90
RT-SVX063E-EN
Table 39.
Ventilation override mode
VOM Input
OUTPUT
OPERATION
Heat Cool Mode Status
Mode A
(Unit Off)
Supply fan
Off/0%
Off
Outdoor air damper
Closed
Relief fan / Relief damper
Off/Closed
VAV Box Relay
Energized
Mode B
(Pressurize)
Supply fan
On/100%
(a)
Fan Only
Outdoor air damper
100%
Relief fan / Relief damper
Off/Closed
VAV Box Relay
Energized
Mode C
(Depressurize)
Supply fan
Off/0%
Fan Only
Outdoor air damper
0%
Relief fan / Relief damper
On/Open
VAV Box Relay
De-engerized
Mode D
(Purge)
Supply fan
On/100%
(a)
Fan Only
Outdoor air damper
Open
Relief fan / Relief damper
On/Open
VAV Box Relay
Energized
Mode E
(Purge with Duct Static Pressure
Control)
Supply fan
On/Duct Static Pressure Control
Fan Only
Outdoor air damper
Open
Relief fan / Relief damper
On/Open
VAV Box Relay
Energized
(a)
Supply fan will operate at full speed or a limited speed not to exceed duct static pressure high limit.
Emergency Override
Emergency override provides the ability for a Building
Automation System to override control of the HVAC
equipment to pressurize, depressurize, purge,
shutdown ventilation to the space for life safety or
smoke control systems. Refer to
Table 40, p.
91
summarizing the unit operation in response to
Emergency Override commands.
Ventilation Override Mode v/s. Emergency Override
Ventilation Override inputs/output directly connect to
fire smoke control station (FSCS) panel. UUKL 864
requires that firefighters have the ability to manually
override automated smoke control equipment. Manual
changes from a FSCS panel will take precedence over
Emergency Override from the Building Automation
System.
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