Nortek SD Ultra Low Nox Series, Installation Instructions Manual

Page: 9 / 48

9
MATERIALS STANDARDS
Schedule 40PVC ......................................................D1785
CPVC ........................................................................D1784
PVC-DWV .................................................................D2665
SDR-21 & SDR-26 ....................................................D2241
ABS-DWV .................................................................D2661
Schedule 40 ABS .....................................................F628
Foam / Cellular Core PVC ........................................F891
*PolyPro ® by DuraVent .............................................ULC-S636
CPVC ........................................................................D1784
*When using PolyPro
®
, all venting and fittings must be from the same
manufacturer with no interchanging of other materials. Refer to specific
instructions supplied with the PolyPro vent kits
When joining PVC to PVC, use cement that conforms to
ASTM standard D2564. PVC primer must meet standard
ASTM F656. When joining ABS to ABS, use cement that
conforms to ASTM standard D2235. When joining PVC
to ABS, use cement as specified in procedure from ASTM
standard D3138
Vent Pipe Length & Diameter
In order for the furnace to operate properly, the combustion
air and vent piping must not be excessively restrictive.
• The venting system should be designed to have the
minimum number of elbows or turns.
• Transition to the final vent diameter should be done as
close to the furnace outlet as practical.
• Always use the same size or a larger pipe for combustion
air that is used for the exhaust vent.
Table 1 indicates the maximum allowable pipe length for a
furnace of known input rate, when installed with piping of
selected diameter and number of elbows. To use the table,
the furnace input rate, the centerline length and the number
of elbows on each pipe must be known.
When estimating the length of vent runs, consideration must
be made to the effect of elbows and other fittings. This is
conveniently handled using the idea of “equivalent length”.
This means the fittings are assigned a linear length that
accounts for the pressure drop they will cause. For example:
a 2” diameter, long radius elbow is worth the equivalent of
2.5 feet of linear run. A 90 degree tee is worth 7 ft.
The equivalent lenghts of tees and various elbows are listed
in
Table 1
. Measure the linear length of your vent run and
then add in the equivalent length of each fitting. The total
length, including the equivalent fitting lengths, must be less
than the maximum length specified in the table.
FURNACE
MODELS
(BTU)
FURNACE
INSTALLATION
SINGLE VENT PIPE LENGTH (FT.)
WITH 1 LONG RADIUS ELBOW†
DUAL VENT PIPE LENGTH (FT.)
WITH 1 LONG RADIUS ELBOW ON EACH PIPE†
OUTLET
2” DIAMETER
OUTLET
3” DIAMETER
INLET / OUTLET
2” DIAMETER
INLET / OUTLET
3” DIAMETER
50,000
Upflow 90 90 90 90
Horizontal 90 90 90 90
100,000
Upflow 90 90 40 90
Horizontal 90 90 40 90
†
NOTES:
1. Subtract 2.5 ft. for each additional 2 inch long radius elbow, 5 ft. for each additional 2 inch short radius elbow, 3.5 ft. for each additional 3 inch long radius elbow,
and 7 ft. for each additional 3 inch short radius elbow. Subtract 5 ft for each 2” tee and 8 ft for each 3” tee.
2. Two 45 degree elbows are equivalent to one 90 degree elbow.
3. This table applies for elevations from sea level to 2,000 ft. For higher elevations, decrease pipe lengths by 8% per 1,000 ft of altitude.
4. A long radius elbow’s centerline radius is equal to or greater than 1.5 times the vent diameter.
Table 1. Vent Pipe Lengths
Vent Pipe Installation
CAUTION:
Combustion air must not be drawn from a
corrosive atmosphere.
This furnace has been certified for installation with zero
clearance between vent piping and combustible surfaces.
However, it is good practice to allow space for convenience
in installation and service.
• In the absence of local codes, the location of any
combustion air inlet relative to any vent terminal must
be at least 8 inches. This includes installations involving
more than one furnace.
• The quality of outdoor air must also be considered. Be
sure that the combustion air intake is not located near
a source of solvent fumes or other chemicals which can
cause corrosion of the furnace combustion system. (See
page 4
for a sample list of substances).
• Route piping as direct as possible between the furnace
and the outdoors. Horizontal piping from inducer to
the flue pipe must be sloped 1/4” per foot to ensure
condensate flows towards the drain tee or PVC trap.
Longer vent runs require larger pipe diameters. Refer to
the Inducer & Venting Options section on
page 13
for
additional information.
• If a Direct Vent (2-pipe) system is used, the combustion
air intake and the vent exhaust must be located in the
same atmospheric pressure zone. This means both pipes
must exit the building through the same portion of exterior
wall or roof as shown in
Figure 26 (page 40)
.
• Piping must be mechanically supported so that its weight
does not bear on the furnace. Pipe supports must be
installed a minimum of every five feet along the vent run
to ensure no displacement after installation. Supports
may be at shorter intervals if necessary to ensure that
there are no sagging sections that can trap condensate.
It is recommended to install couplings along the vent
pipe, on either side of the exterior wall (
Figure 26
). These
couplings may be required by local code.
• If breakable connections are required in the combustion
air inlet pipe (if present) and exhaust vent piping, then
straight neoprene couplings for 2” or 3” piping with hose
clamps can be used. These couplings can be ordered
through your local furnace distributor. To install a
coupling: