46
EXAMPLE FOR
UPFLOW INSTALLATIONS.
MAY BE APPLIED TO
OTHER CONFIGURATIONS.
A12220
Fig. 41 -- Sample Inlet Air Pipe Connection for Polypropylene
Venting Systems
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
NOTICE
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 associated with Table 14. Include a 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 ter-
mination for each pipe.
2. Count the number of elbows for each pipe.
3. For each pipe, multiply the number of elbows by the equiv-
alent length for the type of elbow used. Record the equiva-
lent 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.
5. Calculate Total Equivalent Vent Length by adding the
equivalent lengths of the fittings to the lengths of the indi-
vidual 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 from Table 14 and note the
Maximum 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 fur-
nace. 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 shown in Table 14
FOR THAT SIZE FURNACE
may be
used.
Combustion Air and Vent Piping Insulation
Guidelines
NOTE
: Use closed cell, neoprene insulation or equivalent.
The vent pipe may pass through unconditioned areas. The amount
of exposed pipe allowed is shown in Table 13
.
1. Using winter design temperature (used in load calcula-
tions), find appropriate temperature for your application
and furnace model.
2. Determine the amount of total and exposed vent pipe.
3. Determine required insulation thickness for exposed pipe
length(s).
4. When combustion air inlet piping is installed above a sus-
pended ceiling, the pipe
MUST
be insulated with moisture
resistant insulation such as Armaflex or other equivalent
type of insulation.
5. Insulate combustion air inlet piping when run in warm, hu-
mid spaces.
6. Install the insulation per the insulation manufacturer’s in-
stallation instructions.
