RT-SVX063E-EN
67
C
Co
oo
oll
Cool mode is reported when the control objective is to
provide cooling to maintain building comfort. Direct
expansion cooling is the primary cooling source. Cool
mode is also reported when Economizer cooling,
Dehumidification, Pre-Cool, and Night Purge sub-
modes of operation are active.
For Discharge Air Control units, heat is allowed (when
enabled) to temper cold mixed air conditions to the
desired cooling setpoint. See Cool - Tempering sub-
mode section for more information.
F
Fa
an
n O
On
nlly
y
This mode disables all forms of heating and cooling
capacity but operates the fan continuously at minimum
speed or modulates to maintain duct static pressure.
The outdoor air damper modulates to damper
minimum position setpoint or flow setpoint to provide
ventilation.
Fan Only is also reported in Emergency Override and
Ventilation Override Modes. Heat Cool Mode Request
can also command the Fan Only mode.
M
Ma
ax
xiim
mu
um
m H
He
ea
att
Maximum Heat is a heating mode of operation with the
supply fan operating at maximum speed. The
controller does not provide maximum heat (as the
name infers); instead, the controller provides heat
capacity per the Operating Mode and unit type.
•
M
Mu
ullttii Z
Zo
on
ne
e V
VA
AV
V
Multi Zone VAV control units will transition to
Maximum Heat operation in heating modes (for
example Occupied Heat, Morning Warm Up,
Daytime Warm Up) when the installed heating
capacity requires full air flow. Maximum Heat
can also be a Heat Cool Mode Request
command, which Symbio 800 will remain in the
mode until the mode is released. On the
transition to Maximum Heat the Symbio 800 will
reduce the supply fan to minimum speed,
energize the VAV Box Relay and wait the
duration of the VAV Box Stroke Time
(adjustable). The VAV Box Stroke Time allows
the VAV boxes in the system to open. The
supply fan speed will then increase to 100% or
the maximum speed subject to high duct static
pressure limit. Once the supply fan reaches its
allowed maximum speed, Symbio 800 will
enable heating capacity control to Discharge Air
Heating Setpoint Active. Ventilation is managed
per the operating mode.
The transition from Maximum Heat back to
modulating air flow control modes is as follows:
1. Heat capacity terminates (if active), a 5
minute post heat timer begins.
2. Supply fan speed slows to minimum speed,
a 3 minute minimum speed timer begins
3. VAV Box Relay de-energizes
4. When the 5 minute post heat and 3 minute
minimum speed timer expire, modulating air
flow control is enabled, operating mode
transitions, and capacity control enables.
•
S
Siin
ng
glle
e Z
Zo
on
ne
e V
VA
AV
V ((S
Sp
pa
acce
e T
Te
em
mp
pe
erra
attu
urre
e))
Single Zone VAV control units will also accept a
Maximum Heat command via Heat Cool Mode
Request. On this command the Symbio 800 will
transition to a heat mode while operating the
supply fan at 100% capacity. Heat Cool Mode
Status will report Maximum Heat to indicate the
mode is active.
O
Offff
Off is the reported mode when unit operation is
shutdown due to diagnostics, equipment protections or
normal unit operation.
T
Te
esstt
When a Manual Override is Active such that it overrides
normal capacity control or limits the ability to provide
comfort heating/cooling, Heat Cool Mode Status
reports Test. For example, a Manual Override of a relief
fan will not be reported as Test. See Programming
Guide (RT-SVP011*-EN) for more information.
Operating Modes
The user interface Operating Modes screen provides
Unit and Circuit level mode information valuable to
understanding the equipment operating state. Each
Unit and Circuit mode provide sub-mode information
with valuable details to understand active controls and
limits that are affecting operation. For more
information, see Programming Guide (RT-SVP011*-
EN).
Figure 38.
Operating Modes
Unit
Unit modes provide a status of the equipment
operating state. Each of the Unit modes will have one
or more sub-modes that provide more details about the
functions active in the mode.
S
Se
eq
qu
ue
en
ncce
e o
off O
Op
pe
erra
attiio
on
n
