Page 96 IM-738
Figure 97. 24" Backward Curved Wheel-to-Funnel
(036C, 040C)
Figure 98. Airfoil Wheel-to-Funnel Alignment
Table 26: Airfoil Wheel-to-Funnel Tolerances
Figure 99. 40" Airfoil Wheel-to-Funnel Alignment
(RDT 045 -075)
Table 27: 40"Airfoil Wheel-to-Funnel Tolerances
(RDT 045 -075)
Figure 100. 44" Airfoil Wheel-to-Funnel Alignment
Table 28: 44" Airfoil Wheel-to-Funnel Tolerances
(RDT 045 -075)
Refrigerant Charge
The unit nameplate references proper charge for each refriger-
ant circuit in case a full charge must be added to the unit.
Replacing Failed Refrigerant Sensors
or Switches
The McQuay Rooftop Unit includes the following refrigerant
sensors or switches.
1. Low refrigerant sensing, operating switch
2. SpeedTrol refrigerant sensing, operating sensor [see
“SpeedTrol (NA Unit Sizes 015C - 030C)” on page 64]
3. High refrigerant pressure, safety switch
The low pressure and Speedtrol sensors/ switches sense refrig-
erant pressure through schrader fittings that contain cores. The
cores are stop valves that will not allow refrigerant to flow
through the schrader unless the device is in place. Therefore
the low pressure and Speedtrol sensors/switches can be
replaced without reclaiming the refrigerant.
The schrader that serves the high pressure switch does not con-
tain a core, in order to maximize the functionality of the safety.
Therefore it cannot be replaced unless the refrigerant has
already been reclaimed.
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 dam-
age 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 anti-
freeze solution remaining in the coil must always be concen-
trated enough to prevent freeze-up.
Note: Carefully read instructions for mixing antifreeze
solution used. Some products will have a higher
freezing point in their natural state than when mixed
with water.
Wheel-to-Funnel Relationship (In Inches)
Wheel Diameter Inches) “A” +0.3/ —0.0
27 9.90 (246mm)
30 10.60 (269mm)
33 11.70 (297mm)
WHEEL-TO-FUNNEL RELATIONSHIP
WHEEL DIA. (IN.) “A” (IN INCHES)
40
62
W h e e l
. 1 8 "
F u n n e l
9 . 3 1 "
9 . 3 1 "
C
L
F a n
. 1 8 "
W h e e l
F u n n e l
A
W h e e l
F u n n e l
A
WHEEL-TO-FUNNEL RELATIONSHIP
WHEEL DIA. (IN.)
“A” (IN INCHES)
44 16.21
WARNING
Potential severe loss of charge may occur if the high
refrigerant pressure switch is replaced before reclaiming
the refrigerant.
Replace switch after reclaiming refrigerant.
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