Burnham K2WTC - Design Requirements Unique to Split Vent Systems

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Table 7.21 summarizes all split vent options. Illustrations of split vent systems are shown in Figures 7.22, 7.23, 7.24a and 7.25a.
In addition to the requirements in Section VII - A, observe the following design requirements:
1. Permitted Terminals for Split Venting:
Rigid Vent Systems (Vent Options 11-14)–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 rodent screens (not supplied) is generally recommended for both terminations. These can be fabricated from 2 x 2
(1/2” mesh) stainless steel screen. Rodent screens and are installed as shown in Figure 7.28. Rodent screens are installed as
 showninFigure7.28.Rodentscreens(“birdguards”)forPolyPro,PolyueandInnoFlueareasfollows:
Size/Vent System Rodent Screen (“Bird Guard”)
3” PolyPro DuraVent # 3PPS-BG
  3”Polyue   Selkirk#3PF-HVST
3” InnoFlue Centrotherm # IASPP03
Flex Vent Terminals (Options 15-18)–Theexventkitsshownforoptions15-18includeventterminalsthatmustbe 
installed in accordance with the vent manufacturer’s instructions. In some cases, different terminals are used for Masonry and
B-vent chimney chases.
Air Intake Terminals (Vent Options 11-18) - All split venting options shown in Tables 7.21 terminate in a PVC 90 sweep
elbow pointing down. Use of rodent screens (not supplied) is generally recommended for both terminations. These can be
fabricated from 2 x 2 (1/2” mesh) stainless steel screen. Rodent screens and are installed as shown in Figure 7.28.
2. Vent Terminal Location – Observe the following clearances from roof mounted vent terminals (also see Figures 7.22, 7.23,
7.24a or 7.25a):
• 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, 7.23,7.24a, and 7.25a):
• 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 13.
4. UseofabandonedchimneysasaVentChaseforexiblePolypropyleneVenting(Options15-17) – Vent options 15-17 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 7.24a. 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7.24b).
• Masonry or B vent chimney used as a chase must be structurally sound and in good repair.
 • 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 7.24b).
 • 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.
VII. Venting D. Design Requirements Unique to Split Vent Systems (continued)
D. Design Requirements Unique to Split Vent Systems