Modulating Damper Mixing Box


modulating damper mixing box

The operation of the Airextube is very simple and consists in using the hot air stratified at the top of the building to preheat the cold air introduced before it reaches the work area

The Airextube air make-up system can be used in all applications where the replacement of exhausted air is required due to general ventilation or local extraction. Without this air replacement the building is maintained under negative pressure, reducing the efficiency of exhaust fan and increasing infiltrations and draughts which make the work areas uncomfortable.

How it Works

modulating damper mixing box schematic

The operation of the Airextube is very simple and consists in using the hot air stratified at the top of the building to preheat the cold air introduced before it reaches the work area. The result is a uniform temperature from the top to the bottom of the building. Because the top layer of warm air is usually not utilized, the make-up air can then be considered as "free air". This represents an important advantage over the conventional gas or electric make-up units; the initial cost of an Airextube as well as its operation cost are much lower.

Available Configurations

modulating damper mixing box configurations

The Airextube is available in four different configurations allowing a wide variety of uses. This versatility permits the Airextube to cover every need of the industry.

Single Compensation System (SC)

This unit has one motorized back-draught damper at the rear of the casing (damper X) that closes automatically when the unit stops operating to avoid any air infiltration. The fan and damper are operated by an on-off remote control if needed. This control can be easily interlocked with the evacuation fan controls.

Compensation and Mixing System (CM)

The CM unit is similar to the CS, except for a mixing damper (damper Y) on top of the casing. This second damper, controlled by a thermostat placed in the ducting, pre-mixes the air in the housing during cold weather. As in the CS model, the unit is supplied with an "on-off" switch.

Recirculationg system (RS)

This model has a different function than the two others. It is used where air compensation is not required (ex. warehouses), but where the cost of heating can be lowered by using the stratification in top part of the building. The unit is provided with an opening (Z) at the bottom part of the housing. A recirculating duct must be used to bring the air from the floor level to the "Airextube". The unit is supplied with a "on-off" switch.

Combined System (CR)

This model is provided with a damper (X) at the back and a damper (z) at the bottom of the casing. The unit has two functions : during the day, when the exhaust fans are working, it will act as an air compensation unit (CS); during the night and week ends, it functions as an air recirculation unit (RS). The unit is supplied with a three position remote control (compensation - off-recirculation).

Standard Characteristics

Made in galvanized steel, it includes the supports of the fan and motor. The housing is supplied with a door providing easy access to components and for the electrical connections to the remote control.

Axial type fan, statically and dynamically balanced. It is connected to the motor by means of a shaft mounted on two pillow-blocks and a V-belt drive.

Type TEFC for continuous duty available in 110/220/1/60 or 230/460/575/3/60 for motor2 HP. Available in 230/460/575/3/60 for motors 3 HP et 5 HP.

Motorizeddampers :
Made in steel. The compensation damper (damper-X) is provided with a weather seal. The dampers are controlled by single phase industrial actuator.

Tube :
The tube itself is made of fire retardant polyethylene fabric, 8 mils thick, and supplied with support wire and duct hangers.

Options and Accessories

Weather hood(model CS, CM, CR)
Placed outside thebuilding, it prevents water and snow from entering the unit. It is supplied witha bird screen; it can be provided with a mosquito net as an option.

Recirculating duct(model RS, CR)
A recirculating duct of variable length, provided with a screen at the inlet can be ordered.

Emergency thermostat (model CS, CM, CR)
A protection thermostat in the control box is available as an option. This thermostat stops the unit if the room temperature reaches 7°C (45°F) or less. It is used for protection in case of heating system break-down during weekends and holidays.


modulating damper mixing box specifications

Airextube Model
CFM m³/HR Motor (H.P.) Dim. A. Dim. L. Tube Dia. Tube Length
mm in mm in
mm ft
24 CS 24 CM 7 000 2 30" 762 18" 457,2 24" 610 100’ 30,48
24 RS 24 CR 11 970 30" 762
30 CS 30 CM 10 000 2 36" 915 18" 457,2 30" 762 100’ 30,48
30 RS 30 CR 17 100 36" 915
36 CS 36 CM 14 000 3 42" 1067 24" 609,6 36" 915 100’ 30,48
36 RS 36 CR 23 940 42" 1067
42 CS 42 CM 19 000 5 48" 1219 24" 609,6 42" 1067 100’ 30,48
42 RS 42 CR 32 490 48" 1219
48 CS 48 CM 25 000 5 54" 1372 30" 762 48" 1219 100’ 30,48
48 RS 48 CR 42 750 54" 1372

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