ABAC AB7-21120D 15 HP Two-Stage Duplex Air Compressor - 120 Gallon Horizontal, 175 PSI, 44.6 CFM

The ABAC AB7 Duplex is the largest piston duplex in ABAC's Hybrid Pro range: two independent 7.5 HP motor and pump assemblies on one 120 gallon horizontal ASME tank, producing a combined 44.6 CFM at a maximum 175 PSI. Alternating operation spreads runtime evenly across both pumps, while simultaneous operation covers peak demand that would overwhelm a single-pump machine. The second reason shops choose a duplex is redundancy: if one pump comes out for service, the other keeps the line pressurized instead of shutting the floor down. Choose 230V single-phase (AB7-21120D), 230V three-phase (AB7-23120D), or 460V three-phase (AB7-43120D).

Key specifications

• Models: AB7-21120D 230V single-phase (part 8090304257), AB7-23120D 230V three-phase (part 8090304265), AB7-43120D 460V three-phase (part 8090304273)
• Power: 15 HP total, two 7.5 HP motors, 60 Hz
• Pumps: two T39 two-stage pumps, hybrid aluminum and cast iron construction
• Air delivery: 22.23 CFM per pump, 44.6 CFM combined with both sides running
• Maximum pressure: 175 PSI
• Tank: 120 gallon horizontal, ASME tank and safety valves
• Alternating or simultaneous pump operation for uptime and peak capacity
• Fully programmable control panel with adjustable control parameters
• Belt drive with fully enclosed belt guards
• Weight: 910 lbs | Dimensions: 25 x 79 x 55 in
• 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 while the other side carries the load. The second is staging. Under light or intermittent demand the control alternates the two sides and shares the hours between them rather than loading one pump all day; when demand climbs, both sides run together for the full 44.6 CFM. Each pump then runs cooler, rests longer and reaches its service intervals later than one large pump doing the same total work. That is also why the published rating is 22.23 CFM per side: the machine is designed to spend most of its life running on one pump and to call on the second only when the line asks for it.

How it compares

Within the Hybrid Pro duplex range the choice is capacity on an identical footprint. The AB5-21120D pairs two 5 HP pumps for 33.2 CFM on the same 120 gallon horizontal tank and the same 25 x 79 x 55 in floor space, so the AB7 buys roughly eleven more CFM without asking for another square foot of shop, at 910 lbs against 892. Against a single machine, the AB7-2180V runs one 7.5 HP T39 pump at 22.2 CFM; the duplex doubles that and adds the fallback a single-pump compressor cannot give you. If the duty cycle is hard enough to want full cast iron rather than the hybrid T39, the ABC7-21120HD Ironman duplex is also 15 HP on 120 gallons, at 42 CFM with C1 cast iron pumps, and the ABC7-2112DH2P reaches 52 CFM at the same 15 HP with C2 pumps. Decide on duty cycle first and CFM second: the hybrid pump is the right answer for a shop that works in bursts, the cast iron pump for one that runs air most of the day.

Typical applications

High-demand fabrication shops, collision centers running more than one booth, tire and fleet service bays, and industrial plants where sandblasting, plasma cutting, or several pneumatic stations draw at the same time. Those loads are the case for a duplex: demand arrives in surges rather than steadily, so one pump carries the baseline and the second joins only when the line calls for it, which keeps both motors off the short-cycling that shortens a single large compressor's life. ABAC builds the Hybrid Pro range for professional settings, metal and wood workshops and auto body and repair shops among them.

Power, installation and air quality

Take three-phase power if the panel has it. A three-phase motor draws less current per leg, starts easier and runs cooler on a compressor that cycles all day, and the 460V build keeps the wire size down on a long run from the panel. Each side draws its own load, so size the circuit for both pumps running together even though the control normally alternates them. At 79 inches long the horizontal tank runs along a wall and keeps the overhead clear, but leave room at the belt guards and flywheels for cooling air and service access, and plan the drain, because a 120 gallon receiver collects real water.

Two-stage compression still sends warm, wet air down the line, so size a refrigerated dryer above the compressor's output rather than to the pipe. At 50 CFM the ABAC COOL 50 is the smallest dryer in the COOL range that covers 44.6 CFM with headroom, and it is worth having ahead of a paint booth, a plasma table or any tool line you would rather not run water through. Part of ABAC's 2-Stage Hybrid Pro Duplex range from the Atlas Copco group. Browse the rest of our piston air compressors and our refrigerated air dryers.