REMOVAL OF EXISTING FURNACES FROM COMMON
VENT SYSTEMS — If the furnace being replaced was connected
to a common vent system with another appliance(s), these steps
shall be followed with each appliance remaining connected to the
common vent system placed in operation. Ensure that the other
appliances remaining connected to the common vent system are
not in operation.
1. Seal any unused openings in the common vent system.
2. Visually inspect the vent system for proper size and horizontal
pitch, and determine there is no blockage or restriction,
leakage, corrosion, and other deficiencies which could cause
an unsafe condition.
3. Insofar as is practical, close all building doors, windows, and
doors between the space in which the appliances remaining
connected to the common vent system are located and other
spaces of the building. Turn on clothes dryers and any
appliance not connected to the common vent system. Turn on
any exhaust fans, such as range hoods and bathroom exhausts,
so they operate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
4. Follow the lighting instructions and place the appliance in
operation. Adjust the thermostat so appliance will operate
continuously.
5. Test for flue gas spillage at the drafthood relief opening after
5 minutes of main burner operation. Use the flame of a match
or candle, or smoke from a cigarette, etc.
6. After it has been determined that each appliance remaining
connected to the common vent system properly vents when
tested as above, return doors, windows, exhaust fans, fireplace
dampers, any other gas burning appliances to their previous
condition of use.
7. If improper venting is observed during any of the above tests,
the common vent system must be corrected. The vent system
or vent connectors may need to be resized. When resizing vent
systems or vent connectors, the minimum size of the system or
connector must be as determined using the appropriate table
found in Appendix G of the NFGC, or Section 5 of NSCNG-
PIC for Canadian Standards.
COMBUSTION-AIR AND VENT PIPING — The combustion-
air and vent pipe 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), D2241 (SDR-21 and SDR-26 PVC),
D2661 (ABS-DWV), or F628 (schedule-40 ABS). Pipe cement
and primer must conform to ASTM standards D2564 (PVC) or
D2235 (ABS). See Table 5 for maximum pipe lengths (including
maximum lengths adjusted for high-altitude installations) and Fig.
6 or 7 for exterior piping arrangements.
Table 5—Maximum Allowable Pipe Length (Ft)
ALTITUDE ABOVE
SEA LEVEL
(FT)
NUMBER OF 90° ELBOWS
1
2
3
4
5
0 to 2000
50
50
50
50
50
2001 to 3000
44
43
43
42
42
3001 to 4000
40
39
38
37
36
4001 to 5000
37
36
35
34
33
5001 to 6000
34
32
31
29
28
6001 to 7000
31
29
28
26
25
7001 to 8000
27
25
23
21
19
8001 to 9000
24
22
20
18
16
9001 to 10,000
21
18
16
13
11
NOTE:
1. Up to five 90° elbows may be used, not including the vent termination.
Assume that two 45° elbows equal one 90° elbow.
2. Pipe length based on 2-in. diameter pipe for size 050-12 and 075-12, and
3-in. diameter pipe for size 100-16 and 125-20.
3. Minimum pipe length is 5 ft for all applications.
Table 4—Electrical Data
UNIT SIZE
VOLTS—
HERTZ—
PHASE
OPERATING
VOLTAGE RANGE
MAXIMUM
UNIT
AMPS
MINIMUM
WIRE
SIZE
MAXIMUM WIRE
LENGTH
(FT)‡
MAXIMUM FUSE OR
HACR-TYPE
CKT BKR AMPS†
Maximum*
Minimum*
050-12
115—60—1
127
104
10.5
14
44
15
075-12
115—60—1
127
104
10.5
14
44
15
100-16
115—60—1
127
104
15.0
12
49
20
125-20
115—60—1
127
104
15.0
12
49
20
* Permissible limits of the voltage range at which the unit will operate satisfactorily.
† Time-delay fuse is recommended.
‡ Length shown is as measured 1 way along wire path between unit and service panel for maximum 2 percent voltage drop.
Fig. 6—Sidewall Termination
A91213
FLUE OUTLET
COUPLING
TERMINATION
BRACKET
AIR INLET
VENT
(PVC TEE)
COMBUSTION-AIR
(ELBOW WITH
AIR SPLITTER)
COMBUSTION-AIR INLET
VENT
DRAIN
NOTE: HORIZONTAL VENT
RUNS MUST HAVE A
1
⁄
4
″
SLOPE TOWARD
THE FURNACE FOR
EVERY 12
″
OF PIPE
12
″
MIN
24
″
MAX
1
1
⁄
2
″
MIN
18
″
MAX
WALL THICKNESS
12
″
MIN
24
″
MAX
12
″
MIN
24
″
MAX
TOP VIEW
SIDE VIEW
NOTE: 7
″
MIN CLEARANCE TO NEAREST
BUILDING OR WALL
HORIZONTAL VENT TERMINATION
6
