Fan Operation; Single-Zone Vav/Variable Speed Fan Operation - Trane Tracer UC400 Installation, Operation And Maintenance Manual

S S e e q q u u e e n n c c e e o o f f O O p p e e r r a a t t i i o o n n

Fan Operation

The UC400 Controller can be configured to operate as a 1- or 2-speed fan or as a variable speed
fan in a Single Zone VAV. When the fan is in any occupied mode (including standby and bypass),
the fan can be set up to cycle with heat/cool demand or to continuously run regardless of
demand. The fan defaults to continuous operation, but can be adjusted by toggling BV/1 Supply
Fan Configuration Command. When the fan is in unoccupied mode, the fan turns on only when
the unoccupied setpoints are not being met. The fan mode request can be either communicated
through a BAS or hard wired to the controller from a fan switch. In all configurations, the fan can
be controlled off when the manual output test has been initiated or a latching diagnostic is
present.

Single-Zone VAV/Variable Speed Fan Operation

When configured with a variable speed fan, the UC400 Controller treats all active fan mode
request (with the exception of OFF) as AUTO. When in AUTO, the controller ramps up the fan as
necessary between the lowest and highest speeds in order to meet the demand of the space or in
order to satisfy minimum airflow setting of the unit for specific heating/cool modes (whichever is
higher). The setpoints below can be adjusted as necessary to meet individual specifications. The
following setpoints cannot be configured below the lowest possible speed of the fan:
•
•
•
•
Constant Torque ECM Fans
On vertical models of EX and DX units in ½ Ton to 6 Ton sizes the supply fans are shipping from
the factory programmed as Constant Torque instead of Constant CFM. This change is
represented with a letter "G" as the 4th digit of the model number.
The Constant Torque fans use the same control logic in the controller, but the fan motors are
programmed differently and are not interchangeable with the Constant CFM versions. The
settings for the fan parameters in the controller must be set correctly to ensure proper equipment
operation. Refer to
If adjustments are made to the maximum fan speed (AV17 Supply Fan Speed Maximum Heat
Cool Capacity), then the scaling factor (AV22 Supply Fan Scaling Factor) will be used to
recalculate the default values for the low setting (AV18 Supply Fan Speed Dehumidification,
AV19 Supply Fan Speed First Stage Minimum, and AV20 Supply Fan Speed Ventilation). AV20
Supply Fan Speed Ventilation is the only low setting that can be adjusted from the default
settings and if adjusted by the user the factory recalculation will not take effect.
N N o o t t e e s s : :
38
A A V V / / 2 2 0 0 S S u u p p p p l l y y F F a a n n S S p p e e e e d d V V e e n n t t i i l l a a t t i i o o n n : : when configured for continuous operation, this is the
speed at which the fan operates when heating and cooling stages are not active.
A A V V / / 1 1 9 9 S S u u p p p p l l y y F F a a n n S S p p e e e e d d F F i i r r s s t t S S t t a a g g e e M M i i n n i i m m u u m m : : the lowest speed the fan operates when in
the first stage of heating or cooling. The fan ramps up from this point as necessary to meet
demand. Capacity must be at 100% for 10 minutes before the fan will ramp to AV/17 setting.
A A V V / / 1 1 7 7 S S u u p p p p l l y y F F a a n n S S p p e e e e d d M M a a x x i i m m u u m m H H e e a a t t C C o o o o l l C C a a p p a a c c i i t t y y : : When electric heat is not active,
or a single stage of compressor is active, the fan modulates between AV19 and AV17 to meet
demand. When electric heat is active or the second stage of compressor is active the fan will
run at AV17.
A A V V / / 1 1 8 8 S S u u p p p p l l y y F F a a n n S S p p e e e e d d D D e e h h u u m m i i d d i i f f i i c c a a t t i i o o n n : : the speed the fan operates in the active
dehumidification mode.
Table 11, p. 39
• Constant Torque ECM Fans are available on UC400 controllers with System Build 3.00
and newer.
• On Constant Torque ECM Fan motors a 0% signal represents Off. On Constant CFM
ECM Fan motors a 0% signal represents low speed.
for proper settings.
BAS-SVX065E-EN