Burnham K2WTC - Page 20

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107774-01 - 9/17
VII. Venting A. Vent System Design (continued)
8. Supporting Pipe - Vertical and horizontal sections of pipe must be properly supported. Maximum support spacing is as
follows:
• Support CPVC/PVC horizontally and vertically every 4 feet.
• Support DuraVent PolyPro horizontally near the female end of each straight section of pipe and vertically every 10 feet.
• Support Centrotherm InnoFlue horizontally every 39 inches with additional supports at elbows and vertically every 78”.
• Support3”Polyuehorizontallyevery39”.Supportverticalrunsof3”Polyueevery16ft.
• Support DuraVent FasNSeal horizontally every 6ft or less. Support vertical runs at the base and every 12ft or less.
Les instructions d´installation du système d´évacuation doivent préciser que les sections horizontales doivent être
 supportéespourprévenirleéchissement.Lesméthodesetlesintervallesdesupportdoiventêtrespéciés.Les
instructions divent aussi indiquer les renseignements suivants:
• les chaudières de catégories II et IV doivent être installées de façon à empêcher l´accumulation de condensat: et
• si nécessaire, les chaudières de catégories II et IV doivent être pourvues de dispositifs d´évacuation du condensat.
9. Allowing for Thermal Expansion -
• For CPVC/PVC pipe design, the vent system shall allow 3/8” of thermal expansion for every 10ft of CPVC/PVC pipe.
The boiler will always act as an anchor to one end of the vent system. If at all possible, select and install hangers and
wall thimbles so that the vent system can expand towards the terminal. When a straight run of pipe exceeds 20ft and
must be restrained at both ends, an offset or expansion loop must be provided (Figures 7.3a, 7.3b). When a straight
horizontal run of pipe exceeds 20ft and is restrained at one end with an elbow at the other, avoid putting a hanger or
guidelessthan“Y”inchesfromtheelbowintheadjoiningstraightsection(Figure7.3c).Thermalexpansionttings 
are not permitted.
• Whenproperlyassembled,expansionofPolyPro,PolyueandInnoFlueventsystemsisaccommodatedatthejoints.See
Section VII - F, G & H of this manual for details.
• Stainless steel vent systems must be free to expand and contract in accordance with manufacturer’s installation
instructions.
10. Running PVC Vent Pipe Inside Enclosures and Through Walls - PVC vent pipe must be installed in a manner that permits
adequate air circulation around the outside of the pipe:
• Do not enclose PVC venting - Use CPVC in enclosed spaces, even if PVC is installed upstream.
• PVC venting may not be used to penetrate combustible or non-combustible walls unless all of the following conditions
are met:
a. The wall penetration is at least 66 inches from the boiler as measured along the vent.
b. The wall is 12” thick or less
c. An airspace of at least that shown in Figure 7.4 is maintained around the OD of the vent.
If any of these conditions cannot be met, use CPVC for the wall penetration.
11. Vent Manufacturer’s Instructions – The vent system manufacturer may have additional vent system design requirements.
Readandfollowtheventmanufacturer’sinstructionsinadditiontothoseshownhere.Whereaconictarisesbetweenthe
two sets of instructions, the more restrictive requirements shall govern.