Boiler PVC venting through interior wall

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Old 06-20-17, 10:07 PM
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Boiler PVC venting through interior wall

I'm doing some remodeling to a home and have an opportunity to run some pipes from basement to attic. I know we'll need a new boiler heating system in the future, and I'd like to run the intake and exhaust pipes now while the walls are open. Rather than having pipes sticking out the side of my house through the bandjoist, I can have them go up through my roof, which I think is much neater.

However, I can't seem to find any codes or even mention in some of the install instructions for high efficiency boilers, of routing the pipes through interior walls. They only mention pipe size and distance.

So, is there any problem with running 2" or 3" pvc boiler intake and exhaust pipes up through interior walls to the roof? Obviously pressure testing for leaks would be important. I don't think any heat shielding would be needed since exhaust gas heat is regulated at the boiler to be safe for pvc.

Thanks!
 
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Old 06-20-17, 10:51 PM
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Reading some Weil McClain and Triangle Tube install instructions they do mentioned 3/16" and 1/4" clearances to combustible materials, respectively. The Triangle Tube instructions indicate a galvanized thimble be used at penetrations.

In practice all the boilers I've seen in my area have simple holes through the bandjoist and typically 2" pvc pipe. I don't think I've ever observed any effort to keep a clearance from the wood. It doest seem a bit silly to think the wood would somehow combust as the melting temp of pvc is lower than the ignition temperature of wood.

So I've got a couple scraps of information but the manuals simply don't describe pipes running inside of finished walls. I'd like to know if they are worried about the chase being insulated...
 
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Old 06-25-17, 08:41 AM
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Anyone??

I read through another installation manual of a boiler I'd likely buy and it mentioned a 1" exhaust pipe clearance from combustibles. It further said cpvc should be used if installed in a closet or alcove. I suppose they want the higher temp pipe in places where it can't 'breath', but 2 and 3" cpvc is almost unheard of and incredibly expensive to order.

Another installation manual indicated that 3" exhaust was safer in various installations than 2", which makes sense because 3" would have a lot more surface area to sink and expel heat.

Besides a roof or wall termination kit, I haven't seen any mention of running the pipes coaxially. For example, a 2" exhaust pipe inside a 4" intake pipe.
 
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Old 06-25-17, 06:13 PM
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The pipe must be CPVC pipe and if there are joints there must be an inspection door to inspect pipe joint in the future.
 
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Old 06-25-17, 08:39 PM
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Are you citing code in your area, or a specific manufacturer's install instructions? Personal preference?
 
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Old 06-26-17, 03:51 PM
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National Fuel Gas Code. Call your codes inspector and ask him. After all he will be the one inspecting the job when completed. He would have last say at the local level, although you need to honor the more stringent code.
 
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Old 06-26-17, 10:42 PM
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Can you be more specific so I can read it myself? I checked NFPA 54 and it frequently indicated "according to the appliance manufacturer's instructions". I didn't see anything that indicated stringent guidelines for plastic pipe venting material and clearances.

I've read the instructions for several manufacturers now and they're pretty fuzzy on running the pipes in enclosed spaces.
 
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Old 06-30-17, 07:30 AM
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You can read the codes or mfr's manuals until you're blue in the face but it's how the inspector interprets the code that makes all the difference. Many mfrs don't even allow PVC for venting, only for combustion inlet air.
 
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