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-40341 - Section C403.4.1-Thermostatic controls

Current through Register Vol. 24-14, July 15, 2024
C403.4.1
Thermostatic controls.
The supply of heating and cooling energy to
			 each
zone
shall be controlled by individual thermostatic
			 controls capable of responding to temperature within the
zone
.
			 Controls in the same zone or in neighboring zones connected by openings larger
			 than 10 percent of the floor area of either zone shall not allow for
			 simultaneous heating and cooling. At a minimum, each floor of a building shall
			 be considered as a separate zone. Controls on systems required to have
			 economizers and serving single zones shall have multiple cooling stage
			 capability and activate the economizer when appropriate as the first stage of
			 cooling. See Section C403.5 for further economizer requirements. Where
			 humidification or dehumidification or both is provided, at least one humidity
			 control device shall be provided for each humidity control system.
EXCEPTIONS:
1. Independent perimeter systems that are designed to
						  offset only building envelope heat losses or gains or both serving one or more
						  perimeter
zones
also served by an interior system
						  provided:
1.1. The perimeter system includes at least one
						  thermostatic control
zone
for each building exposure having
						  exterior walls facing only one orientation (within +/-45 degrees) (0.8 rad) for
						  more than 50 contiguous feet (15,240 mm);
1.2. The perimeter system heating and cooling supply is
						  controlled by a thermostat located within the
zones
served by
						  the system; and
1.3. Controls are configured to prevent the perimeter
						  system from operating in a different heating or cooling mode from the other
						  equipment within the zones or from neighboring zones connected by openings
						  larger than 10 percent of the floor area of either zone.
2. Where an interior zone and a perimeter zone are open
						  to each other with permanent openings larger than 10 percent of the floor area
						  of either zone, cooling in the interior zone is permitted to operate at times
						  when the perimeter zone is in heating and the interior zone temperature is at
						  least 5°F (2.8°C) higher than the perimeter zone temperature. For the
						  purposes of this exception, a permanent opening is an opening without doors or
						  other operable closures.
3. Dedicated outdoor air units that provide ventilation
						  air, make-up air or replacement air for exhaust systems are permitted to be
						  controlled based on supply air temperature. The supply air temperature shall be
						  controlled to a maximum of 65°F (18.3°C) in heating and a minimum of
						  72°F (22°C) in cooling unless the supply air temperature is being reset
						  based on the status of cooling or heating in the zones served or it being reset
						  based on outdoor air temperature.
C403.4.1.1
Heat pump supplementary heat control.
Heat pumps equipped with
			 internal electric resistance heaters shall have controls that prevent
			 supplemental heater operation when the heating load can be met by the heat pump
			 alone during both steady-state operation and setback recovery. Supplemental
			 heater operation is permitted during outdoor coil defrost cycles. Heat pumps
			 equipped with supplemental heaters shall comply with all conditions of Section
			 C403.1.4.
EXCEPTIONS:
1. Packaged terminal heat pumps (PTHPs) of less than 2
						  tons (24,000 Btu/hr) cooling capacity and whose ratings meet the requirements
						  shown in Table C403.3.2(4) that have reverse-cycle demand defrost and are
						  configured to operate in heat pump mode whenever the outdoor air temperatures
						  are above 25°F (-3.9°C) and the unit is not in defrost.
2. Heat pumps whose minimum efficiency is regulated by
						  NAECA and whose ratings meet the requirements shown in Table C403.3.2(2) and
						  include all usage of internal electric resistance heating.
C403.4.1.2
Deadband.
Where used
			 to control both heating and cooling, zone thermostatic controls shall be
			 configured to provide a temperature range or deadband of at least 5°F
			 (2.8°C) within which the supply of heating and cooling energy to the zone
			 is shut off or reduced to a minimum.
EXCEPTIONS:
1. Thermostats requiring manual changeover between
						  heating and cooling modes.
2. Occupancies or applications requiring precision in
						  indoor temperature control as
approved
by the
code
						  official
.
C403.4.1.3
Setpoint overlap
			 restriction.
Where a
zone
has a separate heating and a
			 separate cooling thermostatic control located within the zone, a limit switch,
			 mechanical stop or direct digital control system with software programming
			 shall be configured to prevent the heating setpoint from exceeding the cooling
			 setpoint and to maintain a dead-band in accordance with Section
			 C403.4.1.2.
C403.4.1.4
Heated
			 or cooled vestibules and air curtains.
The heating system for heated
			 vestibules and air curtains with integral heating shall be provided with
			 controls configured to shut off the source of heating when the outdoor air
			 temperature is greater than 45°F (7°C). Vestibule heating and cooling
			 systems shall be controlled by a thermostat located in the vestibule configured
			 to limit heating to a temperature not greater than 60°F (16°C) and
			 cooling to a temperature not less than 85°F (29°C).
EXCEPTIONS:
1. Control of heating or cooling provided by transfer
						  air that would otherwise be exhausted.
2. Vestibule heating only systems are permitted to be
						  controlled without an outdoor air temperature lockout when controlled by a
						  thermostat located in the vestibule configured to limit heating to a
						  temperature not greater than 45°F (7°C) where required for freeze
						  protection of piping and sprinkler heads located in the vestibule.
C403.4.1.5
Hot water boiler outdoor
			 temperature setback control.
Hot water boilers that supply heat to the
			 building through one- or two-pipe heating systems shall have an outdoor setback
			 control that lowers the boiler water temperature based on the outdoor
			 temperature.
C403.4.1.6
Operable opening switches for HVAC system thermostatic control.
Operable openings meeting the minimum size criteria of Section C402.5.11 and
			 that open to the outdoors from a conditioned space must have controls
			 configured to do the following once doors have been open for 5 minutes:
1. Disable the mechanical heating to the zone
			 or reset the space heating temperature setpoint to 55°F or less within 5
			 minutes of the door open enable signal.
2. Disable the mechanical cooling to the zone
			 or reset the space cooling temperature setpoint to 85°F or more within 5
			 minutes of the door open enable signal.
EXCEPTION:
Hydronic radiant heating and cooling systems.
C403.4.1.7
Demand responsive
			 controls.
Thermostatic controls for heating or cooling systems shall be
			 provided with
demand responsive controls
capable of increasing
			 the cooling setpoint and decreasing the heating setpoint by no less than
			 4°F (2.2°C). The thermostatic controls shall be capable of performing
			 all other functions provided by the control when the
demand responsive
			 controls
are not available. Systems with
direct digital
			 control
of individual
zones
report to a central
			 control panel shall be capable of remotely increasing the cooling setpoint and
			 decreasing the heating setpoint for each
zone
by no less than
			 4°F (2.2°C).
EXCEPTION:
Health care and assisted living facilities.