Bryant 580J*04--12 Manual de instalación descargar pdf (Pagina 20)

switch input. Inputs 3, 5, 8, and 9 on plug J5 can be

hard-wired to command the unit’s occupancy. The

Occupancy Contact point show the status as on or off, on

is occupied and off is unoccupied.

Indoor (Supply) Fan

The indoor fan can be configured to operate in three

different manors. The configuration point Fan Mode

determines how the fan will run. The fan will always be

disabled if a fire shutdown or safety chain alarm is active.

A valid space temperature and supply air temperature

must be available for the fan to operate. There is a unit

start delay in effect when the unit is transitioning from

unoccupied to occupied. The following describes specific

fan operation based on the Fan Mode configuration value.

Auto

When Fan Mode is set to Auto, RTU Open will cycle the

fan on and off based on the demand for heating, cooling,

and dehumidification. There is a configurable fan off

delay that is upheld before shutting the fan off after

conditioning has ended.

Continuous

When Fan Mode is set to Continuous, RTU Open will

cycle the fan based on occupancy. The fan will run

continuously whenever the unit is occupied and operate in

the auto mode during the unoccupied period.

Always On

When Fan Mode is set to Always On, RTU Open will run

the fan all the time regardless of occupancy or demand.

Fan Off Delay

A Fan Off Delay allows the supply fan to continue

operating after heating or cooling stops. If the following

alarms are active, the fan turns off immediately, regardless

of the occupancy state or demand:

S Fire Shutdown

S Safety Chain

S Supply Air Temp Sensor alarm

The RTU Open does not include smoke--control

functions such as smoke--purge, zone--pressurization, or

smoke--ventilation.

Indoor (Supply) Fan Status

The RTU Open has an optional Supply Fan Status input to

provide proof of airflow. If this is enabled, the point will

look for a contact change whenever the Supply Fan Relay

is on. If it is not enabled then it will always be the same

state as the Supply Fan Relay. The cooling, economizer,

heating, dehumidification, CO

and power exhaust

routines will use this input point for fan status.

Cooling

The compressor outputs are controlled by the Cooling

Control PID Loop and Cooling Stages Capacity algorithm.

They will be used to calculate the desired number of stages

needed to satisfy the space by comparing the Space

Temperature (SPT) to the Occupied Cool Setpoint plus the

T56 slider offset when occupied and the Unoccupied Cool

Setpoint (UCSP) plus the T56 slider offset, if unoccupied.

The economizer, if available, will be used for cooling in

addition to the compressors. The following conditions must

be true in order for this algorithm to run:

S Outdoor Air Temperature, if valid, is greater than the

Cooling Lockout Temperature setpoint.

S Indoor Fan is ON.

S Heat mode has not been active for 5 minutes.

S If occupied and the SPT > (occupied cool setpoint plus

the T56 slider offset).

S Space Temperature and supply air temperature values

are valid.

S If it is unoccupied and the SPT > (unoccupied cool

setpoint plus the T56 slider offset).

S Economizer is unavailable, or if the Economizer is active,

mechanical cooling is available if the economizer is open

> 90% for at least 7.5 minutes, the SAT > [Minimum

Cooling SAT + 5_F(2.7_C)] and SPT > [Effective

Cooling Setpoint + 0.5_F (0.27_C)].

If all of the above conditions are met, the controller uses a

PID logic loop to energize or de--energize compressors to

satisfy the cooling demand.

There is a fixed 3--minute minimum on time and a

5--minute off time for each compressor output.

Any time the compressors are running the RTU Open will

stage down the compressors if the SAT becomes less than

the cooling low supply air setpoint. After a compressor is

staged off, it may be started again after a normal

time--guard period and the supply air temperature has

increased above the low supply air setpoint.

S Cooling – Without humidity control [RH Control =

Disable] or an economizer [Economizer Exists = No],

the operation of the unit is as follows:

If OAT > Cooling Lockout Temperature (45_Fdef)and

SPT > cooling setpoint, then a PID will calculate the

required number of compressor cooling stages required

to satisfy the present space load conditions. After the

minimum compressor off time has expired, then the first

compressor stage will be started. The actual number of

active compressor stages [Active Compressor Stages] is

displayed in the maintenance section.

As the compressor stage(s) operate, the controller monitors

the supply air temperature and compares the measured

value to the configured supply air temperature setpoint

[Stage 1 SAT Stpt if Active Compressor Stages = 1, see

the table below].

The fan will begin to operate (or currently be operating)

at the configured minimum fan speed [Min VFD

Output]. If the measured SAT falls below this setpoint, a

PID will calculate the required VFD output to increase

the fan speed to obtain the configured Stage “X” SAT

Stpt depending on the actual number of the operating

stage (1--3). The fan speed can increase as required but

not greater than the configured maximum speed [Max

VFD Output].

Active Compressor Stages Controlling SAT setpoint

=1 Stage 1 SAT Stpt

=2 Stage 2 SAT Stpt

=3 Stage 3 SAT Stpt

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1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 47 48

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Bryant 580J*04--12 Manual de instalación Pagina 20

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