Kessel Comfort PLUS Original Operation Manual page 51

Mono/Duo ATEX level sensor
Connect the ends of the ATEX level sensor to the Zener "Fig. [22]".
The connection of level sensors is identical for both Mono and Duo systems.
010-700_01
Overview of connections for the level sensor
Wire colour
Red (plus)
Black (minus)
Note: When extending the level probe connection cable, use the KESSEL
terminal box (art. no. 28799).
Fig. [22]
Installation and operating manual
Name on Zener barrier
3
4
(+)
rt/RD
HAZ
bl bl
3 4
(-)
sw/BK
51