Daikin RDT Installation And Maintenance Manual page 81

Entering Fan Temperature Sensor
The entering fan temperature (EFT) sensor and an associated
"Lo Airflow Problem" alarm are provided on VAV units with
MicroTech III control and gas or electric heat. The EFT sensor
is located in the supply fan section of the unit at the supply air
funnel.
Heat is disabled whenever the airflow is detected to be too low
for safe heating operation. This condition is indicated when the
supply air temperature exceeds the mixed air temperature by
more than 60°F (16°C).
NOTE: This value is not always 60°F. It depends on whether
the unit is gas or electric heat and on the burner/
baffling arrangement on gas heat units.
In this case, a "Lo Airflow Problem" alarm is generated and
heat is not enabled until the alarm is manually cleared. Refer
to the operation manual supplied with the unit for information
clearing alarms (OM 920).
Duct High Pressure Limit
The duct high pressure limit control (DHL) is provided on all
VAV units. The DHL protects the duct work, the terminal boxes,
and the unit from over pressurization, which could be caused
by, for example, tripped fire dampers or control failure.
The DHL control is factory set to open when the discharge
plenum pressure rises to 3.5ʺ wc (872 Pa). This setting should
be correct for most applications; however, it is adjustable.
Removing the front cover of the device reveals a scale showing
the current setting. Turning the adjustment screw (located on
the bottom of the device) adjusts the setting up or down.
If the DHL switch opens, digital input MCB BI 14 on the Main
Control Board de-energizes. The MicroTech III controller then
shuts down the unit and enters the Off-Alarm state. The alarm
must be manually cleared before the unit can start again.
Refer to the operation manual supplied with your unit for more
information on clearing alarms
www.DaikinApplied.com
(OM 920).
Variable Frequency Drive Operation
Refer to the vendor instructions supplied with the unit.
Convenience Receptacle/Section Lights
A Ground Fault Circuit Interrupter (GFCI) convenience
receptacle is provided in the main control box on all units. Both
unit-powered and field-powered versions are offered.
To use the field-powered receptacle one of the following is
required:
1. Connect a separate field-supplied 115 V power wiring
circuit to the 115V field terminal block TB7, located in the
main control box.
2. Select the factory powered outlet option at time of
purchase.
Optional lights are available for certain sections in the unit.
Each light includes a switch and convenience receptacle and is
powered by the external 115V power supply connected to TB7.
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