checking for condensation in noncondensing boiler

John_106

if we were having internal condensation? Mine is 84% efficient.

Dave_61

My boiler needs an inlet temp of no less than 140, or condensation will occur, which would cause problems. Currently, I only have a temp gauge on the boiler outlet (will be adding one to the inlet). How can I tell if I'm getting condensation of flue gasses? There is a clear plastic tube in the direct vent flue that has a tiny amount of liquid in it. If we were getting flue gas condensation, would this tube be filling with water? How else could I check for significant condensation?

Constantin

There is a couple of ways to prevent condensation...

... one approach is to use pump logic like Buderus, where the circulator for the boiler circuit does not come on until the boiler reaches an internal temperature of 140°F or higher. TRVs can also be used to bypass the boiler until it's hot. Lastly, you can make the boiler very resistant to condensation by virtue of design like the G215, MPO, and Vitola.

I am not sure what a plastic tube ought to be doing in the flue pipe of a noncondensing boiler, but perhaps one of the professionals here can help clear that up. My educated guess as a homeowner is that this is a condensate drain for the intake air, not the flue gases.

Dave_61

No,

the tubing is definitely in the flue pipe and goes to a drain pipe.

Constantin

In that case,

wouldn't the simplest way to address your concern be to drain the flue condensate into a bucket instead of the drain and reviewing how much condensate the flue pipe produced vs. the amount of fuel you burned?

Another approach could be to measure the flue gases with a combustion analyzer and see what the temperatures are. If the flue gases are above 250°F I have been told that there is little to worry about, if the chimney has been lined properly. Since you have a DV setup, this should be even less of a concern.

Albert Huntermark

Plastic Tubing on the flue pipe.

Is there a a second pipe (air intake)? Is your exhaust pipe stainless steel? Is it a long horizontal run? Burnham PV series boilers don't have air intakes, and because their exhausts can reach over 300 degrees, a drain of clear plastic tubing about 5/8" diameter is attached to a special tee on the exhaust to drain away condensate that is generated in long runs of vent pipe.

Dave_61

I do have an air intake pipe...

both the intake and flue are stainless. The flue travels vertically about 5 feet and then horizontally about 5 feet.

Jason_15

Drain

Not sure what kind of boiler you have, but I have a similar set-up. I have a near condensing boiler 87% efficiency. it won't condense in the boiler itself, but regularly condenses in the stainless steel flue. This is intentional and not a problem. My Weil Mclain VHE is 23 years old and has no evidence of internal condensation, but that plastic drain line from the flue constantly pisses out water to my floor drain in the basement.(after going through a neutralizer)