Installation & Operation Manual
5 Vertical direct venting (continued)
Alternate vertical concentric venting
This appliance may be installed with a concentric vent arrangement where the vent pipe is routed through an existing unused venting system; or by using the existing unused venting system as a chase for vent and combustion air routing.
Concentric Venting Arrangement
The venting is to be vertical through the roof. The annular space between the O.D. of the vent pipe and the I.D. of the existing unused venting system is utilized for the combustion air source.
Figure 5-8 Concentric Vent Example 1
FLUE EXHAUST
SEAL
COMBUSTION AIR
AIR INLET
W/ SCREEN
The minimum size of the existing vent system required to achieve enough annular space for combustion air can be found in Table 5A below.
The upper and lower termination as well as any other unsealed joints in the existing vent system must be sealed to ensure that all combustion air is drawn from under the vent cap as shown in FIG.’s
Approved venting materials must be used as specified in Table 3D on page 19.
12”
MIN.
SEALED
CAP 
FLUE OUTLET 
EXISTING SEAL
Follow all vent / air termination and clearance requirements per this section to the appropriate example. Installation must comply with local requirements and with the National Fuel Gas Code.
*For concept illustration only. Individual installations
may vary due to job site specific equipment.
Figure 5-9 Concentric Vent Example 2
The maximum allowable equivalent vent and air intake lengths for this venting arrangement are to be determined from the General Venting Section.
If an existing unused venting system is converted for use with this method of concentric venting, the installer must ensure that the existing venting system is clean and free from particulate contamination that will harm this appliance and cause increased nuisance calls or maintenance. See Table 1A
SEAL
AIR INLET W/ SCREEN
FLUE EXHAUST
COMBUSTION AIR
on page 10 for a list of corrosive contaminants and sources.
Two example scenarios of a concentric venting arrangement are shown for illustrative purposes in FIG.’s
Table 5A Alternate Vertical Concentric Vent / Chase Sizes
Model | Vent / Air | Minimum Existing | |
Inlet Size | Vent / Chase Size | ||
| |||
51 - 106 | 2" | 4" | |
151 - 211 | 3" | 5" |
SEAL 
FLUE OUTLET 
SEAL EXISTING
SEALED
CAP
*For concept illustration only. Individual installations may
vary due to job site specific equipment.
33 
