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935SB: Installation, Start-up, Operating and Service Maintenance Instructions
The tee may also be connected to the intake air pipe on the side of the
casing (see
Fig.
52).
In any configuration, it will be necessary to add the equivalent length of
the tee (15 feet/5 M) to the Total Equivalent Vent Length of the venting
system.
!
ADDITIONAL INFORMATION FOR POLYPROPYLENE
VENTING SYSTEMS
Polypropylene venting systems include flexible vent pipe. These
flexible vent pipes have a different equivalent vent length than straight
sections of PVC/ABS DWV vent pipe. Be sure to make the appropriate
deductions from the Maximum Equivalent Vent Length (MEVL), or
additions to the Total Equivalent Vent Length (TEVL), when applying
flexible vent pipes in polypropylene venting systems. See the
polypropylene vent system manufacturer's installation instructions for
details.
When using metric-sized venting systems, use these equivalencies for
obtaining the proper MEVL from the Tables:
Use 2" Vent Tables for 60 mm (o.d.) vent systems
Use 3" Vent Tables for 80 mm (o.d.) vent systems
Use 4" Vent Tables for 100 mm (o.d.) vent systems
The measured length of pipe used in a single or 2-pipe termination is
included in the total vent length. Include deductions from the Maximum
Equivalent Vent Length (MEVL) contained in the Venting Tables for
elbows and flexible vent pipe. Factory accessory concentric vent
terminations or pipe lengths and elbows used for "standard" vent
terminations do not require a deduction from the Maximum Equivalent
Vent Length. See vent termination figures
deduction for a Tee when used for Alberta and Saskatchewan
terminations.
NOTE: Polypropylene venting systems MAY require additional
deductions from the MEVL, or additions to the TEVL, for vent
terminations and flexible pipe sections. See the polypropylene venting
system manufacturer's instructions for details on equivalent lengths of
vent terminations and flexible vent pipes, and for calculating total vent
lengths.
To calculate the Total Equivalent Vent Length (TEVL) of the venting
system:
1. Measure the individual distance from the furnace to the termination
for each pipe.
2. Count the number of elbows for each pipe.
3. For each pipe, multiply the number of elbows by the equivalent
length for the type of elbow used. Record the equivalent length of
all the elbows for each pipe.
4. If a Tee is used on the termination (Alberta and Saskatchewan,
when required) record the equivalent length of the Tee used.
NOTE: Only connect combustion air inlet moisture drain downstream
of the furnace trap assembly as shown.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
NOTICE
(Table
16). Include a
Fig. 52 – Recommended Combustion Air Inlet Moisture Trap
5. Calculate Total Equivalent Vent Length by adding the equivalent
lengths of the fittings to the lengths of the individual vent and
combustion air pipes.
6. When using polypropylene venting systems with flexible vent
pipes, perform adjustments for the equivalent length of the flexible
vent pipe to the calculated total equivalent venting system length.
See the polypropylene vent system manufacturer's instructions for
details.
7. Select a diameter of vent pipe
Equivalent Vent Length (MEVL) shown for that application for that
specific furnace input size. Compare the Total Equivalent Vent
Length (TEVL) to the MEVL:
8. If the Total Equivalent Vent Length is shorter than the Maximum
Equivalent Vent Length for the diameter of pipe chosen, then that
diameter of pipe selected may be used.
9. If the Total Vent Length is longer than the Maximum Equivalent
Vent Length for the diameter of pipe chosen, that diameter pipe
MAY NOT be used for venting the furnace. Try the next larger
.
diameter pipe
NOTE: If the calculated Total Equivalent Vent Lengths results in
different diameter pipes for the vent and combustion air, select the larger
diameter for both pipes.
NOTE: If the Maximum Vent Length for diameter of the pipe selected is
longer than the measured length and the equivalent length of all the
fittings and terminations (TEVL), recalculate Total Equivalent Vent
Length using the next smaller diameter. If the Maximum Equivalent
Vent Length is still longer than the longer TEVL of the vent pipe or
combustion air pipe, then that diameter of pipe selected may be used.
When installing vent systems pipe lengths of 10 ft. (3 M) or less, use the
smallest allowable pipe diameter. Using a pipe size greater than required
for short venting systems may result in loss of efficiency, incomplete
combustion, flame disturbance, or flame sense lockout.
For vent systems longer than 10 ft. (3 M), any larger diameter vent pipe
(Table
16) FOR THAT SIZE FURNACE may be used.
A200089
36
A170122a
(Table
16) and note the Maximum
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