Unit installation

17
Space Sensor Control
Space sensor staging control is an adaptive anticipation control that
weighs the actual space demand against the trend of that demand
and the trend of the supply air. It also honors stage time guards and
supply air limits. The demand for cooling in the space is displayed
as the Cooling Demand (Run Status →COOL →DMD.C).The
control tries to anticipate the change in the space because of its
current stage status. This anticipation is based on the Supply-Air
Trend (Operating Modes →COOL →SA.TR) and the Cool
Demand Trend (Operating Modes →COOL →TRD.C).These
trends will show the control how the space is reacting to the current
running conditions and help it decide when to add or remove one
stage from the requested stages. 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. 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.
Compressor Control
The compressor control works hand and hand with the staging
control. As the staging control request stages, the compressor
control determines what is available or running and tries to provide
stages for what is requested. The availability of the compressor or
loader depends on time guards, circuit diagnostics, and outdoor
temperature. The Circuit A Lockout Temp (Configuration
→COOL →CA.LO) configuration set the outdoor temperature in
which the compressor is allowed to run down to. Any time the
outdoor ambient falls below 10 degrees, the loader will be locked
on when the compressor is turned on. The outdoor ambient must
then rise above 15 degrees before the compressor will be allowed
to run without the loader. Timeguard A (Run Status →COOL
→TG.A) and Timeguard Loader (Run Status →COOL →TG.L)
display the time the compressor or loader has before it is available
for use. Circuit diagnostic tests are performed during operation
which may or may not allow the compressor or loader to be used.
The available stages at any given time are displayed as Available
Cooling Stages (Run Status →COOL →AVL.C). The actual
stages running at any given time are displayed as Actual Cooling
Stages (Operating Modes →COOL →ACT.C). Compressor A
(Run Status →COOL →CMP.A), and Circuit A Loader (Run
Status →COOL →LDR.A) are displayed on when the respective
output is turned on. There are time guards to protect the
compressor, Compressor Min On Time (Configuration →COOL
→MRT.C) and Compressor Min Off Time (Configuration
→COOL →MOT.C) apply before the compressor or loader can be
turned back on or turned off.
Outdoor Fan Control
The outdoor fan is controlled electromechanically with the
compressor contactor, not directly by the control system. Refer to
specific unit wiring diagram and or service manual for details on
how the outdoor fan operates. In general, the outdoor fan will be
on full speed when the compressor is turned on. The control
system can override the speed of the outdoor fan for low ambient
operation. When the Outdoor Air Temperature (Temperatures
→AIR.T →OAT) falls below the Low Ambient ODF Setpoint
(Configuration →COOL →LA.SP) the Low Ambient Outdoor
Fan relay (Outputs →COOL →L.ODF) will be energized. When
this happens the outdoor fan will reduce its speed to the pre-set low
ambient RPM. The ambient must then rise 5_F above LA.SP to
allow full speed on the outdoor fan.
Indoor Fan Smart Staging Control
On direct drive fan units the fan will follow simple control. With
one stage of cooling running, the fan will run the low fan speed.
With 2 stages of cooling running, the fan will run high fan speed.
On belt drive VFD fan units the fan will be controlled as described
below. Refer to the Fan operation section for other details on fan
operation.
The indoor fan speed will change throughout cooling operation
based on cooling demand, run time, supply air temperature, and
refrigerant suction temperature. With only one stage of cooling
running the fan will run at Supply Fan Speed 1 (F.SP1) and then
Supply Fan Speed 2 (F.SP2). With 2 stages of cooling running the
fan will run at Supply Fan Speed 3 (F.SP3) and then Supply Fan
Maximum Speed (FS.MX). The fan will wait the Fan Transition
Time (Configuration →Cooling →FTT) between fan speeds 1 and
2 or 3 and max, unless the supply air overrides it. The supply air
temperature (SAT) can override the FTT if it falls below the
Minimum Supply Air Temperature Upper Level (SAT.U) or if its
trend (SA.TR) anticipates a need for more air. The fan will be
allowed to run F.SP3 if the SAT is limiting second stage cooling.
Maximum Speed (FS.MX) will be allowed too after running F.SP3
for halfofFTT.
Any time during cooling after the compressor has been on for 2
minutes, a low refrigerant suction temperature can override the fan
speed to the Supply Fan Maximum Speed (FS.MX). This will
occur if the Sat. Suction Temp A (Temperatures →REF.T
→SST.A) falls below the Fan Low Suction Temp (Configuration
→COOL →SST →FLSU) for one minute. If both cooling stages
are on with the fan at Max speed and the low suction condition
occurs for 1 minute, then the second cooling stage will be
removed. The Fan Low Suction State (Operating Modes →COOL
→LSST) will be set to yes. Cooling stage 2 will be allowed back
on after the Compressor Min Off Time (MOT.C), and the Fan Low
Suction State can be cleared after 5 minutes of running without the
low suction condition. If the suction returns low within the 5 min,
then a stage down of cooling stage 2 will occur again. If this cycle
happens 3 times in a row, the Full Load Lockout (Operating
Modes →COOL →FLLO) will be set to yes and the second
cooling stage will not be allowed back on until the cooling demand
is removed.
Dehumidification Control
Dehumidification operation requires installation and configuration
of either a space relative humidity sensor or a relative humidity
switch input. Space Humidity Switch (Configuration →UNIT
→RH.SW) set to 1 for use of a normally open switch, or 2 for
normally closed switch. The switch is wired to the field connection
terminal board terminals R-2 and HUM. RH Sensor on OAQ Input
(Configuration →UNIT →RH.S) set to Yes for use of a 4 to 20
mA output RH sensor wired to field connection terminal board
terminals LPWR and SPRH (for loop powered). RH Sensor Value
at 4ma (Configuration→AIR.Q→H.4M) sets the % display for a
4mA input from the relative humidity sensor. RH Sensor Value at
20ma (Configuration→AIR.Q→H.20M) sets the % display for a
20mA input from the relative humidity sensor.
IMPORTANT: The HUM terminal on the field connection board
is not wired and requires a isolation relay with gold plated contacts
to wire to MBB J9-5 and 6. The RH sensor input requires the ECB
to be installed if not already.
Dehumidification is a cooling mode function. When using a
humidistat or switch input, the demand for dehumidification is
seen as Space Humidity Switch (Inputs →GEN.I →HUM) being
Low or High. A low value means humidity level is good and a
high value means that dehumidification is needed. When using an
RH sensor, the demand is based on the Space Humidity Sensor
(Inputs →AIR.Q →SP.RH) value compared to the Space RH
Setpoint (Setpoints →RH.SP). If the Space Humidity Sensor
(SP.RH) value is above the Space RH Setpoint (RH.SP), then
dehumidification is needed. If the Space Humidity Sensor (SP.RH)
48/50LC