78
Smoke Detectors
Smoke detectors are available as factory-installed options on
50LC 14-26 models. Smoke detectors may be specified for supply
air only, for return air without or with economizer, or in combina-
tion of supply air and return air. The unit is factory-configured for
immediate smoke detector shutdown operation; additional wiring
or modifications to unit’s Integrated Staging Control (ISC) board
may be necessary to complete the unit and smoke detector config-
uration to meet project requirements.
RETURN AIR SENSOR TUBE INSTALLATION
The return air sampling tube is shipped in the unit’s supply fan
section, attached to the blower housing (see Fig. 88). Its operating
location is in the return air section of the unit (see Fig. 89, unit
without economizer, or Fig. 90, unit with economizer), inserted
into the return air sensor module housing which protrudes through
the back of the control box.
To install the return air sensor sampling tube:
1. Remove the tube from its shipping location.
2. Open the unit end to access the return air sensor (located
on right-hand partition)
3. Orient the tube’s sampling holes into the return air flow
direction. For vertical application, position the sampling
holes on the bottom of the tube, facing into the bottom
return duct opening. For horizontal application, position
the sampling holes on the side of the tube, facing the unit’s
end panel.
4. Insert the sampling tube into the return air sensor module
until the tube snaps into position.
5. Replace end panel or outside air hood.
Fig. 88 — Typical Supply Air Smoke Detector Sensor
Location
Fig. 89 — Return Air Sampling Tube Location in Unit
without Economizer
Fig. 90 — Return Air Sampling Tube Location in Unit
with Economizer
SMOKE DETECTOR TEST MAGNET
Locate the magnet; it is shipped in the control box area.
ADDITIONAL APPLICATION DATA
Refer to Factory Installed Smoke Detectors for Small and Me-
dium Rooftop Units 2 to 25 Tons for discussions on additional
control features of these smoke detectors including multiple
unit coordination.
Step 13 — Install Accessories
Available accessories include:
• Roof Curb (must be installed before unit)
• Electric heaters
• EconoMi$er
®
X (with control)
• Power Exhaust
• Outdoor enthalpy sensor
• Differential enthalpy sensor
• CO
2
sensor
• Temperature and Humidity sensors
• Louvered hail guard
• Phase monitor control
Refer to separate installation instructions for information on in-
stalling these accessories. See 50LC 14-26 Price Pages for a com-
plete list of field-installed accessories.
Step 14 — Check Belt Tension
Measure the belt span length as shown in Fig. 91. Calculate the re-
quired deflection by multiplying the belt span length by
1
/
64
. For
example, if the belt span length is 32 inches:
32 x
1
/
64
=
1
/
2
inch deflection.
BELT FORCE: DEFLECTION METHOD
Check the belt tension with a spring-force belt force deflection
gage.
1. Place a straightedge along the belt between the two pul-
leys. Measure the distance between the motor shaft and the
blower shaft.
2. Set the tension gage to the desired tension (see Table 1 in
Fig. 91). Place the large O-ring at that point.
3. Press the tension checker downward on the belt until the
large O-ring is at the bottom of the straightedge.
4. Adjust the belt tension as needed.
Adjust belt tension by loosing the motor mounting plate front bolts
and rear bolt (see Fig. 92) and sliding the plate towards the fan (to
reduce tension) or away from the fan (to increase tension). Ensure
the blower shaft and motor shaft are parallel to each other (pulleys
aligned). Tighten all bolts securely when finished.
ROTATION
RETURN AIR SAMPLING
TUBE (SHIPPING LOCATION)
RETURN AIR DETECTOR
SAMPLING TUBE
RETURN AIR DETECTOR
SAMPLING TUBE
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