Honeywell SDC Service Manual page 18

Safety instructions
18
The earth connection of the cable shielding must occur on one
side at the protective conductor connection, e.g. at the cladding
plate of the heat generator, protective conductor terminal etc.
Multiple earth connections of a single cable are not permissible
(buzzing loop).
a No earth connection here! b Central device
EN2H-0221GE51 R0812
SDC / DHC