Watlow ez-zone pm - Silencing; Blocking; Current Sensing; Open and Shorted Load Circuit Detection

Watlow EZ-ZONE
®
PMI Controller • 204 • Chapter 9 Features
See the Keys and Displays chapter and the Home Page chapter for more details. An alarm
that is not latched (self-clearing) will deactivate automatically when the alarm condition has
passed. Turn latching on or off with Latching a.La (Setup Page, Alarm Menu).
Silencing
If silencing is on the operator can disable the alarm output while the controller is in an
alarm state. The process value or temperature has to enter the normal operating range
beyond the hysteresis zone to activate the alarm output function again. An active message,
such as an alarm message, will cause the display to toggle between the normal settings and
the active message in the upper display and attn in the lower display.
1. Push the Advance Key ‰ to display ignr in the upper display and the message source in
the lower display.
2. Use the Up ¿ and Down ¯ keys to scroll through possible responses, such as Clear CLr
or Silence siL. Then push the Advance
‰
or Innity ˆ key to execute the action.
See the Keys and Displays chapter and the Home Page chapter for more details. Turn silenc-
ing on or off with Silencing asi (Setup Page, Alarm Menu).
Blocking
Blocking allows a system to warm up after it has been started up. With blocking on, an alarm
is not triggered when the process temperature is initially lower than the low set point or
higher than the high set point. The process temperature has to enter the normal operating
range beyond the hysteresis zone to activate the alarm function. If the EZ-ZONE PM has an
output that is functioning as a deviation alarm, the alarm is blocked when the set point is
changed, until the process value re-enters the normal operating range. Turn blocking on or
off with Blocking a.bL (Setup Page, Alarm Menu).
Current Sensing
When utilizing the Current Sensing capabilities of this control it is important to know that
the measurements taken utilize the AC Line Frequency aC.Lf setting found in the Global
Menu of the Setup Page. If this setting does not represent the incoming line frequency of this
controller the readings will be in error and may appear to be frozen.
Note:
If an alarm is configured to monitor current as its source, the low alarm will be effective
only when the current level is equal to or greater than 2mA. If there is no current pres-
ent, the low alarm will not be activated.
Open and Shorted Load Circuit Detection
A Current Error C.Er (Operations Page, Current Menu) can detect either an open or shorted
load condition. A shorted condition would be present if the control is calling for 0% power
while current is detected as owing through the current transformer. Conversely, an open
condition would be present when the control is calling for power with no current ow de-
tected through the transformer.
A Heater Error h.Er (Operations Page, Current Menu) is used to determine if the load current
ow is within the specied limits as set by the user through the Current Set Points (High Set
Point C.hi and Low Set Point C.Lo); navigate to the Operations Page and than the Current
Menu to modify.