DuraVent FasNSeal 8090 Installation - Manual (Page 5)

Table 3 - Annular Space- Effective Remaining B Vent Diameter
2" Cat IV Liner Dia 3" Cat IV Liner Dia 4" Cat IV Liner Dia 5" Cat IV Liner Dia
5" B Vent 4" 3" N/A N/A
6" B Vent 5" 4" 4" N/A
7" B Vent 6" 5" 5" 4"
8" B Vent 6" 6" 6" 5"
5
INSTALLATION OF LINER WITHIN B VENT
Reference Fig.3 for the components required.
Inspect the area where the Cat I exhausts
come together- typically a "Tee" or "Wye". It is
critical that when the Cat IV liner is installed,
it maintain a slope of at least 45° downward
towards the appliance (Fig.4) throughout
the vent run- This is to ensure proper flow of
condensate back to the appliance / drain. If
the inlet end of the existing (common) B vent
is a tee, either the flex for the Cat IV appliance
vent must route through the bottom end of
the tee (Fig.4a) or the tee should be replaced
with a "wye" (Fig.4b), so the flex can route
through the inclined snout of the wye (to
maintain proper slope). Do not install per
Fig.4c!
4a
Equivalent Vent Length (EVL) specified by the
appliance manufacturer. If specific guidance
is not offered by the appliance manufacturer
regarding EVL for vent components, the
general guidelines in Table 2 may be used for
PolyPro, FNS, FNS W2 and Security Chimney
Secure Seal product.
For sizing of the remaining Cat I appliance
into the B Vent, reference Table 3. This Table
shows B Vent diameter, inner Cat IV liner
diameter, and the resulting annular space in
terms of an "Equivalent" diameter. This data
takes into account flow restriction on the Cat
I flue introduced from the inner flex and has
been experimentally confirmed. Ensure this
"equivalent" diameter is appropriate for your
remaining Cat I appliance via use of Type B
Gas Vent sizing tables / NFPA54 (Chapter 13).
Treat the connector from the Cat I appliance
and the common vent as a single appliance
vent with the height, length, offsets, etc
and verify that the tables confirm adequate
capacity of this annular space before
proceeding.
After confirming the combination vent
system is appropriate for your installation,
inspect the physical condition of existing
B Vent. The B vent must be inspected for
evidence of damage, internal flue blockage,
appropriateness of components including
firestops, supports, etc. The inspection must
also ensure the original installation meets
current codes for termination location,
height, etc. Clean and repair as needed to
bring the vent system into compliance.
Figure 4
4b 4c