AAON Orion VCCX2 User Manual

76
VCCX2 Controller Technical Guide
Heating Mode
Available heating options are Staged Gas, Modulating Gas,
Staged Electric, On/O Hot Water, Modulating Hot Water, and
Modulating SCR Electric.
Occupied Heating is enabled when the temperature at the Mode
Enable Sensor falls one deadband below the Heating Setpoint.
Heating is disabled when the Mode Enable temperature raises
one deadband above the Heating Setpoint.
Unoccupied Heating operation is enabled when the Space
Temperature falls below the Heating Mode Enable Setpoint
minus the Unoccupied Heating Oset.
In the Heating Mode, as the Supply Air Temperature falls
below the Active Supply Air Heating Setpoint (see Supply Air
Temperature Setpoint Reset section for explanation), the heating
will begin to stage on or to modulate. Each stage must meet its
Minimum O Time (adj.) before it is allowed to energize, and
successive stages are subject to a Heating Stage Up Delay (adj).
Heating stages will continue to run until the Supply Air
Temperature rises above the Active Supply Air Temperature
Setpoint plus the Heating Stage Control Window at which point
the heating will begin to stage o. Each stage must meet its
Minimum Run Time (adj.) before it is allowed to stage o, and
successive stages are subject to a Heating Stage Down Delay
(adj.).
Mechanical heating is disabled if the Outdoor Air Temperature
(OAT) rises 1° above the Heating Lockout Setpoint and will
remain disabled until the OAT falls 1° below the Heating
Lockout Setpoint. If the OAT disables mechanical heating while
it is currently operating, mechanical heating will stage o as
minimum run times and stage down delays are satised.
Modulating Heating
The VCCX2 supports various forms of Modulating Heat such as
SCR Electric Heat, Modulating Hot Water Heat, and Modulating
Steam Heat. This references Modulating Heat that is controlled
from AOUT3 on the VCCX2 Controller with a user-adjustable
voltage range between 0-10 VDC. Modulating Gas, which is
controlled by the MODGAS-X Controller, is not included in
this section. Whichever form of Modulating Heating is used,
the VCCX2 will modulate the Heat Source to achieve the Active
Supply Air Temperature Setpoint.
The Modulating Heating Proportional Window is used to
determine the signal to the Modulating Heating Source and is
user-adjustable. The Modulating Heating Signal is calculated
by the dierential between the Supply Air Temperature and the
Active Supply Air Temperature Setpoint based on the Modulating
Heating Proportional Window. The maximum signal adjustment
per Time Period is 10% and is not user- adjustable.
The minimum signal adjustment per Time Period is based on
the Modulating Heating Proportional Window. The larger the
Modulating Heating Proportional Window, the smaller the signal
adjustment will be per Time Period. The Time Period is the delay
between another increase or decrease in the Modulating Heating
source signal and is user-adjustable.
For example, if the Modulating Heating Proportional Window
is 5°F, the signal will be adjusted 2% per °F each Time Period
above or below the Active Supply Air Temperature Setpoint.
When the Supply Air Temperature is above or below the Active
Supply Air Temperature Setpoint by 5°F or more, the signal will
adjust 10% each Time Period.
Hot Water Coil Protection
NOTE: Unless the following sequence is utilized, the Hot
Water Valve is closed (regardless if congured for
direct or reverse acting control) when not being
used for Heating.
Fan On Mode
If anytime the fan is on, the Supply Air Temperature falls below
the user-adjustable Low Supply Air Temperature Cuto Setpoint
for at least one minute, the Hot Water Valve will move to a
user-adjustable position congured with the Hot Water Valve
Protection Position Setpoint. If the Supply Air Temperature rises
back above the Low Supply Air Cuto by 5°F, the valve will
return to its normal position.
If the Supply Air Temperature remains below the Low Supply Air
Temperature Cuto Setpoint for ten minutes, the unit will then
shut down and the Low Supply Air Temperature Cuto Alarm
will be generated. If the Supply Air Temperature rises above the
Low Supply Air Cuto by 5°F, the alarm (if generated) will clear
and the unit will attempt to restart and resume normal operation.
Fan Off Mode
If anytime the fan is o, the Outdoor Air Temperature falls
below the user-adjustable Low Ambient Setpoint, the Hot
Water Valve will move to the user-adjustable Hot Water Valve
Protection Position Setpoint. If the Outdoor Temperature rises
above the Low Ambient Setpoint, the valve will return to its
normal position.
If the Hot Water Valve Protection Position setpoint is left at
the default of 0%, the controller will not initiate this protection
sequence. This operation works during Emergency Shutdown.
SEQUENCE OF OPERATIONS
Heating Mode

AAON Orion VCCX2 Specifications

General

Brand	AAON
Model	Orion VCCX2
Category	Controller
Language	English