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www.DaikinApplied.com 37
IM 893-10 • ROOFPAK SINGLEZONE UNITS
Steam Coil Freeze Conditions
If the air entering the steam coil is below 35°F (2°C), note the
following recommendations:
1. Supply 5 psi (34.5 kPa) steam to coils at all times.
2. Modulating valves are not recommended. Control should
be by means of face and bypass dampers.
3. As additional protection against freeze-up, install the
tap sufficiently far below the coil to provide an adequate
hydrostatic head to ensure removal of condensate during
an interruption on the steam pressure. Estimate 3 ft. (914
mm) for each 1 psi (7 kPa) of trap differential required.
4. If the unit is to be operated in environments with
possible freezing temperatures, an optional freezestat is
additional information.
Figure 40: Steam Valve Package
Damper Assemblies
The optional damper assemblies described in this section
normally are ordered with factory-installed actuators and
linkages. The following sections describe operation and linkage
adjustment of the factory-installed option.
Economizer Dampers
Outside air intake is provided on both sides of the unit, and the
return air path is at the center of the damper set. As the single
actuator modulates the outside air dampers open, the return
air dampers close. Exhaust air exits the unit through the gravity
relief dampers provided at the end of the economizer section.
The damper is set so that the crankarm moves through a
90- degree angle to bring the economizer dampers from full
open to full close (see
). Access to the actuator and
linkage is from the filler section. Mechanical stops are placed in
the crankarm mounting bracket. Do not remove stops. Driving
the crankarm past the stops results in damage to the linkage
or damper. The unit ships with a shipping bolt securing the
linkage crankarm. Remove shipping bolt before use.
NOTE:
For good airflow control, adjust linkages so damper
blades do not open beyond 70 degrees. Opening a
damper blade beyond 70 degrees has little effect on
its airflow.
Do not “overclose” low leak damper blades. The edge
seal should just lightly contact the adjoining blade.
The blades will lock up if they are closed so far the
seal goes over center.
Figure 41: Damper Adjustment
Airflow