GESTRA NRS 1-50 User manual

Original Installation &
Operating Manual
850694-00
Level Switch
NRS 1-50
For TWO electrodes
EN (USA)
English

2NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Contents
Content of this Manual......................................................................................................................... 4
Scope of supply, product package....................................................................................................... 4
How to use this Manual........................................................................................................................ 5
Illustrations and symbols used............................................................................................................ 5
Hazard symbols in this Manual............................................................................................................ 5
Types of warning .................................................................................................................................. 6
Specialist terms, abbreviations ........................................................................................................... 7
Usage for the intended purpose........................................................................................................... 8
Applicable directives and standards.............................................................................................. 8
Improper use ........................................................................................................................................ 8
Basic safety information ...................................................................................................................... 9
Required personnel qualifications..................................................................................................... 10
Notes on product liability................................................................................................................... 10
Function .............................................................................................................................................. 11
Technical data .................................................................................................................................... 12
Rating plate, identification................................................................................................................. 13
Factory default settings ..................................................................................................................... 14
Dimensions of the NRS 1-50 .............................................................................................................. 15
Important notes .................................................................................................................................. 16
Safety information ......................................................................................................................... 16
Preparing for installation ................................................................................................................... 17
Installation.......................................................................................................................................... 18
Electrical connection.......................................................................................................................... 19
Supply voltage............................................................................................................................... 19
Connecting the level electrode....................................................................................................... 19
Connecting the safety circuit.......................................................................................................... 19
Connecting the signal output ......................................................................................................... 20
Wiring diagram of level switch NRS 1-50....................................................................................... 21
Wiring diagram for Class C protection against second faults with automatic prevention of
interlock deactivation in the event of malfunction........................................................................... 22
Example switching combinations ................................................................................................... 23
Key to example switching combinations......................................................................................... 24

3NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Contents
Bringing into service .......................................................................................................................... 25
Changing the configuration............................................................................................................ 25
Checking the switchpoint and function........................................................................................... 26
Operation, alarm and test................................................................................................................... 27
Fault indications and troubleshooting............................................................................................... 27
Checking the level electrode.............................................................................................................. 29
Measuring level switch voltages .................................................................................................... 29
Emergency mode................................................................................................................................ 30
Emergency mode for water level limiters ....................................................................................... 30
Important notes .................................................................................................................................. 31
Action against high-frequency interference.................................................................................... 31
Interlock and interlock deactivation................................................................................................ 31
Checking switchpoints................................................................................................................... 31
Taking out of service.......................................................................................................................... 32
Disposal .............................................................................................................................................. 33
Returning decontaminated equipment.............................................................................................. 33
UL components................................................................................................................................... 33

4NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Content of this Manual
Product:
■ Level Switch NRS 1-50, for TWO electrodes
First edition:
BAN 850694-00/09-2021cm
© Copyright
All rights reserved. Any misuse, particularly reproduction and dissemination to third parties, is not
permitted. The General Terms & Conditions of GESTRA AG apply.
Scope of supply, product package
NRS 1-50
1 level switch NRS 1-50
1 Installation & Operating Manual

5NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
How to use this Manual
This Installation & Operating Manual describes the correct use of the NRS 1-50 level switch. It
applies to persons who integrate this equipment in control systems, install, bring into service, op-
erate, maintain and dispose of this equipment. Anyone carrying out the above-mentioned activities
must have read this Installation & Operating Manual and understood its contents.
■ Read this Manual in full and follow all instructions.
■ Please also read the instructions for use of any accessories.
■ The Installation & Operating Manual is part of the product package. Keep it in an easily acces-
sible location.
Availability of this Installation & Operating Manual
■ Make sure this Installation & Operating Manual is always available to the operator.
■ If you pass on or sell the equipment to a third party, please also hand over the Installation &
Operating Manual.
Hazard symbols in this Manual
Danger zone, dangerous situation
Illustrations and symbols used
1. Action to be taken
2.
■ Lists
◆ Bullet points in lists
A Keys to illustrations
Additional
information
Read the relevant
Installation & Operating Manual

6NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Types of warning
DANGER
Warning of a dangerous situation that results in death or serious injury.
WARNING
Warning of a dangerous situation that may possibly result in death or serious injury.
CAUTION
Warning of a situation that may result in minor or moderate injury.
ATTENTION
Warning of a situation that results in damage to property or the environment.

7NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Specialist terms, abbreviations
Here, we explain some abbreviations, specialist terms, etc., which are used in this Manual.
NRGT .. / NRR.. / NRS.. / URS .. / URB .. / SRL .. / etc.
Equipment and type designations of GESTRA AG.
SELV
Safety Extra Low Voltage
Operating point (of the plant)
The operating point describes the operating parameters within which a plant or boiler is operated
in its nominal range. In a steam boiler, for example, these parameters would be output, pressure,
and temperature.
The design data may be a lot more stringent, however.
A boiler that is operated at 145psi (10bar) and 356°F (180°C) may be designed to withstand a
pressure of 870psi (60bar) and a temperature of 527°F (275°C), for example, which is therefore
not necessarily its operating point.

8NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Usage for the intended purpose
The NRS 1-50 level switch is used in conjunction with NRG 1...-50 level electrodes as a
water level limiter for steam boilers and hot water installations.
Water level limiters switch off the heating when the water drops below the set low water level
(LW). The NRS 1-50 is classified as a protective control Class B (C) in accordance with UL 60730-
1.
When used as intended, the NRS 1-50 level switch is combined in a circuit with the level elec-
trodes stipulated by the directives or standards below:
Level electrodes NRG 1...-..
UL 60730-2-15,
CAN/CSA E60730-2-15
NRG 16-50 NRG 17-50 NRG 19-50
The equipment has been tested and approved for use in the scope governed by the following
directives and standards:
Standards:
■UL 60730-1 and CAN/CSA E60730-1
General Requirements for Automatic Electrical Controls
■UL 60730-2-15 and CAN/CSA E60730-2-15
Requirements for Automatic Electrical Water Level Sensing Controls
Improper use
There is a danger of death due to explosion if the equipment is used in potentially
explosive atmospheres.
Do not use the equipment in potentially explosive atmospheres.
Do not bring any equipment into service that does not have its own specific rating
plate.
The rating plate indicates the technical features of the equipment.
Applicable directives and standards

9NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
There is a risk of electric shock during work on electrical systems.
■ Always switch off the voltage to the plant before performing connection work.
■ Check that the plant is not carrying live voltage before commencing work.
Attempts to repair the equipment will cause the plant to become unsafe.
■ The NRS 1-50 level switch may only be repaired by the manufacturer, GESTRA AG.
■ Only replace faulty equipment with identical equipment from GESTRA AG.
Basic safety information

10 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Required personnel qualifications
Activity Personnel
Integration in control system Specialist staff Plant designer
Installation/
electrical connection/
bringing into service
Specialist staff
The equipment may only be installed, wired
and brought into service by qualified and
competent staff.
Operation Boiler service technician Staff trained by the plant operator.
Maintenance work Specialist staff
Fitting and maintenance work may only be
performed by authorized staff who have
undergone specific training.
Refits Specialist staff Persons trained by the plant operator to work
with pressure and temperature.
Notes on product liability
The manufacturer cannot accept any liability for damages resulting from improper use of the
equipment.

11NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Function
The NRS 1-50 level switch is designed for boiler water conductivities of >=10µS and for the
connection of two or one level electrode(s).
If the water falls below the minimum level, the level electrodes are exposed and an alarm is
triggered in the level switch. This switchpoint is determined by the length of the electrode
extension (level electrode NRG 1...-50).
When the off delay has elapsed, the two output contacts of the level switch open the safety circuit
for heating. The heating cut-off is interlocked in the external safety circuit and this interlock can
only be deactivated again when the level electrode is immersed once more. The NRS 1-50 level
switch must be used in combination with an external manual reset when used as a protective
device per ASME CSD-1
In addition, two signal contacts for external signaling devices close without a delay. An alarm is
also triggered if faults occur in a level electrode and/or the electrical connection.
If the level electrode is installed in a level pot outside the boiler, make sure the connection pipes
are sufficiently large.
The manufacturer recommends connection pipes of ≥ 1.57in (40mm) for steam and ≥ 3.94in
(100mm) for water. If smaller connection pipes or fittings are used, these shall not be smaller
than 1-inch NPS. The level pot must have a suitable flushing device at its lowest point. This de-
vice flushes the connection pipes to the boiler and enables the function of the water level limiter
to be tested. No shut-off valves of any type shall be placed in the piping between the boiler and
the low water cutoff.
An automatic self-test monitors the safety functions in the level switch and the level electrodes. In
the event of a fault, the safety circuit opens without a delay and switches the heating off.
Alarm and fault indications are displayed by LEDs, and furthermore a signal output is actuated
without delay for each level electrode. An alarm can be simulated by pressing a button.

12 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Supply voltage
24 VDC +/–20%, 0.3 A; SELV / PELV / CLASS2
100 – 240 VAC +10/–15%, 47 – 63 Hz, 0.2 A (optional)
Fuse
External 0.5A; UL category JDYX, e.g., RND 170-00012
Power consumption
7 W
Response sensitivity [Water conductivity at 77°F (25°C)]
> 5 ... < 5000 ppm (> 10 ... > 10000 µS/cm)
Level electrode connection
2 inputs for NRG 1...-50 level electrode, 4-pole with shield
Safety circuit
2 volt-free NO contacts, 6A 250 V AC / 30 V DC cos ϕ= 1.
Off delay 3 seconds.
Inductive loads must have interference suppression (RC combination) as specified by the manufacturer.
Signal output
2 volt-free outputs for external signaling without delay, 24V DC, max. 100mA (semiconductor output).
Indicators and controls
2 buttons for testing and diagnosis,
2 red/green LEDs for indicating operating state and alarm.
3 red LEDs for fault diagnosis,
2 2-pole code switches for setting the number of electrodes.
Terminal box
Terminal box material: base of black polycarbonate, front of gray polycarbonate
Wire size: 1 x AWG12 (4.0 mm2) solid, or
1 x AWG14 (2.5 mm2) stranded with sleeve acc. to DIN 46228, or
2 x AWG16 (1.4 mm2) stranded with sleeve acc. to DIN 46228
Terminal strips can be removed separately
Terminal box attachment: Mounting clip on support rail TH 35, EN 60715
Electrical safety
Pollution degree 2, overvoltage category II according to UL 60730-1
Protection
Terminal box: IP 40 according to EN 60529
Terminal strip: IP 20 according to EN 60529
As a UL open type, the equipment must be installed in a control cabinet.
Weight
Approx. 1.1lb (0.5kg)
Ambient temperature
at power-on 32° ... 131°F (0° … 55°C)
in operation 14° … 131°F (-10° … 55°C)
Transport temperature
-4° … 176°F (-20° … +80°C) (<100hours), defrosting time of de-energized equipment
before it can
be put into operation: 24 hours.
Storage temperature
-4° … 158°F (-20° … +70°C), defrosting time of de-energized equipment
before it can be put into operation: 24 hours.
Relative humidity
Max. 95%, non-condensing
Site altitude
Max. 6560 ft (2000 m)
Other information
Incorporated Type 2 action protective control Class B (C)
Pollution degree 2, impulse voltage 2500 V
Technical data

13NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
NRS 1-50
Alarm extern
24VDC
100mA
ZEP
Wasserstandbegrenzer
Water level limiter
Limiteur de niveau d’eau
7W IP40 (IP20)
250V
T2.0A
Niveauschalter
Level switch
Commutateur de niveau
20
29
21
30
3s
10µS/cm
9
2
NRG 1...-50
1. / 2.
1
2
3
1345
10 11 12 13 16 17 23 24 26 27
NRS 1-50
MIN
100 240 V ~
-15 / +10%
-
N
0.5A
L1. / 2.
+
-
Betriebsanleitung
beachten
See installation
instructions
Voir instructions de
montage
GESTRA AG
Münchener Str. 77
28215 Bremen
Made in Germany
Tamb = 55°C)T131°F (
Protective Control Class B (C)
acc. UL60730-1
Input rating: 100-240VAC, 7W
Ambient temperature: 32 131°F (0 55°C)--
Wiring: Use Copper Conductors Only,
Use 60/75°C Conductors,
Use No.18 16 AWG Wire Size Only,
Tightening: Torque 0.79Nm or 7lb in.
-
Use with accessory: NRG 16,17,19,111 11, 50, 50(F), NRG 16 36--- -
OPERATING CONTROL
E513189
Frequency: 50/60Hz Output rating : Pilot duty B300 / R300
NRS 1-50_2E_100-240V
NRS 1-50
Alarm extern
24VDC
100mA
ZEP
Wasserstandbegrenzer
Water level limiter
Limiteur de niveau d’eau
IP40 (IP20)
7W
250V
T2.0A
Niveauschalter
Level switch
Commutateur de niveau
20
29
21
30
3s
10µS/cm
9
2
NRG 1...-50
1. / 2.
12
3
1345
10 11 12 13 16 17 23 24 26 27
NRS 1-50
MIN
0.5A
1. / 2.
+
-
+-
GESTRA AG
Münchener Str. 77
28215 Bremen
Made in Germany
Betriebsanleitung
beachten
See installation
instructions
Voir instructions de
montage
Tamb = 55°C)T131°F (
24V
± 20%
Protective Control Class B (C)
acc. UL60730-1
Input rating: 24VDC, 7W
Ambient temperature: 32 131°F (0 55°C)--
Wiring: Use Copper Conductors Only,
Use 60/75°C Conductors,
Use No.18 16 AWG Wire Size Only,
Tightening: Torque 0.79Nm or 7lb in.
-
Use with accessory: NRG 16,17,19,111 11, 50, 50(F),NRG 16 36--- -
OPERATING CONTROL
E513189
Output rating : Pilot duty B300 / R300
NRS 1-50 24V DC_2E
Rating plate, identification
Type designation
Mains voltage /
Protection
Manufacturer
Wiring
diagram
Safety
information
Disposal
information
Type approval
number
Ambient tem-
perature / Sen-
sitivity
Jumper, provid-
ed by customer
Safety
circuit
Fuse, provided by
customer
Type designation
Mains voltage /
Protection
Manufacturer
Wiring
diagram
Safety
information
Disposal
information
Type approval
number
Ambient tem-
perature / Sen-
sitivity
Jumper, provided by
customer
Safety
circuit
Fuse, provided by
customer
Fig. 1
Fig. 2
NRS 1-50
Alarm extern
24VDC
100mA
ZEP
Wasserstandbegrenzer
Water level limiter
Limiteur de niveau d’eau
IP40 (IP20)
7W
250V
T2.0A
Niveauschalter
Level switch
Commutateur de niveau
20
29
21
30
3s
10µS/cm
9
2
NRG 1...-50
1. / 2.
12
3
1345
10 11 12 13 16 17 23 24 26 27
NRS 1-50
MIN
0.5A
1. / 2.
+
-
+-
GESTRA AG
Münchener Str. 77
28215 Bremen
Made in Germany
Betriebsanleitung
beachten
See installation
instructions
Voir instructions de
montage
Tamb = 55°C)T131°F (
24V
± 20%
Protective Control Class B (C)
acc. UL60730-1
Input rating: 24VDC, 7W
Ambient temperature: 32 131°F (0 55°C)--
Wiring: Use Copper Conductors Only,
Use 60/75°C Conductors,
Use No.18 16 AWG Wire Size Only,
Tightening: Torque 0.79Nm or 7lb in.
-
Use with accessory: NRG 16,17,19,111 11, 50, 50(F),NRG 16 36--- -
OPERATING CONTROL
E513189
Output rating : Pilot duty B300 / R300
NRS 1-50 24V DC_2E
NRS 1-50
Alarm extern
24VDC
100mA
ZEP
Wasserstandbegrenzer
Water level limiter
Limiteur de niveau d’eau
7W IP40 (IP20)
250V
T2.0A
Niveauschalter
Level switch
Commutateur de niveau
20
29
21
30
3s
10µS/cm
9
2
NRG 1...-50
1. / 2.
1
2
3
1345
10 11 12 13 16 17 23 24 26 27
NRS 1-50
MIN
100 240 V ~
-15 / +10%
-
N
0.5A
L1. / 2.
+
-
Betriebsanleitung
beachten
See installation
instructions
Voir instructions de
montage
GESTRA AG
Münchener Str. 77
28215 Bremen
Made in Germany
Tamb = 55°C)T131°F (
Protective Control Class B (C)
acc. UL60730-1
Input rating: 100-240VAC, 7W
Ambient temperature: 32 131°F (0 55°C)--
Wiring: Use Copper Conductors Only,
Use 60/75°C Conductors,
Use No.18 16 AWG Wire Size Only,
Tightening: Torque 0.79Nm or 7lb in.
-
Use with accessory: NRG 16,17,19,111 11, 50, 50(F), NRG 16 36--- -
OPERATING CONTROL
E513189
Frequency: 50/60Hz Output rating : Pilot duty B300 / R300
NRS 1-50_2E_100-240V

14 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Factory default settings
Level switch NRS 1-50
The level switch is delivered with the following factory default settings:
■Off delay: 3 s
■Configuration: Operation with two NRG 1 ...-50 level electrodes. Code switches 4and 5in
OFF position (Fig. 3)

15NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
123456789101112131415
11
ON ON
22
12
2716 17 18 19 20 21 22 23 24 25 26 28 29 30
Test
Fig. 3
Dimensions of the NRS 1-50
1Upper terminal strip
2Lower terminal strip
3Fastening screws (cross recess head screw M3)
4Code switch for switching level electrode 1 or 2 on/off
5Code switch for switching level electrode 1 or 2 on/off
6Terminal box
7Support rail TH 35, EN 60715
Key
The code switches are accessed by undoing the right and left fastening screws and detaching
the lower terminal strip.
1
2
3
4 5
6
7
3.94 in (100 mm)
4.72 in (120 mm)
2.91 in (74 mm)

16 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Safety information
Water level limiters are classed as protective control according to UL 60730-1 and may only be
installed, electrically connected and brought into service by qualified and competent staff.
Fitting and maintenance work may only be performed by authorized staff who have undergone
specific training.
Danger
The terminal strips of the equipment are live during operation!
There is a risk of serious injury due to electric shock.
Always cut off power to the equipment before working on the terminal strips
(installation, removal, connecting cables).
Attention
The rating plate indicates the technical features of the equipment. Do not bring into
service or operate any equipment that does not bear its own specific rating plate.
Important notes
Attention
Pay attention to regulations in your country, e.g., NEC, NFPA, CEC, when using this
equipment.

17NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Preparing for installation
If the control cabinet is to be installed outdoors, outside the protection of a build-
ing, environmental influences may adversely affect function.
■ Pay attention to the admissible ambient conditions in the technical data,
see page 1712.
■ Do not operate the equipment if the temperature is below freezing.
◆ At temperatures below freezing, use a suitable heat source (e.g., control cabinet
heater, etc.).
■ Connect all parts of the plant to a central grounding point to prevent equalizing
currents.
■ Use UV-resistant cable ducts for routing the connecting cable.
■ Take further measures to protect the equipment from lightning, insects and
animals, and salty air.
You will need the following tools:
■Pozidriv screwdriver PZ1

18 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Installation
ATTENTION
Incorrect installation can lead to malfunctions in the plant or the level electrode.
The NRS 1-50 level switch snaps onto a TH 35, EN 60715 support rail in a
control cabinet. Fig. 3 7

19NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
Electrical connection
Connecting the level electrode
Please use the following to connect the level electrode(s):
■For an NRS 1-50 level switch with a response sensitivity of 5ppm (10µS):
Use a shielded, multi-core TC-ER control cable with minimum wire size AWG18, e.g., OELFLEX
CONTROL TM CY 5G1.
Wire the terminal strip as shown in the wiring diagram. Fig. 7. Connect the shields to terminals 5
and 13 and to the central grounding point (CGP) in the control cabinet.
Please connect the safety circuit for the heating to terminals 23, 24 and 26, 27. If using the
equipment as a water level limiter, please connect the output contacts of the two monitoring
channels by adding a wire jumper between terminals 24 and 26.
Provide the output contacts with a slow blow T1A fuse.
Connecting the safety circuit
Note
■In the event of an alarm, the NRS 1-50 level switch interlock does not take place
automatically.
If the installation requires an interlock, this must be implemented in the down-
stream (safety) circuit.
■In order to guarantee Class C function with second fault protection in accordance
with UL 60730-1, both signaling outputs must be monitored during interlock
deactivation.
■It is important that the interlock is not deactivated when the level switch signals
a malfunction to the diagnostic LEDs or the signaling outputs.
Supply voltage
Please provide the NRS 1-50 level switch with an external 0.5A fuse.

20 NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual - 850694-00
A signal output for connecting further external signaling devices, maximum load 100mA, is allo-
cated to each monitoring channel in the level switch. For connection, please use a control cable,
e.g., 2 x AWG20 (0.5mm2). In the event of alarm and fault indications, the signal outputs
(terminals 20, 21 and 29, 30) close without a delay.
Connecting the signal output
Electrical connection
Danger
■A safety power supply unit (SELV / PELV / CLASS2) must be used to supply the
NRS 1-50 level switch with 24V DC. This must provide a level of isolation against
dangerous contact voltages that at least meets the requirements for double or
reinforced insulation in accordance with UL 60730-1 (protective electrical
isolation).
Attention
■ Provide the NRS 1-50 level switch with an external 0.5A fuse.
■Connect the shields to terminals 5 and 13 and to the central grounding point
(CGP) in the control cabinet.
■Provide the safety circuit with a slow blow T1A fuse to protect the switching
contacts.
■Switching off inductive loads produces surges that can have a major adverse
effect on open and closed-loop control systems. Connected inductive loads must
therefore have interference suppression (RC combination) as specified by the
manufacturer.
■Connect terminals 24 and 26 with a wire jumper.
■Route the connecting cables to the level electrodes and the logic unit separately
from power lines.
■Do not use unused terminals as support terminals.
■If, despite the necessary measures being taken, one of the signaling outputs
is activated when a relay closes (terminals 23, 24 and 26, 27), there may be a
dangerous second fault. Check the equipment and replace if necessary.