AERMEC WMT21 Manuel D'installation page 53

CUT-OFF TEMPERATURE FUNCTION
The cutoff temperature function is used to inhibit the fan operation
whenever, in heating mode, the delivery water is not hot enough. In
order to accomplish this function a delivery water sensor must be wired,
alternatively, a bimetallic thermostat can be wired to the same terminals.
In case the delivery water sensor is used, the "water hot enough" threshold
is defined on parameter P23. In case this function is not needed, parameter
P23 can be set to a very low value (0).
In case a bimetallic thermostat is used for this function, parameter P08
must be set to the value "2": in this case the fan operation will be enabled
only when the bimetallic contact is closed.
When this type of bimetallic thermostat is used the water temperature
cannot be displayed, nor the automatic changeover function can be
performed. Please refer to the section "Installer Configuration" to set the
parameters related to the above described functions.
The cut-off temperature function is also available in cooling mode. In
this case the fan operation is inhibited when the water delivery is not
sufficiently cold, according to the threshold defined on parameter P24.
In case this function is not needed, parameter P24 can be set to a very
high value (99).
When the delivery water temperature is not sufficiently hot or cold as per
P23 and P24 thresholds, the display shows the " " icon. The fan is
inhibited and the fan speed symbols flash.
ELECTRIC HEATER SYSTEM
The thermostat can be configured (P01=2) to manage a system with an
electric heater for heating the room and a valve that regulates the cool
water for cooling the room. Follow the wiring diagram in Fig. 12e and
Fig. 12f. In this type of system it is suggested to set a delay on the fan
switch-off on P22, so that when the electric heater is switched off, the
fan keeps running to cool the heater down.
When the fan motor is proportional driven, for the same purpose of cooling
the heater down, it is possible to set on parameter C14 a minimum speed
that will be maintained when the electric heater is on.
In this type of system it is possible to have a neutral zone regulation setting
the automatic heating/ cooling selection (P02=1).
In case the cut-off temperature function is used in this system, the fan will
never be inhibited while in heating mode.
INTEGRATING ELECTRIC HEATER SYSTEM
This regulator can be configured (P01=3) to manage a special plant type
featuring two heating systems: one with a hot water flow controlled by
a valve, the other with an integrating electric heater. In this mode the
regulator is only driving one valve wired at the cooling output and one
integrating electric heater wired at the heating output.
The relevant wiring diagram is in Fig. 12e and Fig. 12f. The valve is driven
as in a two pipes system: according to the heating or cooling setting of the
controller the relevant flow of hot or cool water is managed.
The electric heater is turned on as an additional (integrating) heat source
whenever, in heating mode, the room temperature falls below the set point
temperature by a ∆ setpoint that can be configured in parameter C21.
In cooling mode it is possible to have a neutral zone regulation by setting
a neutral zone width greater than zero on P20. In this case cooling is
achieved by activating the valve, while heating by activating the electric
heater.
In this type of system it is suggested to set a delay on the fan switch-off
on P22, so that when the electric heater is switched off, the fan keeps
running to cool the heater down.
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