IM 1287-6 • REBEL APPLIED ROOFTOP 74 www.DaikinApplied.com
Troubleshooting
Problem Causes Corrective Actions
Multi-Steam discharges
water inside the duct
or AHU
• Steam supply line is
not insulated.
• Steam supply line is
not properly drained or
sloped.
• The Multi-Steam
condensate drain is
blocked or drain line is
not properly sloped.
• The Multi-Steam is not
properly pitched.
• Steam or condensate
is leaking from the
gasket on the Multi-
Steam collapsible.
• Insulate the steam
supply line.
• Install steam trap to
remove the condensate
from the steam supply
line.
• Slope the steam
supply line properly as
per instruction.
• Verify the condensate
drain line.
• Pitch the Multi-Steam
as per instructions in
Fig. Figure 117 and
Figure 118
• Replace the gasket
(p/n SP 6867).
VAV Box Output
In the Heating state, the VAV Output is turned OFF to indicate
that hot air instead of the normal cool air is being supplied to
the VAV boxes. The VAV boxes are driven to their Heating
Position when hot air is provided based on either the normally
open or normally closed contacts of the VAV output. The VFD
will continue to be controlled to maintain the desired duct static
pressure. This output is also OFF when the unit is in the Start
Up or Recirculation states. If this output is in the Heat (OFF)
position when the unit enters the Fan Only state or Minimum
DAT Control state, the output remains OFF for an adjustable
Post Heat Time (while the unit VFDs are driven to minimum
speed) or until the VFD gets to its minimum speed if the Post
Heat Time is set greater than 0. The Post Heat Timer can be
adjusted via the keypad/display Timer Setting menu in the
Extended Menus.
During unoccupied operation, the VAV Box Output is in the
Cool (ON) position unless airow is detected. When airow is
detected, it switches to the Heat (OFF) position.
Entering Fan Temperature Sensor
The entering fan temperature (EFT) sensor and an associated
“Lo Airow Problem” alarm are provided on VAV units with
MicroTech 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 airow 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/
baing arrangement on gas heat units.
In this case, a “Lo Airow Problem” alarm is generated and
heat is not enabled until the alarm is manually cleared. Refer
to the operation manual for information on clearing alarms (OM
1373).
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 re dampers or control failure. The
DHL control is factory set to open when the discharge plenum
pressure rises to 5.0ʺ wc.
If the DHL switch opens, digital input DI5 on the Main Control
Board de-energizes. The MicroTech controller then shuts down
the unit and enters the O-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 (OM 1373).
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. Both unit-
powered and eld-powered versions are oered.
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.
To Next Page
Loading...
