Bypass Damper Modulation; Damper Interface; Bypass Damper Mode; Changeover Cycle - Carrier 33CS Installation, Service And Instructions

BYPASS DAMPER MODULATION

This section describes the functions of the bypass con-
troller that relate to control of the bypass damper and the
operation of the bypass damper as a member of a Carrier
system.
By modulating the bypass damper, the bypass controller
provides sufficient airflow through the heating/cooling equip-
ment and maintains proper static pressure levels in the duct
system.
The bypass controller is capable of controlling dampers
equipped with model ZD(ENC), RD(ENC), MA-08, and HTA
actuators.
The bypass controller modulates the bypass damper de-
pending on the bypass damper mode it has selected. The two
bypass damper operating modes are bypass damper pressure
mode and bypass damper open mode.
Based on the system mode selected, the bypass controller
uses the bypass damper modulation function to determine
proper damper position. When a bypass damper has been
slightly oversized, the Damper Maximum Open Position func-
tion allows the capacity of a bypass damper to be reduced.
As part of a VVT system, the changeover cycle of the by-
pass controller minimizes zone usage of supply air when air
temperatures are counterproductive to zone comfort needs.
The Zone Damper Control function allows the damper po-
sition at each zone damper associated with the bypass con-
troller to be held constant for system balancing of supply
airflow and to establish the correct system pressure set point.

Damper Interface

— The bypass controller is inter-
faced to the bypass damper actuator through its wiring con-
nector board. The bypass controller can be used to control
up to 4 bypass dampers, including one master damper and 3
slave dampers.
NOTE: The bypass controller receives information from and
directly controls only the master damper. Each slave damper
receives and follows the damper position commands sent to
the master damper, but does not send information to the by-
pass controller.

Bypass Damper Mode

lates the bypass damper based on the bypass damper mode
it has selected. The two bypass damper operating modes are
bypass damper pressure mode and bypass damper open mode.
If the bypass controller is a member of a zoning system,
it has an associated system controller (monitor thermostat)
that determines the operation of the system heating/cooling
equipment based on zone demand. The associated system
controller of the bypass controller also determines the op-
erating status of the supply air fan. When the equipment heat-
ing stages are needed, the system mode is heating. When the
equipment cooling stages are needed, the system mode is
cooling.
BYPASS DAMPER PRESSURE MODE SELECTION —
The bypass controller selects the bypass damper pressure mode
during system heating mode, system cooling mode, or when
the supply-air fan is energized.
BYPASS DAMPER OPEN MODE SELECTION — The by-
pass controller selects the bypass damper open mode when
a system mode has not been chosen and the supply air fan
is deenergized, and during changeover.
Bypass Damper Modulation
ler continuously monitors system static pressure through the
pressure sensor.
DAMPER MODULATION DURING THE BYPASS
DAMPER PRESSURE MODE — The bypass controller de-
termines the bypass damper modulation by comparing sys-
tem static pressure to the system pressure set point.
— The bypass controller modu-
— The bypass control-
If the system pressure is greater than the system pressure
set point, the bypass damper is modulated open until the damper
maximum open position is reached or pressure drops to within
3% of the system pressure set point.
If system static pressure is within 3% of the system pres-
sure set points, the bypass damper position does not change.
If the system pressure is less than the system pressure set
point, the bypass damper is modulated closed until the damper
minimum open position is reached or pressure rises to within
3% of the system pressure set point.
When the Change-Over Cycle option is enabled, the by-
pass controller will select a damper mode based on duct air
temperature when entering a system heating or cooling mode.
If the Stand-Alone Operation option is set to ON, the by-
pass controller will operate the bypass damper continuously
in system pressure mode.
DAMPER MODULATION DURING THE BYPASS
DAMPER OPEN MODE — The bypass controller modu-
lates the bypass damper open until the damper maximum
open position is reached.
SYSTEM PRESSURE SET POINT — The System Pressure
Set Point function establishes the supply air static pressure
which is to be maintained by the bypass controller. The fac-
tory setting is 1.0 in. wg. The range of available values is 0.0
to 5.0 in. wg in 0.1 in. wg increments.
To configure the System Pressure Set Point, set
category 3, option 4. Use the left upper and lower informa-
tion buttons to raise or lower the set point.
DAMPER MAXIMUM OPEN POSITION — The Damper
Maximum Open Position function specifies the maximum
open position for the bypass damper(s). The factory setting
is 15. The range of values is 15 (full open) to 08 (50% open).
To configure the Damper Maximum Open Position func-
tion, set category 3, option 1. Use the left information but-
tons to raise or lower the position setting.
DAMPER MINIMUM OPEN POSITION — The Damper
Minimum Open Position function specifies the minimum open
position for the bypass damper(s). The factory setting is 00.
The range of values is 00 (full closed) to 07 (50% open).
To configure the Damper Minimum Open Position func-
tion, set category 3, option 2. Use the left information but-
tons to raise or lower the position setting.

Changeover Cycle

is used to regulate the supply-air temperature delivered to
zones when the system changes from one mode to another
(i.e., heating to cooling). During a changeover, the bypass
controller and the monitor thermostat work together to mod-
erate the temperature of the supply air from the system heating/
cooling equipment before it is delivered to the zones. To de-
termine when the changeover cycle is complete, the bypass
controller compares the supply air temperature to the change-
over set points. The factory setting is ON.
If the Changeover Cycle function is set to ON, the bypass
controller utilizes the Changeover Cycle function system
operation.
NOTE: If the Stand-Alone Operation function is ON, the
Changeover Cycle function is disabled.
If the Changeover Cycle function is set to OFF, the Change-
over Cycle is not used during system operation.
To configure the Changeover Cycle option, set category 3,
option 6. Use the left information buttons to toggle the dis-
play to ON or OFF. The default is ON.
13
— The Changeover Cycle function