Operating Principles; Control Sequences Of Operation; Occupied/Unoccupied; Switching - Trane IntelliPak SCWF 20 Installation, Operation And Maintenance Manual

Operating Principles

Control Sequences of Operation

Occupied/Unoccupied Switching
• Night setback zone sensor
• Field-supplied contact closure (hard wired binary
input to RTM)
• Tracer Summit
•

Factory-mounted time clock

Field-Supplied Occupied/Unoccupied
Input on the RTM
This input accepts a field-supplied switch or contacts
closure, such as a time clock, with a rating of 12 mA at
24 VDC minimum.

Tracer Summit System

The Tracer Summit system can control the occupied/
unoccupied status of the self-contained unit.
Factory-Mounted Time Clock
A time clock can control the occupied/unoccupied
status of the self-contained unit.
Unoccupied Sequence of
Operation
The unoccupied mode helps conserve energy during
times when a building is usually unoccupied. When in
unoccupied mode, the unit will control to the
unoccupied setpoints (usually a lower heating setpoint
and higher cooling setpoint). Setpoints can be
programmed at the HI, Tracer Summit, or the night
setback zone sensor.
The unit enters the unoccupied mode when the RTM
receives a closed signal on the unoccupied input for
more than five seconds. For units with supply air
temperature control entering unoccupied mode, the
following sequence will occur:
• Heating/cooling functions cease and the
economizer option closes fully. The supply fan
shuts down for proper cool-down time of the heat
exchanger. However, the supply fan may remain on
for a short period of time.
• After the supply fan shuts down, the occupied/
unoccupied relay energizes, and the VAV box stroke
time begins. The VAV box stroke time is field
adjustable to allow time for VAV boxes to go to the
full open airflow position.
• After the max VAV box stroke time expires, the
supply fan, economizer (if enabled), compressors,
and heat are enabled to satisfy the unoccupied zone
temperature setpoints.
SCXF-SVX01Q-EN
N N o o t t e e : : Unoccupied economizer operation can be
enabled or disabled at the HI or using Tracer
Summit.
Figure 30. Typical cycling morning warm-up cycle
Morning
Warmup
Temperature
For units without volume control entering unoccupied
mode, the following sequence will occur:
• The occupied/unoccupied relay energizes and the
economizer option fully closes.
• The fan mode is set to auto and the unit will control
to the unoccupied zone temperature setpoints.
With MWU enabled at the HI, if the zone temperature is
below the MWU setpoint, the unit enters the MWU
mode.

Morning Warm-up

This feature can be enabled at the HI, and can be used
with factory- or field-installed heat. If MWU is not
required disable the function in the setup menu at the
HI. MWU transitions the zone from unoccupied to
occupied. It will heat until the MWU setpoint is met.
The unit is then released to occupied mode. Supply
duct static pressure is maintained during this
sequence. MWU can be set (at the HI) to function as
either full or cycling capacity.
Full Capacity Morning Warm-up (MWU)
Full capacity morning warm-up uses full heating
capacity to heat the zone as quickly as possible. Full
heating capacity is provided until the morning warm-
up setpoint is met. At this point, the unit is released to
daytime mode.

Cycling Capacity Morning Warm-up

(MWU)

Cycling capacity morning warm-up provides a more
gradual heating to overcome "building sink" as the
zone is heated. Normal zone temperature control with
varying capacity is used to raise the zone temperature
to the MWU zone temperature setpoint. This method of
warm-up is used to overcome the "building sink"
effect.
MWU
Ventilation
Enable
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