McQuay IM 987 111
Maintenance
Winterizing Water Coils
Coil freeze-up can be caused by such things as air stratification
and failure of outdoor dampers and/or preheat coils. Routine
draining of water cooling coils for winter shutdown cannot be
depended upon as insurance against freeze-up. Severe coil
damage may result. It is recommended that all coils be drained
as thoroughly as possible and then treated in the following
manner.
• Fill each coil independently with an antifreeze solution
using a small circulating pump and again thoroughly drain.
• Check freezing point of antifreeze before proceeding to next
coil. Due to a small amount of water always remaining in
each coil, there will be a diluting effect. The small amount of
antifreeze solution remaining in the coil must always be
concentrated enough to prevent freeze-up.
Note: Carefully read instructions for mixing antifreeze solution
used. Some products have a higher freezing point in
their natural state than when mixed with water.
Control Panel Components
Manual Motor Protector (MMP)
The manual motor protector (MMP) provides coordinated
branch circuit, short circuit protection, a disconnecting means,
a motor controller, and coordinated motor overload protection.
A short circuit indicator with manual reset is mounted along
side of each MMP as a means to differentiate between a short
circuit and overload trip conditions.
The MMP trip points are factory set. Do not change unless the
motor ampacity changes or the MMP is replaced with a new
device with incorrect setpoint adjustment. Any other
non-authorized trip point or setpoint adjustment voids all or
portions of the unit’s warranty. Authorized setpoint adjustment
is accomplished as follows
1 For motors with a 1.15 service factor, rotate the arrow on
the dial to correspond to the motor FLA.
2 For motors with a 1.0 service factor, multiply the motor
FLA by 0.9; then rotate the arrow on the dial to
correspond to that value.
To reset a tripped MMP, clear the trip by rotating the knob
counterclockwise to the OFF (O) position; then rotate knob
clockwise to the ON (I) position. See
Figure 125.
Other MMP Features:
• Three-position rotary operator: OFF (O)-TRIP-ON (I)
(Figure 125).
• Lockout—tagoutable rotary operator: turn the rotary
operator to OFF (O), slide out the extension arm, and insert a
lockout pin.
• Ambient compensated –20°C to +40°C.
• Single-phase sensitivity: if one phase exceeds setpoint, all
three phases open.
• Trip test: insert a 9/64" screw driver in the test slot
(Figure 125) to simulate a trip.
Figure 125: Manual Motor Protector
WARNING
If an overload or a fault current interruption occurs, check
circuits to determine the cause of the interruption.
If a fault condition exits, examine the controller. If damaged,
replace it to reduce the risk of fire or electrical shock.
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