Honeywell UDC 3300 manual Internal cascade, Override rules

Internal cascade	Figure 5-3 is a block diagram of internal Cascade for a 2-loop controller.
Figure 5-3	Functional Overview Block Diagram of Internal Cascade of a 2-loop Controller
	PRIMARY LOOP	SECONDARY LOOP

PV SOURCE

See Loop 2

Block Diagram

PV SOURCE

See Loop 1

Block Diagram

SETPOINT

SOURCE

See Loop #2

Block Diagram

PID

CONTROL ALGORITHM

Loop 2

INTERNAL OUTPUT SIGNAL

SETPOINT

SOURCE

Loop #1

Local Setpoint

Remote Setpoint

PID

CONTROL

ALGORITHM

Loop 1

SP

2SP

3SP

OUTPUT

INTERNAL CASCADE RULES

•Loop #2 must be the primary loop.

•Loop #1 must be the secondary (internal or slave) loop because all output forms exist on Loop 1.

•Loop #1 Remote Setpoint is fixed as loop #2 output.

To Final

Control

Element

24182

Override rules

The UDC 3300 allows you to select high or low output override. Refer to Section 3 - Configuration to select High or Low.

The following rules apply for high/low override:

•Only one physical output is required when override is enabled. It is the output from Loop 1 because Loop 2’s internal output is routed through the selector.

•Loop 2 output can also be available at all times if desired.

•In Manual mode, the Output may be overridden.

•Does not apply for Three Position Step Control.

•OTI on bottom display shows value of the internal Loop 1 output before any override.

ATTENTION The output of the unselected loop tracks the selected loop to within 5 % when in Auto mode to eliminate windup. This tracking is done in the direction opposite to the Override Select configuration; i.e., for High Select, the unselected output tracks within 5 % of lower, and vice versa.

174 UDC 3300 Controller Product Manual 4/00