GESTRA NRS 1-51, Руководство по установке

Страница: 14 / 24

14
Electrical Connection
Connection of level electrode
Connect the control circuit for the feedwater supply / heating to terminals 23, 24 and 26, 27. Wenn
used as high water level alarm to TRD, EN 12952 / EN 12953 connect the output contacts of both
monitoring channels by fitting a wire link between the terminals 24 and 26.
Fuse the output contacts with a 2 A or 1 A (for 72 hours operation acc. to TRD 604) slow-blow fuse.
Connection of control circuit
Installation
Mounting level switch NRS 1-51
The level switch NRS 1-51 is clipped onto the support rail
7
type TH 35, EN 60715 in the control
cabinet.
Fig. 6
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
inter ruption 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 1-51 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 50156.
Connection of supply voltage
Provide the level switch NRS 1-51 with an external semi-delay fuse 0.5 A. If the equipment is supplied
with 24 V DC use a safety power supply unit with safe electrical isolation.
The power supply unit must be electrically isolated from dangerous contact voltages and must meet at
least the requirements on double or reinforced isolation according to one of the following standards:
DIN EN 50178, DIN EN 61010-1, DIN EN 60730-1 or DIN EN 60950.
To connect the level electrode please use:
n
For level switch NRS 1-51 with response sensitivity 10 μS:
Screened multi-core control cable, min. conductor size 0.5 mm 2 , e.g. LiYCY 4 x 0.5 mm 2 ,
max. length 100 m.
n
For level switch NRS 1-51 with response sensitivity 0.5 μS:
Double-screened multi-core low-capacitance data cable, min. conductor size 0.5 mm
2
,
Li2YCY PiMF 2 x 2 x 0.5 mm 2 , max. length 30 m .
Wire terminal strip in accordance with the wiring diagram.
Fig. 7.
Connect screens to terminal 5 and to
the central earthing point
(CEP)
in the control cabinet.