LX Series Unit Ventilator Controller User's Guide
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Alarms are transmitted using the network variables nvoUValarm and
nvoUnitStatus.
A number of alarms respond to the timing of network variables. Some of these are
called heartbeat alarms because they respond to the heartbeat value. The heartbeat
is the maximum length of time that can occur between transmissions of a variable
on the network. If this time is exceeded, an alarm sounds.
Alarm Types
The UVC uses four types of alarms. Table 10 describes these alarm types.
Alarm Procedure
When an alarm condition occurs, the following changes take place:
•
The appropriate bits of nvoStatus and nvoUValarm are set.
•
The in_alarm field of nvoUnitStatus is set to 1.
•
The network variable nvoUnitStatus transmits information about the unit
ventilator object.
The following text sorts the alarms by type, describes the conditions that generate
an alarm, and organizes the associated bits of the nvoStatus and nvoUValarm into a
table.
Alarm Low Limit
Displays a value that is less than the setpoint. When the monitored
variable becomes equal to or less than the alarm low limit, an alarm
message is transmitted over the network. Alarms that use a low limit
are often called low limit alarms. See Figure 28.
Alarm High Limit
Displays a value that is greater than the setpoint. When the monitored
variable becomes equal to or more than the alarm high limit, an alarm
message is transmitted over the network. Alarms using high limits are
often called high limit alarms. See Figure 28.
Table 10: Alarm Types
Alarm Type
Description
Digital Alarms
Monitors the state of digital network variables or hardware inputs. Digital
alarms can also indicate when digital network variables differ in state.
For example, the fan output and the fan state should always be the
same. If they differ, a digital alarm transmits a message on the network.
High Limit Alarms
Reports when an analog network variable or hardware input is greater
than a user-set value called a high limit.
Low Limit Alarms
Reports when an analog network variable or hardware input is less than
a user-set value called a low limit.
Deviation Alarms
Reports when a monitored analog value deviates from its setpoint by
more than a user-set value known as an alarm offset.
Table 9: Alarm Features (Part 2 of 2)
Feature
Description
