Flowserve NRS 2-3 - Manual (Page 7)

7
Explanatory Notes
System description
The level switch type NRS 2-3 is an analogue electronic control instrument (pump
control) for the capacitance level transmitter type NRGT 26-1.
In combination with this transmitter the switch can signal the following levels:
High level, low level, level control unit
ON
/
OFF
and can be used as level controller for steam boilers and pressurized hot-water plants.
Scope of supply
NRS 2-3, design “b”
1 Level switch NRS 2-3
1 Mounting panel for installation in control cabinets
1 Installation manual
NRS 2-3, design “c”
1 Level switch NRS 2-3
2 Guide rails
1 32 pole screw-type connector
1 Installation manual
NRS 2-3, design “d”
1 Level switch NRS 2-3
1 Installation manual
Function
The standardized input current signal is transformed by the resistor into a level-
proportional voltage and then preamplified. This voltage is fed to three voltage
comparators V1, V2, V3 and compared with adjustable reference voltages. Depending
on the comparison result the relays will be (de)energized as follows:
■ If the level voltage across V1 is higher than the reference voltage, relay 1 is
de-energized and the red LED illuminated.
■ If the level voltage across V3 is lower than the reference voltage, relay 3 is
de-energized and the red LED illuminated.
■ If the level voltage across V3 is higher than the reference voltage, relay 3 is
energized and the red LED extinguishes.
V2 works as switching controller, e. g. for the boiler feed pump.
■ If the level voltage across V2 is lower than the reference voltage, relay 2 will switch
on the pump. The yellow LED is illuminated.
The pump switches off in accordance with the adjusted hysteresis, which is adjustable
over 1 % to 50 % of the level transmitter measuring range. Once the adjusted value is
reached the relay 2 switches off the pump and the green LED is illuminated.
D
A
B
A
C