Red-lion TCU User Manual download pdf (Page 33)

Output Module (2-OP)

The controller has parameters that affect how the main control output

(OP1) responds to temperature changes and sensor failures.

Time Proportioning Cycle Time (CYCt)

The selection of cycle time depends on the time constant of the p rocess and

the type of output module used.

CYCt - 0 to 250 seconds

For best control, a cycle time equal to 1/10 of the process time constant, or

less is recommended; longer cycle times could degrade temperature control,

and shorter cycle times provides little benefit at the expense of shortened

relay life. When using a Triac module or a Logic/SSR drive output module

with the SSR Power Unit, a relatively short cycle time may be selected.

A setting of zero keeps the main control output and front panel indicator

off. Therefore, if using the analog output for control, the main output and

indicator can be disabled. This parameter is skipped for Valve Positioner

models.

Output Control Action (OPAC)

For heat and cool applications, the main output (OP1) is normally used for

heating (reverse acting) and the optional cooling output (OP2) is normally

used for cooling (direct acting).

OPAC - rEv (Reverse acting)

drct (Direct acting)

If drct (direct acting) is selected, the main output (OP1) is direct acting and

the cooling output (OP2) is reverse acting.

Note: When using a relay output module, th e control action may also be reversed

by using the normally closed contacts.

The linear DC analog output, when assigned to output power (OP) for

control purposes, tracks the controller output power demand. A direct acting

linear output signal can be implemented in two ways:

1. Use “ direct” for output control action (OPAC).

2. Interchange the two analog output scaling points ANLO & ANHI (see

Linear DC Analog Output, page 27).

Output Power Limits (OPLO & OPHI)

Enter the safe output power limits for the process. These parameters may

also be used to limit the minimum and maximum controller power due to

process d isturbances or setpoint changes, to reduce overshoots by limiting

the process approach level.

OPLO & OPHI - 0 to 100%

If the cooling option is installed, the limits range from:

OPLO & OPHI - -100 to 100%

With the cooling option installed, the Lower Limit can be set to less than

0% to limit maximum cooling or set to greater than 0% to limit minimum

heating. Set the High Limit to less than 0% to limit minimum cooling or

greater than 0% to limit maximum heating. When controlling power in the

manual mode, the output power limits do not take effect.

Sensor Fail Preset Power (OPFL)

If a failed sensor is detected, the control output(s) default to a p reset power

output.

OPFL - 0% (OP1 output full “off”) to 100% (OP1 output full “on”)

If the cooling option is installed, the range is extended from:

OPFL - -100% to +100%

At 0% both outputs are off, at 100% OP1 is on and OP2 is off, and at -100%

OP2 is on and OP1 is off. The alarm outputs always have an up-scale drive

(+9999), independent of this setting, for failed sensor.

For position mode valve controllers, the valve is positioned according to

the setting of this parameter.

For velocity mode valve controllers, the following actions occur:

Velocity mode: OPFL = 0%, valve CLOSE output activates

OPFL = 100%, valve OPEN output activates

OPFL = any other setting, both valve outputs disable

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Red-lion TCU User Manual Page 33

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