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-40344 - Section C403.4.4-Part load controls

Current through Register Vol. 24-14, July 15, 2024
C403.4.4
Part
			 load controls.
Hydronic systems greater than or equal to 300,000 Btu/h
			 (88 kW) in design output capacity supplying heated or chilled water to comfort
			 conditioning systems shall include controls that are configured to:
1. Automatically reset the supply-water
			 temperatures in response to varying building heating and cooling demand using
			 coil valve position, zone-return water temperature or outdoor air temperature.
			 The temperature shall be reset by not less than 25 percent of the design
			 supply-to-return water temperature difference.
EXCEPTIONS:
1. Hydronic systems serving hydronic heat pumps.
2. Hydronic systems with thermal energy storage where
						  resetting the supply-water temperature would reduce the capacity of the
						  storage.
2.
			 Automatically vary fluid flow for hydronic systems with a combined pump motor
			 capacity of 2 hp or larger with three or more control valves or other devices
			 by reducing the system design flow rate by not less than 50 percent or the
			 maximum reduction allowed by the equipment manufacturer for proper operation of
			 equipment by valves that modulate or step open and close, or pumps that
			 modulate or turn on and off as a function of load.
3. Automatically vary pump flow on heating
			 water systems, chilled-water systems and heat rejection loops serving
			 water-cooled unitary air conditioners as follows:
3.1. Where pumps operate continuously or
			 operate based on a time schedule, pumps with nominal output motor power of 2 hp
			 or more shall have a variable speed drive.
3.2. Where pumps have automatic direct
			 digital control configured to operate pumps only when zone heating or cooling
			 is required, a variable speed drive shall be provided for pumps with motors
			 having the same or greater nominal output power indicated in Table C403.4.4
			 based on the climate zone and system served.
4. Where variable speed drive is required by
			 Item 3 of this section, pump motor power input shall be not more than 30
			 percent of design wattage at 50 percent of the design water flow. Pump flow
			 shall be controlled to maintain one control valve nearly wide open or to
			 satisfy the minimum differential pressure.
EXCEPTIONS:
1. Supply-water temperature reset is not required for
						  chilled-water systems supplied by off-site district chilled water or chilled
						  water from ice storage systems.
2. Variable pump flow is not required on dedicated coil
						  circulation pumps where needed for freeze protection.
3. Variable pump flow is not required on dedicated
						  equipment circulation pumps where configured in primary/secondary design to
						  provide the minimum flow requirements of the equipment manufacturer for proper
						  operation of equipment.
4. Variable speed drives are not required on heating
						  water pumps where more than 50 percent of annual heat is generated by an
						  electric boiler.
Table C403.4.4
Variable Speed Drive (VSD) Requirements for
				Demand-Controlled Pumps
Climate Zones 4c, 5b
VSD Required for Motors with Rated
						  Output of at Least
Heating water pumps
[GREATER THAN EQUAL TO]7.5 hp
Chilled water and heat rejection loop pumps
[GREATER THAN EQUAL TO]7.5 hp