OVERVIEW
6
VCB-X Controller Field Technical Guide
Applications
Applications
Variable Air Volume Unit
The VCB-X can be con
fi
gured to control a VFD Supply Fan for Duct
Static Pressure control. If the unit is not equipped with a VFD, but
Duct Static Pressure control is needed, a modulating Zoning Bypass
Damper can be controlled by the VCB-X.
VAV units are typically designed for occupied Cooling with Morning
Warm-up Heating. This option is available with the VCB-X. The
VCB-X can also be used for a Zoning System that needs Duct Static
Pressure control and Occupied Cooling and Heating.
The VCB-X also has the ability to be con
fi
gured for Duct Static
Pressure Control by controlling the Supply Fan VFD for the purpose
of maintaining proper Duct Static Pressure in response to varying
fi
lter loading conditions.
When an indoor humidity sensor is connected to the system, the
VCB-X allows Dehumidi
fi
cation Priority on a VAV unit. This could
be useful on a building with a very low internal sensible load, but
which has a high internal and/or external latent load. During VAV
Dehumidification, the VCB-X activates Cooling based on the
Evaporator Coil Temperature and activates AAON
®
Modulating
Hot Gas Reheat to warm the Supply Air Temperature to the Active
Supply Air Temperature Setpoint.
Constant Air Volume Unit
The VCB-X can be con
fi
gured to activate a Constant Volume Supply
Fan. In most cases, this is a very basic unit with Space Temperature or
Return Air Temperature control. The VCB-X can be used for kitchen,
restaurant, or lab environments that are 100% Outdoor Air part of
the time and Return Air part of the time. The Hood On input allows
the VCB-X to know when to switch to 100% Outdoor Air control
based on an exhaust hood activating. The VCB-X requires Outdoor
and Indoor Air Temperature Sensors to accomplish this application.
Single Zone VAV
This is a hybrid CAV/VAV application for a unit serving a single
space and using Space Temperature Setpoints to enable Heating
and Cooling Modes. Heating and Cooling are controlled to their
respective Supply Air Setpoints while the supply fan modulates
to maintain the Space Temperature Setpoints. Single Zone VAV
applications can be con
fi
gured for VAV Cooling and either VAV or
CAV Heating. VAV operation requires the use of modulating Heating
or Cooling sources.
Make-Up Air Unit
The VCB-X can be con
fi
gured for 100% Outdoor Air control for
Make-Up Air. All HVAC Modes are determined from the Outdoor
Air Sensors. The Outdoor Air Volume must always be at least 50%
or higher to be con
fi
gured for Outdoor Air control.
AAON
®
PAC (Precision Air Control)
This control scheme can only be used on Constant Volume HVAC
units that are equipped with a Return Air Bypass Damper and that
use a Space Temperature Sensor as the Controlling Sensor.
AAON
®
PAC Control provides improved moisture removal
capabilities while utilizing internal space loads for reheat by
redirecting the Return Air path from the upstream side of the DX
Evaporator Coil to the downstream side of the coil.
For AAON
®
PAC con
fi
gured units, the Return Air Bypass Damper
is only used during the Dehumidi
fi
cation Mode. When the VCB-X
Controller is in Dehumidi
fi
cation Mode, the Return Air Bypass
Damper will modulate open as the Space Temperature falls below
the Cooling Setpoint. Modulation of the Return Air Bypass Damper
is controlled using a proportional range from 0% (when the Space
Temperature is equal to the Cooling Setpoint) up to 100% (when the
Space Temperature falls to the halfway point between the Cooling
and Heating Setpoints). A separate Return Air Damper Actuator
will modulate the Return Air Damper slightly further towards its
closed position as the Return Air Bypass Damper opens. This is to
ensure that enough Return Air is bypassed around the Evaporator
Coil through the Return Air Bypass Damper to raise its temperature.
The rate which the Return Air Damper closes while the Return Air
Bypass Damper is open is user-adjustable.
AAON
®
DPAC (Digital Precision Air Control)
This control scheme can only be used on Constant Volume HVAC
units that are equipped with a Return Air Bypass Damper and a
Copeland Digital Scroll™ Compressor. AAON
®
DPAC also uses a
Space Temperature Sensor as the Controlling Sensor.
The AAON® DPAC control scheme provides improved moisture
removal capabilities over the AAON
®
PAC control scheme and
provides for tighter temperature control by combining a Copeland
Digital Scroll™ Compressor with the Return Air Bypass Damper.
Refer to AAON
®
PAC Control previously described for detailed
Return Air Bypass Damper operation.
The Copeland Digital Scroll™ Compressor is used during both
Cooling and Dehumidi
fi
cation Modes. The Return Air Bypass
Damper is used only during the Dehumidi
fi
cation Mode.
Revised 8/14/13
Содержание OE335-26B-VCBX-A
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