ASHRAE-90.1-2022- - Page 090
Extracted Content
Table 6.5.1.2.1 Fluid Economizer Sizing Dry-Bulb and Wet-Bulb Requirements for Computer Rooms
| Climate Zone | Col2 | Water Cooled | Col4 | Air Cooled |
|---|---|---|---|---|
| Climate Zone | Climate Zone | ** Dry Bulb, °F** | ** Wet Bulb, °F** | Dry Bulb, °F |
| 0 | A | NR | NR | NR |
| 0 | B | NR | NR | NR |
| 1 | A | NR | NR | NR |
| 1 | B | NR | NR | NR |
| 2 | A | 40.0 | 35.0 | 30.0 |
| 2 | B | 35.0 | 30.0 | 30.0 |
| 3 | A | 40.0 | 35.0 | 25.0 |
| 3 | B | 30.0 | 25.0 | 25.0 |
| 3 | C | 30.0 | 25.0 | 30.0 |
| 4 | A | 40.0 | 35.0 | 25.0 |
| 4 | B | 30.0 | 25.0 | 25.0 |
| 4 | C | 30.0 | 25.0 | 25.0 |
| 5 | A | 40.0 | 35.0 | 20.0 |
| 5 | B | 30.0 | 25.0 | 20.0 |
| 5 | C | 30.0 | 25.0 | 25.0 |
| 6 | A | 35.0 | 30.0 | 20.0 |
| 6 | B | 30.0 | 25.0 | 20.0 |
| 7 | 30.0 | 25.0 | 20.0 | |
| 8 | 30.0 | 25.0 | 20.0 |
NR—Not required
Table 6.5.1.3 DX Cooling Stage Requirements for Modulating Airflow Units
| Rating Capacity, Btu/h | Minimum Number of Mechanical Cooling Stages | Minimum Compressor Displacementa |
|---|---|---|
| 65,000 and <240,000 | 3 | 35% of full load |
| 240,000 | 4 | 25% full load |
a. For mechanical cooling stage control that does not use variable compressor displacement the percent displacement shall be equivalent to the mechanical
cooling capacity reduction evaluated at the full load rating conditions for the compressor.
6.5.1.4 Economizer Heating System Impact. HVAC system design and economizer controls shall be such that economizer operation does not increase the building heating energy use during normal operation.
Exception to 6.5.1.4: Economizers on VAV systems that cause zone-level heating to increase due to a
reduction in supply air temperature.
6.5.1.5 Economizer Humidification System Impact. Systems with hydronic cooling and humidification systems designed to maintain inside humidity at a dew-point temperature greater than 35°F shall use a fluid economizer if an economizer is required by Section 6.5.1.
6.5.2 Simultaneous Heating and Cooling Limitation
6.5.2.1 Zone Controls. Zone thermostatic control shall prevent
a. reheating ; b. recooling ; c. mixing or simultaneously supplying air that has been previously mechanically heated and air that has
been previously cooled, either by mechanical cooling or by economizer systems ; and d. other simultaneous operation of heating and cooling systems to the same zone.
88 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)