Carrier 33ZCVAVTRM Specifications download pdf (Page 82)

The zone controller can be configured for one of three types

of air terminal control - single duct, series fan or parallel fan. If

configured for parallel fan, the fan will be energized whenever

the there is a demand for heat the system mode is not Heating

and when there is a demand for heat when the zone is unoccu-

pied and the system mode is not Heating. If configured for

series fan, the fan will be energized whenever the zone is

occupied and when the there is a demand for heat when it is

unoccupied. To prevent all series fan zones from starting at one

time, the zone controller will run a start delay algorithm based

on the zone controllers address to stagger the fan start time.

Before starting the fan is started the zone damper will go to the

fully closed position to prevent the fan from starting back-

wards. The following formula is used to delay the fan start in

second:

Delay time in seconds = (((Whole Remainder of Element#/

20)*60)+20)

ZONE DAMPER TEMPERATURE CONTROL — The damp-

er will modulate to adjust the airflow to the space to maintain

its current set point. The damper is controlled by a PID loop to

provide precise control of the damper position. The damper

will be modulated opened if the system mode and local mode

are the same. As the zone temperature gets closer to the set

point, the damper will modulate to the Minimum Damper

Position. The amount the damper will be open at any given

time depends on how far away the temperature is from the set

point, how fast it takes to satisfy the mode, and the Minimum

and Maximum Positions for current mode. Once the zone is

satisfied the damper will go to its Minimum Damper Position

for that mode. Cool/Heat Minimum and Maximum Positions

are defined in the Damper service configuration table.

If the local zone temperature is different from the system

mode then the damper will be at Minimum Position for the

system mode.

ZONE DAMPER REHEAT — If the zone controller has

optional reheat installed, it will use this heat to maintain the

heating set point. There are 4 types of heat options available as

listed below:

• Modulating hot water or steam (requires a supply air

temperature [SAT] sensor for ducted heat or a leaving

water temperature sensor for baseboard heat)

• Two-position hot water or steam (SAT required)

• 1 to 3 stages of electric heat (SAT required)

• Combination of staged baseboard and ducted heat (SAT

required)

If the zone controller is configured for single duct terminal,

the system mode is cooling, and the zone local mode is heating

the damper will go to the configured Reheat Minimum Position

or the Cool Minimum Damper Position (as configured in the

Damper service configuration table) whichever is greater, and

reheat will be energized.

If the zone controller is configured for series or parallel fan

terminal the zone controller will close the damper to the Cool

Minimum Position before energizing the reheat. For parallel

zone terminals the fan will be energized as the first stage of

heat. The zone controller uses a PID algorithm to calculate a

supply air or leaving water temperature, which the reheat will

be controlled to, in order to satisfy the heat demand.

If the system mode is Heating, the zone controller will try to

heat the zone with the central heat but may energize reheat to

satisfy the demand if it is required. If the terminal type is con-

figured for parallel fan the fan will remain off. If no reheat

is desired in the zone while central heat is on or under any

other specific conditions, it can be disabled by forcing the Heat

point in the Status Display table to Disable. Contact your local

Carrier Controls representative if you need assistance with this

application.

ZONE DAMPER VENTILATION — After the zone has sat-

isfied and the system mode is Cooling or Free Cooling and the

SAT is between 65 and 75 F, the damper will go to its Ventila-

tion Position or the Cool Minimum Position, whichever is

greater. If the SAT is less then 65 or greater then 75 or the

system mode changes to Heating, the damper go to the current

system mode Minimum Position. The Ventilation Damper

Position is defined in the Damper service configuration table.

DEMAND CONTROL VENTILATION (DCV) — If the zone

controller has a CO

Demand Ventilation sensor it will be able

to override the temperature controlled damper position if it is

occupied, the system mode is Cooling or Free Cool, and the

zone is does not have a demand for heat. When the IAQ sensor

exceeds the configured Demand Vent set point it will use a PID

algorithm to calculate a higher damper position to allow more

airflow to the zone in order to dilute the CO

levels. The

Demand Ventilation algorithm has a higher priority then the

temperature control algorithm under these conditions so the

damper will be controlled to the greater of the two values. The

DCV mode, when active, overrides the Cool Minimum and

Ventilation Positions. As the CO

levels decrease in the zone

the damper will soon be returned to normal temperature

control.

If the zone is configured for modulating ducted reheat and

the zone temperature decreases to less than half way between

the heat and cool set point then the reheat will be enabled to

prevent the zone from going into the heat mode. If the zone is

configured for any other type of reheat it will NOT be ener-

gized. If the temperature continues to decrease below the heat

set point, the DCV mode will be disabled and the zone will re-

sume normal temperature control.

The zone ZNMAINT maintenance status table will display

the calculated damper position and if the temperature or DCV

is in control of the damper as well as other information such as

occupancy status, heat and cool set points, reheat sub-master

reference and whether local heating or cooling is in effect.

LOADSHED — The zone controller can respond to a redline

or loadshed broadcast from an optional Loadshed module in-

stalled on the Carrier communicating network. The purpose of

this function is to monitor and conserve electrical power usage.

If a redline command is broadcast the zone controller expand

its heat and cool set points by the amount that is configured in

Loadshed Offset Adjust decision in the OPTIONS service con-

figuration table. The default is 2° F so this amount would be

subtracted from the heat set point and added to the cool set

point if is left unchanged. A configurable redline/loadshed de-

lay timer (Maximum Loadshed Time decision in the OPTIONS

service configuration) will also started to prevent the set points

from being expanded indefinitely.

If a Loadshed command is broadcast then the set points will

be expanded and the zone controller will drop 1 stage of reheat

providing that the reheat option is enabled and there is more

than one stage of heat. The set points will be returned to normal

and additional staged heat will be allowed when the redline/

loadshed command is canceled by the Loadshed Module, the

zone controller’s internal redline/loadshed delay timer times

out or the zone becomes unoccupied. Contact your local

Carrier Controls representative for more information on this

application.

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Carrier 33ZCVAVTRM Specifications Page 82

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