Trane S*HF*20-75 Troubleshooting Manual page 9

Commonly Used Acronyms
responds to cooling, heating, and ventilation requests by directing the other modules in the system to energize the proper
unit components. It also directly initiates supply and exhaust fan operations, and economizer operation.
Compressor Module (IU3 IntelliPak II / 1U49 IntelliPak I)
(compressor control, head pressure control, evaporative condensing) The SCM/MCM module upon receiving a request
for mechanical cooling staging from the RTM, energizes the appropriate compressors. It provides protection of the
refrigerant circuit through feedback information it receives from various protection devices. It provides the necessary
sensor interface to provide both air-cooled and water-cooled condenser head-pressure control.
Heat Module (1U6 IntelliPak II / 1U50 IntelliPak I)
(staged heat, modulating heat, air-handler chill water valve control) The HEAT module, directs the unit's heater to stage
up, down, or modulate to bring the controlled temperature to within the applicable heating setpoint. Chill water valve
control is handled by the modulating output and is coordinated with the heat control to insure proper cooling and heating
operation.
Exhaust/Comparative Enthalpy Module (1U5 IntelliPak II / 1U52 IntelliPak I)
(Statitrac building pressure control, comparative enthalpy) The ECEM receives data from the return air humidity sensor,
the return air temperature sensor, and the return air space pressure transducer to control the economizer, exhaust fan and
the exhaust dampers to maintain set space pressure.
Ventilation Control Module (7U14 IntelliPak II / 3U218 IntelliPak I)
(TRAQ dampers, DCV, outdoor air preheat) The VCM receives data from two velocity pressure sensors associated with
front and back TRAQ assemblies to measure fresh air flow entering the unit. These measurements are converted to CFM
and added to give total fresh air flow. This value can be used for monitoring purposes, to maintain flow to a minimum
fresh air flow Setpoint, or to maintain appropriate CO2 levels in the controlled space using its space CO2 sensor input and
the DCV feature. Without TRAQ assemblies installed the VCM can use DCV and the CO2 sensor input to control OA Damper
minimum position to maintain CO2 levels in the space. A preheat control relay output is also provided on this module to
maintain tempered outdoor air during ventilation using the VCM Auxiliary Temperature input. The preheat unit is user-
supplied.
Multi Purpose Module (1U9 IntelliPak II / 1U105 IntelliPak I)
(return fan, energy recovery wheel, evaporative condensing) The MPM supports the function of return plenum pressure
control by providing inputs for measuring return plenum pressure, calibrating that reading, and providing an output to
control the return fan speed (if variable speed configured) in response to control algorithm requests. Energy Wheel control
along with bypass damper control, and interface to the saturated condensing pressure sensors for evaporative
condensing head-pressure control.
Modulating Dehumidification Module (1U15 IntelliPak II / 1U107 IntelliPak I)
(dehumidification hot gas reheat) The MDM supports specific control inputs and outputs for modulating dehumidification
control including modulating reheat and cooling valve control as well as the reheat pumpout coil relay output.
Generic Building Automation System Module (1U10 GBAS(0-5VDC) / 1U11 GBAS(0-10VDC)
IntelliPak II) or (1U51 – GBAS(0-5VDC)/(0-10VDC) IntelliPak I)
(interface to third party BAS controls) The GBAS modules allows a non-Trane building control system to communicate
with the unit and accepts external Setpoints in form of analog inputs (0 - 5 V or 0 - 10 V depending on the module selected)
and a binary Input for demand limit. Five (5) binary outputs are available on 0 - 5 V modules. One (1) binary output and
four (4) analog outputs are available on the 0 - 10 V modules. Refer to the "Field Installed Control Wiring" section of the
Unit Installation, Operation, Maintenance Manual (IOM) for the control wiring to the GBAS module and the various desired
Setpoints with the corresponding DC voltage inputs.
Ventilation Override Module (1U8 IntelliPak II / 1U53 IntelliPak I)
(special ventilation unit operation) The VOM module provides the necessary I/O interface to third party customer controls
and allows specific override operation of the unit's air handling functions such as space pressurization, exhaust, purge,
unit off, etc.
RT-SVP07B-EN 9