Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-11C - State Building Code adoption and amendment of the 2021 edition of the International Energy Conservation Code, Commercial › Section 51-11C-40402 - Section C404.2-Service water-heating equipment performance efficiency

Current through Register Vol. 24-14, July 15, 2024
C404.2
Service
			 water-heating equipment performance efficiency.
Water-heating equipment
			 and hot water storage tanks shall meet the requirements of Table C404.2. The
			 efficiency shall be verified through certification and
listed
under an
approved
certification program, or if no
			 certification program exists, the equipment efficiency ratings shall be
			 supported by data furnished by the manufacturer. Water-heating equipment
			 intended to be used to provide space heating shall meet the applicable
			 provisions of Table C404.2.
C404.2.1
Service water heating system type.
Service hot water shall be
			 provided by an electric air-source heat pump water heating (HPWH) system
			 meeting the requirements of this section. Supplemental service water heating
			 equipment is permitted to use electric resistance or fossil fuel in compliance
			 with Section C404.2.1.4.
EXCEPTIONS:
1. 24 kW plus 0.1 watts per square foot of building
						  area of electric resistance service water heating capacity is allowed per
						  building.
2. Solar thermal, wastewater heat recovery, other
approved
waste heat recovery, ground source heat pumps,
						  water-source heat pump systems utilizing waste heat, and combinations thereof,
						  are permitted to offset all or any portion of the required HPWH capacity where
						  such systems comply with this code and the
Uniform Plumbing
						  Code
.
3. Systems that comply with the Northwest Energy
						  Efficiency Alliance (NEEA) Commercial Electric Advanced Water Heating
						  Specification.
4. Service hot water systems served by a district
						  energy system that serves multiple buildings and that was in service before the
						  effective date of this code.
5. Commercial dishwashers, commercial food service
						  equipment, and other
approved
process equipment are permitted
						  to utilize electric booster heaters for supply water temperatures 120°F
						  (49°C) or higher.
6. Systems connected to a
low-carbon district
						  energy exchange system or a low-carbon district heating and cooling or heating
						  only system
.
7. Essential facilities. Groups I-2 and I-3 occupancies
						  that by regulation are required to have in place redundant emergency backup
						  systems.
C404.2.1.1
Primary heat pump system sizing.
The primary heat pump service
			 water heating system shall be sized to deliver no less than 50 percent of the
			 calculated demand for service hot water production during the peak demand
			 period. Demand shall be calculated using the equipment manufacturer's selection
			 criteria or another
approved
methodology with entering dry
			 bulb or wet bulb outdoor air temperature at 40°F (4°C) for air-source
			 heat pumps, or 44°F (7°C) ground temperature for ground-source heat
			 pumps. Electric air source heat pumps shall also be sized to deliver no less
			 than 25 percent of the calculated demand for service hot water production
			 during the peak demand period when entering dry bulb or wet bulb outdoor air
			 temperature is 24°F (-4°C). The remaining primary service output may be
			 met by fossil fuel, electric resistance, or heat pump water heating systems.
EXCEPTION:
Twenty-five percent sizing at entering dry bulb or wet
						  bulb air temperature of 24°F (-4°C) is not required for air-source heat
						  pumps located in a below-grade enclosed parking structure or other ventilated
						  and unconditioned space that is not anticipated to fall below 40°F
						  (4°C) at any time.
C404.2.1.2
Primary hot water storage
			 sizing.
The system shall provide sufficient hot water to satisfy peak
			 demand period requirements.
C404.2.1.3
System design.
The
			 service water heating system shall be configured to conform to one of the
			 following provisions:
1. For
single-pass heat pump water heaters
,
temperature
			 maintenance
heating provided for reheating return water from the
			 building's heated water circulation system shall be physically decoupled from
			 the primary service water heating system storage tank(s) in a manner that
			 prevents destratification of the primary system storage tanks.
Temperature maintenance
heating is permitted to be provided by
			 electric resistance, fossil fuel, or a separate dedicated heat pump
			 system.
2. For
multi-pass
			 heat pump water heaters
,
recirculated temperature
maintenance water is permitted to be returned to the primary water storage
			 tanks for reheating.
3. For unitary
			 heat pump water heaters, located in conditioned space, are permitted, where
			 they are sized to meet all calculated service water heating demand using the
			 heat pump compressor, and not supplementary heat.
C404.2.1.3.1
Mixing valve.
A
			 thermostatic mixing valve capable of supplying hot water to the building at the
			 user temperature setpoint shall be provided, in compliance with requirements of
			 the
Uniform Plumbing Code
and the HPWH manufacturer's
			 installation guidelines. The mixing valve shall be sized and rated to deliver
			 tempered water in a range from the minimum flow of the
temperature
			 maintenance
recirculation system up to the maximum demand for the
			 fixtures served.
C404.2.1.4
Supplemental water
			 heating.
Total supplemental water heating equipment shall not have an
			 output capacity greater than the total summed capacity of all primary water
			 heating equipment. For the purposes of determining this supplemental water
			 heating allowance, the capacity of primary water heating equipment shall be
			 evaluated at 40°F (4°C) entering dry bulb or wet bulb outdoor air
			 temperature for air-source heat pumps, 44°F (7°C) ground temperature
			 for ground-source heat pumps, and at the nameplate input rate for all other
			 water heater system types. Supplemental heating is permitted for the following
			 uses:
1.
Temperature
			 maintenance
of heated-water circulation systems, physically separate
			 from the primary service water heating system.
2. Defrost of compressor coils.
3. Heat tracing of piping for freeze
			 protection or for
temperature maintenance
in lieu of
			 recirculation of hot water.
4.
			 Backup or low ambient temperature conditions, where all of the following are
			 true:
4.1. During normal operations, the
			 supplemental heating is controlled to operate only when the entering air
			 temperature at the air-source HPWH is below 40°F (4°C), and the primary
			 HPWH compressor continues to operate together with the supplemental heating.
4.2. The primary water heating
			 equipment cannot satisfy the system load due to equipment failure or entering
			 air temperature below 40°F (4°C).
C404.2.1.5
System fault
			 detection.
The control system shall be capable of and configured to send
			 automatic error alarms to building or maintenance personnel upon detection of
			 equipment faults, low leaving water temperature from primary storage tanks, or
			 low hot water supply delivery temperature to building distribution
			 system.