26
Thermostat
Communication objects and ETS parameters
Manual operation of the fans
The user selects the speed used by the thermostat only when
the valve is on; if the valve is off at the time of selection, the
thermostat saves the setting and uses it again the next time the
valve is on. On the display, the fan speed changes from "
AUTO
"
to "
OFF
".
The selection made by the user remains active until the end
of the time (in minutes) set by the "
Time in Manual Fan Mode
(min)
" parameter or the fan speed is set manually onto “
AUTO
”
with the
button or remotely via the communication
object.
Caution: If the "Time in Manual Fan Mode (min)” parameter
is equal to 0 it means that the manual operation of the fan is
never turned off by time.
Automatic three-speed fan coil operation
In the case of a three-speed fan coil in "
AUTO
” mode, the fan
coil speed is controlled automatically by the thermostat. The
speed automatically goes from the higher to the lower speed
gradually as the measured temperature approaches the value
set as the setpoint. The threshold to determine the speed to set
is linked to the following parameters: "
Threshold for the Speed
of Fan 2
" and "
Threshold for the Speed of Fan 3
” while speed
1 is active when the valve is turned on and the "
Switching time
between speeds (min)
“ has passed.
An example of operation is shown in the following figure where
SV2 and SV3 are respectively "
Threshold for the Speed of Fan
2
” and “
Threshold for the Speed of Fan 3
”; ΔTR is instead the
“
Differential Coefficient
” of the on/off setting.
Note
: In the example shown in the figure, the effect of the
"
Fan Speed Hysteresis
” parameter was overlooked and the
"
Switching time between speeds
” parameter was set = 0.
When the measured temperature reaches the setpoint the
thermostat switches off the fan, sends a 1 bit on the Bus for
object no. 45 or no. 92 "
Off – Fan Outputs
” (V0), switches on
V0 and switches off V1. When the temperature deviates from the
desired value, the valve is turned on and the speed V1, after the
value of "
Switching time between speeds
”, is activated. In the
following example figures, this parameter is set to 0.
N.B.: Fore reasons tied to the safety of systems, if the
valve is active the user will be unable to set "OFF" from the
thermostat. It will therefore be necessary to turn off the valve
by setting the thermostat to another mode or by modifying its
setpoint.
Three Speed Fan coil (A/B)
Three Speed Proportional (A/B)
Proportional (A/B)
Setpoint
+ ∆
T
R
Setpoint
Setpoint - S
V2
Setpoint - S
V3
– ∆
T
R
V3
V2
V1
OFF
OFF
