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Fresh air vents question


randyb
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I had the problem with "moisture in basement ceiling from fresh air vents"

and remedied this problem by replacing the vent tubing and sealing up a good size hole that wasn't caulked in the 6" plenum vent at the rim joist side.

I've gone on to rip everything out of my basement because it didn't look good. This picture below is about 15 minutes after I pulled the insulation and removed the wood frame, ice dam in the corner after about 15 minutes.

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Anyway, i have installed 2" blue xps on the walls and 1.5"on top of the blocks. I'm still currently working on putting it in all in the rim joists as well. I'm using great stuff to seal up around all of my utilities (which were not done) sealing up around the treated wood that have 1/4" gaps between the masonary brick, you could actually see outside. Yep getting it sealed tight!

Direct vent furnace

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So, now I notice that on my 4" fresh air vent for the gas hot water heater (that's about 7" off the floor in a 5 gallon bucket) is getting

ice sickles outside on the vent itself.

The 4" is right next to the 6" vent for the plenum.

4' vent on the left and the plenum vent on the right.

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I tied some small plastic strips on both vents and kicked on the furnace.

Both plastic strips are being sucked into the 6" vent, so the air in the 4" tube is being sucked out of the house and back into the 6 inch vent. I placed a piece of wood between the two vents and sure enough the 4" vent plastic just dropped to a neutral hanging postion.

Is this normal?

When the furnace kicks on should air come in the 4" vent as well, or would there be a neutral pressure?

Just this weekend we also noticed on the gas cloths dryer, the cloths have a bit a smell to them. I'm guessing that when the furnace kicks on

it back drafts that a bit. When the drier is off and the furnace is on, the dryer vent is shut good and tight.

Any thoughts?

Thanks,

Randy

We have two carbon monoxide detectors and both have 0 peak readings.

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a quick update..

I've got the furnace turned down so it doesn't kick on.

Drying some cloths right now and decided to check the 4" vent.

It appears to work properly...when the dryer is running fresh air is

being sucked in from outside.

In a bit I'm going to kick up the furnace and check the cloths dryer vent

to see if it's actuall getting closed by the furnace suction.

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I had the problem with "moisture in basement ceiling from fresh air vents"

and remedied this problem by replacing the vent tubing and sealing up a good size hole that wasn't caulked in the 6" plenum vent at the rim joist side.

I'm sorry, I can't make heads or tails of what you just wrote here. First, tell us what you are describing when you say "fresh air vents" in your first sentence and tell us what kind of moisture problem you'd experienced.
I've gone on to rip everything out of my basement because it didn't look good. This picture below is about 15 minutes after I pulled the insulation and removed the wood frame, ice dam in the corner after about 15 minutes.
Ice dam? Do you mean some frost accumulating on the cold concrete because the soil outide that wall is frozen solid and the wall has dropped to freezing? That would be normal in a completely sealed space with no way for moisture to escape and a wall that's 32°F or lower; but I guess you know that and you're only trying to show us that frost is accumulating on the wall.

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So, now I notice that on my 4" fresh air vent for the gas hot water heater (that's about 7" off the floor in a 5 gallon bucket) is getting ice sickles outside on the vent itself.

You just lost me again. What's 7inches off the floor in a five gallon bucket? The water heater? The fresh air vent? Where is this bucket; inside or outside? If outside, don't you mean 7inches off the "ground". Are you now describing a fresh air combustion air vent - meaning that you've got an ordinary gravity vent type of water heater in that space with air pair of combustion air ducts coming into that area?

The 4" is right next to the 6" vent for the plenum.

4' vent on the left and the plenum vent on the right.

Again, very confusing explanation. Is this a 4-inch exhaust or fresh air intake vent next to a a 6-inch exhaust or 6-inch intake vent? When you say "for the plenum" are you talking about a vent that dumps fresh air into the warm air system when an exhaust system comes on to remove moisture-laden air from the house?

If you are talking about a Category IV (direct vent) furnace and Category IV water heater, then you need to be explicit about whether you are describing intake vents or exhaust vents and where they are located, if you expect us to be able to understand correctly what you are describing. Also, if you have a system that uses fresh air pulled into the heated air supply to periodically replace the air in your house; and that's the "plenum" vent you are talking about, you need to more carefully desribe that system to us.

So far, it sounds like you've disconnected a fresh air intake system from the house's return air system - which is going to play hell with indoor humidity. Which vents? Furnace intake vents? Furnace exhaust vents? I see what look like fresh air intake vents of the type one normally sees connected to a pair of ducts that provide combustion air to a space containing gas appliances - one usually ending within a foot of the ceiling and the other within a foot of the floor.

I tied some small plastic strips on both vents and kicked on the furnace.

Both plastic strips are being sucked into the 6" vent, so the air in the 4" tube is being sucked out of the house and back into the 6 inch vent.

I still can't figure out what you're saying because I don't know what each of these "vents" does.
I placed a piece of wood between the two vents and sure enough the 4" vent plastic just dropped to a neutral hanging postion.
If the 6-inch "vent" is a fresh air intake and the 4-inch "vent" is an exhaust outlet, this would be very bad; however, based on the descriptions above I can't even guess what you're saying here.
Is this normal?

When the furnace kicks on should air come in the 4" vent as well, or would there be a neutral pressure?

Can't say until I can understand what it is you've described.
Just this weekend we also noticed on the gas cloths dryer, the cloths have a bit a smell to them. I'm guessing that when the furnace kicks on it back drafts that a bit. When the drier is off and the furnace is on, the dryer vent is shut good and tight.

Any thoughts?

First you said that you had a direct vent furnace but a direct vent furnace gets all of it's combustion air from outside. There is no way that a properly installed direct vent furnace can cause a dryer to backdraft because it's not getting it's combustion air from inside. The same goes for a water heater if it's a direct vent type.

If the water heater is a conventional type with a gravity vent, having a clothes dryer in the same air space as the water heater is dangerous because whenever the dryer kicks on it will depressurize the space around it and cause the water heater to backdraft to the dryer. When you shut the dryer off, the water heater may continue to backdraft into that space if the draft from it's own exhaust vent isn't strong enough.

The only way that the direct vent furnace can cause the dryer to backdraft is if you've got a cold air return intake in close proximity to that dryer. In that case, when the blower in the air handler comes on, the return air intake will depressurize the area around it and cause the pilot (if there is one) or the dryer burner to backdraft if the suction from that fresh air intake exceeds the suction caused by the dryer intake. Also, if there is a cold air return in that basement and you've got a gravity vent type of water heater, and you haven't provided sufficient outside air, every time the furnace air handler kicks on and depressurizes that basement the return air will cause the water heater to backdraft into that basement.

As for the dryer, it sound like you might have a clogged, or nearly completely clogged, exhaust duct on that dryer and exhaust from the dryer is backing up into the drum. In other words, you've got a lint fire waiting to happen and you might be starving the water heater for oxygen. A backdrafting water heater caused by a dryer in close proximity, combined with a clogged dryer vent, would explain a lot of excess humidity in the basement.

Clean the dryer exhaust duct all the way to terminus and eliminate any corrugated flexible ducting or connectors. Make sure that the joints are taped and sealed but don't use any screws at the joints. If the dryer is within close proximity (10ft.) of that water heater (if it's a gravity vent type water heater) - move it much further away and get plenty of fresh air from outside into that basement, or build a room around that furnace and water heater with fresh air into it from outside and seal tha room off from the rest of the basement and especially away from that clothes dryer and any other fan sources in the basement.

That's all I could make heads or tails of. Until you do a better job of describing what you've got, we're all left wondering what the hell you're talking about.

ONE TEAM - ONE FIGHT!!!

Mike

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6 inch connected to return air duct is fresh air

4 inch duct terminates beside water heater as combustion air (into a bucket to diffuse cold air across the floor) some use a U shape made of 4 inch elbows

Furnace PVC does not terminate under the metal hoods.

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Hi Randy,

Here's what my decoder ring is telling me.

Expect more frost

Your flags are not telling you anything

Your furnace has nothing to do with the 4" 'vent'

Your clothes dryer has nothing to do with your furnace

Run this test

Remove the 5 gal pail and hold a paper towel under the 4" 'vent', under the following conditions:

House static-no fans running that includes the kitchen hood and water heater.

Dryer on

Dryer on and kitchen hood

Get back to us with the result

But not so fast, I need you to come back with words like combustion air, fresh air and hoods. And where exactly are the icicles (picture).

Am I giving you a hard time, you bet cuz you need to understand the mechanics of what's happening.

Unfortunately, I won't hand you a fish but I'll be glad to give you a fishing pole.

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