Viessmann Vitodens 333-F Service Instructions Manual page 105

Internal extensions for external connections
Internal extension H2 (accessories)
The internal extension H2 is inte-
grated into the control unit casing
instead of the internal extension H1.
The cylinder primary pump is con-
nected to relay output sK.
Function description
(cont.)
An external extractor interlock can be
connected to aBJ.
105