ASHRAE-90.1-2022- - Page 214

Extracted Content

EER, SEER, COP, and HSPF shall be at AHRI test conditions. Fan energy shall be modeled separately according to Section 12.5.2(h). Supply and return/relief system fans shall be modeled as operating at least whenever the spaces served are occupied, except as specifically noted in Table 12.5.2-1. d. Minimum Outdoor Air Ventilation Rate. Minimum outdoor air ventilation rates shall be the same for

both the budget building design and proposed design . Exhaust air energy recovery shall be modeled for the budget building design in accordance with Section 6.5.6.1. Exceptions to 12.5.2(d):

1. When modeling demand control ventilation in the proposed design for spaces where demand con- trol ventilation is not required per Section 6.4.3.8.
2. Where the minimum outdoor air intake flow in the proposed design is provided in excess of the amount required by Section 6.5.3.8, the baseline building design shall be modeled to reflect the minimum amount required by Section 6.5.3.8. e. Economizers. All budget building systems as listed in Table 12.5.2-1 shall have air economizers in

accordance with Section 6.5.1 and Section 12.5.2(i). The high-limit shutoff shall be in accordance with Table 12.5.2-4. f. Preheat Coils. If the proposed design system has a preheat coil, the budget building design ’s system shall be modeled with a preheat coil controlled in the same manner. g. Supply Airflow Rates. System design supply air rates for the budget building design shall be based on a

supply-air-to-room temperature set-point difference of 20°F or the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards, whichever is greater. For systems with multiple zone thermostat set points, use the design set point that will result in the lowest supply air cooling set point or highest supply air heating set point . If return or relief fans are specified in the proposed design, the budget building design shall also be modeled with fans serving the same functions and sized for the budget system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger. Exceptions to 12.5.2(g):

1. For systems serving laboratory spaces, airflow rate shall be based on a supply-air-to-room temperature set-point difference of 17°F or the required ventilation air or makeup air, whichever is greater.
2. If the proposed design HVAC system airflow rate based on latent loads is greater than the design airflow rate based on sensible loads, then the same supply-air-to-room-air humidity ratio difference (lb) used to calculate the proposed design airflow shall be used to calculate design airflow rates for the budget building design . h. Fan System Efficiency. Fan system efficiency (bhp per cfm of supply air, including the effect of belt

losses but excluding motor and motor drive losses) shall be the same as the proposed design or up to the limit prescribed in Section 6.5.3.1, whichever is smaller. If this limit is reached, each fan shall be proportionally reduced in brake horsepower until the limit is met. Fan electrical power shall then be determined by adjusting the calculated fan hp by the minimum motor efficiency prescribed by Section 10.4.1 for the appropriate motor size for each fan. Exception to 12.5.2(h): When a proposed design includes energy recovery but it is not required in the

budget building design per Section 12.5.2(d), the fan power of those baseline systems shall be equal to either the proposed design system or the fan power limit in Section 6.5.3.1 calculated without fan power credit for energy recovery, whichever is less. i. Equipment Capacities. The equipment capacities for the budget building design shall be sized proportionally to the capacities in the proposed design based on sizing runs, i.e., the ratio between the capacities used in the annual simulations and the capacities determined by the sizing runs shall be the same for both the proposed design and budget building design . Where multiple HVAC zones are combined into a single thermal block or modeled as identical thermal blocks to which multipliers are applied in accordance with Table 12.5.1, the equipment capacities for the budget building design shall be determined as follows:

1. For budget system Types 8 and 10, equipment capacity shall be 9000 Btu/h.
2. For budget system Types 5, 6, 7, 9, and 11, equipment capacity shall be based on the load of the ther- mal block divided by the number of combined HVAC zones .
3. For budget system Types 1, 2, 3, and 4, equipment capacity shall be based on the total load of all associated thermal blocks, including multipliers, divided by the total number of corresponding HVAC systems specified in the design documents.

Unmet load hours for the proposed design or baseline building designs shall not exceed 300 hours (of the 8760 hours simulated). The unmet load hours for the proposed design shall not exceed the unmet

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