Control Unit; Instruments And Their Function - Danfoss VACON NX Commissioning And Maintenance Manual

1 6 VACON
4.2.3 Contr ol unit
The AC drive, VACON
drive is programmed to read the I/O signals from the flow switch (FTSA11), pressure sensor (PT11)
and leak switch (LS11).
Information on the alarms and how to calculate their limits is found in chapter
5.3 STEP 3, CONTROL UNIT
parameters can be found in the VACON
the cooling unit.
The AC drive includes a Fieldbus link card. By connecting to this card, the
customer can view eight different values (parameters), e.g. primary circuit
temperatures, pressures, warnings and shutoffs. This is very useful if the HX-
unit is not monitored locally. Information regarding the connection type is found
®
in the VACON
4.2.4 Instr uments and their function
The flow switch FTSA11 (Figure 4.2-6) measures the speed of the flow inside the pipe. This flow
speed is shown as 0-100% of the measuring range of the instrument. The FTSA11 has two different
flow measuring ranges to choose from, 15-150 cm/s or 30-300 cm/s of which the higher range is
used in the HX-units. The unit also sends the primary circuit temperature as a 4...20mA signal to the
FV11 3-
sent to the HX control unit. The analogue signal is used to control the temperature in the primary
circuit and also to generate temperature alarms and shutoffs. The PNP switch
output that monitors the flow is used to generate a shutdown command.
The flow speed shown in % on the FTSA11 can easily be modified to flow (l/min)
by using the diagram in chapter
switch point of the
FTSA11 high measuring range (30-300 cm/s) and the original pipe inner
diameter.
This flow meter is suitable for concentration of maximum 25% glycol (75% water).
The other instruments found on the HX-unit are a pressure transmitter (PT11) and a pressure gauge
(PI11). The pressure transmitter sends a 4...20mA signal to the HX control unit. The control unit
application then converts this signal into pressure (bar). This pressure input is then used to
monitoring the pump inlet pressure. The idea is to give the user an early warning in case there is a
leak in the primary circuit somewhere outside of the HX-unit. The pressure gauge is used when
filling the primary circuit with liquid or when performing a pressure test on the unit. It can also be
used to get a pressure reference value if the pressure transmitter is thought to be malfunctioning.
4
®
NXP-series (Figure 4.2-5), works as a control/supervision unit for the primary
SETUP. Information on how to modify the control unit
®
5.4.2, Adjusting the system flow and setting the
FTSA11. Note that this diagram is correct only when using the
Local contacts: http:/ / dr ives.danfoss.com/ danfoss- dr ives/ local - contacts/
I NTRODUCTI ON
-unit.
AC
Figure 4.2-5
Figure 4.2-6