Technical Data - GESTRA NRZ 2-1 Instructions De Montage Et De Mise En Service

ENGLISH
Important Safety Notes
The ancillary unit type NRZ 2-1 must only be
used for three-element control, in conjunc-
tion with other GESTRA equipment.
The NRZ 2-1 must only be installed by quali-
fied staff.
Before installing controller cut off power sup-
ply.
All repairs must be performed only by the
manufacturer. Misuse or attempted modifica-
tion of the equipment will endanger plant
safety.
Application
Three-element control in conjunction with
GESTRA level controller type NRR 2-... and
GESTRA vortex flow meters for steam and
feedwater. The system minimises the effect
to steam-boiler level controls caused by a
sudden high steam demand resulting in rapid
expansion of the boiler water.
The three-element controller type NRZ 2-1 is
used with a feedwater control system which
consists of a level probe type NRG 26-... and
a level controller type NRR 2-..., and steam
and feedwater flow meters to form a three-
element control. For this purpose the level in
the boiler, and the steam and feedwater flo-
wrates are measured and converted into a
composite electrical signal. The NRZ 2-1
compares the signals received from the
steam and feedwater flow meters and deter-
mines the difference. This difference is added
to the signal received from the level probe,
and a composite signal is formed. This signal
is then transmitted to the level controller type
NRR 2-... The system therefore corrects the
response of the controller which would other-
wise have reacted to the artificial high level in
the boiler due to rapid expansion of the
water caused by sudden
demand.
Design
NRZ 2-1b (Fig. 4)
With mounting clip for fitting onto a 35 mm
supporting rail or for screwing directly to a
mounting panel.

Technical Data

Inputs
1. Steam flow meter
Stabilized current input 0 to 20 or 4 to 20
mA, max. load 56 ohm.
2. Feedwater flow meter
Stabilized current input 0 to 20 or 4 to 20 mA,
max. load 56 ohm.
Input signal filtering for 1 and 2 ≤ 230 V
amplitude.
3. Boiler level control
From level probe type NRG 26-... with pre-
amplifier type NRV 2-8 or NRV 2-29, voltage
input 0.5 to 7 V d.c.
Output
To level controller type NRR 2-...,
voltage output 0.5 to 7 V d.c.
Indicators and adjustors
One auto/manual switch.
One potentiometer for establishing differenti-
al between steam and feedwater flowrates.
Supply voltage
12 V d.c. from level controller type NRR 2-...
Protection
IP 40 to DIN 40050
Permissible ambient temperature
0 °C to 55 °C
Case materials
Base: Noryl SE 1-GFN 2 UL 94 VO, black
Cover: R-ABS UL 94 VO, stone grey
Approx. weight
0.5 kg
Dimensions
See Fig. 4
Installation
Design "b" (Fig. 4)
On supporting rail (with mounting clip)
1. Clip level switch onto supporting rail
(TS 35x15 mm, DIN 46277).
2. Loosen cover screws
B from its base
On mounting panel
1. Loosen cover screws
from its base
B
2. Unscrew mounting clip
3. Drill the hole
4.3 mm dia.
4. Fasten base with two screws M4 onto
mounting panel.
Notice
To provide sufficient ventilation, ensure a
minimum spacing of 20 mm between
adjacent units.
Wiring
1. Select cable entry
ponding seal.
2. Wiring should be carried out in accordance
with wiring diagram, Fig. 1 for NRZ 2-1 in
high steam
conjunction with level controller NRR 2-1,
or Fig. 2 for NRZ 2-1 in conjunction with
level controller NRR 2-2.
Fig. 3 gives an example of parallel connec-
tion of several units.
For wiring to the probe four-core overall
screened cable is required, minimum con-
ductor size 0.5 mm
100 m.
3. Replace cover
screws.
Notice
Connect screen only to terminal 7 of the
three-element controller.
The screen must not make any other elec-
trical contact.
Initial Adjustments
Step 1
Set auto/manual switch
Turn potentiometer
Commission water-level control and feedwa-
ter flow meter in accordance with relevant
installation and service instructions.
Adjustments differing from those given in the
installation
NRR 2-1 and NRR 2-2:
NRR 2-1: "Adjustment of Set Point"
1. Turn adjustor "B"
2. Fill vessel to required control level.
3. Turn adjustor "A"
cates zero.
4. Raise level in vessel until it reaches the
and unplug cover
A
C .
and unplug cover
A
.
C
.
E
marked in the base to
F
D and remove corres-
2 . Max. cable length
onto base and tighten
B C
in manual position.
22 turns to the left.
and service instructions
10 turns to the left.
until the meter indi-
maximum level that is permissible as devia-
tion (the top of the proportional band).
5. Turn adjustor "B" until the meter
dates +1.
Count the number of turns required to
reach value +1, and continue to turn by
the same number of turns.
NRR 2-2: "Setting of Proportional Band X
The proportional band X
mines the 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 = +/-10 % corresponds then to +/-
p
20 mm. At low load the constant deviation
Xw will be +10 %, viz. 20 mm above the
adjusted set point and at full load -10 %, viz.
20 mm below the adjusted set point. In this
case the proportional band is 40 mm.
To ensure a smooth control the proportional
band X
(adjustor 13) should be chosen as lar-
p
ge as possible. As an initial value we recom-
mend X = 40 %.
p
Step 2
After commissioning water-level control and
feedwater flow meter
switch in automatic position. Turn poten-
tiometer five turns to the left.
Step 3
The optimisation of the three-element con-
troller should be carried out with the boiler
operating. As soon as the steam consumpti-
on increases, observe valve-position meter
of level controller. If at these load conditions
the valve is motored into the closed position,
turn potentiometer one or two turns to the
right. Repeat procedure until, even at ex-
treme load conditions, stable operating con-
ditions are obtained.
If the valve opens and closes periodically the
control system is „hunting". In this case, turn
potentiometer one or two turns to the left.
Important Note
The signal from the level probe is corrected
by the signals received from the steam and
feedwater flow meters. All indications and
adjustments of the level controller depending
on the level are thereby reduced.
This concerns:
Level Controller NRR 2-1
Error-signal meter
Level Controller NRR 2-2
Error-signal meter
MIN/MAX limit value adjustments
Actual-value output
Flowmeter and level electrode outputs are
evaluated by the NRZ 2-1. In the case of hea-
vy load fluctuations the compensated signal
generated by the NRZ 2-1 will not directly cor-
respond with the water level.
Fault Finding
Fault A: The NRZ 2-1 does not react to load
fluctuations.
of
Remedy: Check whether auto/manual switch
is in automatic position.
Fault B: The NRZ 2-1 detects a permanently
steam or feedwater difference.
Remedy: Check whether both input currents
are identical, either both inputs 0 to 20 mA, or
both inputs 4 to 20 mA.
In case of difficulty please contact us.
inci-
"
p
(adjustor 13) deter-
p
set auto/manual