Miscellaneous Output Signals; External Exhaust Fan Status - Daikin MicroTech II Installation And Maintenance Manual

Field Wiring

Miscellaneous Output Signals

The five optional output signals listed below can be provided
by installing field supplied 24 VAC relays wired between
terminal 107 on the field terminal block (TB2) and the
terminals listed in Table 6. Refer to the unit wiring diagrams or
Figure 16 on page 39 (DAC units) or Figure 17 on page 40
(SCC units) for wiring termination details.
The total VA of all field-mounted relays cannot exceed 15 VA
and they must have a 24 VAC Class 2 coil. Other power can
cause unit malfunction.
• Airflow status
• Dirty filter (including optional final filter)
• Gas furnace fail alarm (Heat Fail)
• Freeze alarm (steam or water coils, optional)
• Smoke alarm (optional
)
Table 6: Miscellaneous field signal termination points
Terminal
Description
block TB2
107 Ground
108 Fan operation (airflow indication)
109 Dirty filter indication
111 Heat alarm detected (gas heat flame
failure)
112 Freezestat (freeze condition
detected)
113 Smoke (smoke detected)
20
CAUTION
Energized field
relay indication
NA
Airflow present
Filters dirty
Alarm
Normal
Normal

External Exhaust Fan Status

When a large exhaust fan or group of exhaust fans is started or
stopped during normal rooftop unit operation, the building
static pressure may become too positive or negative. If a field
binary input signal is delivered to the unit when an external
exhaust fan is started, a VAV unit controller that uses "fan
tracking" control can modify its return fan control algorithm to
compensate for the change in exhaust fan airflow. The fan
tracking control feature can reduce or eliminate objectionable
building pressure fluctuations that might otherwise occur.
To take advantage of this exhaust fan airflow compensation
feature, field wire a set of dry contacts across terminals 101
and 103 on the field terminal block (TB2). When these
contacts close, 24 VAC is applied to binary input MCB-BI13,
indicating that the external exhaust fan is on. When the
contacts open, 24 VAC is removed from MCB-BI13,
indicating that the exhaust fan is off. Refer to the unit wiring
diagrams or Figure 16 on page 39 for wiring termination
details.
For detailed information on the fan tracking feature, refer to
the "Return Fan Capacity Control" section of the DAC
operation manual (refer to Table 1 on page 1).
Daikin IM 696-4