Modine Hot Dawg Garage Htr Venting

[ckartson]

I installed a garage htr several years ago and hve gotten a complaint of leakage through the venting. All others that I installed were side wall vent, This particular install was vertical through the roof. I looked at the latested install guide and see that the venting instructions now show a tee and a drip cap at the bottom of the verticle pipe. My original install was "B" vent. I don't think the IOM showed a drip T because I probably would have installed it that way 5 yrs ago when I put it in. Now that winter is here they called me and asked if I can do somthing about the leakage. In the past I/they thought it may be a roof issue so they didn't compain to me about it. I now realize that it is a condensate issue and must take care of it for them. They have been very patient about this but I know that it is my error. I do not do much install or resi work but I must make this right! I have checked with supply houses for the proper materials for this type of venting and I am having a hard time finding drip caps in the 4" size. I have seen boiler rooms that have venting with these types of caps with ball valves installed. Does any body have experience with venting these products and materials to use? Also do you simply caulk the gores?

[tinman]

Sounds to me if it's condensating, the flue gases are too cool. A hot dawg is 80% efficiant and should not condensate. I would use NCI protocols to remedy this situation.

[ckartson]

Condensing because it is in a garage with an ambient of 50 to 60 degrees. The IOM shows T installed in the bottom of the verticle. I installed a 90. Maybe they changed the IOM because of this. Any ideas on venting products that are sealed?

[OldSchoolMech]

How did you size the venting?
I have seen this before with wrong size and type of venting
The hotdawg is a small one 50,000btu

[ckartson]

Here is the page from the IOM. My install needs to be like figure B 10. I originally used Selkirk "B vent with a 90° elbow at the vertical (wrong and I admit it after readind the IOM on line) and I believe I have to change this. Specifically I am asking if anyone has worked with a venting product for this application. Modine realizes that condensing can occure because it is in a garage. They reccomend insulation with a 400°F rating. I should also ask about the insulation. Does anyone know if 1" foilbacked ductwrap is rated for this application. I am not sure of product lines that Are water tight. I think I may have to use S Steel. This is not a sizing issue, it is an expected condensate issue. I truley am not blowing off the sizing comment but this was sized per the IOM.
Thanks.

[OldSchoolMech]

Sounds like you are on the right track. Use proper configuration and insulate it. I use the tables from the TSSA codebook to size vents.

Can you please post before and after pics this will be helpful to us

[rundawg]

I emailed you a couple web sites that have both the drain tee and insulation. I'm not promoting either, just throwing them out as examples.

Also don't forget, if you have the ability to do a combustion analysis, you will be able to tell if this unit is under fired and causing some of the condensation issues you are seeing.

The service manual for these units even addresses checking to see if the unit is under fired for condensation issues.