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-40393 - Section C403.12-High efficiency single zone VAV systems

Current through Register Vol. 24-14, July 15, 2024
C403.12
High
			 efficiency single-zone variable air volume (VAV) systems.
For HVAC systems subject to the requirements of Section
				C403.3.5 but utilizing Exception 2 of that section, a high efficiency
				single-zone VAV system may be provided without a separate parallel DOAS when
				the system is designed, installed, and configured to comply with all of the
				following criteria (this exception shall not be used as a substitution for a
				DOAS per Section C406.6 or as a modification to the requirements for the
Standard Reference Design
in accordance with Section
				C407):
1. The single-zone VAV system
			 is provided with airside economizer in accordance with Section C403.3 without
			 exceptions.
2. A direct-digital
			 control (DDC) system is provided to control the system as a single zone in
			 accordance with Section C403.4.11 regardless of sizing thresholds of Table
			 C403.4.11.1.
3. Single-zone VAV
			 systems with a minimum outdoor air requirement of 1,000 cfm (472 L/s) or
			 greater shall be equipped with a device capable of measuring outdoor airflow
			 intake under all load conditions. The system shall be capable of increasing or
			 reducing the outdoor airflow intake based on Section C403.7.1, Demand
			 controlled ventilation.
4.
			 Allowable fan power shall not exceed 90 percent of the allowable fan power
			 budget as defined by Section C403.8.1.1.
5. Each single-zone VAV system shall be
			 designed to vary the supply fan airflow as a function of heating and cooling
			 load and minimum fan speed shall not be more than the greater of:
5.1. 30 percent of peak design airflow;
			 or
5.2. The required ventilation
			 flow assuming no occupants.
6. Spaces that are larger than 150 square
			 feet (14 m2) and with an occupant load greater than
			 or equal to 25 people per 1000 square feet (93 m2)
			 of floor area (as established in Table 403.3.1.1 of the
International
			 Mechanical Code
) shall be provided with all of the following features:
6.1. Demand control ventilation (DCV) shall
			 be provided that utilizes a carbon dioxide sensor to reset the ventilation
			 setpoint of the single-zone VAV system from the design minimum to design
			 maximum ventilation rate as required by Chapter 4 of the
International
			 Mechanical Code
.
6.2.
			 Occupancy sensors shall be provided that are configured to reduce the minimum
			 ventilation rate to zero and setback room temperature setpoints by a minimum of
			 5°F, for both cooling and heating, when the space is
			 unoccupied.
7.
			 Single-zone VAV systems shall comply with one of the following options:
7.1. Single-zone VAV air handling units with
			 a hydronic heating coil connected to systems with hot water generation
			 equipment limited to the following types of equipment: Gas-fired hydronic
			 boilers with a thermal efficiency, Et, of not less than
			 92 percent, air-to-water heat pumps or heat recovery chillers. Hydronic heating
			 coils shall be sized for a maximum entering hot water temperature of 120°F
			 for peak anticipated heating load conditions.
7.2. Single-zone VAV air handing units with a
			 chilled water coil connected to systems with chilled water generation equipment
			 with IPLV values more than 25 percent higher than the minimum part load
			 efficiencies listed in Table C403.3.2 (3), in the appropriate size category,
			 using the same test procedures. Equipment shall be listed in the appropriate
			 certification program to qualify. The smallest chiller or compressor in the
			 central plant shall not exceed 20 percent of the total central plant cooling
			 capacity or the chilled water system shall include thermal storage sized for a
			 minimum of 20 percent of the total central cooling plant capacity.
7.3. Single-zone VAV air handling units with
			 DX cooling, heat pump heating or gas-fired furnace shall comply with the
			 following requirements as applicable:
7.3.1.
			 Have a DX cooling coil with cooling part load efficiency that is a minimum of
			 15 percent higher than the minimum SEER or IEER listed in Tables C403.3.2(1),
			 C403.3.2(2), and C403.3.2 (14).
7.3.2. Have a gas-fired furnace with a
			 thermal efficiency, Et, of not less than 90 percent or
			 heat pump with a minimum heating HSPF or COP efficiency that are a minimum of
			 10 percent higher than the minimum heating efficiency in Tables C403.3.2(1),
			 C403.3.2(2), and C403.3.2 (14).
7.3.3. Heating coils or burner output shall
			 be modulating or have a minimum of 2 stages with the first stage being less
			 than 50 percent of total heating capacity. Cooling coils shall be modulating or
			 have a minimum of 2 stages with the first stage being less than 50 percent of
			 the total cooling capacity.
8. The DDC system shall include a fault
			 detection and diagnostics (FDD) system complying with the following:
8.1. The following temperature sensors shall
			 be permanently installed to monitor system operation:
8.1.1. Outside air.
8.1.2. Supply air.
8.1.3. Return air.
8.2. Temperature sensors shall have an
			 accuracy of +-2°F (1.1°C) over the range of 40°F to 80°F
			 (4°C to 26.7°C).
8.3. The
			 single-zone VAV air handling unit controller shall be configured to provide
			 system status by indicating the following:
8.3.1. Free cooling available.
8.3.2. Economizer enabled.
8.3.3. Compressor enabled.
8.3.4. Heating enabled.
8.3.5. Mixed air low limit cycle
			 active.
8.3.6. The current value of
			 each sensor.
8.4. The
			 single-zone VAV air handling unit controller shall be capable of manually
			 initiating each operating mode so that the operation of compressors,
			 economizers, fans and the heating system can be independently tested and
			 verified.
8.5. The single-zone VAV
			 air handling unit shall be configured to report faults to a fault management
			 application able to be accessed by day-to-day operating or service personnel or
			 annunciated locally on zone thermostats.
8.6. The FDD system shall be configured to
			 detect the following faults:
8.6.1. Air
			 temperature sensor failure/fault.
8.6.2. Not economizing when the unit should
			 be economizing.
8.6.3. Economizing
			 when the unit should not be economizing.
8.6.4. Outdoor air or return air damper not
			 modulating.
8.6.5. Excess outdoor
			 air.