Bryant 580J*04--12 Instrukcja Instalacji Pobierz pdf (Strona 23)

value becomes the final minimum damper position of the

economizer output.

If the IAQ minimum position calculated by the control is

greater than the DCV Max Vent Damper Pos configured,

then it will be clamped to the configured value.

Dehumidification

The RTU Open will provide occupied and unoccupied

dehumidification only on units that are equipped with the

Perfect Humidity

option from the factory. This function

requires a space relative humidity sensor or a humidistat

for control. The space relative humidity senor can be

installed and configured as one of the two analog input

channels (inputs 1 or 2 on J4), or a humidistat can be

installed and configured as switch input 9 on J5. When

using a relative humidity sensor to control

dehumidification, occupied or unoccupied dehumidification

setpoints are use accordingly. When using a humidistat,

setpoints are not used and the dehumidification call comes

when the humidistat indicates high humidity.

When the indoor relative humidity becomes greater than the

dehumidification setpoint (or switches from low to high), a

demand for dehumidification demand is identified.

Compressor state is monitored and time guards are honored.

If a compressor was just turned off prior to the dehum call

the dehumidification output will be delayed the 5 minute

minimum off time of the compressor. When ok to

dehumidify, the dehumidification output (J11--7, 8) will be

energized. This will bring on the supply fan (at high fan

speed if Fan Control is set to “Two Speed” or “Variable

Speed”), all compressors, and the dehumidification relay

placing the unit in Hot Gas Reheat dehumidification mode.

If dehumidification is called for during cooling or cooling is

called for during dehumidification, the unit will run in

Subcooling dehumidification mode. Individual unit circuits

can be in different dehumidification modes based on the

demand. Refer to the base units operation for additional

information.

NOTE: There is a fixed 5% hysteresis that the indoor

relative humidity must drop below the active setpoint to

end the dehumidification mode and de--energize the

dehumidification output. The output will also de--energize

if the fan relay is de--energized.

Demand Limit

If the RTU Open receives a level 1 (one degree offset), 2

(two degree offset), or a 3 (4 degree offset) to the BACnet

demand limit variable, the controller will outwardly expand

the heating and cooling setpoints by the configured demand

limit setpoint value and remain in effect until the BACnet

demand limit variable receives a 0 value.

Unoccupied Free Cooling

When the unit is equipped with an economizer, the control

can run a night time free cooling (NTFC) mode called

Unocc Free Cooling. In this mode the damper is utilized

to bring in outdoor air for free cooling during unoccupied

periods. The following conditions must be true for

unoccupied free cooling to operate:

S Unocc Free Cool Enable set to Enable

S The system is unoccupied

S The outside air temperature is below the Economizer

High OAT Lockout Temp

S The outside air temperature is less than the space

temperature

S Enthalpy (if enabled) is Low

When the RTU Open schedule is unoccupied and the

space temperature rises at least 1 degree above the

Occupied Cooling Setpoint, the supply fan starts. The

economizer damper opens as necessary to cool the space.

The RTU Open continues to operate in this mode until the

space is satisfied or the outside air conditions are no

longer suitable for free cooling.

Optimal Start

The RTU Open may utilize Optimal Start, which adjusts

the effective setpoints to achieve the occupied setpoints

by the time scheduled occupancy begins. The algorithm

works by moving the unoccupied setpoints toward the

occupied setpoints. The rate at which the setpoints move

is based on the outside air temperature, design

temperatures, and capacities. The Optimal Start recovery

period may begin as early as 4 hours prior to occupancy.

To disable Optimal Start, set the optimal start type to

None. The following conditions must be true for optimal

start to operate:

S Under SETPOINT, Optimal Start Value must be set

greater than zero

S The Optimal Start type must not be None

S The system is unoccupied

S The RTU Open has a valid outside air temperature

S The RTU Open is running occupancy based on a local

occupancy schedule, where next time occupied is known.

Fire Shutdown

Fire Shutdown may be configured on Binary Input 5. A

typical application involves a smoke detector or fire

shutdown contact, which, when active, immediately shuts

down equipment operation.

Compressor Safety

Compressor Safety may be configured on Binary Input 3.

This feedback can be provided by a Compressor

Lock--Out (CLO) device or current switch when field

installed. A Compressor Safety Alarm indicates that the

equipment requires attention. Cooling, heating, and supply

fan outputs are not interrupted. Normal operation resumes

when the compressor safety circuit is de--energized.

Fan Status

Fan Status may be configured on any unused binary input

channel. A typical application would be an airflow switch,

current sensing relay, or other device that provides a supply

fan running verification. Enabling this function displays the

supply fan’s status on the equipment graphic. If the

controller loses fan status during operation, heating and

cooling are disabled, the economizer damper (if available) is

closed, and an alarm for loss of status is indicated. If the fan

status is on when the controller is commanding the fan off,

the unit remains in the off state. An alarm is generated

indicating that the fan is running when it should be off.

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