Phason
VTC-1D user manual
11140010
5
Displaying and adjusting parameters
Switch position
Function
Displays the ambient temperature
Allows you to view and adjust the temperature set point
Clears alarms
Allows you to view and adjust the differential (
di
), off set-back (
oS
), and idle
speed (
id
). Each time the switch is clicked and then held in this position, the
next parameter is displayed. The display flashes between the parameter code
(two letters) and it's setting (two digits). You can adjust the parameter at this
point. The cycle starts over after the last parameter. To restart at the beginning
of the cycle, click the switch to the right.
Parameter
Code
Range
Factory setting Location
Temperature set point
N/A
32 to 99°F (0 to 38°C)
N/A
External knob
Idle speed
id
0 - 99%
N/A
External knob
Temperature differential
di
1 to 20°F (0.6 to 12°C)
6°F
Internal trimmer
Off set-back
oS
0 to 16°F (0 to 9°C)
5°F
Internal trimmer
°F or °C (ambient temp.)
°
F
/ °
C
-22 to 99°F (-30 to 38°C)
°F
Internal jumper
About hysteresis
The VTC-1D has a 1°F (0.5°C) hysteresis. This means the fan will turn off 1°F below the temperature at
which it turned on.
For example, if temperature set point is 75°F, the fan turns on at 75°F, off at 74°F. This prevents the fan
from flickering on and off when the temperature is at the set point.
Setting the off set-back and selecting the mode of operation
Auto shut-off (OSB) mode
In auto shut-off mode, also called OSB mode, the fan shuts off when the temperature is below the off set-
back temperature. For more information, see
Example 1: shut-off (OSB) mode
on page 9.
Idle mode
In idle mode, the fan runs at the idle speed when the temperature is below the temperature set point. For
more information, see
Example 2: idle mode
on page 10.