McQuay IM 987 97
Check, Test, and Start Procedures
Fan Start-up
1 Verify all duct isolation dampers are open. Unit mounted
isolation dampers may be mounted in the supply or
return sections.
2 Place the unit into the Fan Only mode through the
keypad menu System Summary\System\Ctrl Mode= Fan
Only.
3 Turn Switch S7 to ON. The controller should enter the
Startup Initial operating state. If the fan does not run:
a Check fuses F1 and F3.
b Check the manual motor protectors or that the circuit
breakers have not tripped.
c Check the optional phase monitor.
4 If the fans are equipped with optional spring isolators,
check the fan spring mount adjustment. When the fans
are running they should be level. Refer to "Spring
Isolated Fans"‚ page 52.
5 Verify the fan rotation is correct.
6 Verify the DHL safety is opening at a pressure
compatible with duct working pressure limits.
Note: The supply and return fan drives usually are selected for
operation in the drive's midspeed range. The return fan
drives are usually shipped with fixed pitch sheaves that
will provide the selected fan speed; however, the supply
fan drives are usually shipped with variable pitch
sheaves that are adjusted to provide the minimum fan
speed. Both drives should be adjusted for proper airflow
during air balancing. For more information, refer to "Air
Balancing"‚ page 98.
Economizer Start-up
1 Check whether the outdoor air is suitable for free cooling
by displaying the keypad menu Temperature\OA
Damper\OA Ambient=. Low indicates low outdoor air
enthalpy; High indicates high outdoor air enthalpy. See
"Enthalpy Control"‚ page 84 to verify that the enthalpy
changeover control is working properly. You may want
to take temperature and humidity measurements.
2 At the keypad, set the cooling setpoint low enough so the
controller calls for cooling. Adjust the value in
Temperature\Zone Cooling\Occ Clg Spt= below the
temperature shown in Temperature\Zone
Cooling\Control Temp=. In addition, on DAC units,
adjust the value in Temperature\Discharge Cooling\DAT
Clg Spt= below the temperature shown in
Temperature\Discharge Cooling\Disch Air=.
3 Place the unit into cooling mode through the keypad
menu System Summary\System\Ctrl Mode= Cool Only.
4 Observe the outdoor air dampers:
d If the outdoor enthalpy is low, the control algorithm
should start to modulate the dampers open to maintain
the discharge air setpoint.
e If the outdoor enthalpy is high, the dampers should
maintain their minimum position. Look at menu
Temperature\OA Damper\MinOA Pos=. Change this
entry to another value. Verify that the dampers move
to the new minimum position setpoint.
5 If the unit is equipped with the electromechanical
enthalpy changeover control (Honeywell H205) and the
outdoor air condition is borderline, attempt to change its
input to the MicroTech III controller by turning the
switch adjustment to A or D. Check enthalpy status in
keypad menu Temperature \ OA Damper \ OA Ambient=.
If this reading is Low, go to Step 4a. If it is High, go to
Step 4b.
Note: It may not be possible to check the economizer
operation in both low and high enthalpy states on the
same day. If this is the case, repeat this procedure on
another day when the opposite outdoor air enthalpy
conditions exist.
Perform the following procedure on all units:
1 At the keypad, set the cooling setpoint low enough so
that the controller will call for cooling. The value in
Temperature \ 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=.
2 Place the unit into cooling mode through the keypad
menu System Summary \ System \ Ctrl Mode= Cool Only.
3 Close the S1 switch. Now cooling is enabled and circuit
#2 is disabled. After CS1 is closed, the MT III board
starts its 5-minute timing cycle. Note that if the unit has
an economizer and the outdoor air enthalpy is low, the
economizer must fully open before the controller will
energize cooling.
4 When the outdoor air damper has fully opened and the
time delay has expired, the chilled water valve will open.
a Verify that there is a call for cooling by checking the
keypad menu System Summary \ System \
UnitStatus=. This should be in Cooling.
b Check the keypad menu System Summary \ System \
Clg Status=. The compressors will only run if this
reads either All Clg or Mech Clg.
c Trace the control circuits.
CAUTION
Adjust dampers properly. Improper adjustment can
damage the dampers.
When an economizer is ordered without an actuator, the
linkage requires a 3.14" linear stroke to open it fully. Do not
allow dampers to be driven beyond their normal full closed or
full open position.