Crown Boiler PHNTM080 - Design Requirements Unique to Split Vent Systems

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D. Design Requirements Unique to Split Vent Systems
Table 7.21 summarizes all split vent options. Illustrations of split vent systems are shown in Figures 7.22, 7.23, and 7.24. In
addition to the requirements in Part VII-A, observe the following design requirements:
1. Permitted Terminals for Split Venting:
Rigid Vent Systems (Vent Options 25-32)–Ventterminatesinaplainend(couplingforPVC,bellendforPolypro,Polyue,
and plain end pipe for InnoFlue). Intake terminates in a PVC 90 sweep elbow pointing down. The section of Polypro,
 PolyueorInnoFlueexposedtotheoutdoorsmustbeUVresistant.
Use of a rodent screen is generally recommended for the vent termination. A rodent screen suitable for 3” PVC terminals
is supplied with the boiler and is installed under the termination coupling as shown in Figure 7.28. If 2” CPVC is used, this
 screencanbecuttotintothesmallertting.Rodentscreens(“birdguards”)forPolyPro,PolyueandInnoFlueareas 
follows:
Size/Vent System Rodent Screen (“Bird Guard”)
2” Polypro DuraVent # 2PPS-BG
3” Polypro DuraVent # 3PPS-BG
  2”Polyue   Selkirk#2PF-HVST
  3”Polyue   Selkirk#2PF-HVST
2” InnoFlue Centrotherm # IASPP02
3” InnoFlue Centrotherm # IASPP03
Flex Vent Terminals (Options 33-38)–Theexventkitsshownforoptions33-38includeventterminalsthatmustbe 
 installedinaccordancewiththeventmanufacturer’sinstructions.DifferentterminalsareusedforMasonryandB-vent 
chimney chases.
Air Intake Terminals (Vent Options 25-38) - All split venting options shown in Tables 7.21 terminate in a PVC 90 sweep
elbow pointing down. Use of a rodent screen is generally recommended for the intake termination. A rodent screen suitable
for 3” PVC terminals is supplied with the boiler and is installed under the intake termination elbow coupling as shown in
 Figure7.28.If2”CPVCisused,thisscreencanbecuttotintothesmallertting.
2. Vent Terminal Location – Observe the following clearances from roof mounted vent terminals (also see Figures 7.22, 7.23, or
7.24):
 • Bottomofterminalmustbeatleast12”abovethenormalsnowlineanticipatedontheroof.
 • Exhaustopeningmustbeatleast2ftaboveanyportionoftherooforstructurelocatedwithinhorizontallywithin10ft.
3. Horizontal Air Intake Terminal Location - Observe the following limitations on the intake terminal location (also see Figures
7.22, 7.23, or 7.24):
 • Thebottomofallterminalsmustbeatleast12”abovethenormalsnowline.Innocaseshouldtheybelessthan12”
above grade level.
 • Ifpossible,installtheintaketerminalonawallawayfromtheprevailingwind.Reliableoperationofthisboilercannot
be guaranteed if the intake terminal is subjected to winds in excess of 40 mph.
 • Airintaketerminalmustnotterminateinareasthatmightcontaincombustionaircontaminates,suchasnearswimming
pools. See WARNING on page 12.
4. Use of abandoned chimneys as a vent chase (Options 33-38)–Ventoptions33-38permitexiblepolypropyleneventing
to be routed to the roof using an abandoned masonry or B- vent chimney. In these applications combustion air is drawn
horizontally from a wall terminal. See Figure 7.23 or 7.24. When using one of these vent options, observe the following
requirements:
 • Whenamasonrychimneycontainingmultipleuesisusedasachase,ALLuesmustbeabandoned(Figure7.26).
 • MasonryorBventchimneyusedasachasemustbestructurallysound.
 • UseofexpolypropyleneoutsideofamasonryorB-ventchimneyisnotpermittedunlessallowedbythevent 
manufacturer and permitted by local codes.
 • AllventingispolypropylenesuppliedbytheventmanufacturershowninTable7.21.Theportionofthisventingwithin
  themasonryorB–ventchimneyisexible.
 • Allexpipemustbeinstalledvertically.Uptotwooffsets(fourbends)maybemadeintheverticalrunofexpipe.
Bends used to make these offsets may not exceed 45 degrees (Figure 7.25).
 • Becausetheexpipeiscorrugated,ithasahigherpressuredropthantherigidpipeusedelsewhereintheventsystem.
  EquivalentlengthsforexventingareshowninTable7.14.Reducethemaximumallowableventlengthshownin 
  Table7.21bythisequivalentlengthforeachfootofexpipeused,aswellasforeachelbowinadditiontotherst.The
  rstelbowandterminationarenotcounted.Ifoffsets(describedabove)arepresent,theequivalentlengthofthebends
in these offsets can also be ignored.