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-40335 - Section C403.3.5-Dedicated outdoor air systems

Current through Register Vol. 24-14, July 15, 2024
C403.3.5
Dedicated outdoor air systems (DOAS).
For buildings with
			 occupancies as shown in Table C403.3.5, outdoor air shall be provided to each
			 occupied space by a dedicated outdoor air system (DOAS) which delivers 100
			 percent outdoor air without requiring operation of the heating and cooling
			 system fans for ventilation air delivery.
EXCEPTIONS:
1. Occupied spaces that are not ventilated by a
						  mechanical ventilation system and are only ventilated by a natural ventilation
						  system in accordance with Section 402 of the
International Mechanical
						  Code
.
2. High efficiency variable air volume (VAV) systems
						  complying with Section C403.6.10 for occupancy classifications other than
						  Groups A-1, A-2 and A-3 as specified in Table C403.3.5, and high efficiency VAV
						  systems complying with Section C403.12 for occupancy classification Groups A-1,
						  A-2 and A-3 as specified in Table C403.3.5. This exception shall not be used as
						  a substitution for a DOAS per Section C406.6.
Table C403.3.5
Occupancy Classifications Requiring DOAS
Occupancy
						  Classificationa
Inclusions
Exempted
A-1
All occupancies not specifically exempted
Television and radio studios
A-2
Casinos (gaming area)
All other A-2 occupancies
A-3
Lecture halls, community halls, exhibition halls,
						  gymnasiums, courtrooms, libraries, places of religious worship
All other A-3 occupancies
A-4, A-5
All occupancies excluded
B
All occupancies not specifically exempted
Food processing establishments including commercial
						  kitchens, restaurants, cafeterias; laboratories for testing and research; data
						  processing facilities and telephone exchanges; air traffic control towers;
						  animal hospitals, kennels, pounds; ambulatory care facilities
F, H, I, R, S, U
All occupancies excluded
E, M
All occupancies included
a. Occupancy classification from the
International Building Code
Chapter 3.
C403.3.5.1
DOAS with energy recovery
			 ventilation.
The DOAS shall include energy recovery. The
energy
			 recovery ventilation
system shall have a 68 percent minimum sensible
			 recovery effectiveness of the energy recovery device as calculated in
			 accordance with Equation 4-9 or provide an enthalpy recovery ratio of not less
			 than 60 percent at design conditions in accordance with Section C403.7.6. The
			 airflow rate thresholds in Section C403.7.6 that define when the energy
			 recovery requirements in that section do not apply, are not applicable to this
			 section. The return/exhaust air stream temperature for heat recovery device
			 selection shall be 70°F (21°C) at 30 percent relative humidity, or as
			 calculated by the registered design professional.
(Equation 4-9)
Click
				to view image
EXCEPTIONS:
1. Systems installed for the sole purpose of providing
						  makeup air for systems exhausting toxic, flammable, paint, or corrosive fumes
						  or dust, dryer exhaust, or commercial kitchen hoods used for collecting and
						  removing grease vapors and smoke.
2. Heat recovery and energy recovery ventilators
						  (H/ERV) that are rated and listed in accordance with HVI 920 can demonstrate
						  compliance with the sensible recovery effectiveness requirement using the
						  adjusted sensible recovery effectiveness (ASRE) rating of the equipment at
						  32°F test conditions. Applied flow rate for ASRE rating shall be no less
						  than the design flow rate or the closest value interpolated between two listed
						  flow rates.
3. The energy recovery systems for Group R-2
						  occupancies are permitted to provide 60 percent minimum sensible heat recovery
						  effectiveness in lieu of 68 percent sensible recovery effectiveness in
						  accordance with Section C403.7.6. The return/exhaust air stream temperature for
						  heat recovery device selection shall be 70°F (21°C) or as determined by
						  an
approved
calculation procedure.
C403.3.5.2
DOAS fan power.
For a
			 DOAS that does not have at least one fan or fan array with fan electrical input
			 power [GREATER THAN EQUAL TO] 1 kW, the total combined fan power shall not
			 exceed 1 watt per cfm of outdoor air as calculated in accordance with Equation
			 4-10 using design maximum airflows and external static pressures. For a DOAS
			 with at least one fan or fan array with fan electrical input power [GREATER
			 THAN EQUAL TO] 1 kW, the DOAS shall comply with the fan power limitations of
			 Section C403.8.1. DOAS total combined fan power shall include all supply,
			 exhaust and other fans utilized for the purpose of ventilation. This fan power
			 restriction applies to each DOAS in the permitted project, but does not include
			 the fan power associated with the zonal heating and cooling equipment.
(Equation 4-10)
Click
				to view image
C403.3.5.3
Heating and cooling system
			 fan controls.
Heating and cooling equipment fans, heating and cooling
			 circulation pumps, and terminal unit fans shall cycle off and terminal unit
			 primary cooling air shall be shut off when there is no call for heating or
			 cooling in the
zone
.
EXCEPTION:
Fans used for heating and cooling
						using less than 0.12 watts per cfm may operate when space temperatures are
						within the setpoint deadband (Section C403.4.1.2) to provide destratification
						and air mixing in the space.
C403.3.5.4
Decoupled DOAS supply
			 air.
The DOAS supply air shall be delivered directly to the occupied
			 space or downstream of the terminal heating and/or cooling coils.
EXCEPTIONS:
1. Active chilled beam systems.
2. Sensible only cooling terminal units with pressure
						  independent variable airflow regulating devices limiting the DOAS supply air to
						  the greater of latent load or minimum ventilation requirements.
3. Terminal heating and/or cooling units that comply
						  with the low fan power allowance requirements in the exception of Section
						  C403.3.5.3.
C403.3.5.5
Supplemental heating and
			 cooling.
Supply air stream heating in the DOAS system shall comply with
			 Section C403.7.3. Cooling is permitted for dehumidification only. Cooling coil
			 shall be sized to meet peak dehumidification requirement at design outdoor
			 temperatures, and no larger. Cooling coil shall be controlled to maintain
			 supply air relative humidity or
zone
relative humidity.
			 EXCEPTION: Fans used for heating and cooling using less than 0.12 watts per cfm
			 may operate when space temperatures are within the setpoint deadband (Section
			 C403.4.1.2) to provide destratification and air mixing in the space.
EXCEPTIONS:
Heating permitted for defrost control shall be locked
						  out when outside air temperatures are above 35°F (2°C). Supplemental
						  heating for defrost shall modulate to 10 percent of the peak capacity, and
						  shall be sized to prevent frost/damage dame to the unit at design temperatures
						  and provide supply air less than or equal to 55°F (13°C).
C403.3.5.6
Impracticality.
Where
			 the
code official
determines that full compliance with one or
			 more of the requirements in Sections C403.3.5.1 through C403.3.5.5 is
			 impractical, it is permissible to provide an approved alternate means of
			 compliance that achieves a comparable level of energy efficiency as the
			 requirement(s) deemed impractical. For the purposes of this section,
			 impractical means that an HVAC system complying with all requirements in
			 Section C403.3.5 cannot effectively be utilized due to an unusual use or
			 configuration of the building.