Nortek FG7SC, Installation Instructions Manual

12

Outdoor Terminations - Vertical Venting

Termination spacing requirements from the roof and from 

each other are shown in 

Figure 10

. The roof penetration must 

be properly flashed and waterproofed with a plumbing roof 

boot or equivalent flashing. Vent and combustion air piping 

may be installed in an existing chimney which is not in use 

provided that:
•  Both the exhaust vent and air intake run the length of the 

chimney.

•  The top of the chimney is sealed and weatherproofed.

• The termination clearances shown in 

Figure 10

 are 

maintained.

• No other gas fired or fuel-burning equipment is vented 

through the chimney.

Vent Freezing Protection

 CAUTION:

When the vent pipe is exposed to temperatures 

below freezing (i.e., when it passes through 

unheated spaces, chimneys, etc.) the pipe 

must be insulated with 1/2 inch thick sponge 

rubber insulation, Armaflex-type insulation or 

equivalent. Insulating pipe is important to avoid 

condensate icing.

• 

Table 2

 lists the maximum length of flue pipe that can 

travel through an unconditioned space or an exterior 

space. The total vent length must not exceed the lengths 

noted in 

Table 1 (page 10)

. For Canadian installations, 

please refer to the Canadian Installation Code (CAN/

CSA-B149.1 or 2) and/or local codes.

• For extremely cold climates or for conditions of short 

furnace cycles (i.e. set back thermostat conditions) 

the last 18 inches of vent pipe can be reduced. It is 

acceptable to reduce from 3” to 2-1/2”, 3” to 2”, or 2” to 

1-1/2” if the total vent length is at least 15 feet in length, 

and the vent length is within the parameters specified in 

Table 1

. The restriction should be counted as 3 equivalent 

feet. Smaller vent pipes are less susceptible to freezing, 

but must not be excessively restrictive. The length of the 

2 inch pipe must not be longer than 18 inches.

Figure 9. Alternate Horizontal Vent Installation

Support

NOTE: 

Vent Configuration to Provide 

12" Minimum height above Snow Level.

1/2" 
Armaflex
Insulation or
Equivalent
(if required)

12" Above

Maximum

Expected

Snow Level

19" Max.

(See Note)

Outside 

Wall

Figure 10. Vertical Vent Termination

Comb

ustion Air

Exhaust 

V

ent

12” Above Maximum

Expected Snow Level

(Both pipes)

Elbows on the combustion air 

inlet must be positioned pointing

 away from the exhaust vent.

8" Min.
36" Max.

Plumbing Vent Roof Boot

(Both Pipes)

WINTER DESIGN

TEMPERATURE

MAXIMUM FLUE PIPE LENGTH (FEET)

IN UNCONDITIONED & EXTERIOR SPACES

WITHOUT INSULATION

WITH INSULATION*

20

45

70

0

20

70

-20

10

60

*NOTE:

 Insulation thickness greater than 3/8 inch, based on an R value 

of 3.5 (ft x F x hr) / (BTU x in.)

Table 2. Vent Protection

•  If furnace is installed horiziontally, make sure the drainage 

port on the in-line drain assembly is pointed downward to 

ensure proper drainage of condensate. For *SC series, 

see 

Figure 40 (page 42)

 & 

Figure 41 (page 43)

. For 

*SD series, see 

Figure 45 (page 47)

.

• To prevent debris or creatures from entering the 

combustion system, a protective screen may be installed 

over the combustion air intake opening. The screens hole 

size must be large enough to prevent air restriction.

Existing Installations

 When an existing furnace is removed from a vent system 

serving other appliances, the existing vent system may not be 

sized properly to vent the remaining appliances (For example: 

water heater). An improperly sized venting system can result 

in the formation of condensate, leakage, or spillage. The 

existing vent system should be checked to make sure it is in 

compliance with NFGC and must be brought into compliance 

before installing the furnace.

NOTE:

 If replacing an existing furnace, it is possible you will 

encounter an existing plastic venting system that is subject 

to a Consumer Product Safety Commission recall. The pipes 

involved in the recall are High Temperature Plastic Vent 

(HTPV). 

If your venting system contains these pipes

DO 

NOT reuse this venting system!

 This recall does not apply 

to other plastic vent pipes, such as white PVC or CPVC. 

Check for details on the CPSC website or call their toll-free 

number (800) 758-3688.

Condensate Disposal

The method for disposing of condensate varies according 

to local codes. Consult your local code or authority having 

jurisdiction. Neutralizer kit is available for use with this furnace. 

Refer to the technical sales literature for part numbers. 

Please 

follow the instructions provided with the kit

.

This furnace has multiple options for positioning the vent 

pipe as described in the, Vent and Inducer Assembly Options 

section (

page 15

). Each of the condensate drain lines must 

be J-trapped using field supplied parts. After the condensate 

lines are J-trapped, they may be combined together when 

routed to the drain.