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Vent Termination

mccaslin15 Member Posts: 17
I am installing a concentric vent for a condensing boiler and I noticed there is no screen on the vent. It seems to me that there should be something there to prevent birds or whatever from getting in there and blocking the exhaust. Is it normal for there to be no screen? If I need one, where could I get one or what could I make one from?



  • 4Johnpipe
    4Johnpipe Member Posts: 479
    Check with the manufacturer of the vent kit. I have never used one without a screen of some sort. It may have been packaged without one accidently.
    Considerate People, Considerate Service, Consider It Done!
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  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    I have never seen a screen on concentric exhausts, only intakes.
  • JStar
    JStar Member Posts: 2,752
    Around here, the screens must have wasp pheromone infused in them because every year we're scraping away their nests from the combustion piping. The screens also make a nice base for birds' nests. In other words, we don't install screens on our piping. I find that little critters don't like the smooth surface of the pipe, so they tend to stay away.
  • mccaslin15
    mccaslin15 Member Posts: 17
    Thanks for the comments everyone.

    I had my inspection with the town and they want me to have a screen on both the intake and the exhaust. I guess they have had problems with mice getting in the intake piping and making nests over the winter. The boiler manufacturer did include screens for 2 inch piping which I found out can fit on the exhaust of my concentric vent, but I'm not sure what to do for the intake screen. Should I make something from chicken wire or hardware cloth or is there a product which is made for this?

    Thanks again

  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    Wow, I would get documentation from the mfr before putting a screen on the exhaust, Luke. If they say no then it's no to the inspector. Accident waiting to happen.
  • mccaslin15
    mccaslin15 Member Posts: 17
    The attached picture from the installation manual does show a screen on the exhaust vent. The picture does not show a concentric vent, but I don't think that would change much about the effect of the screen. Please let me know if you disagree as I obviously want to push back if this isn't the right thing to do.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    Hmm. Ok. I would think in freezing regions there would be a frost/ice issue, eventually blocking the term.
  • mccaslin15
    mccaslin15 Member Posts: 17
    Yeah that's a good comment. This discussion has made me pretty nervous about having a screen. I'll have another discussion with the inspector. I will also be sure to monitor it whether or not I put the screen in and add a couple extra carbon monoxide detectors.

    You mentioned that you have seen screens on the intake. Is there a product made specifically for that or were they just some kind of wire mesh?
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    edited September 2014
    Yes, it's a scary thought to have any obstruction on the exhaust side. You want that stuff the hell out and gone with no obstacles. IMHO of course.

    I do mainly sidewall flat concentrics or roof concentrics so I have a pile of OEM screens at the shop. They are sized to fit inside the hub of a PVC fitting. 2, 3 and 4". The screens are heavy mesh, about 3/8 plus spacing, possibly stainless. Friction fit.

    Having said that, I am using a dryer hood with the flap removed and the plastic lint screen attached on my own house for the intake, then it transitions to schedule 40 PVC to boiler. I am venting the exhaust up thru the old chimney with Polypro flex. Reason is that the terms have to be in the front of the house and the wife doesn't want to see steam coming out there. I think it's cool but....;)
  • Spence
    Spence Member Posts: 316
    A few words from a former code official:

    Fuel burning appliances of an AFUE of 90% or more, commonly known as condensing furnaces or boilers, are Category IV appliances. These units shall be vented, whether Direct Vent or Non-direct Vent, in strict accordance with the manufacturers installation instructions. It is flat-out a life safety issue. In the case of a deviation from the IOM resulting in a tragedy, the installer has no legally defensible position.

    Mr. Inspector, please be considerate enough to read the code you are attempting to enforce, especially when the code is designed to prevent more innocent people from becoming a horrible statistic.