Danfoss VLT HVAC Series, Programming Manual, Page: 227 / 338

2) In systems where the pressure or temperature is controlled by an external PI controller, the wake-up conditions cannot be based on feedback from
the pressure/temperature transducer as the setpoint is not known. In the example with a boost system, desired pressure Pset is not known. par.
1-00
Configuration Mode
must be set for Open-loop.
Example: Boost system.
When low power or low speed is detected the motor is stopped, but the reference signal (f
ref
) from the external controller is still monitored and because
of the low pressure created, the controller will increase the reference signal to gain pressure. When the reference signal has reached a set value f
wake
,
the motor restarts,.
The speed is set manually by an external reference signal (Remote Reference). The settings (par. 22-3*) for tuning of the No Flow function must be set
to default.
Configuration possibilities, overview:
Internal PI Controller
(par.1-00
Configuration Mode
: Closed-loop)
External PI controller or manual control
(par.1-00
Configuration Mode
: Open-loop)
Sleep mode Wake up Sleep mode Wake up
No Flow detection (pumps only) Yes Yes (except manual setting
of speed)
Low speed detection Yes Yes
External signal Yes Yes
Pressure/Temperature (transmit-
ter connected)
Yes No
Output frequency No Yes
VLT ® HVAC Drive Programming Guide 3 Parameter Description
MG.11.C6.22 - VLT ® is a registered Danfoss trademark
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3