Application

Sequence of Operation

Control Loop

Siemens Industry, Inc. 140-1341

Restricted 2015-11-09

 DISPLAY RES is the COV limit for exhaust volume readings.

NOTE:

If you set DISPLAY RES to zero, the ODP continuously displays the value of EXH

FLOW. Resetting DISPLAY RES to a value other than zero displays the EXH FLOW

incrementally. The factory default is 5, cfm values displayed will be in increments of 5

(for example, 80, 85, 90, 95, 100, etc.). If the actual filtered cfm is 84, 85 will be

displayed.

These two points affect the ODP display only; they do not affect the values in the

controller or values sent to the network.

Control Loop

The PID loop controls the damper based on the values of EXH VOL and EXH STPT.

The loop output, DMPR CMD, controls EXTN DO1 and RETC DO2 through a time

modulation scheme. The DMPR CMD ranges of -100 to 100%.

 -100% is the maximum extend which closes the damper at full speed.

 0% holds the damper at its current position.

 100% is the maximum retract which opens the damper at full speed.

For example, if you command the point to -50, the damper will still close the drive but

not as quickly as if it were commanded to -100.

The controller sends a separate signal to each of the two inputs that reside on the

damper actuator. For values of 100% to 0%, the controller sends a decreasing

percentage of the full signal length to the retract input. For values of 0% to -100%, the

controller sends an increasing percentage of the full signal to the extend input.

Warning Limits

The Fume Hood Controller contains high and low flow warning limits, HI WARN LMT

and LOW WARN LMT, respectively.

The warning limits are defined as a percentage of the controller setpoint; therefore, the

warning limits apply to EXH STPT during normal control.

For either of the warnings to become active, the warning condition must be maintained

for the time specified in ALARM TIME.

When the actual flow is greater than HI WARN LMT or less than LOW WARN LMT for

a time greater than ALARM TIME, the yellow LED illuminates and HIGH WARN or

LOW WARN turns ON.