Carrier 50EJQ Technical Information PDF herunterladen (Seite 4)

Variable Frequency Drives — The evaporator fan is

controlled by a variable frequency drive (VFD). The output

that normally controls the indoor-fan motor (CV/HP) en-

ables the variable frequency drive.

Thermistors — The unit control system gathers infor-

mation from the sensors to control the operation of the unit.

CONTROL LOGIC

The following describes the general control logic se-

quence of operation for CV, VAV, and heat pump units. The

initialization software in each base control module deter-

mines CV or VAV operation from DIP (dual in-line package)

switch no. 1 and thermostat or sensor (CCN) operation from

DIP switch no. 2 on the control module.

Sequence of Operation (CV or Heat Pump Units)

1. The control module is powered up.

2. All internal software parameters are initialized.

3. All alarms and alerts are cleared.

4. The Input/Output database is re-mapped for CV

operation.

5. Maximum heat stages is set to 2.

6. Maximum cool stages is set to 3.

7. DIP switch no. 3 is read. If the Switch is OPEN, the

internal ﬂag is set for expansion board operation.

8. If thermostat operation is selected (DIP switch no. 2 set

to CLOSED), thermostat-based control is performed by

monitoring the Y1, Y2, W1, W2, and G inputs and con-

trolling the economizer, Cool 1, Cool 2, Heat 1, Heat 2,

and Indoor Fan accordingly, while maintaining required

time guards and delays when cycling equipment. The

ﬁrst time after control power-up, the indoor fan is de-

layed by a random 1 to 63 seconds.

9. If thermostat operation is not selected (DIP switch no.

2 set to OPEN), occupancy state is determined based on

Time Schedules or Remote Occupied/Unoccupied in-

put. If Temperature Compensated Start is active the unit

will be controlled as in Occupied mode.

10. The occupied or unoccupied comfort set points are read.

The space temperature offset input is used, if present.

11. The appropriate operating mode and fan control is set

based on conditioned space temperature and user con-

ﬁgured set points. The indoor fan will turn ON if the

unit is in Occupied mode or if the unit is in Unoccupied

mode and the space temperature is outside of the un-

occupied comfort set points (Unoccupied Heat or Un-

occupied Cool). When the unit goes into Occupied mode,

the start of the indoor fan is delayed by a random 1 to

63 seconds. The random delay will be applied to the first

fan start after control power-up, regardless of the oper-

ating mode.

12. The space temperature is monitored against the comfort

set points and heating or cooling stages are controlled

as required.

13. If the unit is in Occupied mode, Economizer control is

performed.

14. If the unit is in Unoccupied mode, Unoccupied Free

Cooling and IAQ Pre-Occupancy purge are performed

as required.

15. If DX (direct expansion) cooling is on, Outdoor Fan Con-

trol is performed.

16. Two stages of CV power exhaust are controlled by the

economizer position or Power Exhaust Enable output based

on indoor fan state. Power exhaust operation is selected

by DIP switch no. 5.

17. The control will run Diagnostics to monitor alarms and

alerts at all times.

18. The control will respond to CCN communications and

perform any conﬁgured network POC (Product Out-

board Control) functions such as Time/OAT Broadcast

and Global Occupancy Broadcast.

19. In heat pump units, the control will monitor defrost

inputs during heating and perform defrost cycles as

required.

Sequence of Operation (VAV Units)

1. The control module is powered up.

2. All internal software parameters are initialized.

3. All alarms/alerts are cleared.

4. The Input/Output database is re-mapped for VAV

operation.

5. The maximum heat stages is set to 1.

6. The maximum cool stages is set to 6 (plus economizer).

7. The DIP switch no. 3 is read. If the DIP switch is open,

the internal ﬂag is set for expansion board operation.

8. The control will determine if Linkage is active and if

the unit will operate in DAV mode. If yes, the local com-

fort set points will be replaced and space temperature,

return-air temperature, and occupancy status will be sup-

plied with linkage data.

9. The occupancy state is determined based on Time Sched-

ules, Remote Occupied/Unoccupied input, Global occu-

pancy, or DAV. If the Temperature Compensated Start is

active the unit will be controlled as in Occupied mode.

10. The control will set appropriate operating mode and fan

control. The Variable Frequency Drive (VFD) will be

turned ON if the unit is in Occupied mode. If the unit is

in Unoccupied mode and the space temperature reading

is available (either from sensor or DAV), the set point

temperature (SPT) is monitored against the unoccupied

heat and cool set points. The VFD is started whenever

SPT is outside of the set points (Unoccupied Heat or

Unoccupied Cool). The VFD may also be started by Night-

time thermostat via remote Occupied/Unoccupied Input

or by the Temperature Compensated Start algorithm. When

the unit goes into Occupied mode or the ﬁrst time after

power-up, the start of the VFD is delayed by a random

1 to 63 seconds.

11. When the VFD is running in a normal mode, the control

will start Heating or Cooling as required to maintain

Supply-Air Temperature (SAT) at Supply-Air Set Point

plus reset. The reset value is determined by the SAT re-

set and the Space Temperature Reset algorithms.

12. When the indoor fan is ON, the Power Exhaust Enable

output will energize the external Modulated Power Ex-

haust controller.

13. When in Heating mode, the Heat Interlock Relay output

is energized to drive the VAV boxes open.

14. If the unit is in Occupied mode, Economizer control is

performed.

15. If the unit is in Unoccupied mode, the control will per-

form Unoccupied Free Cool and IAQ Pre-Occupancy

purge as required.

16. If DX (direct expansion) cooling is on, the control will

perform Outdoor Fan control.

17. The control will run Diagnostics to monitor alarms and

alerts at all times.

18. The control will respond to CCN communications and

perform any conﬁgured network POC (Product Out-

board Control) functions such as Time/OAT Broadcast

and Global Occupancy Broadcast.

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