothes washer, etc.)

The "shuffle" or combination of DHW draw events used in the model depends on the number of bedrooms in the home (CBECC-Res) or apartment (CBECC-Com). This is all defined in the DHWDU.txt file that you mentioned (renamed to DHWDU2.txt recently), and is the approach used in both CBECC-Res and CBECC-Com. For CBECC-Com, there are multiple unique "shuffles" of DHW draw events for the same number of apartment bedrooms to capture the randomness of draws across the building. For example, a "1BR-A" set of draws is applied to a one-bed apartment and a different "1BR-B" set of draws is applied to a different one-bed apartment.

I'll note that this approach was applied to residential zones (apartments, common areas on residential floors, etc.) in multifamily projects of the new CBECC 2022. The non-residential zones (commercial retail, office, etc. typically on ground floor) in multifamily projects of CBECC 2022 CBECC-Com uses a simpler approach in EnergyPlus/OpenStudio (typical peak flow rate and hourly schedule for when draw events occur) instead of CSE because there is no data for non-residential draw patterns.

Below is an example of defining the annual "shuffle" of DHW draw events for a 1-BR home in CBECC-Res:

#define DHWSF1BR01 choose1(
  $dayofyear,
  "1H09",
  "1D19",
  "4E01",
  ...

Basically, for each day of the year, apply a different day of DHW draw events. The same for a 1-BR apartment in CBECC-Com would be named "DHWMF1BR01" (see lines 16-28 in DHWDU2.txt). For each daily draw name, letters signify the day type -- "H" for holiday, "D" for weekday, and "E" for weekend (see lines 37-40 in DHWDU2.txt).

Below is the DHW draw events for Jan 1 -- "1H09" -- defined with a DHWDAYUSE object:

DHWDAYUSE "1H09"
  DWSH(  9.97,  1.500, 1.358,   0) 
  DWSH( 10.11,  1.000, 1.162,   0) 
  DWSH( 10.22,  1.333, 1.350,   0) 
  FAUC(  9.20,  0.262, 0.778,   0)
  ...

Each line is using a macro to set the type of draw (dishwasher for the first three, faucet for the fourth) and the other three DHW draw descriptors I mentioned at the top (when they start [hour of day], how long they last [minutes], what the average flow rate is over the draw event [gpm]). Here are the draw types (see lines 4786-4821 in DHWDU2.txt) that are defined with a DHWUSE object:

• SHWR: shower
• CWSH: clothes washer
• FAUC: faucet
• BATH: bath
• DWSH: dishwasher

If you wanted to review outputs of hourly draw flow ... (more)