Honeywell DHC, Service Manual

Page: 150 / 262

Hydraulic Components SDC / DHC
150 EN2H-0221GE51 R0812
7.2.5 Hot-water pre-regulator with district heating systems
The hot-water pre-control function is necessary for the controlled
filling of hot water storage tanks with layered loading from the
district heating network. Generally, such loading is carried out
through a separate heat exchanger.
The function is activated via a new setting in the "Hydraulics"
menu, parameters 03 and 04.
Function number: 30
In the parameter tree for the heating circuits, parameters 14, 15,
18, 19, 20, 21 and 22 are available. With the return flow limit
activated, parameter 17 is displayed, too.
With the FLOW display, the symbol WW for hot-water pre-mixing
is displayed to the lower left.
When the pump status is displayed, the string DEMAND is
displayed instead of the control mode.
When the hot-water pre-control is active, the respective mixed
heating circuit cannot be used as a heating circuit anymore.
When the hot-water pre-control is active, the request for hot-water
loading is not sent directly to the energy management unit (and
further to the district heating valve), but instead to the hot-water
pre-control.
The hot-water pre-control forwards the setpoint, taking into
account the parameter-defined offset, to energy management and
adjusts to the nominal value, which was received from hot-water
loading, at the mixed heating circuit actuator.
Any parameter-defined return flow limiter sensor (setting 7/8 at
the variable input) acts according to its set function on the
actuator of the hot-water pre-control.
The switching behaviour of the tank loading pump is described in
a separate demand.
The hot-water pre-control must be activated in the same control
device as the associated hot-water loading.
The mixed heating circuit minimum and maximum limits are not
adjustable and have no effect.
The run-down time of the mixed heating circuit pump runs parallel
with the tank loading pump extended running time.
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