ASHRAE-90.1-2022- - Page 176
Extracted Content
10.4.6.1 Part-Load Controls and Efficiency. Compressed air systems where the total motor power is 25 hp or more shall be equipped with appropriately sized trim compressor(s) and primary storage. The compressed air system shall comply with either of the following:
a. The compressed air system shall include one or more variable-speed-drive (VSD) compressors. For sys-
tems with more than one compressor, the total combined capacity of the VSD compressor(s) acting as trim compressors must be at least 1.25 times the largest net capacity increment between combinations of compressors. The compressed air system shall include primary storage of at least 3 gal per actual cubic feet per minute (acfm) of the largest trim compressor . b. The total effective trim capacity of a compressor system is the size of the continuous operational range
where the specific power of the compressor(s) ( kW /100 acfm) is within 15% of the specific power at their most efficient operating point. The total effective trim capacity of the system is the sum of the effective trim capacity of the trim compressors .
Systems shall include primary storage of at least 4 gal/acfm of the largest trim compressor and meet (1) or (2) as follows:
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S ystems with more than one compressor, not including backup compressors, shall include a compressor or set of compressors with total effective trim capacity at least the size of the largest net capacity increment between combinations of compressors, or the size of the smallest compressor, whichever is larger.
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For s ystems with one compressor, not including backup compressors, the total effective trim capacity shall include the range from 70% to 100% of rated capacity. Exceptions to 10.4.6.1:
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Alterations where the total combined added or replaced compressor motor power is less than the average per-compressor power of all compressors in the system .
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Alterations where all added or replaced compressors are VSD compressors and the compressed air system includes primary storage of at least 3 gal/acfm of the largest trim compressor.
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Compressed air systems that have been approved by the authority having jurisdiction as having demonstrated that the system serves loads for which typical air demand fluctuates less than 10%.
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Alterations of existing compressed air systems that include one or more centrifugal compressors.
10.4.6.2 Controls. Compressed air systems with three or more compressors, including backup compressors, with a combined input power of more than 150 hp shall operate with controls that are able to choose the most energy -efficient combination and loading of compressors in the system based on the current compressed air demand.
10.4.6.3 Monitoring. Compressed air systems having a combined input power rating equal to or greater than 150 hp shall have an energy and air demand monitoring system with the following minimum requirements:
a. Measurement of system pressure b. Measurement or calculation of current or power of each compressor c. Measurement or determination of total airflow from all compressors in acfm d. Data logging of pressure, power in kW, airflow in acfm, and compressed air system specific power in kW /
100 acfm at intervals of five minutes or less e. The equipment shall be configured to record not less than six months of data and shall be capable of
exporting the data. f. Visual trending display of each recorded point, load, and specific power.
10.4.6.4 Leak Testing of Compressed Air Piping. Compressed air system piping shall be pressure tested after being isolated from the compressed air supply, storage tanks, and end uses. The piping shall be pressurized to the design operating pressure and the pressure allowed to stabilize. Test pressures shall be held for no less than 30 minutes, with no loss of pressure greater than 1.0%.
For piping less than or equal to 50 adjoining feet in length, connections shall optionally be tested with a noncorrosive leak-detecting fluid or other leak detecting methods at the discretion of the authority having jurisdiction .
10.4.6.5 Pipe Sizing. For new systems and additions to systems with operating pressures above 50 psig, compressed air piping greater than 50 adjoining feet in length shall be designed and installed to minimize frictional losses in the distribution network.
Service line piping that delivers compressed air from distribution piping to end uses shall have inner diameters greater than or equal to 1 in.
Added or replaced piping in existing systems shall meet the requirements of Section 10.4.6.5(a). New systems shall meet the requirements of either Section 10.4.6.5(a) or (b).
174 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)