Carrier 33ZCSECTRM Specifikace stáhnout pdf (Strana 12)

The Linkage Master will determine if the air source is oper-

ational (the fan is on/off) by determining if terminal airflow can

be achieved. If the terminal’s damper is open and the controller

does not measure a corresponding minimum airflow, then the

linkage master zone controller concludes that the air source is

off. If airflow is achieved, then the linkage master concludes

that the air source in on.

Once the air source is determined to be operational, the link-

age master will attempt to determine the air source mode (heat-

ing or cooling) by measuring the supply air temperature from

the air source. A primary air duct temperature sensor must be

connected to the primary air temperature input of the linkage

master zone controller. The sensor should be placed in the sup-

ply air duct at a point where airflow is not dependent on any

specific terminal. If a sensor is not installed, or the sensor fails,

then the linkage master will default the mode to cooling.

If the PAT sensor is installed and operational, the linkage

master determines the air source mode (Heating or Cooling

On/Off) based on the temperature reading.

OFF MODE — Off mode is determined when the minimum

cooling CFM for the linkage master zone is configured with a

value other than zero. The linkage master calculates the CFM

for that master zone and compares it that value to the config-

ured minimum cooling CFM for that zone. If the actual CFM is

less than the minimum cooling CFM and the damper position

is opened greater than the configured maximum damper posi-

tion (as defined by the configured Reset Maximum Damper

Position in the Linkage Configuration [MAXDP]) for

1 minute, then the linkage master zone controller will declare

the primary air source’s fan OFF. The linkage master will then

issue the OFF Mode to all zone controllers associated (linked)

with that master.

If the airflow increases above the minimum cooling CFM,

then the linkage master zone controller will determine the pri-

mary air source’s fan is on. Once the Master zone controller de-

termines the fan is on, it then proceeds to determine if the

equipment is operating in Heating, Cooling, or Free Cooling

mode.

HEAT MODE — When the fan is determined to be on, the

linkage master zone controller reads the primary air tempera-

ture value. If the temperature is greater than the average occu-

pied zone temperature, as calculated by the linkage master

zone controller, plus 5 degrees F, the mode is determined to be

heating.

In heating mode, the zone controller will modulate the pri-

mary air damper to maintain the minimum heating CFM, un-

less the system is configured for VAV Central Heating. If a

zone controller is configured for VAV heating, the zone con-

troller will modulate the primary air damper between the mini-

mum and maximum Heating CFM positions.

COOL MODE — When the fan is determined to be on, the

linkage master zone controller reads the primary air tempera-

ture value. If the temperature is less than the average occupied

zone temperature, as calculated by the linkage master zone

controller, minus 2 degrees F, the mode is determined to be

cooling.

FREE COOLING MODE — The following conditions must

be present for free cooling mode:

• the fan is determined to be on by the linkage master zone

controller

• the average zone temperature value is greater than the

average unoccupied zone cooling temperature set point,

as determined by the master zone controller

• the current time is between 3:00 AM and 7:00 AM

• the equipment is providing cooling to the system

If the above conditions are true, then the mode is deter-

mined to be Free Cooling. This mode is then communicated to

all the zone controllers associated (linked) with that master

zone controller.

NOTE: Any time a zone controller is not receiving an update

from a linkage master zone controller, that zone controller will

determine the air source mode based upon its supply air sensor

(only if the zone controller is configured for ducted heat). In

this case, no determination for heat, cool and on/off modes is

made until after the heating operation ceases. In other cases

where a supply air temperature sensor is not used, the mode

will default to cooling.

Communications Alarms with Linkage —

If the

linkage master detects that a previously polled air terminal is

no longer responding, then it will generate a CCN alarm mes-

sage indicating the loss of communications with that terminal.

If a terminal that was previously polled by a linkage master

stops being polled, it will generate a CCN alarm message indi-

cating a loss of communications from the linkage master. It

will then operate in stand-alone mode (Linkage in effect =

NO). A return to normal will not be issued until successful

communication updates have been received.

If the linkage master fails to communicate with the config-

ured CCN air source, then an air source communication alarm

message will be generated.

The linkage master will operate as

defined for a Non-CCN air source to determine the air source-

operating mode.

OCCUPANCY (LOCAL/GLOBAL)

Overview —

Each zone controller has a software time-

clock. The software time clock must be initialized after any

power failure, either by receiving a Time Broadcast (the con-

troller will request time from the network), or by a manually

updating the time, through the controller time function.

When designing a system with an air source (that has a PIC

that supports linkage), the linkage master zone controller will

determine the system scheduling if local occupancy schedules

are used at each zone controller.

NOTE: The PIC should be configured with a similar time

schedule as the linkage master, so in the event of a failure the

PIC will automatically revert back to its configured schedule.

The system occupancy function will provide to the air

source a composite view of the current occupancy status of all

the zones. If any zone is occupied, the system will indicate to

the air source that it should be in occupied mode. If no zones

are occupied then the system will indicate to the air source that

it should be in unoccupied mode. In addition the system will

provide a composite view of the next occupied time, next unoc-

cupied time, and last unoccupied time for the zones.

NOTE: If a single occupancy schedule is used, it should be

configured in the linkage master, although it is not required.

Local Occupancy —

Each zone controller will have its

own time schedule through which its occupancy state is

controlled.

When the control is configured to use its local occupancy

schedule, and the zone controller’s software time clock has

been initialized, then the local schedule shall determine occu-

pancy status.

The software timeclock will require periodic updates from a

time broadcaster in a networked device (with hardware clock).

If the software clock has not been initialized, the zone control-

ler will default to the occupied state.

Global Occupancy —

A zone controller’s occupancy

state can be controlled through the network. This will be

referred to as global occupancy. Any zone can be configured

to broadcast a global occupancy schedule to any zone control-

ler on any bus with the same schedule number. Each CCN sys-

tem can support up to a maximum of 35 global occupancy

schedules.

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