This appendix documents the methods
and assumptions used for calculating the hourly energy use for residential water
heating systems for both the proposed design and the standard design. The hourly
fuel and electricity energy use for water heating will be combined with hourly
space heating and cooling energy use to come up with the hourly total fuel and
electricity energy use to be factored by the hourly TDV energy multiplier. The
calculation procedure applies to low-rise single family, low-rise multifamily,
and high-rise residential.
Calculations are described below
for gas and electric water heaters. The internal water heater modeling is
performed within the CSE simulation engine. The compliance modeling rules
documented here are implemented in the CBECC-Res ruleset and determine the input
values passed to CSE.
When buildings have multiple water
heaters, the hourly total water heating energy use is the hourly water heating
energy use summed over all water heating systems, all water heaters, and all dwelling units being
modeled.
The following diagrams illustrate
the domestic hot water (DHW) system types that shall be recognized by the compliance
software.
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1 |
One distribution system with
one or multiple water heaters serving a single dwelling unit. The system
might include recirculation loops within the dwelling unit.
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2 |
Two water heaters with
independent distribution systems serving a single dwelling unit. One or
more of the distribution systems may include a recirculation loop within
the dwelling unit. |
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3 |
One distribution system
without recirculation loop and with one or multiple water heaters serving
multiple dwelling units.
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4 |
One distribution system with
one or multiple recirculation loops and with one or multiple water heaters
serving multiple dwelling units.
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