GESTRA NRS 1-41, Original Installation Instructions

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6
Scope of supply
NRS 141
1 Level switch NRS 141 (plugin unit in plastic case with terminals)
1 Terminating resistor 120 Ω
1 Installation manual
Description
The switching controller type NRS 141 is a selfmonitoring highwater level limiter with periodic self
checking and monitoring feature of the output relay contacts designed to be used in conjunction
with one level electrode type NRG 1641, 1741 or 1941. The switching controller has the following
function:
n
Highwater level alarm with one level electrode
The equipment detects the max. water level (highlevel limiter) and complies with the German regula
tions for use in steam and hotwater plants operating without constant supervision according to
TRD 604, sheets 1 and 2 (24/72 hrs operation) as well as DIN EN 12952 and DIN EN 12953.
This item of electrical equipment complies with the Technical Regulations on Protection Circuits
DIN EN 501561.
The level data are transferred from the electrode NRG 1…41 to the switching controller via CAN bus
using the CANopen protocol. Only one highlevel limiting system may be used per CANbased network.
Explanatory Notes
Function
At regular intervals the level electrode NRG 1…41 sends a data telegram to the switching controller
NRS 141. The data transfer is effected by means of a CAN bus according to ISO 11898. The transferred
measuring data are constantly evaluated by the controller. A periodic selfchecking routine tests every
3 seconds the integrity of the system and its safety functions, with a malfunction in the switching
controller resulting in immediate boiler shutdown. When the CAN bus line and, consequently, the data
transmitting cycle are interrupted, the controller sends a visual signal to indicate a faulty condition and
the relays are instantaneously deenergized (failsafe position).
The switching controller also facilitates userfriendly performance tests and detection/evaluation of
malfunctions.
To guarantee the correct and safe functioning of the highlevel limiter a min. electrical conductivity of
0.5
µ
S/cm at 25 °C is required.
The relay deenergizing delay is normally set to 3 seconds at the factory but delays of 15 to 25 seconds
are available on request.
Apart from the burner protection circuit there is also a separate PhotoMOS make contact output for
remote indication.
The automatic selftesting routine of the switching controllers checks every 3 seconds their safety
functions. The corresponding functions of the level electrodes will be tested by the electrode’s self
checking routine every 10 sec. The malfunction information is updated with every selftest. If no faults
have occurred the malfunction information will be deleted automatically. If faults persist the malfunction
information remains stored. If a malfunction is detected, the signal output of the control unit (terminal 7
and 8) is opened and closed in a clock pulse controlled way. As part of the automatic selftesting routine
of the switchting controller, the switchingoff of the output relays every 6 hrs is checked, too.