How close can pvc and PEX be to boiler flue?

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Pisti

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My understanding is 6” horizontally is required. I have a doubled wall flue so I believe this means it is a type B. Does that mean a pvc vent and PEX can be located more like 3” away? I have read but can't really verify that you can put pipe closer to type B.
 

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John Gayewski

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I believe a b vent can come in contact with combustible material. Not that it's good to do so, but I think your fine with 3". As for a precise answer you might have to take the temp of the b vent while in peak use and make a phone call to the actual manufacturer of the pipe.

PVC can't be exposed to temps at or above 140. Pex is 200 (there are different conditions that can change those numbers).
 

Fitter30

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UL 441​

Is the listing standard for type B and BW venting. It allows for a maximum rise on surface temps in the test structure of 90*F above ambient when the stabilized flue gases read 400*F above ambient for 1.5 hrs then 117*F after that. The test structure for B-vent is 3/8" plywood while BW requires 3/4". Thermocouples are placed strategically all over the box and in the vent.

Once the vent has reached equilibrium, measurements are taken at 4 circumferential points 48" off the floor inside the vent and on its outer jacket. There must be a min. 10*F temperature differential btw those readings.

If the vent is listed for a zero clearance at any point to combustibles, the outer surface of that vent cannot rise more than 90*F above ambient.
Run copper in the chase. Insulate with 1" thick fiberglass pipe covering. Have no idea what long term would do to the pex or pvc.
 
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Pisti

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What if I took sheet metal to incase the flue kind of what they did where the flue comes through the basement floor and enters the boiler?

I am also not opposed to running copper. I am confident in my skills to sweat pipe, but the copper is right against the floor joist and subfloor below. It makes me pretty nervous in those conditions.
 

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Fitter30

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What if I took sheet metal to incase the flue kind of what they did where the flue comes through the basement floor and enters the boiler?

I am also not opposed to running copper. I am confident in my skills to sweat pipe, but the copper is right against the floor joist and subfloor below. It makes me pretty nervous in those conditions.
Think that's b vent that was shorten to install that crimped end of a standard flue pipe tee. Have the holes for the pipe in take the stick of copper main floor and feed it down sweat your pipe and fitting on. Raise it back up.
 

Pisti

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I assume putting drywall would be the same as metal and a non combustable layer. In the attic I just saw it actually says Type R in several places. Unsure what this means.

Running copper would solve the Pex issue, but ideally I still have the vent from the sink below up there. Unfortunately where the floor joists are below I can't just run them through into the wall nicely.
 

Jeff H Young

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Well I cant say I know exactly but there is a 6 inch minmum clearance from a heat source with pex. I dont think that would allow sheet metal with zero clearance stuffed between a b vent and pex. drywall a 1 inch from the bvent and pex imediatly the other side of the drywall I think flys without issue. Ill leave you to confirm , althgough id like to know for sure if you find out whether sheet metal eliminates any and all clearances Id like to know
 

Fitter30

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I assume putting drywall would be the same as metal and a non combustable layer. In the attic I just saw it actually says Type R in several places. Unsure what this means.

Running copper would solve the Pex issue, but ideally I still have the vent from the sink below up there. Unfortunately where the floor joists are below I can't just run them through into the wall nicely.
Above my pay grade. Shark Bite fittings
 
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