Flowserve NRS 1-40 - Manual (Page 7)

7
At regular intervals the level electrode NRG 1...-40 sends a data telegram to the
controller NRS 1-40. 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 controller resulting in immediate boiler shut-
down. 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 controller also facilitates user-friendly performance tests and detection/
evaluation of malfunctions. To guarantee the correct and safe functioning of the low-
level limiter a min. electrical conductivity of 0.5 µS/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 sec. 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 ocurred the
malfunction information will be deleted automatically. If faults persist the malfunction
information remains stored.
As part of the automatic self-testing routine of the switching controller, the switching-off
of the output relays every 6 hrs is checked, too. If a fault is detected the information on
this malfunction will be saved accordingly.
Explanatory Notes
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Description
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■ Low-water level alarm with one level electrode
The equipment detects the min. water level (low-level limiter) and complies with the
German regulations for use in steam and hot-water plants operating without constant
supervision according to TRD 401, TRD 602 and TRD 604.
When used with two level electrodes type NRG 16-40, 17-40 or 19-40, the controller
NRS 1-40 constitutes a high-integrity low-water level limiter system with periodic self-
checking. The controller features the following function:
■ Low-water level alarm with two level electrodes
This equipment combination detects the min. water level (low-level limiting system) and
complies with the German regulations for use in steam and hot-water plants operating
without constant supervision according to TRD 604, sheet 1 and 2 (24/72 hours
operation without constant supervision).
This item of electrical equipment complies with the Technical Regulations on Protection
Circuits to DIN VDE 0116 (prEN 50156).
The level data are transferred from the electrode NRG 1...-40 to the controller via CAN
bus using the CANopen protocol. Only one low-level limiting system may be used per
CAN-based network.
Function