Trane Intellipak 2 Service Manual

							Unit Startup
RT-SVX24K-EN101
Set Drain Duration Timer
Enter service test mode from unit Human Interface.
Navigate to the compressor condenser fan submenu.
Under head pressure control, use manual control.
Close drain valve and energize water inlet solenoid valve
until water reaches nominal level. Once level is achieved,
de-energize fill solenoid. Open drain valve and time how
long it takes for the water level to drop one inch, make sure
to take into account the closing time of the valve.
Chemical Water Treatment Tree
TheTrane evaporative condenser comes with a PVC tree to
allow easier inputs for third party water treatment.The tee
labeled A is a ¾ inch NPT threaded input, see Figure 65.
Tees B and C are 1/2 inch NPT threaded inputs. The ball valve can be used to stop the water flow through the tree
to allow the customer to add hookup of water treatment,
or to change and update water treatment with the unit
running.
Units with Dolphin WaterCare™or conductivity sensor will
have the conductivity sensor installed into the ¾ inch tee
with the other tees plugged. For all other units, A, B and C
will be plugged, see Figure 65. Ensure the ball valve is in
the open position when water treatment is being operated
in the system to make sure water flows through the tree
and transports treatment to the unit sump.
Conductivity Controller
Upon startup, the conductivity controller must be
calibrated and setup for operation. Below are the
necessary steps to accomplish those tasks. The controller
has two setpoints that control two relays. Both of these
setpoints will need to be set by Dolphin or a local water
treatment expert.
1. The first setpoint is the standard point blowdown point.
– When the setpoint is exceeded the relay (K1) will beenergized and a blowdown request will close the
Water treatment request binary input on the MCM.
Figure 63. Actuator shaft adapter removal/assembly
Figure 64. Actuator is shipped in “Drain during power
loss” configuration
Locking clip
Shaft adapter
1
2
To drain during power loss,
set shaft adapter to 0 degrees To hold during power loss,
set shaft adapter to 90 degrees
Figure 65. Chemical water treatment tree 
						

							Unit Startup
10 2RT-SVX24K-EN
2. The second setpoint will be the emergency point
– The second setpoint will open the normally closedK2
 relay which will interrupt the sump proving
circuit which will generate a manual lockout. This
second setpoint will be used to protect the unit from
extremely high conductivity that would indicate a
failure in the system.
3. Inside the enclosure for the controller, there will be a thermostat
 and strip heater that will protect LCD from
cracking at low ambient conditions. The thermostat
closes at 15°F and opens at 25°F.
Procedure to calibrate conductivity
Note: Visit this webpage for additional documentation:

Use a calibrated thermometer and a known conductivity
rating. There are two different options for having a liquid
with known conductivity. Purchase a liquid with known
conductivity rating and purchase a handheld conductivity
reader.
1. Close the ball valve on the chemical treatment tree and remove the conductivity sensor from the tree.
2. Enter service test mode on the unit and turn the pump on,
 ensuring the compressors are set to Off.
3. With the conductivity controller connected to the sensor
 and power, enter the CALIBRATE menu by
holding down the enter key for 2 seconds.
4. When asked for the calibration key code, hit the UP-UP- UP
 -DOWN arrow keys in sequence.
5. Using the UP and DOWN arrows go to Chan 1 Cell: Standard.
 Ensure this channel is set to standard.
6. If not press the RIGHT arrow key and set to standard then
 press the ENTER key to return to the
CALIBRATION menu.
7. Using the UP and DOWN arrows go to Chan 1 Cell. Ensure
 that the cell constant is set to 1.0.
8. If not press the RIGHT arrow key and set the cell constant
 to 1.0 then press the ENTER key to return to
the CALIBRATION menu.
9. Using the UP and DOWN arrows go to Chan 1 Set: T
 emperature and press the RIGHT arrow key to enter
the edit mode.
10. Adjust the temperature on the controller to match the actual
 temperature.
11. Press the ENTER key to save the input and return to the CALIBRA
 TE menu.
12. Using the UP and DOWN arrows, go to the Chan 1 Set: Conducti
 vity and press the RIGHT arrow key to enter
the edit mode.
13. Adjust the conductivity on the controller to match the actual
 conductivity rating of the liquid. 14. Press the ENTER key to save the conductivity rating
and
 return to the CALIBRATE menu.
15. When finished calibrating the controller, press the UP and
 DOWN key simultaneously to return to normal
operating mode.
Procedure to set purge setpoints on the
conductivity controller
Note: Visit this webpage for additional documentation:

Work with local water treatment expert to identify nominal purge and emergency purge conductivity value.
1. Close the ball valve on the chemical treatment tree and remove the conductivity sensor from the tree.
2. Enter Service test mode on the unit HI and energize the sump
 pump, ensuring the compressors are set to
OFF.
3. With the conductivity controller connected to the sensor
 and power, enter the CALIBRATE menu by
holding down the enter key for 2 seconds.
4. When asked for the calibration key code, hit the UP-UP- UP
 -DOWN arrow keys in sequence.
5. Using the UP and DOWN arrows, go to Relay 1 S
 etpoint: and press the RIGHT arrow key to enter edit
mode (K1).
6. Adjust the set point to the nominal blowdown conducti
 vity value.
7. Press the ENTER key to return to the CALIBRATE menu.
8. Using the UP and DOWN arrows, go to Relay 2 S
 etpoint: and press the RIGHT arrow key to enter edit
mode (K2).
9. Adjust the set point to the emergency conductivity value.
10. Press the ENTER key to return to the CALIBRATE menu.
11. When finished setting the values, press the UP and DO
 WN key simultaneously to return to normal
operating mode.
Units Without an Economizer
Upon entering an “occupied” mode of operation, the RTM
receives input from the remote panel to start the supply
fan. For constant volume applications, the RTM supply fan
contacts close which energizes the supply fan contactor.
When the supply fan starts, the fan proving switch closes, signaling the RTM that airflow has been established and
the VFD will begin to ramp the fan (if equipped).
When a cooling request is sent to the RTM from a zone temperature sensor, the RTM evaluates the operating
condition of the system using the supply air temperature
input and the outdoor temperature input before sending
the request to the MCM. Once the request is sent to the
MCM, the compressor module checks the compressor 
						

							Unit Startup
RT-SVX24K-EN10 3
protection circuit before closing “Stage 1. After the first
functional stage has started, the compressor module
monitors the saturated refrigerant temperature and closes
the condenser fan output contact, when the saturated
refrigerant temperature rises above the “lower limit”
setpoint.
Units with an Economizer
Upon entering an “occupied” mode of operation, the RTM
receives input from the remote panel to start the supply
fan. For constant volume applications, the RTM supply fan
contacts close which energizes the supply fan contactor.
When the supply fan starts, the fan proving switch closes, signaling the RTM that airflow has been established. The
RTM opens the economizer dampers to the specified
“minimum position”.
When a cooling request is sent to the RTM from the zone temperature sensor, the RTM evaluates the operating
condition of the system using the supply air temperature
input and the outdoor temperature input before sending
the request to the MCM for mechanical cooling. If the
outdoor conditions are suitable for cooling (temperature
and humidity are within specified setpoints), the RTM will
attempt to maintain the zone temperature without using
any compressors. If the zone temperature can not be
maintained within the setpoint deadband, the RTM sends
a cooling request to the MCM. The compressor module
checks the compressor protection circuit before closing
“Stage 1. After the first functional stage has started, the compressor module monitors the saturated refrigerant
temperature and closes the condenser fan output contact,
when the saturated refrigerant temperature rises above
the “lower limit” setpoint.
Units with TRAQ™ Sensor
The outside air enters the unit through the TRAQ Sensor assemblies and is measured by velocity pressure flow
rings. The velocity pressure flow rings are connected to a
pressure transducer/solenoid assemblies. The solenoid is
used for calibration purposes to compensate for
temperature swings that could affect the transducer. The
Ventilation Control Module (VCM) utilizes the velocity pressure inputs, the RTM outdoor air temperature input,
and the minimum outside air CFM setpoint to modify the
volume (CFM) of outside air entering the unit as the
measured airflow deviates from setpoint.
When the optional temperature sensor is installed and the Preheat function is enabled, the sensor will monitor the
combined (averaged) outside air and return air
temperatures. As this mixed air temperature falls below
the Preheat Actuate Temperature Setpoint, the VCM will
activate the preheat binary output used to control a field
installed heater. The output will be deactivated when the
temperature rises 5 above the Preheat Actuate
Temperature Setpoint.
When the optional CO
2sensor is installed and DCV is
enabled, the OA damper will be modulated to control CO
2
concentrations. If the CO2concentration is greater than
the Design Minimum CO
2Setpoint the OA damper will be
opened to the Design Minimum OA Damper Setpoint (w/
oTRAQ) or until the Design Minimum OA Flow Setpoint is
met (w/ TRAQ).
If the CO
2concentration is less than the DCV Minimum
CO
2Setpoint the OA damper will be closed to the DCV
Minimum OA Damper Setpoint (w/o TRAQ) or until the
DCV Minimum OA Flow Setpoint is met (w/ TRAQ).
If the CO
2concentration is between the Design Minimum
CO
2Setpoint and the DCV Minimum CO2Setpoint the OA
damper will be modulated proportionally between the
Design Minimum OA Damper Setpoint and the DCV
Minimum OA Damper Setpoint (w/ TRAQ) and between
the Design Minimum OA Flow Setpoint and the DCV
Minimum OA Flow Setpoint (w/o TRAQ).
Frostat™ Control
The compressor module utilizes an evaporator temperature sensor, 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.
Lead/Lag Operation
When Lead/Lag is enabled, each time the system cyclesafter having stages 1 and 2 “On”, “Stage 2 and the
corresponding condenser fan output 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.
Units equipped with 100% modulating
exhaust
The exhaust dampers are controlled through an Exhaust/ Comparative Enthalpy Module (ECEM).The ECEM module
receives input from a space transducer and modulates the
exhaust dampers to maintain the space pressure to within
the specified setpoint controlband.
Modulating Dehumidification (Hot Gas
Reheat) Sequence of Operation
When the relative humidity in the controlled space (asmeasured by the sensor assigned to space humidity
sensing) rises above the space humidity setpoint,
compressors and the supply fan will energize to reduce the
humidity in the space.
All compressors on both refrigerant circuits will be staged up during active dehumidification. Circuit #1 is designated
the reheat circuit and will feature additional refrigerant 
						

							Unit Startup
10 4RT-SVX24K-EN
control devices as well as a split condenser coil with one
section in the indoor air stream and the other in the
outdoor coil compartment.
During active dehumidification the discharge air will be
controlled to the Supply Air Reheat Setpoint by
modulating the amount of reheat produced by the reheat
coil. The Supply Air Reheat Setpoint, Occupied and
Unoccupied Dehumidification Setpoints are adjustable via
the human interface, BAS/Network control, or GBAS.
Active dehumidification will be terminated when the humidity in the space is reduced to the active space
humidity setpoint - 5% or when an overriding condition
such as heating or cooling demand or a failure occurs in a
component required for dehumidification.
On VAV units, at startup, satisfying the VAV Occupied
Cooling setpoint, MWU setpoint, and DWU setpoint will
have priority over dehumidification mode. Once heating
modes are satisfied, and the unit is satisfying the SA
Cooling Setpoint, dehumidification mode will be entered if
no more than half the unit mechanical cooling capacity is
requested.
On SZVAV units, dehumidification will be similar to VAV
modulating dehumidification with the exception of a
dynamic Supply Air Reheat Setpoint. Rather than utilizing
a static Supply Air Reheat Setpoint, once the unit enters
dehumidification, the Discharge Air Setpoint will be
calculated based on the Zone temperature vs. Zone
Cooling Setpoint error and will be capped at the user
selected Supply Air Reheat setpoint.
Dehumidification is not allowed during VAV Heating
Modes (Changeover input closed). Once active,
dehumidification control will remain active for a minimum
of three minutes unless a priority unit shutdown request is
received or the High Pressure Control input opens on
either circuit.
Dehumidification control can be enabled separately for
occupied and unoccupied modes of operation via the
Human Interface and is overridden/disabled whether
active or inactive by the following methods:
– Priority unit shutdown conditions (Emergency stop,Ventilation Override, Network Stop, etc.)
– Compressor circuit manual reset lockouts on either circuit. Low Refrigerant Charge monitoring is active
during dehumidification mode and will lockout
compressor circuits based on the same criteria
used for cooling mode.
– Outdoor Air Temp is less then 40°F or greater the 100°F.
– Humidity Sensor Failure
– For VAV units, (in occupied) dehumidification will be disabled if space temp is less than the Dehumid
Override Low Zone Setpoint or higher than the
Dehumid Override High Zone Setpoint. If
dehumidification is inactive it will not be allowed
until it space temp rises higher than the Dehumid Override Low Zone Setpoint + 1.0°F or lower than
the Dehumid Override High Zone Setpoint - 2.0°F.
– For SZVAV units, dehumidification will be disabled if space humidity levels have fallen below the
Active Occ/Unocc Dehumidification Setpoint -5% Dehumidification Hysteresis Offset, the zone
temperature has dropped too close to the Zone
Heating Setpoint in any unit mode (Zone Temp. is
less than ZHSP + 0.5°F), the zone temperature rises
above the Zone Cooling Setpoint +2°F in any unit
mode, Entering Evaporator Temperature falls too
low, Froststat input becomes active, or
Dehumidification/Reheat becomes disabled.
– For CV and all units in unoccupied, if space temp is less than the Zone Heating Setpoint (ZHSP) + 0.5° F
if dehumidification is active, or less than ZHSP + 1.0°
F if not dehumidification mode will be disabled. If
zone conditions result in a cooling request for more
than one-half the available cooling capacity of the
unit dehumidification will be disabled and will
transition to cooling control. If dehumidification is
inactive, dehumidification will not be allowed until
the active unit cooling capacity request drops to
half the available cooling capacity or less, unless
the space temp is less than the Zone Cooling
Setpoint.
– In CV units in occupied mode, if the unit is not in “AUTO” system mode and is set to “HEAT” systemmode via the HI, BAS, or Zone Sensor device,
dehumidification control will be disabled at space
temps above Occupied ZCSP + 1.0° F. If
dehumidification is inactive it will not be allowed to
activate if space temp is greater than the OZCSP.
All units configured for modulating dehumidification will have a reheat condenser coil purge function to ensure
proper refrigerant distribution in the reheat circuit. This
feature is always enabled and will monitor the amount of
cumulative compressor run time while the reheat
condenser coil pumpout relay is in a certain state. If
compressors accrue an amount of run time equal to the HI-
adjustable purge interval time without the pumpout relay
changing states a purge cycle will be initiated lasting for
three minutes.
During this cycle all compressors but the 2nd compressor
on circuit #1 will be energized if not already, the reheat
valve and cooling valves to will be set to 50%, and the
reheat coil pumpout relay will be toggled to its opposite
state. After the three-minute purge cycle completes the
purge interval timer will be reset and all system
components will return to the state they were in prior to
entering purge.
During dehumidification control an evaporator frost
control function designed specifically for reheat modes
will be active.This function will reduce refrigeration circuit
capacity to 50% (1st compressor on each circuit remaining
on) when the Entering Evaporator Temp drops below a 
						

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RT-SVX24K-EN10 5
non-adjustable limit of 35° F for 10 continuous minutes.
Once capacity is reduced, it will remain reduced until the
current cycle of dehumidification is terminated or a purge
cycle occurs.
If the Entering EvaporatorTemp remains below 35° F for an
additional 10 minutes both circuits will be de-activated and
remain off until the Entering EvaporatorTemp rises above
45°F. Even though all compressors have been de-activated
the unit will remain in dehumidification mode and re-
enable compressors up to 50% capacity when the Entering
Evaporator Temp rises to 45°F or greater.
Energy Recovery Sequence of Operation
The primary components of the energy recovery system
are the energy recovery wheel, exhaust air bypass
damper, outdoor air bypass damper, and the energy
recovery preheat output. See Figure 67, p. 106 Figure 68,
p. 107 A filter is also placed between the wheel and the
outdoor air damper and an indicator scheme similar to that
for final filters is provided to notify the user when that filter
needs to be changed.
The energy recovery wheel will only be energized when both the Supply Fan and Exhaust Fan are requested on by
the various functions that control them. Energy recovery is
a passive function and can not request fan operation.
Once the required airflow is present the wheel will be
commanded on if the indoor vs. outdoor conditions are
such that energy can be recovered. This is assessed
differently in cooling and heating modes.
In cooling mode, wheel activation conditions are assessed
based on indoor (return air) vs. outdoor enthalpy. Indoor
and outdoor enthalpy values are calculated using the
same sensors as used for comparative enthalpy. If the
outdoor enthalpy is 3 BTU/lb. greater than indoor enthalpy
the wheel is activated to remove energy from the
incoming outdoor air. In heating mode the wheel is
activated based on indoor vs. outdoor dry bulb
temperature. If the outdoor temperature is 5° F less than
the indoor temperature. the wheel is activated to recover
heat energy from the exhaust air.
In cooling mode the exhaust air bypass damper is held
closed, providing 100% energy recovery capacity during
cooling modes of operation. In heating modes, including
CV heating, VAV Heating, CV Supply Air Tempering, VAV
Supply Air Tempering, Morning Warm-up, and Daytime
Warm-up the exhaust air bypass damper is controlled to discharge air temperature. The damper is modulated to
keep the supply air temp at the Supply Air Heating setpoint for VAV control, or for CV control, supply air temp will be
controlled to a calculated Supply Air Heat Setpoint based
on conditions in the space.
If the wheel is active, supplemental heat (electric,
hydronic, gas) control algorithms will be disabled until the
exhaust air bypass damper is fully closed (maximum
heating capacity from the wheel). At this point,
supplemental heat algorithms are released to calculate
supplemental heat capacity requests using standard
setpoints until the setpoints are satisfied. In VAV occupied
modes the energy recovery wheel will remain active after
termination of supplemental heat above heating setpoint
until the exhaust air bypass damper is opened fully for 3
minutes (indicating minimal capacity requested from the
wheel). In CV occupied heating mode the wheel will
remain active after termination of a heating cycle until the
zone temp rises above the Occupied Zone Heating
Setpoint + 1.0°F and the exhaust air bypass damper is fully
open. The wheel will remain active if these conditions
persist continuously until the expiration of a HI-adjustable
time-out period or until the zone temp rises above the
Occupied Zone Cooling Setpoint - 0.5°F.
During active Economizing control the energy wheel will
be disabled but the outdoor air bypass damper will open
an amount that tracks the opening of the OA damper
proportionally from minimum position to fully open.
To protect the wheel from frost build-up in heating modes a frost avoidance function is included. This feature will
energize the energy recovery preheat output (if
configured) and modulate the outdoor air bypass damper
open (to reduce incident cold outdoor air on the wheel) as
necessary when the Leaving RecoveryTemp Sensor value
is less than the Recovery Frost Avoidance Setpoint. The
Leaving Recovery Temp Sensor is installed in the leaving
air stream on the exhaust-fan side of the energy wheel.
Figure 66 provides the exhaust air temperature setpoint
for 70ºF return air at various percents of relative humidity.
Where variable effectiveness / outside air bypass is not enough to prevent frosting conditions, the energy
recovery wheel shuts off. Turning the wheel off during
frost conditions is a reliable method of preventing the
wheel from frosting, however, energy is not being
recovered and the extreme heating load must be handled
otherwise. Extreme winter design condition for energy
recovery units may require return air preheat.
An energy recovery wheel proving function is also provided to indicate when the wheel is not turning after it
has been commanded on.
WARNING
Toxic Hazards!
Do not use an energy wheel in an application where the
exhaust air is contaminated with harmful toxins or
biohazards. Failure to follow this instruction could
result in death or serious injury. 
						

							Unit Startup
10 6RT-SVX24K-EN
Figure 66. Energy recovery wheel exhaust air setpoint temperatures
Figure 67. Energy recovery wheel operation
 Outside Air Intake Damper
(Mist Eliminator not shown)
 Exhaust Air,
 Leaving Energy Recovery Wheel, 
 Path to Exhaust Fan
 Building Return Air
 Outside Air Bypass Damper
 Unit Return
 Airflow
 Exhaust Air
 Bypass Damper
 Energy Recovery Wheel
 Conditioned Outside Air
 Return Air Damper
 Path to Filters & Coil
 ERW Unit Entering Air 
 (Mixed Return Air &
 Conditioned Outside Air) 
						

							Unit Startup
RT-SVX24K-EN10 7
Gas Heating Sequence of Operation
Standard
Two Stage Gas Furnace
The control system for the rooftop units are wired to
ensure that the heating and cooling do not occur
simultaneously. Refer to the wiring diagram that shipped
with the unit while reviewing the following sequence of
operation.
Honeywell Ignition System
(850 & 1100 MBH Two Stage Natural Gas)
When a heating requirement exists, the Rooftop Module(RTM) starts the supply fan and sends a request for heat to
the Heat Module. The Heat Module closes contacts and
starts the combustion blower motor. The combustion
blower motor starts on low speed through the normally
closed combustion blower relay contacts.
The supply airflow switch and the combustion air switch closes. Power is applied through the high limit cutout to
the Honeywell ignition control board. The ignition control
board starts a pre-purge timing cycle. At the end of the pre-
purge cycle, the ignition transformer and the pilot
solenoid valve are energized. This starts a 10 second trial
for pilot ignition. When the pilot flame is established and
sensed by the flame sensing rod, stage 1 of the main gas valve and the 60 seconds sequencing time delay relay is
energized.
The system will operate in the low heat mode until an additional call for heat is established by closing the
contacts on the Heat Module. The sequencing time delay
relay will energize the combustion blower motor relay
which switches the combustion blower motor to high
speed and energizes the 2nd stage solenoid on the gas
valve after approximately 60 seconds.
If the flame rod does not detect a pilot flame within the 10
second trial for ignition period, the control will lockout. If
a flame failure occurs during operation, the gas valve, the
sequencing time delay relay, and the combustion blower
relay is de-energized. The system will purge and attempt
to relight the pilot. If a flame is not detected after this
attempt, the Honeywell ignition control will lock out. The
combustion blower motor will continue to operate as long
as a heating demand exists and the system switch is “On”.
Once the heating demand has been satisfied, the
combustion blower and the Honeywell ignition control
board is de-energized.
Note: The above sequence is the same for Propane. The
orifices are smaller and the manifolds are adjusted
to different values
Figure 68. Energy recovery wheel economizer operation
 Outside Air Intake Damper
(Mist Eliminator not shown)
 Exhaust Air,
 Path to Exhaust Fan
 Building Return Air
 Outside Air Bypass Damper
 Unit Return
 Airflow
 Exhaust Air
 Bypass Damper
 Un-
 Conditioned
 
Outside Air
 Return Air Damper
 Path to
 Filters
 & Coil
 Path to
 Filters
 & Coil 
						

							Unit Startup
10 8RT-SVX24K-EN
(1800 & 2500 MBH Two Stage Natural Gas)
When a heating requirement exists, the Rooftop Module
(RTM) starts the supply fan and sends a request for heat to
the Heat Module. The Heat Module closes contacts and
starts the combustion blower motor through the
combustion blower relay.
The supply airflow switch and the combustion air switch closes. Power is applied through the high limit cutout to
the Honeywell ignition control board. The ignition control
board begins the pre-purge timing cycle with the damper
in the light off position and the low fire start interlock is
closed
At the end of the pre-purge cycle, the ignition transformer and the pilot solenoid valve are energized.This starts a 10-
second trial for pilot ignition.
When the pilot flame is established and sensed by the flame sensing rod, the stage 1 of the main gas valve will
begin. The gas butterfly control valve is in the low fire
setting by the linkage arm connection between the
combustion air actuator and the butterfly valve.
The system will operate in the low heat mode until there is an additional call for heat established by closing the
contacts on the Heat Module.
If the flame rod does not detect a pilot flame within the 10
second trial for ignition period, the ignition control board
will lockout. The combustion blower motor will continue
to operate as long as a heating demand exists and the
system switch is “On”.
Once locked out on flame failure, the IC board will not
reactivate the ignition/combustion control circuit until it is
reset manually. To do this, press the reset button on the
front of the IC board case.
A set of relay contacts is available for external use for heat fail (Information Only).
Once the heating demand has been satisfied, the
combustion blower and the Honeywell ignition control
board is de-energized.
Modulating Gas Sequence of Operation
The control system for the rooftop units is wired to ensure that the heating and cooling do not occur simultaneously.
Refer to the modulating heat wiring diagram that shipped
with the unit while reviewing the following sequence of
operation. As you review the sequence of operation, keep
the following in mind:
1. The furnace will not light unless the manual gas valves are open and the control circuit switch is closed.
2. The control systems are wired to ensure that heatingand cooling cannot occur simultaneously.
3. The unit supply fans must run continuously so airflow switc
 h will stay closed.
4. Modulating Gas heat is available during both occupied and
 unoccupied operation. When there is a call for heat, the heat module energizes the
combustion
 blower which causes the combustion air flow
switch to close. The ignition control board will energize
providing that the indoor air flow switch, high limit, and
low and high pressure gas switches are closed.
The ignition control board then causes the combustion air actuator to drive the inlet air damper to the fully open
position for a 30 second pre-purge. The pre-purge time
does not begin until the purge interlock switches are made.
After the pre-purge, the combustion air actuator drives the inlet air damper and the gas butterfly control valve to a
nearly closed position for light off. When the Low fire
interlock switch is closed the ignition transformer is
energized, the igniter begins to spark and the pilot valve
opens.
This begins a 10-second trial for ignition period during which the flame rod must detect the flame. If does not
detect a flame at the end of the period, it will shut down
and lock out the ignition/ combustion circuit.
Once the pilot flame has been established, the heat
module will open the main gas valve and auxiliary gas
valve. After the main flame is established, the pilot valve
closes. The ignition sequence is completed and the heat
module will drive the combustion air actuator to a firing
rate based on a 2-10 VDC signal. The gas butterfly control
valve will respond through the connecting linkage.
The heater will continue to run until the call for heat is removed or a limit opens.
Following the completion of the call for heat, there is a 15-
second post-purge.
Flame Failure
In the event that (IC) board loses the “proof-of-flame”
input signal during furnace operation, it will lock out and
the must be manually reset (Combustion blower motor
continues to run as long as a heating requirement exists
and control circuit switch is ON.)
Once locked out on flame failure, the (IC) board will not
reactivate the ignition/combustion control circuit until it is
reset manually. To do this, press the reset button on the
front of the (IC) board case.
A set of relay contacts is available for external use for heat fail (Information Only).
Note: The modulating gas heaters are factory adjusted
for safe operation and to reach the nameplate rated
firing MBH for most areas of the country. The
proper air/gas ratio must be reached by the service
tech during startup..
Electric Heat Sequence of Operation
The control system for the rooftop units are wired toensure that heating and cooling do not occur
simultaneously. Refer to electric heat wiring diagrams that
shipped with the unit while reviewing the following 
						

							Unit Startup
RT-SVX24K-EN10 9
sequence of operation. As you review the sequence of
operations, remember these points:
1. The high limit switch will trip if exposed to a
temperature greater than the trip point, and will reset
automatically once the temperature falls below the
reset point.
2. The linear high limit switch is encased in a capillarythat extends across the unit supply air opening. The
limit will trip if any 6” span of the capillary exceeds the
trip point. Refer to Table42, p. 135.
3. Electric heat will only energize if both of the high limit safety
 controls are closed.
Electric Heat—CV, VAV Daytime Warm-up
CV electric heat operation is done with discrete stages of
electric heat. Stages 2 and 3 will not energize unless Stage
1 is already operating and unable to satisfy the heating
load. The heat will be staged to control to the Heating
Setpoint.
VAV Active Occupied Discharge Heating
When the changeover input is closed (or whencommanded by BAS) the unit will control discrete stages
of electric heat to the active supply air heating setpoint.
VAV occupied electric heating operation is done with discrete stages (steps) of electric heat. The heat staging is
dependent on unit tonnage and heater selection.The heat
will be staged to control to the Supply Air Heating
Setpoint.
SZVAV Occupied Heating
Single Zone VAV heating will only be available with
modulating types of heat - IPak II units can use hydronic
and modulating gas and will include electric heat. During
SZVAV heating, the unit will calculate a discharge heating
setpoint based on zone heating demands, and the unit will
modulate heat to maintain the discharge temperature to
this setpoint.
Demand Control Ventilation Sequence of
Operation
Note: CO2sensor used with Demand Control Ventilation
must be powered from an external power source or
separate 24 VAC transformer.
Sequence of Operation without TRAQ
If the space CO2level is greater than or equal to the Design
Minimum CO
2Setpoint, the outdoor air damper will open
to the Design Minimum Outdoor Air Damper Setpoint. If
there is a call for economizer cooling, the damper may be
opened further to satisfy the cooling request.
If the space CO
2level is less than or equal to the DCV
Minimum CO
2Setpoint, the outdoor air damper will close
to the DCV Minimum Outdoor Air Damper Setpoint. If there is a call for economizer cooling, the damper may be
opened further to satisfy the cooling request.
If the space CO
2level is greater than the DCV Minimum
CO
2Setpoint and less than the Design Minimum CO2
Setpoint, the outdoor air damper position is modulated
proportionally to the space CO
2level relative to a target
position between the DCV Minimum CO
2Setpoint and the
Design Minimum CO
2Setpoint. If there is a call for
economizer cooling, the damper may be opened further to
satisfy the cooling request.
Sequence of Operation with TRAQ
If the space CO2level is greater than or equal to the Design
Minimum CO
2Setpoint, the outdoor air damper will open
to the Design Minimum Outdoor Air Flow Setpoint. If there
is a call for economizer cooling, the damper may be
opened further to satisfy the cooling request.
If the space CO
2level is less than or equal to the DCV
Minimum CO
2Setpoint, the outdoor air damper will close
to the DCV Minimum Outdoor Air Flow Setpoint. If there is
a call for economizer cooling, the damper may be opened
further to satisfy the cooling request.
If the space CO
2level is greater than the DCV Minimum
CO
2Setpoint and less than the Design Minimum CO2
Setpoint, the outdoor air damper position is modulated
proportionally to the space CO
2level relative to a target
position between the DCV Minimum CO
2Setpoint and the
Design Minimum CO
2Setpoint. If there is a call for
economizer cooling, the damper may be opened further to
satisfy the cooling request.
Return Fan Sequence of Operation
Whenever the Supply Fan is turned ON, the return fan will be turned ON. The speed of the return fan will control to
the Return Air Plenum Pressure Target. The target is
calculated internal to the control and will be between the
Minimum Return Air Plenum Pressure Setpoint and the
Maximum Return Air Plenum Pressure Setpoint
depending on unit operation conditions. A Return Air
Pressure High Limit will be set at 3.5 IWC. If the pressure
inside the return plenum exceeds the limit the unit will
shut down.
Unit Clustering
A cluster is a master unit and one or more similarlyconfigured slave units operative cooperatively, as a group,
to provide higher capacity and/or redundancy at partial
capacity. Clustering is accomplished by binding variables
between unit LCI-I modules, communicating common
setpoints and allowing each unit to run independent
algorithms. A cluster will share a common supply and
return duct network.
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 
						

							Unit Startup
11 0RT-SVX24K-EN
Temperature Differential Setpoint minus 5°F but not the
Evaporator Temperature 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.
Wet Heat Sequence of Operation
Electrical circuitry for units with steam or hot water heat is
limited to the connections associated with the modulating
valve actuator and the freezestat.
Like the furnaces described earlier, steam and hot water
heat control systems are wired to ensure that
simultaneous heating and cooling do not occur. The
supply fan will cycle “On” and “Off” with each call for heat
during both an occupied and unoccupied period.
Whenever there is a call for heat, the relay on the heat
module energizes. This allows a modulated voltage
signal to be sent to the “Wet” heat actuator. The value of
this signal regulates the flow of steam or hot water
through the coil by positioning the valve stem at some
point between fully closed (6 VDC) and fully open (8.5
VDC).
Freeze Protection
A freezestat is mounted inside the heat section of hot water and steam heat units to prevent the “wet” heat coil from
freezing during the “Off” cycle.
If the temperature of the air leaving the heating coils falls
to 40 F, the freezestat normally open contacts close,
completing the heat fail circuit on the UCM. When this
occurs:
a. The supply fan is turned “Off”.
b. “Wet” heat actuator fully opens to allow hot wateror steam to pass through the heating coil and
prevent freeze-up.
c. A “Low Air Temperature Unit Trip” diagnostic is displayed on the Human Interface LCD screen.
For heating control settings and time delay specifications,
refer to Table 45, p. 158.
Unit Startup Check List
Use the following checklist, in conjunction with the
“General Unit Requirement” checklist”, to ensure that the unit is properly installed and ready for operation. Be sure
to complete all of the procedures described in this section
before starting the unit for the first time.
[ ]Turn the field supplied disconnect switch, located
upstream of the rooftop unit, to the “Off” position.
 [ ] Turn the 115 volt control circuit switch 1S2 to the “Off” position. It is located in the secondary of the 1T1transformer.
 [ ]Turn the 24 volt control circuit switch 1S3 to the “Off” position.
 It is located in the secondary of the 1T2 - 1T5
transformers.
 [ ] Turn the “System” selection switch (at the Remote P
 anel) to the “Off” position and the “Fan” selection
switch (if Applicable) to the “Auto” or “Off” position.
 [ ] Check all electrical connections for tightness and “point
 of termination” accuracy.
 [ ] Verify that the condenser airflow will be unobstructed.
 [ ] Check the compressor crankcase oil level. Oil should be
 visible in the compressor oil sight glass. The oil
level should be 1/2 to 3/4 high in the sight glass with the
compressor “Off”.
 [ ] Verify that all refrigerant service valves are back seated
 on each circuit.
Do not start the unit in the cooling mode if the ambient
temperature
 is below the following minimum
recommended operating temperature:
Standard unit with or without HGBP-+45°F
 [ ] Check the supply fan belts for proper tension and the fan
 bearings for sufficient lubrication. If the belts
require adjustment, or if the bearings need lubricating,
refer to the Service/Maintenance section of this
manual for instructions.
 [ ] Inspect the interior of the unit for tools and debris. Install
 all panels in preparation for starting the unit.
Electrical Phasing
Scroll compressors are phase sensitive. Proper phasing of
the electrical supply to the unit is critical for proper
operation and reliability. The compressor motor is
WARNING
Hazardous Voltage!
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Failure to disconnect power
before servicing could result in death or serious injury.
CAUTION
Compressor Damage!
Do not allow liquid refrigerant to enter the suction line.
Excessive liquid accumulation in the liquid lines could
result in compressor damage.Compressor service
valves must be fully opened before startup (suction,
discharge, liquid line, and oil line).