HDG M299, Operation Manual

Page: 39 / 176

4 Planning and installation – Connections
39
For these reasons, a return temperature control must be installed for
the HDG M299/300/350/400 heating system. The return temperature
control causes the water from the boiler return line to be mixed with
the water from the boiler supply line until the minimum return
temperature has been reached.
✎
The minimum return temperature is listed in chapter “3 Mode of
operation”, section “3.3 Technical data”.
The return temperature is regulated by the HDG control unit.
The return temperature control consists of a 3-way mixing valve with
a 230 V servo drive (running time 120-240 s) and a circulation pump.
For the HDG M299/300/350/400, we recommend:
• Wilo Stratos 50/1-12, 3-way mixing valve DN 80
The hydraulic system must be installed in accordance with specific
technical principles of the heating construction industry. Take into
account the stop cocks required for maintenance work and repairs.
The return temperature control must be installed according to the
specifications of HDG Bavaria.
The pipe dimensions must be adapted to meet the requirements at
the site. Take the water-side connections of the boiler for the supply
and return into account.
✎
See chapter “3 Mode of operation”, section “3.3 Technical data”.
The return temperature control is not designed for the use of a
gravity brake and this should therefore not be installed.