CenCon
16
The base blower delay off time is automatically set according to the application and type of heating device,
according to the table below.
Application * Damper delay Exchanger Warm
up delay
Cool down delay
MUA
On 90 sec
Off 20 sec
DJ: 75 sec
DG/DJX: 75 sec
Other: 0 sec
DJ: 90 sec
DG: 90 sec
DJX : 90 sec
HE: 8 sec
Other: 30 sec
Mixbox
On 10 sec
Off 10 sec
DJ: 75 sec
DG: 75 sec
Other: 0 sec
*The damper off delay starts when the blower is shut off
DAMPER CONTROL
MAKE UP AIR
Make up air equipment will normally use a 2 position actuator to open or close the inlet dampers.
DAMPER END SWITCH
A damper end switch is a mechanical device used to prove the dampers have opened. The switch may be
independent, or an auxiliary contact from the damper actuator. If used, when the damper end switch ‘makes’
and inputs 24Vac to terminal DES, the fan delay timer truncates to zero, and the fan will start.
AMBIENT COMPENSATION
On blow through heat exchangers, the blower sees greatly varying inlet temperatures. As the air temperature
changes, so does the air density and volume. The blower delivers a constant volume of ‘cold’ air. As this air is
warmed by the heat exchanger, it expands causing the outlet air volume to increase. With the extra air
volume, the temperature rise falls and there may not be enough heat on a design day.
The ambient compensation attempts to correct this by partially closing the inlet damper enough to add enough
system static to compensate for the expansion effect. The compensation starts to reduce the damper opening
at 30°F and reaches maximum effect at -40°F. The low limit operation has no effect on the ambient
compensation package. This option requires a modulating damper actuator and opposed blade dampers.
ECONOMIZER
Economizer damper control will mix the return and outside air streams to achieve the required discharge air
temperature. The CenCon may also be configured to employ an additional mixed air sensor downstream of the
mixing dampers.
It is possible for the economizer to operate while in heating or cooling mode. While the display will show
either heating of cooling, the analog output to the economizer will be active and show a value greater than the
minimum position.
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