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24
Step 5 — Field Fabricate Ductwork
Cabinet return-air static pressure (a negative condition) shall not
exceed 0.5 in. wg (87 Pa).
For vertical ducted applications, secure all ducts to roof curb and
building structure. Do not connect ductwork to unit.
Fabricate supply ductwork so that the cross sectional dimensions
are equal to or greater than the unit supply duct opening dimen-
sions for the first 18-in. (458 mm) of duct length from the unit
basepan.
Insulate and weatherproof all external ductwork, joints, and roof
openings with counter flashing and mastic in accordance with ap-
plicable codes.
Ducts passing through unconditioned spaces must be insulated
and covered with a vapor barrier.
If a plenum return is used on a vertical unit, the return should be
ducted through the roof deck to comply with applicable fire codes.
A minimum clearance is not required around ductwork.
Step 6 — Rig and Place Unit
Keep unit upright and do not drop. Spreader bars are not required
if top crating is left on unit. Rollers may be used to move unit
across a roof. Level by using unit frame as a reference. See Table 2
(on page 19) and Fig. 19 for additional information.
Lifting holes are provided in base rails as shown in Fig. 19. Refer
to rigging instructions on unit.
Before setting the unit onto the curb, recheck gasketing on curb.
POSITIONING ON CURB
Position unit on roof curb so that the following clearances are
maintained:
1
/
4
-in. (6 mm) clearance between the roof curb and the
base rail inside the right and left,
1
/
2
-in. (12 mm) clearance be-
tween the roof curb and the base rail inside the front and back.
This will result in the distance between the roof curb and the base
rail inside on the condenser end of the unit being approximately
equal to Details A and B in Fig. 20-22.
Do not attempt to slide unit on curb after unit is set. Doing so will
result in damage to the roof curb seal.
Although unit is weatherproof, guard against water from higher
level runoff and overhangs.
Flue vent discharge must have a minimum horizontal clearance of
48-in. (1220 mm) from electric and gas meters, gas regulators, and
gas relief equipment. Minimum distance between unit and other
electrically live parts is 48-in. (1220 mm).
Flue gas can deteriorate building materials. Orient unit such that
flue gas will not affect building materials. Locate mechanical draft
system flue assembly at least 48-in. (1220 mm) from an adjacent
building or combustible material.
After unit is in position, remove rigging skids and shipping
materials.
Step 7 — Horizontal Duct Connection
Depending on the unit size, see either Fig. 3 and 4 (size 14),
Fig. 8 and 9 (size 20), or Fig. 13 and 14 (sizes 24 and 26) for lo-
cations and sizes of the horizontal duct connections. Note that
there are two different return air duct connection locations – one
for non-VAV units without an economizer (on back side of unit)
and a different one for LC*B VAV units with the integrated
economizer (on left end, under the economizer hood). The sup-
ply air duct connection is on the back side. See Fig. 23 for top
view depicting typical horizontal duct arrangements.
Field-supplied (
3
/
4
-in.) flanges should be attached to horizontal
duct openings (see Fig. 23) and all ductwork should be secured
to the flanges. Insulate and weatherproof all external ductwork,
joints, and roof or building openings with counter flashing and
mastic in accordance with applicable codes.
Fig. 23 — Horizontal Duct Opening Dimensions
Step 8 — VAV Duct Pressure Transducer and
Field Tubing Installation
Before a VAV rooftop unit can operate correctly, installation of the
factory-supplied duct pressure transducer (DPT) and plastic pneu-
matic tubing (field supplied) is required. The DPT is mounted in
the unit control box for shipping purposes and is shown in Fig. 24.
Remove the screw holding the DPT and disconnect quick con-
nects from the transducer terminals. For correct pressure sensing,
mount the DPT externally to the main trunk duct approximately
two-thirds (
2
/
3)
of the way from the unit. Install factory-supplied
duct pressure tap (located in the installer’s packet) at the DPT lo-
cation by inserting tap perpendicular to duct airflow with the ar-
row on pressure tap flange matching airflow direction.
Connect
1
/
4
-in. plastic pneumatic tubing (field supplied) to barbed
fitting on pressure tap and connect the other end to “High” fitting
of pressure transducer. Leave “Low” pressure connection open to
the atmosphere. Connect 20 or 22 AWG insulated wire [35°C
(95°F) minimum] to DPT “+” and “-” terminals. Route wiring
back to rooftop unit along with the low voltage VAV terminal field
control wiring. Connect wire from DPT “+” terminal to quick
CAUTION
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in damage to roofing
materials.
Membrane roofs can be cut by sharp sheet metal edges. Be
careful when placing any sheet metal parts on such roof.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage.
All panels must be in place when rigging. Unit is not designed
for handling by fork truck when packaging is removed.
If using top crate as spreader bar, once unit is set, carefully
lower wooden crate off building roof top to ground. Ensure
that no people or obstructions are below prior to lowering the
crate.
Return Air Duct
LC*B VAV unit
with Integrated
Economizer
Return Air Duct
Non-VAV LC unit
w/o Economizer
Horizontal
Supply Air
SUPPLY
NON-VAV
UNIT RETURN
LC*B-VAV
UNIT RETURN
Location
Back
Back
Left end
Height
In. (mm)
15
7
/
8
(402)
49
3
/
8
(1253)
18
3
/
8
(467)
Width
in. (mm)
29
3
/
4
(756)
23
3
/
8
(593)
61
5
/
8
(1564)
Summary of Contents for WeatherExpert 48LC B14 Series
Page 4: ...4 Fig 2 48LC B14 Vertical Airflow ...
Page 5: ...5 Fig 3 48LC B14 Horizontal Airflow ...
Page 6: ...6 Fig 4 48LC B14 Back View and Condensate Drain Location ...
Page 7: ...7 Fig 5 48LC B14 Corner Weights and Clearances ...
Page 8: ...8 Fig 6 48LC B14 Bottom View ...
Page 9: ...9 Fig 7 48LC B17 20 Vertical Airflow ...
Page 10: ...10 Fig 8 48LC B17 20 Horizontal Airflow ...
Page 11: ...11 Fig 9 48LC B17 20 Back View and Condensate Drain Location ...
Page 12: ...12 Fig 10 48LC B17 20 Corner Weights and Clearances ...
Page 13: ...13 Fig 11 48LC B17 20 Bottom View ...
Page 14: ...14 Fig 12 48LC B24 26 Vertical Airflow ...
Page 15: ...15 Fig 13 48LC B24 26 Horizontal Airflow ...
Page 16: ...16 Fig 14 48LC B24 26 Back View and Condensate Drain Location ...
Page 17: ...17 Fig 15 48LC B24 26 Corner Weights and Clearances ...
Page 18: ...18 Fig 16 48LC B24 26 Bottom View ...
Page 21: ...21 Fig 20 48LC B14 Roof Curb Details ...
Page 22: ...22 Fig 21 48LC B17 20 Roof Curb Details ...
Page 23: ...23 Fig 22 48LC B24 26 Roof Curb Details ...
Page 30: ...30 Fig 40 48LC B14 26 VAV RTU Open Control Wiring Diagram ...
Page 31: ...31 Fig 41 48LC B14 26 Power Wiring Diagram ...
Page 53: ......