Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Compressed Air Systems
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## The compressor type shall be selected to match the facility duty cycle, required air quality, and maximum operating pressure.
−## For general facility service (shops, maintenance, light laboratory) the lubricated rotary screw with a refrigerated dryer is the 80% case: it offers continuous-duty capability, good efficiency, and the lowest installed cost for its capacity. Oil-free machines carry a significant cost premium and are justified only where the application genuinely cannot tolerate any oil carryover. Reciprocating machines remain economical for intermittent-duty shops at lower first cost. {note}
+## For general facility service (shops, maintenance, light laboratory) the lubricated rotary screw with a refrigerated dryer is the most common selection: it offers continuous-duty capability, good efficiency, and the lowest installed cost for its capacity. Oil-free machines carry a significant cost premium and are justified only where the application genuinely cannot tolerate any oil carryover. Reciprocating machines remain economical for intermittent-duty shops at lower first cost. {note}
## The compressor type and lubrication class shall be as scheduled.
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max: 200
step: 5
−setpoints: [100, 110, 125, 150, 175, 200]
+setpoints: [90, 100, 110, 125, 150, 175, 200]
```
## The compressor drive motor shall be sized and wired in accordance with NEC Article 430.
−## Branch circuit conductors for a continuous-duty motor are sized at not less than 125% of full-load current, and direct-on-line starting draws six to eight times full-load current, which governs disconnect and overcurrent selection. The motor full-load and locked-rotor amperes must be confirmed with the electrical engineer. {note}
−
```datasheet
label: Compressor motor voltage
…6 unchanged lines
```
+## Branch circuit conductors for a continuous-duty motor are sized at not less than 125% of full-load current, and direct-on-line starting draws six to eight times full-load current, which governs disconnect and overcurrent selection. The motor full-load and locked-rotor amperes must be confirmed with the electrical engineer. {note}
+
# Receiver {toc}
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## The required air purity class shall be specified at each point of use per ISO 8573-1.
−## Typical class assignments by application: general shop and maintenance air at Class 3.4.3 (particles.water.oil); instrument air at Class 2.2.1; general laboratory air at Class 2.2.2; food-contact air at Class 1.2.1 or better. The class drives the dryer dew point and the filtration grades and must be set before the train is selected. {note}
−
```datasheet
label: Required ISO 8573-1 purity class (particles.water.oil)
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```
+## Typical class assignments by application: general shop and maintenance air at Class 3.4.3 (particles.water.oil); instrument air at Class 2.2.1; general laboratory air at Class 2.2.2; food-contact air at Class 1.2.1 or better. The class drives the dryer dew point and the filtration grades and must be set before the train is selected. {note}
+
## An aftercooler shall be provided downstream of the compressor to reduce discharge air temperature and condense the bulk of the moisture before it enters the dryer.
−## Removing the heat of compression here drops out most of the water as liquid, which the moisture separator captures, so the dryer receives a far smaller moisture load. {note}
−
```datasheet
label: Aftercooler type
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```
+## Removing the heat of compression here drops out most of the water as liquid, which the moisture separator captures, so the dryer receives a far smaller moisture load. {note}
+
## A moisture separator with automatic drain shall be installed downstream of the aftercooler to remove condensed liquid before the dryer.
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```
−## A refrigerated dryer shall deliver a pressure dew point of 35°F to 39°F (2°C to 4°C) at operating pressure.
−
−## This dew point is adequate for general-service air distributed entirely within heated indoor space and is the 80% case for shop and maintenance systems. It is not adequate where any piping is exposed to freezing temperatures. {note}
−
−## A desiccant dryer shall be provided where the application requires a pressure dew point of −40°F (−40°C) or lower, such as instrument air or any freeze-exposed distribution.
−
−## Refrigerant-circuit refrigerated dryers shall comply with ASHRAE 15.
−
−## Desiccant dryers reach −40°F pressure dew point routinely and −100°F for extreme cases. {note}
−
```datasheet
label: Required outlet pressure dew point
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```
−## Point-of-use coalescing and particulate filtration shall be provided to achieve the specified oil and particle classes at the use point.
+## A refrigerated dryer shall deliver a pressure dew point of 35°F to 39°F (2°C to 4°C) at operating pressure.
−## Coalescing filters remove oil aerosol and fine particulate; a particulate after-filter protects against desiccant fines where a desiccant dryer is used. Filtration grade is selected to meet the ISO class, not over-specified, because each filter stage adds pressure drop. {note}
+## This dew point is adequate for general-service air distributed entirely within heated indoor space and is the usual choice for shop and maintenance systems. It is not adequate where any piping is exposed to freezing temperatures. {note}
+## A desiccant dryer shall be provided where the application requires a pressure dew point of −40°F (−40°C) or lower, such as instrument air or any freeze-exposed distribution.
+
+## Refrigerant-circuit refrigerated dryers shall comply with ASHRAE 15.
+
+## Desiccant dryers reach −40°F pressure dew point routinely and −100°F for extreme cases. {note}
+
+## Point-of-use coalescing and particulate filtration shall be provided to achieve the specified oil and particle classes at the use point.
+
```datasheet
label: Point-of-use filtration grade
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```
+## Coalescing filters remove oil aerosol and fine particulate; a particulate after-filter protects against desiccant fines where a desiccant dryer is used. Filtration grade is selected to meet the ISO class, not over-specified, because each filter stage adds pressure drop. {note}
+
# Distribution Piping {toc}
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## A high-pressure header with pressure-reducing stations shall be provided where specialty equipment requires pressure above the general-service level.
−## Where part of the facility needs 150 to 200 psig and the rest needs 100 psig, a dedicated high-pressure header fed by a booster, with regulators dropping to general service at the use points, is more efficient than running the whole facility at the higher pressure. {note}
−
```datasheet
label: System pressure architecture
…5 unchanged lines
```
+## Where part of the facility needs 150 to 200 psig and the rest needs 100 psig, a dedicated high-pressure header fed by a booster, with regulators dropping to general service at the use points, is more efficient than running the whole facility at the higher pressure. {note}
+
## Distribution mains should be looped and sized with reserve capacity for future expansion.
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## The compressor shall be isolated to limit structure-borne noise and vibration transmitted to adjacent occupied spaces.
−## Untreated compressors are a chronic source of complaints in occupied buildings because vibration travels through the slab and piping into walls and ceilings. Isolation at the machine and at every pipe connection interrupts that path. {note}
−
−## Spring vibration isolators shall be provided under each compressor rated above 10 hp.
−
−## Flexible pipe connectors not less than 18 in. long shall be installed at all compressor air connections.
−
−## The flexible connector decouples the rigid distribution piping from the vibrating compressor so that pulsation and vibration are not transmitted into the building piping. {note}
−
```datasheet
label: Compressor vibration isolation
…5 unchanged lines
```
+## Untreated compressors are a chronic source of complaints in occupied buildings because vibration travels through the slab and piping into walls and ceilings. Isolation at the machine and at every pipe connection interrupts that path. {note}
+
+## Spring vibration isolators shall be provided under each compressor rated above 10 hp.
+
+## Flexible pipe connectors not less than 18 in. long shall be installed at all compressor air connections.
+
+## The flexible connector decouples the rigid distribution piping from the vibrating compressor so that pulsation and vibration are not transmitted into the building piping. {note}
+
# Testing {toc}
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## Equipment and piping shall be delivered in the manufacturer's packaging and protected from weather, dust, and physical damage until installation.
−## Pipe ends and equipment connections capped at the factory must stay capped until connected, because debris that enters open piping migrates to filters and valves during startup. {note}
+## Pipe ends and equipment connections capped at the factory must stay capped until connected, because debris that enters open piping migrates to filters and valves during startup.
## Pipe and fitting openings shall remain capped or plugged until the piping is connected.
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- Compressor lubricant (first change)
```