Flowserve NRS1-41 - Manual (Page 7)

7
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.
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. If a fault is detected,
the information on this malfunction will be saved accordingly.
Explanatory Notes
– continued –
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:
■ High-water level alarm with one level electrode
The equipment detects the max. water level (high-level limiter) and complies with the
German regulations for use in steam and hot-water plants operating without constant
supervision according to TRD 604, sheets 1 and 2 (72 hrs operation).
This item of electrical equipment complies with the Technical Regulations on
Protection Circuits DIN VDE 0116 (prEN 50156).
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.