Flowserve NRS 1-51 - Manual (Page 13)

3
Electrical Connection
Connection of level electrode
To connect the level electrode use screened multi-core control cable with a min. conductor size
0.5 mm  , e.g. LiYCY 4 x 0.5 mm  .
Max. length 00 m with an electrical conductivity of the boiler water > 0 μS/cm at 5 °C.
Max. length 30 m with an electrical conductivity of the boiler water < 0 μS/cm at 5 °C.
Wire terminal strip in accordance with the wiring diagram.
Fig. 5.
Connect screens only to terminal 5.
Connect the control circuit for the feedwater supply / heating to terminals 3, 4 and 6, 7. Wenn
used as high water level alarm to TRD, EN 95 / EN 953 connect the output contacts of both
monitoring channels by fitting a wire link between the terminals 4 and 6.
Fuse the output contacts with a  A or  A (for 7 hours operation acc. to TRD 604) slow-blow fuse.
Connection of control circuit
Installation
Mounting level switch NRS 1-51
The level switch NRS -5 is clipped onto the support rail 7 type TH 35, EN 6075 in the control
cabinet. Fig. 6
For connecting the level switch with the logic unit use a control cable, e. g.  x 0.5 mm  .
The control voltage must not exceed 36 V DC.
Connection of logic unit (standby input)
Note
n
A high level alarm prevents the water level from exceeding the preset max. liquid
level (HW). For this purpose it can, for instance, interrupt the feedwater supply. If the
interruption of the feedwater supply endangers the heating surfaces in the feedwater
preheater (economizer), the heating must be switched off, too.
n
In the event of an alarm the level switch NRS -5 does not interlock automatically.
If a lockout function is required by the installation it must be provided in the follow-up
circuitry (control circuit). The circuitry must meet the requirements of the EN 5056.
Mains supply
Provide the level switch NRS -5 with an external semi-delay fuse 0.5 A.