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Old 11-13-2007, 11:08 AM  
Hack
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Default Venting problem.

I recently moved my water heater to a more central location in the basement to try and get hot water to all places faster. It is now located next to the furnace in the basement (they share the same flue).

Now, when I turn on the furnace, I get a slight flue gas odor in the basement like the flue is not drawing. This never happened before, even when it was just the furnace using that vent flue.

One other thing changed. When we had the roof redone last year, the roofers lost the rain cap on the furnace vent flue. They replaced it with a different unit that looks to have slots on the side of a round cap rather than the bigger openings on the old unit.

Is it possible that this new flue rain cap is more restrictive than the original one?



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Old 11-13-2007, 12:17 PM  
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Could you take the flue cap off temporarily for a test?

Also you could keep a carbon monixide detector in the area to see if there is CO being dispersed into the basement.



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Old 11-13-2007, 01:16 PM  
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Could you take the flue cap off temporarily for a test?

Also you could keep a carbon monixide detector in the area to see if there is CO being dispersed into the basement.
Great idea...Thanks! I can take it off for a test, but I think I need a taller ladder. Mine is only 25'
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Old 11-13-2007, 03:14 PM  
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Great idea...Thanks! I can take it off for a test, but I think I need a taller ladder. Mine is only 25'
You can rent ladders - I think even Home Depot rents 'em.
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Old 11-13-2007, 06:34 PM  
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Hey Jeff:
The American Gas Association has a sizing chart for gas vents (or you can go to Hart and Cooley to get one). Was it always a shared vent? If it was not the backflow indicates that the furnace vent is too small to carry the water heater vent too.
If you feel that the cap is restricting the flow you can still get the one that looks like the Chinaman's hat.
Glenn

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Old 11-15-2007, 12:06 PM  
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Thanks for the resources.

I tend to believe that it is the vent cap because even when one of the two is running, I have this problem (which I didn't have before).

I'm heading out to get a Chinaman's Hat type vent today and swap it out. Only one problem...I think I need to know the PC term for that cap here in CA . I might get called out by the ACLU otherwise

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Old 11-15-2007, 12:39 PM  
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Thanks for the resources.

I tend to believe that it is the vent cap because even when one of the two is running, I have this problem (which I didn't have before).

I'm heading out to get a Chinaman's Hat type vent today and swap it out. Only one problem...I think I need to know the PC term for that cap here in CA . I might get called out by the ACLU otherwise

Just ask to see the chimney caps, then point out the one you need.
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Old 11-26-2007, 11:05 AM  
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O.K. It worked. I purchased a "high wind" rain cap which has quite a bit more opening around the sides. I got the high wind version because we do have quite a bit of wind.

After it was installed, no more smell

I also bought, and still plan to install vents up high on the basement wall as well. Installation guidelines say to do this, but I just hadn't done it yet...

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Old 11-26-2007, 12:46 PM  
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Thanks for reporting back. Your experience will help others.

And congratulations for sticking with it until you solved the problem.

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Old 12-17-2007, 11:24 AM  
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Well, I was a bit early with my celebration of success. When I went down to the basement the next day to do some work, it smelled in the basement. I could also detect the smell in the house just a bit...

So, back to the hardware store to get some more parts and change the layout of the venting to better the flow path of the flue gases.

Below are the before and after layouts of the vent piping. Before, there was a "TEE" where the water heater tapped into the flue from the furnace. When the water heater was on, flue gases would get to the "tee" and go both directions.

Now, I've re-routed both to a "TEE" up higher. This prevents backdraft of flue gases.

So far, so good



layout.jpg   layout 2.jpg  
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