Indication of Auto/Manual operation is the LED located on the AUTO/MAN key.
When the LED is ON, the control is in the Manual operation, an alarm condition
is present, and the output de-energizes. When the LED is OFF, the control is in
AUTO operation and the alarm is energized. When the LED flashes, press the
key again within five seconds to complete the change in operation. If the sensor
is open and LOC = 0 or 1, the Series 985 switches to Manual operation (time
proportioned % power), if the output was stable before the break occurred.
When transferring from auto to manual operation, the control output(s) will not
change (“bumpless,” smooth transition). When transferring from manual to
automatic operation, the control output(s) may change significantly. In manual,
the output value (% power) appears in the lower display. In automatic operation,
the set point appears.
Using Alarms
The Series 985 has two alarms types, Process or Deviation. A
Process alarm
sets an absolute temperature when the process exceeds that absolute tem-
perature limit. The Process alarm points may be independently set high, low,
or high/low.
A
Deviation alarm
alerts the operator when the process strays too far from set
point. The operator can enter independent high and low alarm settings. The
reference for the deviation alarm is the set point. Any change in set point
causes a corresponding shift in the deviation alarm. Example: If your set point
is
lOO°F,
and you have a deviation alarm set at ±7°F as the high limit, and -5°F
as the low limit, the high alarm will trip at 107°F, and the low alarm at 95°F. If
you change the set point to 130°F, the alarms will follow the set point and trip at
137°F and 125°F.
Alarm Silencing
for alarm output A1 is available with the deviation alarm. This
overrides alarm A1 during power up. The non-latching mode automatically
enables alarm output A1 on initial power up. In the latching mode, the operator
must manually disable the alarm by pressing the AUTO/MAN key once. In both
cases alarm silencing disables the A1 alarm output relay, but the A1 LED
displays the alarm condition until the process value is within the “safe” region of
the deviation alarm band. Once the process value crosses into the “safe”
region, both a latching or a non-latching alarm is ready. Any future deviation
outside this safe band triggers an alarm.
Both Process and Deviation alarms can be latching or non-latching. The
operator must manually reset a latching alarm before the alarm will reset. The
operator must also remove the condition that created the alarm. When the
operator removes the condition causing the alarm, a non-latching alarm auto-
matically resets the alarm output.
Flashing ‘LO” or “HI” in the lower display indicates an alarm.
The Lower display alternately displays information from the current parameter
and the “LO” or “HI” alarm message at one second intervals. The alarm output
(Output 2) is de-energized and the LOAD 2 LED is lit.
To clear an alarm...
l
The alarm condition must first be corrected...
• If the alarm is latching...
Clear manually; press the AUTO/MAN key once as soon as
the process temperature is inside the alarm limit by 3°F/l.7°C for 1°
RTD units, and 0.3°F/0.17°C for 0.1° RTD units.
Figure 31 -
Alarm Display
Examples
Press once -
Clear
a latched
and
corrected
alarm.
Tuning and Operating, Chapter 5 WATLOW Series 980/985 User’s Manual 31
