PART THREE - OPERATION
SECTION 7 - RELAY OVERFEED TIMER FEATURE
Model C53 Conductivity Analyzer (universal-mount 1/2 DIN)
Rev. 5-1000
80
S
ECTION
7
7.1 Why Use an
Overfeed Timer
7.2 Configuring Relay
Overfeed Timers
7.3 Overfeed Timer
“Timeout” Operation
7.4 Resetting Overfeed
Timers
7.5 Interactions with Other
Analyzer Functions
The useful relay overfeed timer feature,
only available to a
CONTROL relay
, is described in more detail in this section.
Suppose that you configure a CONTROL relay with a high
phase to operate in response to increasing measured value.
The CONTROL relay will then turn on whenever the meas-
ured value exceeds its preset setpoint. When the measured
value decreases below the setpoint by an amount you pre-
set (the deadband setting), the relay will turn off. But what if
a damaged sensor or a process upset condition keeps the
measured value above the setpoint or deadband setting?
The control element (valve, pump, etc.) switched by that
relay would then continue to operate. Depending on the ap-
plication control scheme, this may excessively dispense
costly chemical additives or overly drain or divert the proc-
ess. Also, the control element itself could be damaged due
to excessive continuous or unusual operation such as a
pump that is running dry. The useful overfeed timer pre-
vents undesirable conditions like these from happening. It
restricts how long the relay and its connected control ele-
ment will remain on regardless of conditions.
To set a relay overfeed timer, use its respective configura-
tion menu screen. The time you set to restrict how long the
relay stays on (0-999.9 minutes) should be just enough to
provide acceptable results. An excessive setting may waste
chemicals or the process itself. Initially, set this time as an
estimate. Then, by experimenting and observing the re-
sponse, periodically “fine tune” to optimize the setting.
When a CONTROL relay is on and its overfeed timer “times
out,” its annunciator will blink. This indicates that the relay
is now off and will remain off until you manually reset the
overfeed timer. After reset, the relay annunciator stops
blinking. (All overfeed timers are reset simultaneously.)
To manually reset all relay overfeed timers, please refer to
PART THREE, Section 6.3.
A relay overfeed timer can, and often will, interact with other
analyzer functions while those functions are in use. Table E
on the next page explains common overfeed timer interac-
tions.
RELAY OVERFEED TIMER FEATURE
