Gestra NRS1-7B Level Electrode

Issue Date: 4/05
GESTRA Steam Systems
Product Range B1
Level Switch
NRS 1-7 Self-Monitoring Low-Level Alarm with Periodic Self-Checking Routine to DIN VDE 0116
NRS 1-7
Purpose and Application
Technical Data
Self-monitoring low water-level limiter with periodic self-checking feature to be used in conjunction with the
GESTRA level electrodes types NRG 16-11, PN 40,
NRG 16-11S, PN 40, NRG 17-11, PN 63, NRG 19-11,
PN 160 or NRG 111-11, PN 320. The equipment combination detects the low water level (low-level alarm).
The equipment meets the German regulations for use in steam-boiler plants operating in accordance with TRD
602 and TRD 604 sheet 1 and sheet 2 as well as EN 12952 and EN 12953.
Type-approval no.
TÜV · WB · 01-354
EG 01 202 931-B-01-0077
EG 01 202 931-B-01-0075 Input Four terminals for the connection of one level electrode
type NRG 16-11, PN 40 type NRG 16-11S, PN 40 type NRG 17-11, PN 63 type NRG 19-11, PN 160
type NRG 111-11, PN 320
Design
Output Two volt-free relay contacts (mounted in series in the case of design “b”);
max. contact rating: 250 V, 300 W, 3 A resistive with a life of 5 x 105 switching cycles or 0.35 A inductive with a
life of 2 x 106 cycles;
contact material silver, hard-gold plated Delay of response Set at our factory to 3 s
(up to 25 s – TÜV approval required)
NRS 1-7 Plug-in unit in plastic case for installation in control cabinets. The terminals in the case are accessible after
loosening two screws and unplugging the unit from its base.
To avoid confusion with other plug-in units of the
GESTRA range, inserts are fitted in the bases so that only the correct unit may be plugged into each base.
The plug-in units may be snapped onto a 35 mm supporting rail or screwed into position on a mounting
panel.
Function The level switch type NRS 1-7 is a two-channel unit provided with an automatic self-checking circuitry in
accordance with DIN VDE 0116 (directives for protection circuits). The self-checking is effected periodically. The
test includes the checking of the cable between electrode and level switch and the self-checking circuitry
(redundancy). The output relays are not influenced by the internal tests.
In addition to this self-checking routine, the level switch can also be tested manually by pushing the button
“TEST 1” simulating a defect in the electrode. The test switch “TEST 2 / INSPECTION” is provided for checking
the function of the checking circuitry.
As the circuit of the relay contacts of the level switch is normally closed, alarm will also be signalled in the event
of a mains failure.
The level switch can signal the following three operating conditions:
■ Normal operation (correct level) ■ Alarm
(low level)
■ Alarm
(defect in level switch or electrode) The green LED indicates mains ON. The alarm state low
level or malfunction of the system is indicated by two red LEDs. The failure of one channel (loss of redundancy) is signalled by the illumination of a single red LED.
The combination of electrode NRG 16-11, NRG 16-11 S,
NRG 17-11, NRG 19-11 or NRG 111-11 and level switch
NRS 1-7 provides fail-safe protection against a first fault, i. e. the system will still continue to provide the safety
function even after the occurrence of a first fault.
System Components Level electrode NRG 16-11, PN 40, NRG 16-11S, PN 40,
NRG 17-11, PN 63, NRG 19-11, PN 160, NRG 111-11,
PN 320 as low-level limiter.
Sensitivity 10 µS/cm at 25 °C when used in conjunction with level electrode without measuring surface extension (cell constant C = 0.3).
0.5 µS/cm at 25 °C when used in conjunction with level electrode with measuring surface extension (cell constant
C = 0.13), see data sheet NRG 16-11, NRG 111-11).
Indicators and adjustors Two LEDs “Alarm” One LED “Operation” One button “TEST 1”
One switch “TEST 2/INSPECTION” Mains supply 230 V ± 10 %, 50/60 Hz (please state voltage when
ordering) Special voltage: 115 V ± 10 %, 50/60 Hz or 24 V ± 10 %, 50/60 Hz;
24 V d.c. supply also possible with the ancillary unit type URN-1.
Power consumption 5 VA Protection Design NRS 1-7 IP 40 to EN 60529 Permissible ambient temperature
0 °C – 55 °C Case materials Base: Noryl SE 1-GFN 2 UL 94 VO, black Cover: R-ABS UL 94 VO, stone grey
Approx. weight 0.6 kg
CE marking 0525
NRS 1-7