Unit installation

16
override condition is cleared the speed will go to the next
commanded speed.
Supply Fan Speed 1, 2, and 3 (F.SP1,F.SP2,andF.SP3)
These configurations define the intermittent fan speeds used during
cooling. Supply Fan Speed 2 (F.SP2) is pre set to the optimum
energy efficiency part load speed. Changing this might affect the
overall efficiency of the unit. Supply Fan Speed 1 and 3 (F.SP1
and F.SP3) are pre set to transition the fan during cooling stage up,
and to aid in dehumidification. These 2 speeds can be adjusted in
the field to optimize dehumidification, load balancing, or
efficiency.
Fan Speed - Ventilation (FS.VN)
This configuration defines the fan speed used in Ventilation
(fan-only) mode. Ventilation mode is when the supply fan is
running, but there is no demand for heating or cooling. In
thermostat mode, this is with just a G call. In space sensor control,
this is when the unit is Occupied mode and the indoor fan is
configured to always run while occupied (Configuration →I.FAN
→OC.FN = YES). If the indoor fan is configured for intermittent
fan (OC.FN = No), the fan will be off instead of this speed during
ventilation. The economizer damper will adjust its position based
on how far away this speed is from max speed.
IMPORTANT: It is important that the ventilation rate is check after
setting this speed to verify that the unit can properly ventilate the
space per requirements. Adjusting this configuration or the
economizer minimum setting curve should be performed to meet
job requirements.
Traditional Fan Operation
On units with a belt drive VFD, traditional fan operation can also
be selected. When Smart Fan Control (Configuration → I.FAN →
SMT.F) is set to NO, the fan will operate with simple logic and
run the fan as an electromechanical unit would. When in
ventilation mode, the fan will run at the Fan Speed – Ventilation
(FS.VN) fan speed. When cooling requests the fan, the fan will run
at Supply Fan Speed 2 (F.SP2). Supply Fan Maximum Speed
(FS.MX) will be active anytime 2 cooling stages are requested or
running. In free cooling the fan will run at F.SP2 until the damper
is 100% for 4.5 minutes when the fan will ramp to FS.MX. When
heating request the fan, the fan will run at FS.MX. Advanced
dehumidification function will not be allowed to run. The fan will
still honor respective off delays.
Cooling Operation
The 48/50LC unit’s cooling operation consists of: demand and
mode determination, staging request to satisfy the demand, and
handling a request with the unit’s resources. These resources can
include compressor, a loader, an economizer, and fan speed based
on options. This section covers mechanical cooling. For
economizer and dehumidification refer to their respective sections.
In general, the unit enters a cooling mode based on a demand,
decides how to satisfy the demand, executes its plan, and then
leaves the cooling mode.
Cooling Mode Control
The cooling HVAC mode (Run Status →MODE →HVAC=3) has
4 different expandable texts: Cooling, Free Cooling, Unoccupied
Free Cooling, and Dehumidification. These are all part of a general
cooling mode and resemble the specific type of cooling that being
performed at any given time. All types of cooling are still performed
under the general cooling function, and the expanded text is for user
reference only. The control will display if it is ok to select the
cooling mode (Operating Modes →COOL →OK.CL= Yes).
Thermostat Control
For the unit to enter cooling mode, three things must be true: the
indoor fan must be ok to use, the mode changeover time guard
must be expired, and there must be a cooling demand (Y1, Y2, or
dehum demand). The unit will remain in cooling until the cooling
demand is dropped or if any of the above conditions turn false. If
only a dehum demand exists and a heat demand (W1, W2) occurs,
the unit will end cooling. The cooling mode can not officially end
until the compressor is off.
Space Sensor Control
For the unit to enter cooling mode, four things must be true: the
indoor fan must be ok to use, the mode changeover time guard
must be expired, the unit must have a valid space temperature, and
there must be a cooling or dehum demand. The unit will remain in
cooling for at least one minute and until the demand is dropped or
if any of the above conditions turn false. If only a dehum demand
exists and the heat demand becomes greater than the Dehum Heat
Setpoint Deadband (Setpoints →RH.HB), the unit will end
cooling. The cooling mode can not officially end until all
compressors are off.
Cooling Staging Control
Once the unit is in a cooling mode, it must decide what the demand
is and how to satisfy. If an economizer is installed and can be used
for cooling (Operating Modes →COOL →OK.EC= Yes), the unit
will use it first (see economizer section for its operation). If the
economizer cannot be used or additional cooling is needed, a
mechanical cooling check is performed. OK to use Compressors?
(Operating Modes →COOL →OK.MC), will be set to yes when
the compressor is enabled and not locked out. Based on the unit
control configuration, requested cooling stages (Run Status
→COOL →REQ.C) will be determined then passed to compressor
control to actually add the cooling stages.
Thermostat Control
There are two ways of requesting stages when thermostat control is
enabled, Traditional Thermostat control or Adaptive control.
Traditional Thermostat control is used if the Thermostat Control
Type (T.CTL) is set to 1, 2, or 3 and the unit cannot use the
economizer for free cooling. If Thermostat Control (T.CTL) is set
for 0 or any time the economizer is available for free cooling, the
unit will use Adaptive control for staging.
T.CTL = 0 (Adaptive Control)
Stage timers, Supply air trend, and supply air temperature limits
apply when determining the request for stages. The first request
(REQ.C=1) comes immediately when the Y1 input is active. The
Cool Stage Increase Time (Configuration →COOL →C.INC) or
the Cool Stage Decrease Time (Configuration →COOL
→C.DEC) has to expire before another stage can be added or a
stage can be subtracted. The Supply-Air Trend (Operating Modes
→COOL →SA.TR) decides if the next stage can be requested or
should be subtracted based on the Y2 input status. If the Y1 and
Y2 inputs are dropped, the supply air trend is not considered
because cooling is no longer needed. If at any time the Supply-Air
Temperature (SAT) falls below the Minimum Supply Air
Temperature Upper Level (Configuration →COOL →SAT
→SAT.U), the requested stages will not be allowed to increase. If
at any time the SAT falls below the Minimum Supply Air
Temperature Lower Level (Configuration →COOL →SAT
→SAT.L), the requested stages will be reduced by one without
honoring C.DEC. If SAT.L and SAT.U are configured so that they
are close together, the last stage might cycle rapidly, slowed only
by its minimum on and off-time requirements.
T.CTL=1or2(1StageY1or2stageY1)
Stage timers, Supply air trend, and supply air temperature limits do
not apply when determining the request for stages. Request staging
will follow the thermostat inputs directly. Y1 will request one
stage. Y2 will request all stages.
T.CTL = 3 (Digital)
Stage timers, Supply air trend, and supply air temperature limits do
not apply when determining the request for stages. Request staging
will follow the thermostat inputs directly. Y1 will request one
stage. Y2 will request two stages. Y1 and Y2 will request all
stages.
48/50LC