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RT-SVD03L-EN 59
Table 17. Economizer fault detection and diagnostics for units with or without Traq ™ ™ (continued)
Cooling
Request
Enthalpy
Decision
Indoor Fan -
(Ventilation
Requested)
Damper
Command VS
Feedback
Not
Economizing
When It
Should Be
Economizing
When It
Should Not Be
Outdoor
Air
Damper
Not
Modulat-
ing
Excessive
Outdoor
Air
YES Disabled ON
Feedback High
FAULT
YES Disabled ON Feedback Low FAULT
(a) Dehumidification mode and heating mode are considered minimum ventilation.
When an economizer fault has been detected, the unit
controller will latch an Auto-Reset Diagnostic and
report it through the TD-5. It will also generate a
diagnostic through BAS (LCI/BCI if installed). Reset
Auto-Reset Diagnostic when the economizer returns to
the valid range or if the unit leaves Active Cooling
Mode.
Mixed Air Temperature Low Limit
Diagnostic
In all conditions on all ReliaTel ™ controlled units, if the
mixed air temperature falls below 45°F, mixed air
temperature low limit is active and the economizer
actuator will close to the active minimum position. On
Title 24 compliant units, ReliaTel
™ will set an auto-
reset diagnostic to be used by BAS and TD-5 when the
mixed air temperature low limit is active.
The RTEM will revert to normal operation when the
mixed air temperature rises above 48°F. The diagnostic
will be reset when the mixed air temperature low limit
is inactive.
BACnet ® ® Communications Interface
(BCI)
Refer to the list below for a list of objects in the BCI
interface that require specific handling in regards to
economizer fault detection and diagnostics:
• Diagnostic: Unit Not Economizing When It Should
Be
• Diagnostic: Unit Economizing When It Should Not
Be
• Diagnostic: Outdoor Air Damper Not Modulating
• Diagnostic: Excessive Outdoor Air
• Diagnostic: Mixed Air Temperature Low Limit
Active
LonTalk ™ ™ Communications Interface
(LCI)
Refer to the list below for the variables in the LCI
interface that require specific handling in regards to
economizer fault detection and diagnostics:
• nvoAlarmMessage.Unit Not Economizing
• nvoAlarmMessage.Unit Economizing
• nvoAlarmMessage.OA Damper Not Modulating
• nvoAlarmMessage.Excessive Outdoor Air
• nvoAlarmMessage.Mixed Air Temperature Low
Limit Active
Failure and Overriding Conditions
Economizer FDD will continue to be in effect during the
following cases:
• Service Test Mode
• Ventilation Override
• OFF or Stop Mode
Multi-Speed Indoor Fan
There will be two types of multi-speed indoor fan
control: the first type will control discrete fan speeds
based on active heating or cooling stages and the
second will be a modulating type control based on
various inputs.
Two-Speed Fan Control
This control scheme will cover all unit operation for
units configured for two-speed fan operation. Units
requiring discrete relay outputs or voltage signals (5
Vdc & 10 Vdc) will fall under this form of control.
Table 18. Control scheme - two speed fan control
Unit
Configura-
tion
Low Speed Output High Speed Output
2-Speed
Relay
Controlled
RTRM Supply Fan
RTRM J2-5
Output
RTRM Supply Fan
Output
2-Speed
5Vdc/10Vdc
Output
RTRM Supply Fan
RTOM
Indoor Fan Speed @
50% of maximum
RTRM Supply Fan
RTOM
Indoor Fan Speed @
100% of maximum
Unit Operation for Two-Speed Fan Control
Standard unit operation for cooling, heating, and
dehumidification will continue on units equipped with
a two-speed indoor fan and all unit functions will
operate normally, except for the control of the indoor
fan speed. All units configured with any type of heating
or reheat/dehumidification will operate as normal
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