Trane S*HF*20-75 Troubleshooting Manual page 7

Commonly Used Acronyms
Deadband.
A narrow band of sensor range equally spaced above and below the setpoint that defines a region where
the algorithm will be satisfied and the controlled output will be maintained without change.
Dehumidification Override High Zone Temp.
The temperature in the critical zone on VAV units where
Dehumidification is disabled to prevent over-heating the space due to excess reheat.
Dehumidification Override Low Zone Temp.
The temperature in the critical zone on VAV units where
Dehumidification is disabled to prevent sub-cooling the space due to insufficient reheat.
Demand Control Ventilation (DCV).
An ASHRAE compliant ventilation scheme that varies the Outside Air Damper
minimum position or Fresh Air Flow (TRAQs) between minimum and maximum ventilation Setpoints based on CO2 level.
Dry Bulb.
An outdoor temperature above which economizing will be disabled (unless comparative enthalpy is the
economizer control type being used.)
Economizer Zone Temp Setpoint Suppression.
A parameter used for setting the active economizer cooling control
point to a value lower than the Zone Temp Cooling Setpoint to optimize economizer operation.
Emergency Stop.
A binary input on the RTM, connected to a field-supplied switch, when set to OPEN causes a unit
shutdown with a manual reset diagnostic.
Energy Recovery Wheel.
A wheel that rotates through the outdoor and exhaust air streams, transferring energy
between the two, to optimize unit efficiency.
Evap Diff.
Evaporator Differential is a parameter indicating performance of a refrigeration system. It is calculated by
determining the difference between the entering and leaving temperatures of the evaporator. If this value rises too high
it may indicate a problem with the system.
External Stop.
A binary input on the RTM, connected to a field-supplied switch, when set to OPEN causes a unit stop
request.
Hot Gas Bypass.
A feature to reduce a refrigeration circuit's cooling capacity by bypassing hot discharge line
refrigerant directly to the evaporator coil of the system to more effectively operate in low load conditions.
Humidification Control.
During modes of continuous fan operation a relay is energized when the Humidity measured
in the controlled space drops below an adjustable Humidification Setpoint. The humidifier device is a user supplied device
placed in the supply air stream.
IntelliPak™ I.
Units covering the 20 through 130 ton capacity IntelliPak cabinet sizes, and containing the latest control
modules and software.
IntelliPak™ II.
Units covering the 90 through 150 ton capacity IntelliPak II cabinet sizes, and containing the latest control
modules and software.
®
LonTalk .
An open, device networking communications protocol for controls. This protocol is defined in ANSI approved
typical EIA/CEA-709.1-A-1999.
Low Ambient Compressor Lockout.
A function which prevents compressor operation at low outdoor ambient
temperatures.
Night SetBack (NSB).
Applies to the control of the rooftop unit during unoccupied periods. Also refers to the NSB
panel, a communicating wall sensor with night setback capability.
Rapid Restart.
Certain unit applications require override of the normal unit startup sequence after a power outage.
Target cooling requirements are established within a specified time to meet extreme high return air temperatures.
Reference Enthalpy.
An outdoor enthalpy value, set at the HI, above which economizing will be disabled.
Remote Human Interface. (See Interprocessor Communication Module).
A human interface module designed
to be mounted remotely from the unit. There are some functional differences between a unit mounted and a remote
mounted human interface module.
RT-SVP07B-EN 7