Crown Boiler PHNTM080 - Page 29

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Terminal Option J: Diversitech Concentric Terminal (Acceptable for Vent Options 10 & 11) - This terminal is shown in
Figure 7.16 and may be used with CPVC/PVC vent systems. See Part VII-E of this manual and the Diversitech instructions
provided with the terminal, for installation details.
Terminal Option K: DuraVent PolyPro Concentric Terminal (Acceptable for Vent Options 12, 13) - This terminal is shown
inFigure7.18andmaybeusedwithDuraVent2”or3”PolyProventsystems.UseacompatibleDuraVentroofashingand
storm collar in accordance with the DuraVent instructions for this terminal See Part VII-F of this manual and the DuraVent
instructions provided with the terminal, for installation details.
2. Vertical Vent and Air Intake Location – Observe the following clearances from roof mounted terminals:
 • Bottomofairintakeopening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.
 • ForterminaloptionH,maintainatleast12”ofverticalseparationbetweentheexhaustandintakeopeningasshownin
Figure 7.15 and 7.17.
3. Requirements for B-Vent Air Chase Options – Observe the following additional requirements when using an abandoned
B-vent chimney as an air chase as described in Options #18-21. Also refer to Figures 7.19 & 7.20.
 • Bventmustbecleanandingoodcondition.
 • UseofexpolypropyleneoutsideofB-ventchimneyisnotpermitted.
 • AlljointsandseamsintheB-ventmustbesealedwithRTV.Iftheseseamsarenotaccessible,ventoptions18-21cannot
be used while complying with the National Fuel Gas Code (as an alternative, the B-vent chimney can be used as a chase
for the vent pipe while combustion air is piped from an outside wall - see Part VII-D for additional details).
 • AllventingispolypropylenesuppliedbytheventmanufacturershowninTable7.13b.Theportionofthisventingwithin
  theB–vent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.
 • 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
  7.13bbythisequivalentlengthforeachfootofexpipeused,aswellasforeachelbowinadditiontotherst.The 
termination is not counted. If offsets (described above) are present, the equivalent length of the bends in these offsets
can also be ignored.
Example: A 100MBH model is to be installed as using Vent Option 18 as shown in Figure 7.19. The following components
are used:
Vent:
2” DuraVent Poly-Pro (Rigid) – 4ft
2” DuraVent Poly-Pro Flex – 20ft
Poly-Pro elbows – 2
DuraVent 2PPS-VFT Terminal (exhaust side)
Intake:
2” PVC – 6ft
2” PVC Sweep 90 – 3
Turn in B vent Tee
 StraightB-vent(5”orlarger)containingexvent–20ft
DuraVent 2PPS-VFT Terminal (intake side)
Vent Equivalent length – First elbow is ignored. The terminal is also ignored. From Table 7.14, the equivalent length of 2”
DuraVent Poly-Pro Flex is 2.0ft. From Table 7.1 the equivalent length of the second 90 elbow is 4.5ft. The equivalent length
of the vent system is therefore:
4 + 4.5 + (20 x 2.0) = 48.5ft.
Since Vent Option 18 shows a max vent length of 60ft, the planned vent length of OK.
Intake Equivalent length - First elbow and the turn in the B vent tee are ignored, leaving two sweep 90 elbows that must be
counted. From Table 7.1, the equivalent length of each of these elbows is 2.6ft. From Table 7.14 the equivalent length of the
 Bventcontainingexis1.0ft.Equivalentlengthoftheintakesystemistherefore:
(2 x 2.6) +6 +(20 x 1.0) = 31.2ft.
Since this is less than 60ft, the planned intake length is OK.