Sidewall Vent below modcon boiler?

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Jadnashua

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Is that boiler a closed combustion device, i.e., have an air intake as well? If so, you probably don't want it there. The instruction manual will have the appropriate restrictions. Since a vent may not seal perfectly, even though it is an exit, there are restrictions on potential co intake.

Modcons don't like intake air with stuff like potentially chlorine, lint, or other chemicals in it, either. Those could be coming out of the vent. Again, your best thing is the installation manual and potentially, the local inspector's office, but they usually go by the restrictions in the installation manual.
 
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Jadnashua

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All of the guides I've read, show diagrams of the minimum clearances required to things like overhangs, windows, doors, walkways, and other vents. If you are adhering to those, then you should not have problems. When I had my mod-con installed, where it was the easiest to run the vent lines would have been within a few feet of two dryer vents and another heater's exhaust, so I had to run it out the opposite wall of the house. Still within the limits of length, but much more of a pain.
 

Splashoil

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All of the guides I've read, show diagrams of the minimum clearances required to things like overhangs, windows, doors, walkways, and other vents. If you are adhering to those, then you should not have problems. When I had my mod-con installed, where it was the easiest to run the vent lines would have been within a few feet of two dryer vents and another heater's exhaust, so I had to run it out the opposite wall of the house. Still within the limits of length, but much more of a pain.

The exhaust and combustion air are intended to return the condensate to the boiler. There is a drain assembly to receive it.
My TT can make as much as a gallon of acidic condensate per day. Imagine the potential damage 180 plus gallons/year could cause to your foundation and landscaping. Read the Manual again.
 

Splashoil

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Found my Vent Supplement. I used 3” and the maximum length is given as 100’ deduct 3’ per 45 and 5’ for 90. Long sweep Ells. Vent system must be sloped toward boiler. I went through the roof with 3” using a concentric coaxial termination. Just used shot offsets above boiler. Slope is .63 inch/per foot toward boiler.
2” is 55’ max did not want to bottleneck the venting.
 

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Also see termination details: Exhaust must terminate vertical. Going below the boiler would fill the pipe with condensate in the trap created.
 
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