10
Table 2—
Maximum Gas Flow Capacity*
NOMINAL
IRON PIPE
SIZE (IN.)
INTERNAL
DIAMETER
(IN.)
LENGTH OF PIPE (FT)†
10
20
30
40
50
60
70
80
90
100
125
150
175
200
1/2
.622
175
120
97
82
73
66
61
57
53
50
44
40
—
—
3/4
.824
360
250
200
170
151
138
125
118
110
103
93
84
77
72
1
1.049
680
465
375
320
285
260
240
220
205
195
175
160
145
135
1--1/4
1.380
1400
950
770
600
580
530
490
460
430
400
360
325
300
280
1--1/2
1.610
2100
1460
1180
990
900
810
750
690
650
620
550
500
460
430
*Capacity of pipe in cu ft of gas per hr for gas pressure of 0.5 psig or less. Pressure drop of 0.5--in. wc (based on a 0.60 specific gravity gas). Refer to Table, National Fire Protec-
tion Association NFPA 54.
{
This length includes an ordinary number of fittings.
1. Open all electrical disconnects before starting any service
work.
2. Remove horizontal (metal) duct covers to access vertical
(downflow) discharge duct knockouts in unit base.
3. Use a screwdriver and hammer to remove the panels in the
bottom of the unit base (See Fig. 10).
4. If unit ductwork is to be attached to vertical opening flanges
on the unit base (jackstand applications only), do so at this
time.
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in property damage.
Collect ALL screws that were removed.
Do not
leave screws
on rooftop as permanent damage to the roof may occur.
CAUTION
!
5. It is recommended that the base insulation around the
perimeter of the vertical return--air opening be secured to the
base with aluminum tape. Applicable local codes may
require aluminum tape to prevent exposed fiberglass.
6. Cover both horizontal duct openings with the provided duct
covers. Ensure opening is air-- and watertight.
7. After completing unit conversion, perform all safety checks
and power up unit.
NOTE
: The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
nonresidence--type air conditioning and ventilating systems, NFPA
90A or residence--type, NFPA 90B; and/or local codes and
ordinances.
SUPPLY
DUCT
OPENING
RETURN
DUCT
OPENING
VENT HOOD
SHIPPING
LOCATION
A05143
Fig. 9 -- Supply and Return Duct Opening
DUCT COVERS REMOVED
C99012
Fig. 10 -- Vertical Duct Cover Removed
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. Units are shipped for horizontal duct installation (by
removing duct covers).
2. Select and size ductwork, supply--air registers, and
return--air grilles according to American Society of Heating,
Refrigeration and Air Conditioning Engineers (ASHRAE)
recommendations.
3. Use flexible transition between rigid ductwork and unit to
prevent transmission of vibration. The transition may be
screwed or bolted to duct flanges. Use suitable gaskets to en-
sure weather--tight and airtight seal.
4. All units must have field--supplied filters or accessory filter
rack installed in the return--air side of the unit.
Recommended sizes for filters are shown in Table 1.
5. Size all ductwork for maximum required airflow (either
heating or cooling) for unit being installed. Avoid abrupt
duct size increases or decreases or performance may be
affected.
6. Adequately insulate and weatherproof all ductwork located
outdoors. Insulate ducts passing through unconditioned
space, and use vapor barrier in accordance with latest issue
of Sheet Metal and Air Conditioning Contractors National
Association (SMACNA) and Air Conditioning Contractors
of America (ACCA) minimum installation standards for
heating and air conditioning systems. Secure all ducts to
building structure.
7. Flash, weatherproof, and vibration isolate all openings in
building structure in accordance with local codes and good
building practices.
48E
S
