Walchem WBLW100 Series Instruction Manual - page 22
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Start Time
Enter the time of day to start the event.
Duration
Enter the amount of time that the relay will be on.
Bleed
Select the relay to be used for Bleed/Blowdown
Prebleed Time
If lowering the conductivity prior to feeding biocide is desired using a fixed time instead
of a specific conductivity setting, enter the amount of time for the prebleed. Also may be
used to apply a time limit on a conductivity based prebleed.
Prebleed To
If lowering the conductivity prior to feeding biocide is desired, enter the conductivity
value. If no prebleed is required, or if a time-based prebleed is preferred, set the
conductivity value to 0.
Cond Input
Select the sensor to be used to control the prebleed relay selected above.
Bleed Lockout
Enter the amount of time to lockout bleed after the biocide feed is complete.
Add Last Missed
Select Enabled if the controller should delay start the most recent Biocide cycle until
immediately after an Interlock clears, or Disabled if all Biocide feed should be skipped
if there is an Interlock condition at the time the add was due to start.
5.3.8
Relay, Alarm Mode
Output Details
The details for this type of output include the relay on/off state, HOA mode or Interlock status, accumulated on-time,
alarms, current cycle on time and relay type.
Settings
Press the Settings key view or change the settings related to the relay.
Alarm Mode
Select the alarm conditions that will put the relay into the alarm state:
All Alarms
S1 Low Alarms (+LoLo Alarm, Sensor Range Error, or Sensor Fault)
S1 High Alarms (+HiHi Alarm, Sensor Range Error, or Sensor Fault)
S2 (Temperature) Low Alarms (+LoLo Alarm, Sensor Range Error, or Sensor Fault)
S2 (Temperature) High Alarms (+HiHi Alarm, Sensor Range Error, or Sensor Fault)
D1 Alarms (Flowswitch/State, Flow Total, Flowmeter Range)
D2 Alarms (Flowswitch/State, Flow Total, Flowmeter Range)
Relay Alarms (Output Timeout, Control Failure, Event Skipped) for ALL relays
Output
Select if the relay will be active when in the alarm state (Normally Open) or if the relay
will be active when not in the alarm state (Normally Closed).
5.3.9
Relay, Time Proportional Control Mode
Output Details
The details for this type of output include the relay on/off state, HOA mode or Interlock status, accumulated on-time,
alarms, current cycle on time and relay type.
Settings
Press the Settings key view or change the settings related to the relay.
Set point
Enter the sensor process value at which the relay will be off for the entire Sample Period.
Proportional Band
Enter the distance that the sensor process value is away from the set point at which the
relay will be on for the entire Sample Period.
Sample Period
Enter the duration of the sample period.
Input
Select the sensor to be used by this relay.
Direction
Select the control direction.
5.3.10
Relay, Intermittent Sampling Control Mode
ONLY AVAILABLE IF HVAC MODES ARE ENABLED IN CONFIG MENU – GLOBAL SETTINGS
In an Intermittent Sampling with Proportional Blowdown control mode, the controller reads an analog input on a
timed schedule, and the relay responds to maintain the conductivity value at the set point by activating for a program-
mable amount of time that varies with the deviation from the set point.
The relay goes through a sequence of activation/deactivation as described below. The intended purpose of this
algorithm is boiler blowdown. A sample cannot be supplied to the sensor continuously in many boilers because a
recirculating loop is not possible, and it would be a waste of hot water to constantly run a sample to a drain. A valve
is opened intermittently to supply a sample to the sensor.
Where a non-ideal installation of the sensor can cause the sample to flash to steam, and give a false low reading, this
can be corrected by taking the reading with the sample held in the pipe with the sampling valve closed, so the sample
is at boiler pressure and therefore back in the liquid state. Enable Trap Sample if this is the case. Because the con-
ductivity reading cannot be trusted while the valve is open, the blowdown is timed rather than in direct response to a
sensor reading. Rather than relying upon a fixed time, where the blowdown could be much longer than necessary if
the reading is just barely off the set point value, proportional blowdown adjusts the time appropriately.
If Trap Sample is Disabled, then the blowdown is not timed, and the Hold Time and Maximum Blowdown time are
not used. The blowdown valve will stay open until the conductivity is below set point. In this case the Output Time
Limit menu is available to stop the blowdown if the sensor is unresponsive.
Note that the software will not allow two relays using Intermittent Sampling to be assigned to the same sensor input;
the previous relay set up will change to Off mode.
Output Details
The details for this type of output include the relay on/off state, relay status (HOA mode, Interlock status, Intermit-
tent Sampling cycle step, etc.), time remaining for the active Intermittent Sampling cycle step, alarms, current cycle
on time and relay type.
Settings
Press the Settings key view or change the settings related to the relay.
Set point
Enter the conductivity value below which the controller will not start a blowdown cycle.
Proportional Band
(only shown if trap sample is enabled) Enter the conductivity value above the set point at
which the maximum blowdown time will occur. For example, if the Set point is 2000 uS/
cm, and the Proportional Band is 200 uS/cm, then if the conductivity is above 2200 uS/
cm the blowdown valve will open for the Maximum Blowdown time described below. If
the conductivity of the trapped sample is 2100 uS/cm, the blowdown valve will open for
half the Maximum Blowdown time.
Deadband
(only shown if trap sample is disabled) Enter the sensor process value away from the set
point at which the relay will deactivate.
Sample Time
Enter the length of time the blowdown valve will be open in order to capture a fresh
sample of boiler water.
Hold Time
(only shown if trap sample is enabled) Enter the length of time the blowdown valve will
be closed in order to ensure that the captured sample is at boiler pressure.
Maximum Blowdown
(only shown if trap sample is enabled) Enter the maximum length of time that the
blowdown valve will be open, when the conductivity of the captured sample is above the
set point plus the proportional band.
Cond Input
Select the sensor to be used by this relay.
Wait Time
Enter the time to wait to sample the water again once the captured sample is below set point.
Trap Sample
Enable or disable trapping of the sample.