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allowable v entlength. R eturning t oourexample,
we consultTable5 anddetermine that for an
80,000Btu/hfurnacethemaximum ventlength
for2"diameter p iping is 60feetor for3"diameter
pipingis 150feet.Notethatthe maximum vent
length giveninTable 5 includes onelongradius
elbow.Therefore, forourexample, wehave three
additional longradius elbows forwhich wemust
add to our piping.Eachlong radiuselbowis
equivalent to 2.5feet,so wemustadd7.5feet
toourventlength. Therefore, theequivalent vent
length forourinstallation i s47.5feet.We compare
thiswiththe maximum ventlengthfor2"and3"
diameter p iping. F orbothcases,ourequivalent
ventlength is lessthanthe maximum allowable
ventlength, s o forour"one-pipe" installation w e
canuseeither2"or 3"diameter p iping.
Condensing f urnace combustion p roducts have
very littlebuoyancy, so Table5 is to be used
withoutconsideration o f anyvertical r isein the
piping.
NOTE: Alwaysuse the sameor largersize
pipingfor combustion air as is used for the
exhaust v ent.
Pipingmustbemechanically supported sothat
itsweightdoesnotbearon the furnace.Sup-
portsmustbe at intervals no greaterthanfive
feet, andat smallerintervalsif necessary to
ensurethat there are no saggingsectionsto
trapwater.(SeeFigure 16.)It is recommended
toinstall c ouplings a longtheventpipe,oneither
sideof the exterior w all.Thesecouplings may
berequired by local c ode.
Figure 18illustrates v ent a ndcombustion a irpipe
sizesexiting thefurnace. T ransition t othecorrect
pipesizemustbedonecloseto thefurnaceso
thatthefulllengthofpipeis of proper size.
Straight n eoprene couplings aresupplied with
the downfiow furnacesonly. Thesecouplings
areto be installed in thecombustion airinlet(if
present) a ndexhaust v entpipingatthefurnace
asshownin Figures 16. Foran upfiow furnace
installation, ifbreakable c onnections arerequired
inthecombustion a irinlet(ifpresent) a ndexhaust
ventpiping, t henstraight n eoprene c ouplings for
2" or 3"pipingwith hoseclampscan be used.
Thesecouplings can be orderedthrough your
localfurnace distributor.
Vent Pipe installation
Pipe Routing and Support
Route piping as directly
as possible between
the furnace
and the outdoors
and remember
that routing affects pipe size requirements
per
the preceding
section.
If a two pipe system is
used, locate the combustion
air intake and the
vent exhaust in the same atmospheric
pressure
zone - i.e. both must exit the building though the
same portion of exterior wall or roof (See Figure
22). Vent piping must be sloped upwards not
less than 1/4" per foot in the direction from the
furnace to the terminal.
This is to ensure that
any condensate flows back to the furnace (where
it can be disposed of through the condensate
disposal system).
The quality of outdoor air must also be consid-
ered. 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.
CAUTION:
Combustion
air must not be drawn
from a corrosive atmosphere.
To install a coupling, slide the rubber coupling
over the end of the pipe that is attached to the
furnace and secure it with one of the hose clamps.
Then slide the other end of the rubber coupling
onto the other pipe from the vent and secure the
coupling with the second hose clamp. Ensure that
the connection
is tight and leak free.
NORDYNE condensing furnaces have been certi-
fied 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.
Location of Outdoor
Terminations
Horizontal
Venting
Vent and combustion
air intake terminations
must be as shown in Figure 19 and 20. Vent
termination
clearances shall be consistent with
the National Fuel Gas Code, ANSI 2223.1/NFPA
54 and/or the CSA B149.1,
Natural Gas and
Propane Installation Code.
All minimum
clearances
specified
must
be
maintained
to protect building materials
from
degradation
by flue gases.
20
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