Forced Air Inlet Code Definition Clearance ?

heathead

In the code book it refers to vent terminations must terminate at least 3 feet above any forced air inlet located within 10 feet. This Doesn't apply to direct vent appliances. I know I am over thinking this. I have a Buderus 115 Oil Direct vent that has a field controls direct vent system. FT4 Vent termination. This direct vent system has a barometric damper on the air intake pipe. Is the Buderus really a direct vent system because of the damper on the intake to the oil burner. When reading Canada venting they don't let dryer vents or anything with a damper within the 10 feet either. What is the code definition of forced air inlet? For the US. I am trying to add a natural gas direct vent Boiler on the same wall. The closer to that Buderus exhaust the better to avoid winds from a lake, but the farther from that I am thinking the more wind exposure toward the lake. I think longer vent pipe and wind exposure is better that exhaust being blown in if closer than 10 feet and coming through the damper. I can make 2 inch pipe fit the manufacture specs 90's and length, but would 3 inch which is also listed for longer lengths gain anything for winds agains the burner operation. I think the 2 inch would have more volocity and dilute better before being blow back into wall if it did happen to do that. I know the main intent is not to vent into prevailing winds. Thanks for your thought sorry for the long question.

ScottSecor

We've installed many direct vent appliances, I don't think one inspector has commented on the exhaust termination, location, vent size, vent material, etc. That being said, we follow the code and the installation manual.

I agree with your concept of trying to blow the exhaust gases with high velocity, but I would be hesitant to push the limits of the blower. In other words make sure your not 'off the chart' when it comes to vent length, that includes fittings.

With regard to vent location, your correct in being cautious. We do not see many oil fired boilers these days especially with direct vent. As a result, I cannot offer much advice (almost every home around here has a masonry chimney). However, I would do everything possible to follow the Buderus and the Field instruction manual. Hopefully someone that is more familiar with your setup will chime in.

heathead

Scott,

Thank you, for your comments. The Buderus has been there working great the last 15 years and is going to be used as a backup, if natural gas price go way past oil. I Know not very likely. I may put gas power burner in later for backup. I am adding a Viessmann Boiler. The venting will be within spec for the 2 inch, but trying to figure out if 3 inch is less load on blower with wind or will the 3 inch pipe bring more air into burner when the wind blows, will that make wind have less of an effect with to 3 inch vs the two inch.