GESTRA NRS 1-50 Instruction Manual

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Test
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Water Level Limiter
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Level Switch
NRS 1-50
For TWO electrodes
Test
Description
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.
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Water level limiters switch off the heating when the water drops
below the set low water level (LW).
The NRS 1-50 level switch can be combined in a circuit with
the level electrodes stipulated by the standards below:
Standard
UL 60730-2-15,
CAN/CSA E60730-2-15
Function
The NRS 1-50 level switch is designed for different boiler water
conductivities and for the connection of two level electrodes.
If the water falls below the minimum level, the level elec-
trodes are exposed and an alarm is triggered in the level
switch. This switchpoint is determined by the length of the
electrode extension.
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.
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 device 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 electrode. 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 an alarm
can be simulated by pressing a button.
Technical data
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)
Type of level electrode
Connecting the level electrode
NRG 16-50
Please use the following to connect the level electrode(s):
NRG 17-50
A shielded, multi-core TC-ER control cable with a minimum
n
NRG 19-50
wire size of AWG18, e.g., OELFLEX CONTROL TM CY 5G1.
Max. length 328 ft (100 m).
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) in accordance with the manu-
facturer's specification.
Signal output
2 volt-free outputs for external signaling without a de-
lay, 24 V DC, max. 100 mA (semiconductor output).
Connection of control cables 2 x AWG20 (0.5 mm
Indicators and controls
2 buttons for testing and diagnosis, 4 red/green LEDs for indi-
cating 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. 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 °F ... +176 °F (-20 °C ... +80 °C) (<100 hours),
defrosting time of de-energized equipment before it can be
put into operation: 24 hours.
Storage temperature
-4 °F ... 158 °F (-20 °C ... +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)
Data sheet 850711-00
Issue date: 09/21
USA
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