Danfoss AB-QM Pressure Independent Control Valve (PICV) DN 15-250

Overview

The Danfoss AB-QM is a pressure independent control valve (PICV) that combines two functions in one body: a differential pressure controller and a control valve with an adjustable flow limiter. The built-in pressure controller keeps the differential pressure across the control part constant, so the valve always has full authority and automatically limits flow to the value set on the dial. Fitted with an actuator, it controls temperature at terminal units such as fan coils, air handling units, chilled beams, induction units and heat exchangers; without an actuator, it acts as an automatic flow limiter. The range covers DN 15 to DN 250, for flows from 200 l/h up to 500 m³/h.

Seven Star LLC supplies the Danfoss AB-QM, its actuators and installation accessories to MEP contractors, consultants and facility managers across Oman and the GCC, with engineering support in Muscat. In chilled water systems, which carry most of the cooling load in Gulf buildings, poor hydronic balance shows up as overflowing terminal units near the pump, starved units at the end of the line, low delta-T at the chillers and more pumps running than designed. A correctly sized PICV addresses all of these at source.

Operating Principle

Inside the valve, a diaphragm-operated pressure controller senses the pressure before and after the control cone and adjusts its own opening to hold that differential constant. Whatever the pump head or the opening and closing of other circuits, the pressure drop across the control valve therefore stays the same, and the flow through the Danfoss AB-QM depends only on the stroke position set by the actuator and on the maximum flow preset on the dial. The control part has a linear characteristic, which an actuator such as NovoCon S or AME 110 can convert to equal percentage for water-to-air applications.

Because the valve limits flow on its own, a system built with Danfoss AB-QM valves is balanced at every load, not only at full design load. Danfoss specifies a control range of 1:1000, and regardless of the setting the valve can modulate below 1 % of set flow. At the minimum differential pressure, the valve reaches at least 90 % of nominal flow. The practical consequences are stable room temperature with minimal hysteresis, no hunting at part load, and pumping energy that matches the actual demand.

Engineering Design of the Danfoss AB-QM

Threaded Danfoss AB-QM 4.0 valves from DN 15 LF to DN 32 HF have DZR brass bodies, EPDM membranes and O-rings, PPSU guide parts and stainless steel springs, with a 4 mm stroke and PN 25 rating. They are available with external thread to ISO 228/1 (G¾A to G1½A) or internal thread to ISO 7/1 (Rp½ to Rp1¼), and with or without test plugs. Threaded DN 40 and DN 50 and all flanged sizes use grey iron EN-GJL-250 bodies, PN 16 rating and longer strokes of 10 to 36 mm. Flanged connections follow EN 1092-2.

The flow setting of the Danfoss AB-QM is always visible on the valve, and the test plugs allow the actual flow to be verified with a measuring instrument during commissioning or troubleshooting. Medium temperature is +2 to +95 °C for DN 15 to 32 and +2 to +120 °C for larger sizes, with operation down to -20 °C possible when the spindle is protected by vapour-tight insulation. Danfoss tested the valves with 50 % ethylene and propylene glycol, and the AB-QM 4.0 range has EPP insulation shells available for DN 15 to 32.

Key Features

The Danfoss AB-QM brings control and balancing together in one component:

• Integrated differential pressure controller gives 100 % valve authority at every load.
• Automatic flow limitation removes the need for separate static balancing valves.
• Sizes from DN 15 LF to DN 250 HF, with nominal flows from 200 l/h to 500,000 l/h.
• Setting range of 10 to 100 % on AB-QM 4.0 threaded valves and 40 to 100 % on DN 40 and above, with the setting always visible.
• Test plugs on the AB-QM 4.0 for on-site flow verification.
• Linear characteristic with a control range of 1:1000 and modulation below 1 % of set flow.
• Leakage class IV to IEC 60534-4 with recommended actuators on threaded DN 15 to 32, and shut-off to ISO 5208 class A.
• Compatible with the NovoCon S digital actuator for BACnet or Modbus control and data.

Industrial Applications

The Danfoss AB-QM is specified for the chilled water side of commercial towers, hotels, hospitals, malls, universities and government buildings, where hundreds of fan coil units and air handling units must each receive their design flow. In Muscat and across the GCC, many of these buildings are connected to district cooling plants that charge for low delta-T, so the ability of a PICV to stop overflow at part load has a direct cost impact. Data centres and pharmaceutical facilities use the same valves on precision cooling coils that need stable flow regardless of other loads.

For larger plant applications, flanged Danfoss AB-QM valves up to DN 250 regulate flow to chillers, secondary heat exchangers and energy transfer stations. Seven Star LLC supplies the Danfoss AB-QM together with matching actuators, union and welding tailpieces, and the official data sheet, and can help translate a terminal unit schedule into valve sizes and flow settings for projects in Muscat, Sohar, Duqm and Salalah.

Technical Specifications

The data below for the Danfoss AB-QM is taken from the Danfoss data sheet AI309581732428en-030601 (2026.01):

How to Order

To request a quotation for the Danfoss AB-QM, send Seven Star LLC the terminal unit schedule with design flows, pipe sizes, available differential pressure, control signal or BMS protocol and preferred connection type. Our Muscat team will confirm valve sizes and actuators, advise on stock and lead time for Oman and the GCC, and provide the official Danfoss data sheet. Other Danfoss products on our site include the Danfoss MBS 3000 pressure transmitter and the Danfoss VLT AutomationDrive FC 302, and chilled water energy can be measured with the pFlow E5 ultrasonic energy meter.