GESTRA NRG 111-11, Руководство по установке

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6
Explanatory Notes
– continued –
Function
The water level limiter comprises a level electrode type NRG 1...-11 and a level switch type NRS 1-7.
The level electrode NRG 1...-11 consists of two concentrically arranged electrodes (measuring elec-
trode and compensating electrode) which are isolated from each other by special insulating seals.
The level limiter operation is based on the conductive measuring principle using the electrical
conductivity of water for signaling water level. During normal, trouble-free operation the level electrode
tip is immersed in boiler water and no low level alarm is given. A low level alarm will only be raised if
the electrode tip is exposed for more than 3 seconds. A low level alarm will also be activated if the
insulating seals placed between the electrodes and the body are no longer pressure tight, allowing
water to penetrate into the body. However in this instance the alarm is caused by a malfunction of the
electrode, and confirmation should always be done by checking if there is water in the gauge glass.
The equipment combination NRG 1...-11 and NRG 1-7 provides fail safe protection against a first fault
in accordance with TRD 604.
System components
NRS 1-7
Level switch NRS 1-7 . Two channel level limiter (redundancy) with periodic self-checking routine to
EN 50156-1.
Design
NRG 16-11, NRG 17-11, NRG 19-11
Screwed ¾" BSP, DIN EN ISO 228-1
Electrical connection: Four pole connector, terminal box made from aluminium (optional)
NRG 111-11
Screwed 1" BSP, DIN EN ISO 228-1
Electrical connection: Terminal box made from aluminium