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Important Notes
Usage for the intended purpose
The level switch NRS 2-50 / NRS 2-51 in conjunction with level electrodes NRG 2.-.. and level transmit-
ter NRGT 26-1is used as limit switch and water level controller, for instance in steam boilers, (pressu-
rized) hot-water installations as well as condensate and feedwater tanks. The level switch detects and
indicates when the preset MIN and MAX water level is reached and switches the feedwater pump on
and off (NRS 2-51).
The level switch NRS 2-50 / NRS 2-51 is designed to be used with level electrodes NRG 21-.. and
NRG 26-21 as well as the level transmitter NRGT 26-1.. .
The level switch NRS 2-50, NRS 2-51 uses the level-dependent voltage signal emitted by the level
electrodes NRG 2..-.. or the level-dependent current signal emitted by the level transmitter NRGT 26-1.
The level switch NRS 2-50 / NRS 2-51 adjusts the input signal to 0 and 100 % of the boiler measuring
range and the switchpoints for MIN / MAX water level are correspondingly adjusted within this measur-
ing range. During normal operation the actual value is indicated on the seven-segment LED display.
When the MIN or MAX water level is reached, the MIN or MAX output contact is switched over after the
de-energizing delay and the MIN or MAX LED is illuminated.
The level switch NRS 2-51 also works as on-off water level controller (fill or discharge control,
switch-selectable). If the lower or upper switchpoint for water level control is reached, the controller
output switches over according to the preset function and, consequently, switches the feedwater pump
on or off. The amber LED is illuminated when the feedwater pump is switched on by the level switch.
Any faults or malfunctions in the level electrode, the level transmitter, the electrical connection or the
settings will be indicated by the seven-segment LED display. In the event of a malfunction a MIN and
MAX alarm will be triggered.
If errors occur only in the level switch NRS 2-50 / NRS 2-51, a MIN and MAX alarm is raised and the
system is restarted.
Parameter settings can be changed or a MIN/MAX alarm be simulated by operating the rotary button.
For external level indication the equipment is available with an actual-value output 4 - 20 mA.
Function
Safety note
The equipment must only be installed, wired and commissioned by qualified and competent staff.
Retrofitting and maintenance work must only be performed by qualified staff who - through adequate
training - have achieved a recognised level of competence.
Danger
The terminal strips of the equipment are live during operation.
This presents the danger of electric shock!
Always cut off power supply to the equipment before mounting, removing or connect-
ing the terminal strips!
Attention
The name plate specifies the technical features of the equipment. Note that any piece of
equipment without its specific name plate must neither be commissioned nor operated.
