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-40343 - Section C403.4.3-Hydronic systems controls

Current through Register Vol. 24-14, July 15, 2024
C403.4.3 Hydronic systems controls.
The heating of
				fluids that have been previously mechanically cooled and the cooling of fluids
				that have been previously mechanically heated shall be limited in accordance
				with Sections C403.4.3.1 through C403.4.3.3. Hydronic heating systems comprised
				of multiple-packaged boilers and designed to deliver conditioned water or steam
				into a common distribution system shall include automatic controls configured
				to sequence operation of the boilers. Hydronic heating systems comprised of a
				single boiler and greater than 500,000 Btu/h (146,550 W) input design capacity
				shall include either a multi-staged or modulating burner.
C403.4.3.1 Three-pipe system.
Hydronic systems
				that use a common return system for both hot water and chilled water are
				prohibited.
C403.4.3.2 Two-pipe changeover system.
Systems
				that use a common distribution system to supply both heated and chilled water
				shall be designed to allow a dead band between changeover from one mode to the
				other of at least 15°F (8.3°C) outside air temperatures; be designed to
				and provided with controls that will allow operation in one mode for at least 4
				hours before changing over to the other mode; and be provided with controls
				that allow heating and cooling supply temperatures at the changeover point to
				be no more than 30°F (16.7°C) apart.
C403.4.3.3 Hydronic (water loop) heat pump
				systems.
Hydronic heat pump systems shall comply with Sections
				C403.4.3.3.1 through C403.4.3.3.3.
C403.4.3.3.1 Temperature dead band.
Hydronic heat
				pumps connected to a common heat pump water loop with central devices for heat
				rejection and heat addition shall have controls that are configured to provide
				a heat pump water supply temperature dead band of at least 20°F
				(11.1°C) between initiation of heat rejection and heat addition by the
				central devices.
EXCEPTION:
Where a system loop temperature optimization controller
						  is installed and can determine the most efficient operating temperature based
						  on real time conditions of demand and capacity, dead bands of less than
						  20°F (11°C) shall be permitted.
C403.4.3.3.2 Heat rejection.
The following shall
				apply to hydronic water loop heat pump systems:
1. Where a closed-circuit cooling tower is
			 used directly in the heat pump loop, an automatic valve shall be installed to
			 bypass the flow of water around the closed-circuit cooling tower, except for
			 the minimum flow necessary for freeze protection. Flow controls for freeze
			 protection shall not allow water through the closed-circuit cooling tower when
			 outdoor temperatures are above the freezing point of the glycol/water solution,
			 i.e., 32°F (0°C) for 100 percent water applications and 18°F
			 (-7.8°C) for 20 percent by mass propylene glycol solution.
2. Where an open-circuit cooling tower is
			 used directly in the heat pump loop, an automatic valve shall be installed to
			 bypass all heat pump water flow around the open-circuit cooling
			 tower.
3. Where an open-circuit
			 cooling tower is used in conjunction with a separate heat exchanger to isolate
			 the open-circuit cooling tower from the heat pump loop, heat loss shall be
			 controlled by shutting down the circulation pump on the cooling tower
			 loop.
EXCEPTION:
Where it can be demonstrated that a heat pump system
						  will be required to reject heat throughout the year.
C403.4.3.3.3 Isolation valve.
Each hydronic heat
				pump on the hydronic system having a total pump system power exceeding 10
				horsepower (hp) (7.5 kW) shall have a two-way (but not three-way) valve. For
				the purposes of this section, pump system power is the sum of the nominal power
				demand (i.e., nameplate horsepower at nominal motor efficiency) of motors of
				all pumps that are required to operate at design conditions to supply fluid
				from the heating or cooling source to all heat transfer devices (e.g., coils,
				heat exchanger) and return it to the source. This converts the system into a
				variable flow system and, as such, the primary circulation pumps shall comply
				with the variable flow requirements in Section C403.4.6.
Statutory
				Authority:
				RCW
				  19.27A.025,
				19.27A.045, and
				19.27.074. WSR 13-20-120, §
				51-11C-40343, filed 10/1/13, effective 11/1/13. Statutory Authority:
				RCW
				  19.27A.020,
				19.27A.025 and
				chapters
				19.27 and
				34.05 RCW. WSR 13-04-056, §
				51-11C-40343, filed 2/1/13, effective 7/1/13. WSR 13-20-001, §
				51-11C-40343, filed 9/18/2013, effective
				10/19/2013