Chapter 6 Verifying operation and communication
88 CNT-SVX05B-EN
Comm LED (yellow)
The yellow Comm LED indicates the communication status of the control-
ler. Table 60 describes Comm LED activity.
Required inputs for unit operation
The following locally wired sensor or communicated inputs are required
for each control function listed in Table 61. If any one of the sensors does
not exist, the controller operates the control function.
Table 60. Comm LED (yellow)
LED activity Explanation
LED is Off continuously The controller is not detecting any communica-
tion (normal for stand-alone applications).
LED blinks The controller detects communication (normal
for communicating applications, including data
sharing).
LED is On continuously An abnormal condition that may occur during
discovery. The LED may flash fast enough to
look as if it is on continuously. If this LED activity
occurs at any other time, the site may have
excessive radio frequency interference (RFI).
Table 61. Required inputs
Control function
Input required to be present
(locally wired sensor or
communicated value)
Controller operation if input is not
present
Variable-air-volume control Duct static pressure Diagnostic shutdown
Discharge air temperature control Discharge air temperature Diagnostic shutdown
Space temperature control Space temperature
Discharge air temperature
Diagnostic shutdown
Diagnostic shutdown
Economizer operation Outdoor air temperature
Mixed-air temperature
Economizer disabled
Space dehumidification Space relative humidity Dehumidification disabled
Two-pipe changeover Entering water temperature Hydronic capacity assumed to be
appropriate for cooling
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