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30
AF24-MFT (-S) US
Proportional Damper Actuator, Spring Return Fail-Safe, Multi-Function Technology
®
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Application
For proportional modulation of dampers and control valves in HVAC systems.
The AF24-MFT US provides mechanical spring return operation for reliable fail-
safe application.
Default/Configuration
Default parameters for 2 to 10 VDC applications of the AF24-MFT US actuator are
assigned during manufacturing. If required, custom versions of the actuator can
be ordered. The parameters noted in the Technical Data table are variable.
These parameters can be changed by three means:
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Operation
The AF24-MFT US actuator provides 95° of rotation and is provided with a
graduated position indicator showing 0° to 95°. The actuator will synchronize
the 0° mechanical stop or the physical damper or valve mechanical stop and use
this point for its zero position during normal control operations. A unique
manual override allows the setting of any actuator position within its 95° of
rotation with no power applied. This mechanism can be released physically by
the use of a crank supplied with the actuator. When power is applied the manual
override is released and the actuator drives toward the fail-safe position.
The actuator uses a brushless DC motor which is controlled by an Application
Specific Integrated Circuit (ASIC) and a microprocessor. The microprocessor
provides the intelligence to the ASIC to provide a constant rotation rate and to
know the actuator’s exact position. The ASIC monitors and controls the
brushless DC motor’s rotation and provides a Digital Rotation Sensing (DRS)
function to prevent damage to the actuator in a stall condition. The position
feedback signal is generated without the need for mechanical feedback
potentiometers using DRS. The actuator may be stalled anywhere in its normal
rotation without the need of mechanical end switches.
The AF24-MFT US is mounted directly to control shafts up to 1.05" diameter by
means of its universal clamp and anti-rotation bracket. A crankarm and several
mounting brackets are available for damper applications where the actuator
cannot be direct coupled to the damper shaft. The spring return system provides
minimum specified torque to the application during a power interruption. The
AF24-MFT US actuator is shipped at +5° (5° from full fail-safe) to provide
automatic compression against damper gaskets for tight shut-off.
NOTE: Please See Documentation on Multi-Function Technology, page 287.
Dimensions
(Inches [mm])
1.97"
3.15" [80]
3.86" [98]
3.25" [82.7]
2.24"
[57]
[50]
1.93"
[49]
2.64"
[67]
0.26" [6.5]
5.85" [148.5]
10.47" [266]
0.35" [9]
0.39" [10]
0.65" [16.5]
0.19" [5]
K4-2 US
(supplied)
1/2" Centered
(Default)
3/4"
Centered
(Field
Selectable)
1.05"
Centered
(Field
Selectable)
K4-1 US
(optional)
3/4" to 1.05"
Adjustable
K4 US
(optional)
3/8" to 3/4"
Adjustable
D001
Technical Data
AF24... US
Power supply
24 VAC, ± 20%, 50/60 Hz
24 VDC, ±10%
Power consumption
running 6 W
holding 2.5 W
Transformer sizing
10 VA (Class 2 power source)
Electrical connection
3 ft, 18 GA appliance cable
1/2” conduit connector
Overload protection
electronic throughout 0 to 95° rotation
Operating range Y*
2 to 10 VDC
4 to 20 mA (w/500
7
, 1/4
7
resistor) ZG-R01
Input impedance
100 k
7
for 2 to 10 VDC (0.1 mA)
500
7
for 4 to 20 mA
1500
7
for PWM, Floating point and On/Off control
Feedback output U*
2 to 10 VDC, 0.5 mA max
Torque
min 133 in-lb (15 Nm)
Direction of rotation*
spring reversible with cw/ccw mounting
motor reversible with built-in switch
Mechanical
angle of rotation*
95°, adjustable 35° to 95° w/ZDB-AF2 US
Running time
motor*
spring
150 seconds constant
<20 sec spring return fail safe position
Angle of Rotation
adaptation
Off (Default)
Override control*
Min. (Min Position) = 0%
- ZS (Mid. Position) = 50%
- Max. (Max. Position) = 100%
Position indication
visual indicator, 0° to 95°
(0° is spring return position)
Auxiliary switches
(AF24-MFT-S US)
2 x SPDT 7A (2.5A) @ 250 VAC, UL Approved one
set at +5°, one adjustable 25° to 85°
Manual override
3 mm hex crank (supplied)
Humidity
5 to 95% RH, non-condensing
Ambient temperature
-22 to 122° F (-30 to 50° C)
Storage temperature
-40 to 176° F (-40 to 80° C)
Housing
NEMA 2, IP54
Housing material
zinc coated metal
Noise level
less than 45 dB (A)
Agency listings
cULus acc. to UL 873 and
CAN/CSA C22.2 No. 24-93
Quality standard
ISO 9001
Servicing
maintenance free
Weight
6.0 lbs. (2.7 kg)
* Variable when configured with MFT options
K20901 - 01/09 - Subject to change. © Belimo Air
controls (USA), Inc.