ASHRAE-90.1-2022- - Page 200

Extracted Content

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c. Night flush controls shall be configured with the following sequence, or another night flush strategy shall

be permitted where it is demonstrated to be effective, avoids added morning heating, and is approved by the authority having jurisdiction .

1. Summer mode shall be activated when outdoor air temperature exceeds 70  F and shall continue uninterrupted until deactivated when outdoor air temperature falls below 45  F. During summer mode, the occupied cooling set point shall be set 1  F higher than normal, and the occupied heating set point shall be reset 2  F lower than normal.
2. Night flush shall be activated when all of the following conditions exist: i. Summer mode is active in accordance with item (c)(1). ii. Outdoor air temperature is 5  F or more below indoor average zone temperature. iii. Indoor average zone temperature is greater than morning occupied heating set point . iv. In climate zones 0A through 3A, outdoor dew point is below 50  F, or outdoor air enthalpy is less than indoor air enthalpy. v. Local time is between 10:00 pm and 6:00 am.
3. When night flush is active, automatic night flush controls shall operate outdoor air economizers at low fan speed not exceeding 66% during the unoccupied period with mechanical cooling and heating locked out. d. The project shall demonstrate a contractual obligation for postoccupancy commissioning and control tun ing in the spring or fall season to tune the summer mode activation set points and occupied heating set point, or other algorithms to achieve minimal morning heating due to night flush activation, while maintaining comfort conditions. Commissioning shall include monitoring of time-series space temperature, heating, and cooling operation to demonstrate both night cooling and minimization of morning heating along with monitoring of post-tuning operation to verify tuned parameters. Operating manuals shall include recommendations for tuned parameters and narrative training for operating staff on night flush automated settings.

Informative Note: The simplified night flush sequence described will operate in summer mode below the 70  F outdoor air trigger temperature until outdoor air of 45  F is reached and summer mode is deactivated. Summer mode is reestablished when the outdoor air rises above 70  F again. These set points need to be tuned under actual occupancy conditions, as building load characteristics vary. Other strategies may be implemented that cool the space below the heating set point and adjust the morning heating set point to avoid morning reheating.

11.5.3 Base Energy Credits Available. Base energy credits are shown in Tables 11.5.3-1 through 11.5.3-9, where the table is selected for the building use type, and the base credit is selected for the climate zone of the building .

11.6 Alternative Compliance Path (Not used)

11.7 Submittals 11.7.1 General. Compliance documentation and supplemental information shall be submitted in accordance with Section 4.2.2 of this standard.

11.7.2 Permit Application Documentation. Construction documents shall list which credits w ere used to meet the requirements of Section 11.5 for this project.

11.7.3 Completion Requirements. Construction documents shall require that equipment, controls, or sys- tems installed to meet the requirements of Section 11.5 shall meet completion requirements as specified in Sections 5.7.3, 6.7.3, 7.7.3, 8.7.3, 9.7.3, and 10.7.3.

11.8 Product Information (Not used)

11.9 Verification, Testing, and Commissioning. Building envelope components, equipment, controls, or systems installed to meet the requirements of Section 11.5 shall meet verification, testing, and commission- ing requirements as specified in Sections 5.9, 6.9, 7.9, 8.9, 9.9, and 10.9.

198 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)