Honeywell DHC, Service Manual

Page: 140 / 262

Hydraulic Components SDC / DHC
140 EN2H-0221GE51 R0812
7.1.15 OpenTherm
• OpenTherm is the plug & play bus system!
• OpenTherm has developed into a standard in heating
technology. Many gas condensing boilers today feature an
OpenTherm connection or manufacturers offer an optional
OpenTherm interface.
• The OpenTherm bus uses simple bi-directional 2-wire
communication between the heat generator and the room
controller.
The simple OpenTherm 2-wire bus allows bi-directional
communication between the room controller and heat generator,
i.e. data exchange occurs in both directions.
In use, the simplicity of the OpenTherm system is key.
The boiler setpoint is transmitted from the SDC controller to the
automatic stokers via
OpenTherm , and feedback of the boiler
actual value occurs from the automatic stokers (in addition to the
hot-water actual and outside temperature and fault messages, if
appropriate).
Setting in the "Heat Generator" menu, parameter 1, setting 5
(automatically detected when a heat exchanger bus
(
OpenTherm ) is connected (AUTOSET), however).
If the OpenTherm function is active, the boiler minimum limit is
automatically set to 5°C.
To use the OpenTherm function, the boiler must have an
OpenTherm logo .
Terminals 37/38 on SDC Electrical connection