Dura Vent question

[burgie]

Good morning folks...

Around mid-summer I installed my Big Maxx 50K natural gas heater in my shop and ran double wall Dura Vent from the heater exhaust up through the roof. I used 3 short sheet metal screws at each joint and wrapped each with 3" wide aluminum tape. The setup is pretty straightforward; elbow out the back of the unit, 24" straight run, elbow to transition to vertical, then a 60" straight run through the roof (with roof boot and rain skirt) with a cap.

A couple weekends ago I ran the natural gas lines (brand new 3/4" black pipe), everything tested good (i.e. no leaks) and it has been operational for a couple weeks now. Works awesome; no leaks from the roof, no smells, perfect job heating my 400 square foot garage/shop.

Then I noticed that embossed directional arrow on the Dura Vent...pointing in versus out. Son-of-a-b...

So...my question is this: Is my setup still OK...or do I have to tear out the exhaust and redo it?

So, I see absolutely no difference in the performance of the exhaust. I see no leaks, no flow issues, no erratic cycling of the heater, no exhaust smell, as-expected exhaust at the top of the exhaust cap and normal temperature at the exhaust. (My neighbor has nearly the same setup but with a longer horizontal run and he is seeing around 120°F surface temperature at the exhaust pipe via an IR thermometer about 12" from the exhaust port and I am seeing about the same). Yes I realize there is a reason for the directional arrow and will change the system around if necessary...but so far I see no compelling reason to change it because it seems to be working perfectly.

I'd welcome any feedback please...

Thanks much...Burgie

 

[RedBKM]

If it were a wood stove I would redo but its just a gas heater. Does it leak without the taped joints?

 

[burgie]

I really don't know...I applied the adhesive aluminum tape as an added measure of protection even before I started it up...because I did the hanging and exhaust work several months prior to the gas plumbing. I think it is fine but wanted to hear some other opinions...

 

[Jackfre]

Any condensation that takes place in the vent will drain into the end of the pipe, one joint to the next. If installed properly the moisture will shed one joint down to the next but the moisture will stay inside the flue. You may not be seeing much moisture except on cold start-up, but every system condenses some. It is called the "wet time" it is the period where the flue gases and vent are not hot enough to prevent the stack temp from being below the dew point. Proper system design will allow the vent to heat up and dry off quickly minimizing the wet time. Your problem is that the comdensation is acidic, appro 3.2Ph. Over time, any accumulation in the reversed joints will deteriorate the pipe. The system looks good as installed, but....! It's your call. It will work as installed. How long it takes the vent to rust out is anyone's guess

 

[burgie]

Jackfre...thank you for that excellent and very informative answer. I now have a better understanding of the possible risks associated with installing the exhaust in reverse. With a stainless steel interior and galvanized exterior I should be OK till spring...and then I'll change it so the components are facing the proper direction. It's only 3 pieces so it isn't difficult...just embarrassing