Trane IntelliPak Installation, Operation And Maintenance Manual page 88

Unit Start Up
When the optional CO sensor is installed and the CO
2
Reset is enabled, as the CO
above the CO Reset Start Value, the VCM will modify the
2
minimum outside air CFM setpoint to increase the amount
of outside air entering the unit.The setpoint will be
adjusted upward until the CO
reached.The maximum effective (reset) setpoint value for
outside air entering the unit is limited to the systems
operating CFM. As the CO
effective (reset) setpoint value is adjusted downward
toward the minimum outside air CFM setpoint.
Figure 54. CO reset
2
Low Charge Protection
For each refrigeration circuit, the entering and leaving
evaporator temperatures are used to calculate superheat.
When the calculated superheat exceeds the Evaporator
Temperature Differential Setpoint minus 5°F but not the
EvaporatorTemperature Differential Setpoint, an
information only, auto-reset, High Superheat diagnostic is
initiated.
If the calculated superheat exceeds the Evaporator
Temperature Differential Setpoint, a manual reset, low
refrigerant charge diagnostic is initiated and all
compressors on the circuit are locked out.
Note that on circuits with the Variable Speed Compressor
option, the EvaporatorTemperature Differential Setpoint
for that circuit will be reset based on the active compressor
capacity and the user selected EvaporatorTemperature
Differential Setpoint.
™
Frostat Control
The compressor module utilizes an evaporator
temperature sensor (3RT14 & 15), mounted on the suction
line of each circuit, to protect the evaporator from freezing.
If the evaporator temperature approaches the specified
setpoint, adjustable between 25°F and 35°F , the
compressor(s) will be cycled "off" .
The compressors will not be allowed to restart until the
evaporator temperature has risen 10°F above the specified
cutout temperature and the compressor(s) have been off
for a minimum of three minutes.
Note that on circuits with the Variable Speed Compressor
option, the Active Coil Frost CutoutTemperature Setpoint
88
concentration increases
2
Maximum Reset Value is
2
concentration decreases, the
2
for that circuit will be 5F higher than the user selected Coil
2
Frost CutoutTemperature Setpoint.
Lead-Lag Operation
With Lead Lag operation each time the system cycles after
having stages 1 and 2 "On" , "Stage 2" (K11 on SCM or K3
on MCM) and the corresponding condenser fan output
"2A" will start first.
The compressor module cycles the compressors "On" and
"Off" to keep the zone temperature within the cooling
setpoint deadband.The condenser fans are cycled "On"
and "Off" to maintain the saturated refrigerant
temperature within the specified controlband.
Lead-Lag is not available with the variable speed
compressor option.
Units Equipped with 100% Modulating
Exhaust Dampers
The exhaust dampers are controlled through an Exhaust/
Comparative Enthalpy Module (ECEM).The ECE module
receives input form a space transducer and modulates the
exhaust dampers to maintain the space pressure to within
the specified setpoint controlband.
Units equipped with Hot Gas Reheat
(Modulating Dehumidification)
When space humidity exceeds setpoint and the unit is
loaded 50% or less, the modulating dehumidification
function activates the reheat mode, providing
dehumidification of the space.
The reheat valve and cooling valve are modulated to
control the discharge air temperature to the reheat
discharge air temperature setpoint. In reheat mode, the
reheat valve is commanded to control the discharge air (15
to 85%) to the reheat setpoint; the cooling valve mirrors
the reheat valve position (85 to 15%).The reheat coil
pumpout valve is energized when the unit is in active
cooling, and de-energized during all other times -
including reheat mode.
Units with Evaporative Condenser Sequence
of Operation
Upon a power up without water in the sump, the
condenser sump drain will be controlled to allow the sump
to hold water.The fill relay will be energized if there is a call
for mechanical cooling and if the outdoor air temperature
is greater than 10°F on units with a sump heater installed
or greater than 40°F on units without sump heat.
Once the fill solenoid is energized, the sump will begin to
fill.The minimum water level switch will close and the fill
relay will be de-energized.The sump water temperature
sensor is invalid unless the minimum water level switch is
closed.
If the sump water temperature is less than the setpoint
(default is 38°F), the sump heater will be energized until
the water temperature reaches the setpoint plus 5 degrees
(43°F for default).The fill solenoid will remain closed for 20
RT-SVX36K-EN