Carrier 33ZCSECTRM Especificaciones descargar pdf (Pagina 23)

For modulating control, the supply air needed is compared

to the actual supply air to either drive the valve open or closed.

There is a deadband on the supply air deviation where the valve

will be left at the current position until the error gets larger than

the deadband.

For modulating type heat, the floating point function com-

pares the submaster reference from the PID loop to the supply

air temperature to calculate the direction and time to position

the valve. The control prevents both outputs from operating si-

multaneously.

Configuration determines the logic output type for normally

open or normally closed type two-position valves. Hysteresis is

determined by the Heating Proportional Gain configured.

Heating with IAQ Control

— A feature is provided for situa-

tions in which additional primary air is required for ventilation

(IAQ).

The heating set point is calculated as the midpoint between

the current heating and cooling set points.

The standard heating algorithm is used except the control

set point is raised. The algorithm prevents the space tempera-

ture from falling below the set point before heating is activated.

The air terminal must be in the cooling mode and the equip-

ment must be providing cooling.

33ZCFANTRM VAV Zone Controller Informa-

tion —

The zone controller will control the operation of the

fan (start and stop), whenever the zone controller is configured

for use with a series or parallel fan terminal. The control algo-

rithm determines the required fan state, based on the local

mode, equipment mode, and the terminal type configuration.

For parallel or intermittent fan powered terminals (type 2

configuration), the fan operates as follows:

1. The fan is energized:

a. When ever SPT< current heating set point

The primary air damper is set to the fully closed

position if the air source mode is OFF and heating

is required. After heating is disabled, or if the

equipment begins to operate, the primary air

damper returns to normal operation.

b. If the Primary Damper Reference drops below the

configured Parallel Fan On value

2. The fan is deenergized:

a. Whenever SPT > current heating set point and

heating is disabled

b. If the Primary Damper Reference rises above the

configured Parallel Fan ON value

For series or constant volume fan powered terminals (type 3

configuration), the fan operates as follows:

1. The fan is energized:

a. During occupied periods

b. Whenever SPT < current heating set point

c. Whenever the air source mode is not off

NOTE: Whenever the terminal fan transitions to

ON, a fan start-up routine will run to ensure the

fan rotates in the proper direction.

2. The fan is deenergized:

a. If in Unoccupied mode and heating is not

required, or if the air source is off

b. during the fan start-up routine.

Series Fan Terminal Applications —

In a series

fan terminal, the fan is located in the primary air stream and,

therefore, must be running in order to achieve proper airflow.

The series fan terminal allows for a variable temperature, con-

stant volume airflow. Maintaining constant volume airflow is

not a function of the zone controller. The fan itself will main-

tain a constant airflow. Therefore, as the primary airflow is

modulated to control temperature, more or less air will be in-

duced from the return air plenum to maintain constant volume

airflow.

The fan is turned on whenever the central air source is on, or

whenever unoccupied heating is required. The zone controller

will energize the fan. Since the fan is located in the primary air

stream, the fan may be rotating even if the fan is not energized.

Due to the nature of the fan blade geometry, the fan will actual-

ly rotate backwards. Energizing the fan motor while the blades

are rotating backwards will cause the fan to run backwards.

The zone controller handles this condition by closing the pri-

mary damper before starting the fan. Closing the damper will

stop any airflow which may cause the fan to rotate in reverse.

Once the fan is started, the damper will be controlled normally.

100%

MAX COOL LIMIT

(DAMPER OVERRIDE

PRESSURIZATION

MODE)

MAX HEAT LIMIT

MIN HEAT LIMIT

MIN COOL LIMIT

FULL HEATING

FULL COOLING

DEADBAND

COOL

WARM

OCCUPIED

COOLING

NTFC

SETPOINT

OCCUPIED

HEATING &

MORNING

WARM-UP

SETPOINT

DAMPER

OVERRIDE-

EVACUATION

MODE

% AIRFLOW

SPACE TEMPERATURE (DEGREES)

PROPORTIONAL

HOT WATER HEAT

OPEN CLOSED

REHEAT LIMIT

LEGEND

Fig. 12 — Sequence of Operation for Single Duct Air Terminal

with Proportional Hot Water or Steam Heat

Air Source Supplying Heated Air

Air Source Supplying Cooled Air

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 43 44

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