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Important safety notes
No user serviceable parts are contained within the
equipment. All repairs must be performed only by the
manufacturer. Misuse or any attempted modification of the
equipment will lead to considerable safety risks!
Purpose
Level controller for modulating control for use in conjunc-
tion with the GESTRA level probe type NRG 21 or NRG 26
and a control valve with electric actuator.
Design
Controller with manual control station, adjustors and
indicators in a case for panel mounting in accordance
with DIN 43700 for installation into control desks or
cabinets.
Technical data
Function
Three-position stepping controller with proportional action
used with level probe type NRG 26 or NRG 21 for modu-
lating fill or discharge control with high and low-level
alarms and current output.
Type-approval no.
TÜV · WR · 96-320
Input
Three connections for NRG 26 or NRG 21
Output
Output to control valve via two volt-free contacts, max.
contact rating: 250 V, 500 W, 3 A ohmic with a life of
4 x 10
switching cycles or 0.35 A inductive with a life
5
of 2 x 10
cycles.
6
Contact material silver, hard-gold plated.
Current output 0 ... 20 mA for remote indication or record-
ing, can be changed to 4 ... 20 mA by establishing a wire
link, max. load 500 Ω.
Limit values
MIN and MAX alarm via volt-free relay contacts, indivi-
dually and continuously adjustable within the adjusted
probe measuring range.
Contact rating as under "Output".
Measuring range
Depending on probe length. Zero point and measuring
range adjustable on front panel.
Set point
Continuously adjustable within the range 0 ... 100 % of
the adjustable measuring range.
Proportional band
5 ... 50 %, continuously adjustable on front panel.
Dead band
± 1.5 %
Feedback
Via valve positioning potentiometer 1000 Ω.
Manual control station
With auto/manual switch and 2 push buttons for valve
position OPEN and valve position CLOSED.
Indicators
One error-signal meter, scale ± 20 %
One valve-position meter, scale 0 ... 100 %
Four LEDs for signalling valve OPEN, valve CLOSED,
MAX alarm and MIN Alarm
Mains supply
220 V +10 % / –15 %, 50 Hz, 7 VA
120 V +10 % / –22 %, 60 Hz, 7 VA
240 V +10 % / –15 %, 50 Hz, 7 VA
Protection
IP 40 for design with front panel,
IP 54 for design with clear lid,
IP 00 for connecting terminals.
Permissible ambient temperature
0 °C ... 50 °C
Materials
Body: Glass-fibre reinforced polycarbonate, black
Front panel: Aluminium, anodized
Weight
Approx. 0.8 kg
Dimensions
See Fig. 1
Installation
DIN case for panel mounting
1. Provide panel cut-out 138
mm x 68
+1
43700) in control cabinet or panel. Maximum panel
thickness 15 mm (Fig. 1).
2. Turn back screws of fixing clamps
Push fixing clamps towards front panel and remove
A
from case
.
A
3. Insert case
into panel cut-out and push fixing
B
clamps
into case. Tighten screws.
Wiring
Wiring should be carried out in accordance with wiring
diagram (Fig. 3).
For wiring to the probe screened four-conductor cable
is required. e. g. 4 x 0.5 mm
, maximum cable length
2
150 m.
Wiring to the control valve
Actuators with single-phase alternating-current motors,
max. power consumption 50 VA, can be connected direct-
ly. For a higher power consumption auxiliary contactors
must be connected between controller and actuator.
Direction of action of controller
The controller is supplied for feed control. By establishing
a wire link between terminals 19 and 20 it operates as
drain controller.
Connection of a remote level indicator or recorder
A remote level indicator or recorder can be connected to
the level controller.
Terminals 16 and 17 provide a current output proportional
to the level of 0 to 20 mA at maximum 500 ohm. By link-
ing terminals 18 and 19 an output current of 4 to 20 mA
is obtained corresponding to 0 to 100 % of the level.
MIN and MAX alarms
The contacts in the wiring diagram (Fig. 3) are shown in
the alarm position (relays de-energized).
Important notes
The resistance of the feedback potentiometer in the
n
control valve actuator must be 1000 ohm.
Use a separate, screened cable for wiring to the po-
n
tentiometer.
Connect screen of potentiometer cable only to terminal
n
12 of the controller, but not at the potentiometer.
Connect screen of probe cable only to terminal 15 of
n
the controller, but not at the probe.
The screens must not make any other electrical contact.
n
The switch contacts should be fused with 2.5 A (anti-
n
surge fuse).
The mains voltage is indicated on the name plate.
n
Initial adjustments
Step 1
Adjustment of 0 % level (zero point)
1. Turn 100 % adjustor
2. Set auto/manual switch
3. Turn set-point adjustor "W"
4. Fill boiler until level is just visible in the lower part of
the water-level gauge glass.
5. Turn 0 % adjustor
5
shows 0 %.
Step 2
Adjustment of 100 % level
1. Set auto/manual switch
2. Turn set-point adjustor "W"
3. Raise water level in boiler to upper edge of water-level
mm (DIN
+0.7
gauge glass.
4. Turn 100 % adjustor
5
"X
"
shows 0 %.
B
w
to screw thread.
Step 3
Accurate re-adjustment of 0 % level adjustment
1. Lower water level in boiler until level is just visible in
the lower part of the water-level gauge glass.
2. Set auto/manual switch
3. Turn set-point adjustor "W"
4. Turn 0 % adjustor
5
shows 0 %.
Step 4
Adjustment of high-level alarm
The high-level alarm is set with the "MAX" adjustor
6
. Any alarm point can be chosen within the adjusted
measuring range (0 to 100 %).
Step 5
Adjustment of low-level alarm
For setting the low-level alarm the "MIN" adjustor
provided. Again, any alarm point can be chosen within the
measuring range. The MIN alarm point should, however,
be situated below the MAX alarm point.
Step 6
Adjustment of control valve closed position
1. Set auto/manual switch
2. Move valve by means of push button
hand crank into closed position.
3. Turn adjustor
4. Turn adjustor
tion meter "Y"
Step 7
Adjustment of control valve open position
1. Set auto/manual switch
2. Move valve by means of push button
hand crank into open position.
3. Turn adjustor
position meter "Y"
Step 8
Setting of proportional band X
The proportional band X
maximum and minimum deviation of the actual level from
the adjusted set point as a function of the load condition
in the boiler.
Example: A measuring range of 200 mm on the water-
level gauge glass corresponds to 100 %; X
corresponds then to ± 20 mm. At low load the constant
1
ten turns to the left.
2
in position
.
3
to 0 %.
4
until the error-signal meter "X
2
in position
.
3
to 100 %.
1
until the error-signal meter
2
in position
.
3
to 0 %.
4
until the error-signal meter "X
7
2
in position
.
8
9
five turns to the left.
0
to the right until valve-posi-
!
shows 0 %.
2
in position
.
"
9
to the right until the valve-
!
shows 100 %.
p
§
(adjustor
) determines the
p
= ± 10 %
p
"
w
"
w
is
or
or
5
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