CenCon
15
OPERATION
MODE SELECTION
The CenCon can operate under up to 4 distinct modes; heating, economizer, ventilation and cooling, in
addition to combinations. There is a delay between changing from one mode to another in order to prevent
cycling of the equipment. Mode selection is determined by the demand call and the ambient temperature.
The CenCon must have an ambient sensor installed either within the appliance, or remotely located to measure
the ambient temperature.
OCCUPIED / UNOCCUPIED
During night, or unoccupied, operation, when the modulating room thermostat is calling for more than 60%
heating demand, the heater will operate at the maximum discharge setpoint until the room thermostat demand
falls below 20%.
FAN CONTROL
VARIABLE AIR VOLUME
On a blower start signal, and before the blower is started, the VFD feedback signal is checked for a false
signal. If a false feedback signal is detected the unit will go into alarm and not start. If the signal remains
above the trip set point for 30 seconds, the SA flow alarm is set. After the blower is started, the feedback
signal must rise above the low flow trip point. If it does not, after 30 seconds the SA flow alarm is set and the
equipment shuts down.
Compressors, electric heat or direct fired burners are not allowed to run until the air flow is above minimum
feedback. While the blower is normally operating and the feedback drops 5% below the low air flow set point,
a low air flow warning is displayed and the 15 second alarm timer is started. If the air flow rises above the low
flow set point within 15 seconds, the low flow timer resets and the unit reverts to normal operation. During
this 15 sec time delay, compressors and heat exchanger style burners are allowed to stay running.
AIR PROVING SWITCH
On a blower start signal the air proving switch must be in the open position. If a closed position is detected,
the fan is not allowed to start and a 30 second alarm timer is initiated. The alarm will automatically clear if
the switch opens within 30 seconds.
If the flow proving switch is open, the blower can start normally. After the blower starts, the CenCon needs to
see the air switch close (prove) within 30 seconds. If the switch does not close, the low air flow alarm is
triggered. If during normal operation, the flow proving opens, a 15 second low air flow lock out timer is
started. During this time, compressors and heat exchanger style burners are allowed to stay running. Once
the 15 second timer has elapsed, the equipment will shut down on low air flow alarm.
WARMUP/COOLDOWN
A blower warmup/cooldown delay may be required to preheat or cool down the heat exchanger. For DG and
DJ style heat exchangers a full heat exchanger warm up delay is required when the ambient temperature is
below the low limit set point or when the ambient temperature is 8°F or more colder than the discharge set
point but above the full warmup required ambient.
