Is there any advantage of one verses the other performance wise. I live in an area that will see winter temps as low as -5F. I have read the Concentric vents may ice up a little more. I'm good with all the requirements for vent location. 3500Sq shop building, 15' sidewall, I am siding the structure currently and I will be placing one or two bezels on the side wall for furnace provisions. Furnace will be a 120K Natural gas force air condensing.
Side wall concentric furnace vent verses separate intake and exhaust.
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Ohmthis
Well-known member
The main benefit to me is one penetration. It doesn’t get that cold here, but definitely below freezing. I’ve had no issues with the ones for my house or the ones I’ve installed. I think it’s more important to keep the pvc runs as short as possible and with the least amount of elbow fittings.
I have done both. One penetration or two doesn't really matter as the concentric might be a 5" hole versus a couple 1-1/2 or two inch holes.
What seems to matter is location to windows, air intakes, or what is in the way in the basement that often helps decide which is better.
For example, running a concentric out parallel to the floor joists is easy, but try run on 90 degrees to the joist and get through the rim joist. Often you will have to bore through the rim and the next joist in before you have room. At least in my house it would be a pain, plus others have been in. It that situation might be a lot easier to run two pipes out instead.
Also, if the home has two furnaces in the same general area you can often run two concentric side by side where if you two pipe each furnace you might have to separate the terminations by a few feet.
What seems to matter is location to windows, air intakes, or what is in the way in the basement that often helps decide which is better.
For example, running a concentric out parallel to the floor joists is easy, but try run on 90 degrees to the joist and get through the rim joist. Often you will have to bore through the rim and the next joist in before you have room. At least in my house it would be a pain, plus others have been in. It that situation might be a lot easier to run two pipes out instead.
Also, if the home has two furnaces in the same general area you can often run two concentric side by side where if you two pipe each furnace you might have to separate the terminations by a few feet.
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PoorUB, very good point on the clearance hole diameter. I looked it up and you are correct. I will be running 3" exhaust which will require a 5" hole using a Concentric vent. My bezel plates are Hardie trim 1" thick X 7.25" X 10" tall. I don't think I want to fight with a 5" carbide grit hole saw going through Hardie. It also leaves me only 1.125" material at best on the sides. Separate intake and exhausts for me. Thanks for the pointers, Ohmthis and PoorUB.
When I represented Rinnai I ended up selling about 400k units total over 30 yrs. 98% of which were concentric and there were very few problems, but that was with Rinnai’s termination. I do not know what your vent looks like so cannot speak to reliability of your termination. Being in Fargo, as I recall it snows. In extreme circumstances your vent can get buried with either single of dual pipe. Get up the wall above the 12” minimum.On clearances, a direct vent appliance <50kbtu has a 9” clearance to a door or window, typically 12” to an inside or outside corner, but in my experience you want more. Air currents around corners can pose problems. DV’s >50kbtu have a 12”clearance to a door or window.
75gmck25
Well-known member
Another consideration for using dual wall pipe is that in my experience its very expensive. I installed a Mendota fireplace that used a 5" concentric chimney that I wanted to run all the way to the roof. The Duravent DirectVent piping I used was quite expensive for a run to the top of a two story house.
This is the termination of my Rinnai fireplace. 3” pipe and that termination os about 6“ diameter right out the back of the appliance. Rinnai US, mistakenly imho, dropped the gas fireplaces which are manufactured in NZ in the crash of ‘08. Terrific product but didn’t get traction within the company. I ordered this from NZ a couple years ago and it has provided us out heat for the past couple years. QUIET, modulating burner and blower and jsut a good companion in the home.
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My exhaust will be about 7' above ground level, and the intake will be directly above at 9' above ground level. If the snow level reaches the exhaust, I need to move.
I have a Mendota natural gas fireplace with duel venting all the way up a 35' brick chimney. I have not been impressed with it so far. Ignition is hit or mis with the remote control. Currently it will not ignite anymore. Probably next month I will have to pull it out of the former wood burning fireplace to see what the problem is. For $6500 and five years old I would buy a different brand next time.
Back when I did HVAC service I went out to do start up on a 90+ furnace one of the other guys installed. I looked it over and everything looked fine, but the venting caught my eye. Like most installs he went through the wall and 90 degree up a foot or so and 90 degree out on both the intake and exhaust. In this case I asked to the installer why he did that? His answer was that is the way the manual shows it. I told him, yes, to get above snow level, but you came out of the house about ten feet off the ground! You could have came straight out with the exhaust and 90 degree down for the intake and called it good.My exhaust will be about 7' above ground level, and the intake will be directly above at 9' above ground level. If the snow level reaches the exhaust, I need to move.
Read the manual for the furnace. Generally the exhaust is directed straight out and the intake might be cut closer to the wall, straight out or angled down.
You said it was a 120K BTU. Probably 3", but pay attention to the instructions. Often you can penetrate the outside wall with 2"