ABAC ABC5-21120HD 10 HP Ironman Duplex Air Compressor - 120 Gallon Horizontal, 175 PSI, 32 CFM C1 Cast Iron Pump

The ABAC ABC5-21120HD is the Ironman duplex built around redundancy: two independent 5 HP motor and pump assemblies on a single 120 gallon horizontal ASME tank. Each side runs a C1 two-stage cast iron pump rated 16 CFM, for 32 CFM combined at a maximum 175 PSI. Because the two assemblies are separate, one can come down for service while the other keeps air on the line, which is the reason most shops step up to a duplex rather than buying one larger simplex machine. Choose 230V single-phase (ABC5-21120HD), 230V three-phase (ABC5-23120HD), or 460V three-phase (ABC5-43120HD).

Key specifications

• Models: ABC5-21120HD / ABC5-23120HD / ABC5-43120HD
• Power: 10 HP total (2 x 5 HP)
• Pumps: two C1 two-stage pumps, cast iron cylinders
• Air delivery: 32 CFM combined (16 CFM per pump)
• Maximum pressure: 175 PSI
• Tank: 120 gallon horizontal, ASME tank and safety valves
• Power supply: 230/1/60, 230/3/60, or 460/3/60
• Belt drive with fully enclosed belt guards
• Weight: 1120 lbs
• Dimensions: 25 x 79 x 52 in (230V single-phase), 25 x 79 x 55 in (three-phase)
• Assembled in the USA

Why a duplex instead of one bigger compressor

A duplex buys two things a single machine cannot. The first is uptime: a failed pump, a belt change, or an oil service takes half the capacity offline instead of all of it, so the floor keeps working. The second is staging. Under light or intermittent demand only one side needs to run, and an alternating control shares the hours between the two pumps rather than loading one of them all day. Each pump then runs cooler, rests longer, and reaches its service intervals later than a single pump doing the same total work. Both sides use the fully cast iron C1 pump of the Ironman range, where the extra mass absorbs heat and damps vibration through long run times, and both are two-stage, so 175 PSI arrives in two compression steps with cooling in between instead of one hot single-stage squeeze.

Sizing and how it compares

Size on CFM, not on horsepower. 32 CFM covers a multi-bay shop running impact wrenches, ratchets, grinders and a spray gun at the same time. If the duty is the same but cast iron is more pump than the work needs, the AB5-21120D is the hybrid T39 pump duplex on the same 120 gallon platform. Stepping up, the 15 HP ABC7-21120HD pairs two 7.5 HP sides for 42 CFM, and the 20 HP ABC10-23120HD reaches 64 CFM. If redundancy is not the point and 16 CFM is enough, the single-pump 5 HP ABC5-2180V does the same work on an 80 gallon vertical tank in a far smaller footprint.

Typical applications

Production shops, multi-bay service and tire centers, fabrication and welding bays, body shops, and fleet maintenance operations where several air tools draw at once and a compressor going down stops the whole floor. It also suits a facility with a process that cannot tolerate an air outage, where the second pump is insurance rather than extra capacity. At 79 inches long the horizontal tank runs along a wall and keeps the overhead clear.

Power, installation and air quality

Take three-phase power if the panel has it, since three-phase motors start easier and run cooler on a compressor that cycles all day, and the 460V build keeps the wire size down on a long run. Each side draws its own load, so size the circuit for both running together even if the control normally alternates them. Leave clearance around the belt guards and the flywheels for cooling air and for service access, and plan the drain: a 120 gallon receiver collects real water. Air leaves any piston compressor hot and saturated, so pair it with a refrigerated air dryer ahead of a paint booth, a plasma table, or any tool line you would rather not run water through.

Part of ABAC's Ironman cast iron range from the Atlas Copco group. See the rest of our 5 to 15 HP piston air compressors and the full piston air compressor range.