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WEBVISION™
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To perform Min/Max Balancing:
Complete the following procedure to do min/max balancing.
NOTE: To do min/max balancing ensure that the VAV device
is online.
1. Damper position and Sensed airflow displays the
current damper position and flow sensed by the device.
2. Click the Start Zero Balance to attain the zero flow
setpoint. Job progress status is shown at the bottom of
the page, once the setpoint is attained, confirmation
message is displayed.
3. Once the Zero airflow setpoints is attained, flow sensed
by the device is displayed. Update the actual flow
sensed in the Measured Airflow field and click Apply
Measured Flow.
4. Enter Max Airflow Setpoint value and click Change
Max Setpoint to write the value to the device.
5. Click Start Max Balance to attain the maximum airflow
setpoint. Job progress status of maximum balancing is
shown at the bottom of the page, once the setpoint is
attained, confirmation message is displayed.
6. Update the actual flow sensed in the Measured Airflow
field and click Apply Measured Flow.
7. Enter Min Airflow Setpoint value and click Change
Min Setpoint to write the value to the device.
8. Click Start Min Balance to attain the minimum airflow
setpoint. Job progress status of minimum balancing is
shown at the bottom of the page, once the setpoint is
attained, confirmation message is displayed.
9. Once the balancing is completed, Click Done to set the
device back to Auto mode and go to the balancing
summary screen.
Demand Limit Control (DLC)
Demand Limit Control (DLC) continuously monitors the
building's rate of energy consumption. It automatically sheds
or restores loads to prevent the demand (load) from
exceeding the maximum allowable level or configured
setpoint. It is based on the building's power requirements and
operating characteristics. For DLC to have control over
energy savings, the configured setpoint must be less than the
actual demand allocated by the power generating plant. DLC
sheds or adjusts the loads during peak usages only. DLC is
driven from the current KW demand, which is an
instantaneous value averaged over a period of time (demand
averaging window period). It is a good practice to adjust the
DLC window close to the utility company's demand window
period. This in turn will help WebVision to follow the same
criteria as that of the utility company when taking KW demand
shed decisions. The energy history log must also match the
peak demand recorded by the utility company.
Load Assignments
Each device is considered to be an external object when
assigning it to a load. A load consists of a local configuration
that defines the behavior of the load and its association with
an object or a set of objects. These objects are discovered
Excel 10 or Excel 15C devices, which in turn control the
external electrical loads. All the objects associated under one
load assignment are shed at once, restored at once and
overwritten at once depending on the configuration of the load
assignment. Each load assignment is identified by a load
assignment number ranging from 1 to 50.
The following are the two types of loads that DLC sheds to
maintain demand below the peak setpoint:
Off Continuous Loads
Off Continuous loads are the first loads that are shed by DLC.
Once shed, they are not restored immediately. Loads marked
as Off Continuous generally control the loads that are least
important to overall operation of the facility. When KW
demand exceeds the peak setpoint, Off Continuous loads are
shed first starting from the lowest numbered load (1) to the
highest (50). These loads are shed until the demand goes
below the peak setpoint limit. The first load is shed at staging
interval seconds after the KW exceeds the peak setpoint.
Additional loads are shed at staging interval, seconds until the
KW is less than the peak setpoint. Off Continuous loads, once
shed are the last to be restored when demand is less than the
normal level (setpoint minus the dead band). Off continuous
loads are restored in the order reverse to which they were
shed (highest load (50th) is restored first). Any Off Continuous
load that is shed remains inactive for at least the configured
Minimum Shed Time.
Rotating Loads
Rotating loads are shed or adjusted after shedding Off
Continuous loads, as DLC needs to reduce the demand.
Loads marked as Rotating have more important equipment
assigned to them than the loads marked as Off Continuous.
Rotating loads are shed or adjusted only after all the Off
Continuous loads are shed and if the KW demand still
exceeds the peak setpoint. DLC sheds the Rotating loads in
sequence starting with the lowest numbered load first. When
demand is below the normal level (peak setpoint minus the
dead band), the Rotating loads are restored on a priority
basis; highest priority is given to the load that has been shed
for the longest period. If restoration of a Rotating load causes
KW to raise above the peak setpoint, then the next eligible
Rotating load (usually the next higher numbered Rotating
load) is shed.
NOTE: Note: Rotating loads are restored before Off
Continuous loads when KW demand is below the
normal level (less than the peak setpoint minus the
dead band).
Rotating loads are not eligible for shed until their
Minimum On Time has elapsed after restoration.
Once shed, a Rotating load cannot be shed again
until all the other eligible Rotating loads are shed.
Rotating loads are not restored until their Minimum
Shed Time has elapsed.
Rotating loads can't be in Shed time not more than
the Max Shed time.
DLC Load Shedding and Restoring Methods
DLC monitors the current KW levels at every staging interval
and averages it over a period of time.
• If the current KW demand is above the configured peak
setpoint, then DLC sheds loads at defined intervals until
the demand drops below the peak setpoint.
• If the KW demand drops below the normal level (peak
setpoint minus the dead band), then the previously shed
loads are actively restored at every staging interval until
the KW demand rises back above the normal level.