3.4.4 Supply/extract air tracking control
Fig. 8: Supply/extract air tracking control
1
Supply air controller (master), compact controller
2
Extract air controller (slave), compact controller
3
Volume flow rate operating range (q
vmin
and q
vmax
)
4
Room temperature controller (control signal for
supply air controller)
5
Volume flow rate actual value for the supply air con-
troller
6
Volume flow rate actual value for the extract air con-
troller
In individual rooms and closed-off office areas, where the balance between supply and extract air flow rate has to be
maintained. Otherwise, annoying whistling noises can occur at door gaps, and the doors can be difficult to open. For
this reason, the extract air should also have variable control in a VAV system.
The control signal from the room temperature controller is switched to the supply air controller in this example. The
actual value signal of the supply air controller is then connected to the extract air controller (slave controller) as a
setpoint value signal. The actual volume flow rate of the supply air controller (master) is thus used as the reference
value for the extract air controller (slave). The connection can be made as an analogue signal or digitally via the
Modbus. As a consequence, the extract air always follows the supply air.
Setting for the slave controller in the simplest case (same VAV terminal units and dimensions):
q
vmin
= 0 m³/h
q
vmax
= q
vnom
ð
q
vnom
is specified on the adjustment sticker.
When using different VAV terminal unit types or dimensions for tracking control, special setting instructions for q
vmin
and q
vmax
of the slave controller must be observed due to the different nominal volume flow rates.
Alternatively, the control signal of the room temperature controller can also be connected in parallel to the supply air
and the extract air controller. The limitation due to the technical data of the controller outputs (current) and the con-
troller inputs (input resistances) must be observed.
Structure and functional description
Operating modes > Supply/extract air tracking control
Control component Compact XM0 • XS0 for VAV terminal unit TVE
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