Danfoss AB-QM 4.0 Flexo, DN 15-20, PN 25

Description

The Danfoss AB-QM 4.0 Flexo, featuring an AB-QM valve, a 3-way ball valve design, and an 80mm center distance, is a compact and time-saving connection set. It is designed for creating optimal hydronic balance in cooling and heating applications with variable flow, such as those found in fan coil units (FCU) or chilled beams. Flow is controlled by the AB-QM pressure independent control valve to prevent overflow and maintain thermal unit efficiency.

Benefits: Installation

• Saving time and space
• Pre-assembled design
• Reduced installation time
• Easy setting and sizing, 100% authority and perfect control.

Trouble-free installations

• Compact and space-saving installation
• Pressure tested from factory - Nominal pressure PN25

Service

• Enable fast servicing, maintenance, and trouble shooting
• Easy flushing ✔️
• Easy draining ✔️
• Easy bypass ✔️
• Easy cleaning of filter ✔️
• Enables pressure and flow validation ✔️

Energy efficiency

Pressure independent flow control with AB-QM 4.0 offers improved indoor comfort with the best performance and energy savings, ensuring efficient energy transfer and minimal pumping costs.

Applications

The AB-QM 4.0 Flexo is a pre-assembled, pressure-tested set used for terminal units, such as Fan Coil Units (FCU). The Danfoss AB-QM 4.0 Flexo solution includes an H-body (with integrated shut-off valves and the possibility to mount measuring plugs), strainer, drain, and the associated Danfoss AB-QM 4.0 pressure independent control valve.

The AB-QM ensures and controls the required flow at every terminal unit, maintaining hydronic balance within the system. The control valve has 100% authority, ensuring control stability. At partial load, it prevents overflow, unlike conventional solutions, by always limiting the flow to the required amount. Installing the AB-QM divides the entire system into independent control loops.

A wide range of Danfoss actuators are available for the AB-QM 4.0, suitable for all control needs. These actuators are available as On/Off, 0-10 Volt, 4-20 mA, and digital via field bus.

Ordering

AB-QM 4.0 Flexo with AB-QM valve

AB-QM 4.0 Flexo Accessories

For a complete range of AB-QM actuators, accessories, and spare parts, please refer to the AB-QM data sheet.

Technical Data

Notes:

1. Factory setting of the valve is done at the nominal setting range.
2. Regardless of the setting, the valve can modulate below 1% of the set flow.
3. At minimum differential pressure, the valve reaches at least 90% of the nominal flow. Declaration of performance is available upon request.
4. AB-QM 4.0
5. Flexo connection set without AB-QM 4.0
6. If the medium temperature when using AB-QM DN 15-20 is below 2°C, then ice forming on the spindle must be prevented; therefore, the valve should be insulated with dedicated cooling insulation.

According to suitability and usage, especially in not oxygen-tight systems, please mind the instructions given by the coolant producer. Pc - pressure controller part; Cv - Control valve part.

Design

The AB-QM 4.0 Flexo assembly consists of the following components:

• 1. AB-QM 4.0 valve
• 2. Strainer
• 3. Drain connection & measuring station
• 4. Black handle
• 5. 3-way return valve
• 6. 3-way inlet valve
• 7. Bypass
• 8. Optional test plug connections
• 9. Stainless steel pipe

Presetting

The calculated flow can be adjusted easily without using special tools. The change of presetting (factory setting is 100%) can be done by following these steps:

1. Remove the blue protective cap or the mounted actuator.
2. Turn the pointer (clockwise to decrease) to the new setting.

Diagram illustrating the AB-QM 4.0 presetting dial for DN 15, 20, showing a scale from 0-10.

Installation

The small installation dimensions allow for easy installation of the Flexo connection set, even in limited spaces. The PICV valve should be installed in the return pipe from the thermal unit, with the flow directed according to the arrow on the AB-QM valve body. Danfoss highly recommends installing the Flexo using flexible pipes.

Diagram showing the installation of the AB-QM 4.0 Flexo in the return pipe from a Fan Coil Unit, connected to an HVAC System, with emphasis on flow direction and flexible pipe usage.

Note: The connection set can be installed in both cooling and heating applications.

Sizing

Example:

Given: Design flow in system 0.2 l/s (0.72m³/h = 720l/h).

Solution: In this case, we can select the AB-QM 4.0 DN15HF (Fig. 2) with Qnom = 1200 l/h for the AB-QM and presetting. The setting on the AB-QM DN 15 HF valve is the design flow divided by the nominal valve capacity: 720 l/h divided by 1200 l/h = 60%.

Flushing

There are three basic modes during flushing:

Forward flushing and draining

System flushing and draining should be done via the drain connection. Use the following procedure to drain (Fig. 3):

1. Connect a pipe to the drain connection.
2. Adjust the outlet 3-way valve to open the bypass [bypass symbol ①].
3. Open the 3-way valve on the inlet side [inlet valve symbol ②].
4. Open the shut-off valve on the drain [drain valve symbol ③].
5. Drain the system.

Diagram illustrating the flushing setup with connections and valve operations, including a scale for measuring tool dimensions (5 mm, 3.5-4.5 mm x 0.7 mm) and CLOSE/OPEN indicators.

Flushing (continuous)

Flushing of main pipe (bypass)

High-level cleanliness of the main pipe network flushing is achievable since thermal units are isolated. Use the following procedure for flushing the main pipe via the bypass pipeline (Fig. 4):

1. Adjust both 3-way valves to open the bypass [bypass symbol ① ②].
2. Start with the flushing procedure.

Diagram showing the bypass flushing setup for the main pipe, with the Fan Coil Unit isolated and connected to the HVAC System.

Backward flushing and draining

This offers cleaning of the thermal unit. Backward flushing of the fan coil should be done only with a fully open valve or a fully open actuator mounted on the valve. Use the following procedure for flushing the main pipe via the bypass pipeline (Fig. 5):

1. Connect a pipe to the drain connection [drain connection symbol ①].
2. Close the inlet 3-way valve [inlet valve symbol ②].
3. Open the shut-off valve on the drain [drain valve symbol ③].
4. Start with the flushing procedure.

Diagram illustrating the backward flushing setup, including a scale for measuring tool dimensions (5 mm, 3.5-4.5 mm x 0.7 mm) and CLOSE/OPEN indicators.

Tender Text

The terminal units shall be connected to the system by way of a valve assembly. This valve assembly shall have the following characteristics:

• The valve set shall comprise of the following components: PICV, H-piece valve body, measuring points, strainer valve, drain, and operating handles.
• The assembly shall have a bypass line that, by manipulating the ball valves, will enable insulation of the terminal unit and PICV to allow for forwards- and backward flushing of the system.
• The valve set shall have extended handles to allow operation with insulation.
• It shall be possible to shut off the bypass.
• The set shall be suitable for 25 Bars of static pressure (PN25).
• The set shall be leak tested.
• If required, the set shall be insulated by an EPP form-fitting shell.

The PICV shall have the following characteristics:

• Flow limitation function.
• Modulating below 1% of set flow, regardless of the setting.
• Authority of 1 at all settings.
• Able to close against 16 bars of differential pressure.
• Linear control characteristic.
• Setting scale in the percentage of flow.
• Control ratio 1:1000.
• Test plugs for pump optimization and flow measuring.
• Characteristic changed from linear to equal percentage characteristic at all sizes by adjusting actuator settings.
• Leakage rate Class IV.

Dimensions

Diagram showing the overall dimensions (A through H) of the AB-QM 4.0 Flexo assembly for different models.

Diagram showing connection port dimensions.

Diagram showing additional dimension measurements.