Installation manual
IM-487 Page 75
ture \ Zone Cooling \ Occ Clg Spt = will need to be
adjusted below the temperature shown in Temperature \
Zone Cooling \ Control Temp =. In addition, on DAC
units, the value in Temperature \ Discharge Cooling \ DAT
Clg Spt = will need to be adjusted below the temperature
shown in Temperature \ Discharge Cooling \ Disch Air =.
3. The chilled water value (VMS) will modulate to maintain
set point as follows: See also “Typical Actuator Circuit”
on page 56.
• MCB B08 closes to increase chilled water flow and
increase cooling capacity.
• MCB B07 closes to close off chilled water flow and
decrease cooling capacity.
Adjusting MicroTech II Controls and
Servicing Control Panel Components
Adjusting MicroTech II Controls
In order to read values, adjust setpoints, clear faults, etc., on
the MicroTech II unit controller, the main unit control panel
must be energized. If the unit has a factory mounted discon-
nect switch, the switch's bypass mechanism must be used in
order to open the main control panel door without de-ener-
gizing the control panel. The bypass mechanism is activated
by turning the screw at the bottom of the disconnect switch
clockwise while pulling the door open. Use of the disconnect
switch bypass mechanism must be done only by a qualified
service technician.
Whenever the main control panel is accessed with the control
panel still energized, the inner deadfront protective panels
must remain closed to avoid exposure to high voltage power.
Servicing Control Panel Components
All electric power to the unit must be disconnected whenever
servicing control panel components located behind the protec-
tive deadfront panels. The components behind the protective
deadfront panels are energized with high voltage unless electric
power is disconnected to the unit. Units must always be
inspected for multiple disconnects to verify all power is removed
from the control panel and its components before servicing.
Air Balancing
Air balancing should be performed by a qualified air balanc-
ing technician. Note that the supply fan motors are usually
shipped with variable pitch sheaves which are typically set at
the low end of the drive's fan rpm range. See “Mounting and
Adjusting Motor Sheaves” on page 77. The return fan motors
are usually shipped with fixed pitch sheaves.
Perform the following as part of the air balancing procedure:
1. Check the operating balance with the economizer dampers
positioned for both full outdoor air and minimum outdoor air.
2. Verify that the total airflow will never be less than that
required for operation of the electric heaters or gas furnace.
3. For VAV units that are using fan tracking control, adjust the
parameters for the MicroTech II controller's VaneTrol algo-
rithm. For complete information on using this feature, see the
"Return Fan Airflow" section in Bulletin OM 137, "Micro-
Tech II Applied Rooftop Unit Controller: DAC Control".
4. When the final drive adjustments or changes are complete,
check the current draw of the supply and return fan motors.
The amperage must not exceed the service factor stamped on
the motor nameplate.
5. Upon completion of the air balance, replace variable pitch
motor sheaves (if any) with comparably sized fixed pitch
sheaves. A fixed pitch sheave will reduce vibration and pro-
vide longer belt and bearing life.
Sheave Alignment
Mounting:
1. Verify both driving and driven sheaves are in alignment
and the shafts are parallel. The center line of the driving
sheave must be in line with the center line of the driven
sheave. See Figure 73 on page 76.
2. Verify that all setscrews are torqued to the values shown
in Table 19 on page 86 before starting drive. Check set-
screw torque and belt tension after 24 hours of service.
WARNING
Electrical shock hazard.
May cause severe injury or death.
All protective deadfront panels must be closed when mak-
ing adjustments to the MicroTech II unit controller.
WARNI
DANGER
NG
Electrical shock hazard.
May cause severe injury or death.
Disconnect electric power before servicing equip-
ment. More than one disconnect may be required to
de-energize the unit.
WARNING
Moving machinery hazard. Can cause severe
personal injury or death.
Use a strobe tachometer to measure the speed of return
fans. Do not use a mechanically driven tachometer on this
fan arrangement.