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Thermostat
FAQ
The KNX system uses the 1-byte object "Thermostat Mode"
to read the status of the thermostat. If you do not want to
use the Byte, you can set the 1-bit mode change object to
read. However, this is not the ideal solution because the bits
will have to be read explicitly given that the information is not
sent automatically.
11. Are there any particular precautions to take when using
the 0-100% proportional valve control?
Never use the "Control Value" object. This is a debug object
left inside the application for KNX certification purposes. In
this specific case replace it with "Cooling Valve" to obtain the
desired function.
However, some types of valves with proportional control
require a cyclic refresh of the control value. In this case it is
necessary to activate cyclic sending of the control value
to the valve. To control the proportional solenoid valves you
must use the "Cooling/Heating Valve" object (object no. 34
and 81) in read/write mode (which appears only for "2-Pipe
Proportional" systems, selected by the parameter "Valves")
or objects no. 34 "Cooling Valve" and no. 35 "Heating Valve"
will appear if "System Type" is set with the "Proportional
4-Pipe Circuit" parameter.
12. When do the "snowflake" and "flame" icons appear on
the display? Do these icons indicate respectively the
summer and winter modes?
These icons do not indicate summer/winter mode. They
appear whenever the thermostat is controlling the relay or
corresponding valve (if the thermostat is in heating mode, the
flame appears; if it is in air conditioning mode the snowflake
appears) and then disappear when the desired temperature
has been reached. If the room temperature has already
reached the desired value, the icon is not displayed (opera-
tion is similar to that of conventional thermostats). The object
to be associated with the summer/winter change of season
is a different object from the one used for reading the season:
nos. 19 and 18 and nos. 66 and 65.
13. We need to have a group that goes to "0" when the ther-
mostat is set to "Off" (by the guest or the supervisor) and
returns to "1" when the thermostat is returned to "CMF".
How can we do this?
This is an application that allows the input of a Daikin with
KNX interface to be forced so that it turns the machine off
if the thermostat is Off and back on if it is "CMF" without
necessarily starting the system (heating is subsequently acti-
vated depending on the messages sent by the thermostat to
the valve). In practice the guest wants to use the thermostat
for On/Off control of a device that has its own temperature
control function.
To do this you have to use an object (such as a KNX logic)
that sends an On/Off message according to the thermostat
mode (using the "Mode" object).
14. How should a window's N.C. contact be managed when
it is connected to the thermostat for window open sig-
nalling?
The input to which the window contact is connected must
be set with the "Status Send" function so that one message
is sent when it is opened and another one when it is closed.
If an N.C. contact is used, it will be necessary to set "Off" for
the falling edge (opening of window and contact) and "On"
32
for the rising edge (closing of the window and contact). If
the contact is an N.O. type, the two parameters must be set
respectively to "On" and "Off" (when the window is opened
the contact is closed and vice versa). If you set the input
as "Window Sensor", opening the window will stop the
thermostat writing an "04" byte (antifreeze) to the datapoint
"Mode status" and "00" to the datapoint "Cooling/Heating
Valve" (closes the valve); closing the window will set the pre-
vious status; you can also choose a delay time for opening
the window after which the thermostat will stop. If together
with this internal thermostat management you also want a
"0" bit to be sent to the bus when the window is opened
and a "1" bit when it is closed, you must set the thermo-
stat IN input as "General Use" so as also to display object
no. 110 "Input". If the window contact is connected to the
thermostat's input, this new object must be associated with
a group with the "Window Sensor" object no. 52 or no. 99
whereas if you use the IN input of another KNX device this
will be associated with the "Window Sensor" object.
15. Which functions are considered most important for use of
the thermostats on hotel systems with the Well-contact
Suite management/supervision (and other) software?
a. Current Temperature: this is useful for displaying the ther-
mostat temperature in the software (it is advisable to set
cyclic sending amongst the parameters; to be considered
in the event of a large number of devices).
b. Thermostat Mode or alternatively Comfort, Energy Saving,
Protection: these are important for sending thermostat
operating mode controls via Well-contact Suite.
c. Thermostat Mode - status: this is important to see the
current operating mode of the thermostats in the soft-
ware.
d. Summer/Winter status: this is important to see the cur-
rent seasonal operating mode of the thermostats in the
software.
e. Enable Summer/Winter: this is essential for sending
seasonal thermostat operating mode controls via Well-
contact Suite software.
f. Current Setpoint: this is useful for displaying the set ther-
mostat temperature in the software (it is advisable to set
cyclic sending amongst the parameters; to be considered
in the event of a large number of devices).
g. Winter Comfort Setpoint, Winter Standby Setpoint,
Winter Energy Saving Setpoint, Winter Protected
Setpoint, Summer Comfort Setpoint, Summer Standby
Setpoint, Summer Energy Saving Setpoint, Summer
Protected Setpoint (objects from 25 to 32 and from 72 to
79): they are useful for displaying and setting the various
"Basic Setpoints" in the two seasonal operating modes
in the software.
Note. To be able to view the values, you have to set the
read flag for these properties manually in ETS.
h. Management case studies Heating/air conditioning
speed for thermostats:
Proportional Three Speed Control:
1. Proportional (0-100%) - Fan Inputs (objects 38 and
85): useful for sending the proportional speed maxi-
mum value.
2. Proportional (0-100%) - Fan Outputs (objects 44 and
92): useful for displaying the proportional speed max-
imum value in the software.
On/Off management:
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