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650.75-N4U
TABLE 5 - DOWNFLOW /HORIZONTAL UNITS -
INTAKE/VENT PIPING 2-PIPE SYSTEM
Pipe
Model
Size
40 /37 / 800 / A
60 /55 / 1200 / B
2"
80 /75 / 1200 / B
80 /75 / 1600 / C
100 /95 / 1000 / C
40 /37 / 800 / A
60 /55 / 1200 / B
3"
80 /75 / 1200 / B
80 /75 / 1600 / C
100 /95 / 1000 / C
120 /112 / 2000 / D
3" Only
NOTE: Elbow count does not include (2) 90 ° elbows required to pipe
intake into burner box or those for the termination. See
Step 4 under Combustion Air/Vent Pipe Sizing
1. Long radius elbows are required for all units.
2. Elbows are assumed to be 90 degrees. Two 45 degree
elbows count as one 90 degree elbow.
3. Elbow count refers to combustion air piping and vent piping
separately. For example, if the table allows for 5 elbows,
this will allow a maximum of 5 elbows in the combustion
air piping and a maximum of 5 elbows in the vent piping.
4. For all models, three vent terminal elbows (two for vent
pipe and one for air intake pipe) are already accounted for
and should not be counted in the allowable total indicated
in the table. See section on vent terminal. These parts are
shown shaded.
For downflow/horizontal models only two additional el-
bows are also accounted for and also should not be
counted. These parts are shown shaded.
5. Combustion air and vent piping must be of the same diameter.
FIGURE 13 - UPFLOW AIR INTAKE/VENT LOCATIONS
12
Max. Elbows vs.
One Way Vent Length (Ft.)
5-30
35
40
60
6
5
4
N/A
8
7
6
5
6
5
4
N/A
6. All combustion air/vent pipe and fittings must conform to
American National Standards Institute (ANSI) standards
and American Society for Testing and Materials (ASTM)
standards D1785 (Schedule 40 PVC), D2665 (PVC-
DWV), F891 (PVC-DWV cellular core). D2241 (SDR-21
and SDR-26 PVC), D2261 (ABS-DWV), or F628 (Sched-
ule 40 ABS. Pipe cement and primer must conform to
ASTM Standards D2564 (PVC) or D2235 (ABS).
7. The use of flexible connectors or no hub connectors in the
vent system is not allowed. This type connection is allowed
in the combustion air pipe near the furnace for air condi-
tioning coil accessibility.
VENT TERMINATION (2-PIPE)
Side wall horizontal vent terminals and roof mounted vertical termi-
nals may be field fabricated. Standard PVC/SRD fittings may be used.
Terminal configuration must comply as detailed in this section.
NOTE: Combustion air and vent pipes must terminate together in
the same atmospheric zone, either through a roof or sidewall.
NOTE: Accessory concentric intake/vent terminations, models
1CT0302 and 1CT0303 are available and approved for use
with these furnaces. Refer to Form 650.75-N2.4V for
installation details.
When selecting the location for combustion air/vent termination
the following should be considered:
1. Comply with all clearance requirements as listed below.
2. Termination should be positioned where vent vapors will not
damage plants or shrubs or air conditioning equipment.
3. Termination should be located where it will not be affected
by wind gusts, light snow, airborne leaves or allow recircu-
lation of flue gases.
4. Termination should be located where it will not be dam-
aged or exposed to flying stones, balls, etc.
5. Termination should be positioned where vent vapors are
not objectionable.
FIGURE 14 - DOWNFLOW / HORIZONTAL
AIR INTAKE/VENT
LOCATIONS
Unitary Products Group
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