Belimo VRD2 - TROX

Belimo VRP
Pressure Independent Control Characteristic
Pressure differential
1000
Pa
800
600
400
200
V min
� V
Volume flow
‡ max set value =
‡ min set value =
‡ max M
‡ min M
·
Vmax set value =
=
‡ max S
‡ max M
‡ max
‡ nom
‡ min
‡ max
‡ max S
‡ min S
.
. 100 %
. 100 %
‡ nom M
‡ nom S
V max
� V
20 40 60 80 100
% of ‡ nom
. 100 %
3
Volume Flow Control
The volume flow controller works independently of
the duct pressure, i.e. pressure fluctuations cause no
changes to volume flow
To prevent the volume flow control becoming unstable, a
dead zone is allowed within which the damper does not
move. This dead zone and the accuracy of site measurements
lead to volume flow deviation �‡ shown opposite.
If the conditions given in the sales brochure (static minimum
pressure differential, inlet flow conditions etc.) are
not observed, greater deviations must be expected.
V · max Setting
The ‡ max value corresponds to the volume flow which is
set with a 10 VDC control signal or ‡ max override control.
The setting range is from 30 to 100 %. The percentage
figures relate to ‡ nom.
V · min Setting
The ‡ min value corresponds to the volume flow which is
set with a 2 VDC control signal or ‡ min override control.
‡ min may be set between 0 and 80 % of ‡ max. The percentage
figures relate to the ‡ max volume flow setting. If
‡ min is set to 0 %, a tight shut off of the damper is not
guaranteed. The controller closes the damper until the
actual value signal is 2 VDC corresponding to 0 l/s.
Measurement tolerances mean that a leakage air flow is
present. Override control should be used for tight shut
off.
Slave Control
The VRP only provides for ratio control, i.e. the supply
and extract air must be in the same ratio under all
operating conditions.
The volume flow ratio is set using the ‡ max adjustment
knob on the slave controller, according to the formula
shown opposite. Where the volume flows are the same
and the units of equal size, the setting will be 100 %.
The setting range is from 30 to 100 %. If ‡ max set value
>100 %, the master and slave functions must be reversed.
As a rule, the ‡ min adjustment knob on the slave
is set to 0 %.