# Please help with high-efficiency furnace

**URL:** <https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081>\
**Category:** Inspecting HVAC Systems\
**Created:** [August 7, 2007, 1:31am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081 "2007-08-07T01:31:18Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![mmorgan](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@mmorgan](https://forum.nachi.org/u/mmorgan)\
**Post date:** [August 7, 2007, 1:31am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081/1 "2007-08-07T01:31:18Z")

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This is a Trane furnace.

Please take a look at the picture. On the left side of the top picture you can see the large PVC pipes. My understanding is the one is to intake combustion air and the other is to exhaust combustion gases. In the second picture you can see that the two pipes tie together just before they exit through the roof. On the roof, there is simply an open pvc pipe that will allow rain water in. This just doesn’t seem right to me. Am I missing something?

Thanks!!!

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**Author:** ![kbraun](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/kbraun/32/57038_2.png) [@kbraun](https://forum.nachi.org/u/kbraun)\
**Post date:** [August 7, 2007, 1:39am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081/2 "2007-08-07T01:39:10Z")

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In short, it appears that the intake/ exhaust terminate at a “concentric vent” kit. Any moisture should drain out through the condensate drain.

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**Author:** ![mthomas2](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@mthomas2](https://forum.nachi.org/u/mthomas2)\
**Post date:** [August 7, 2007, 2:12am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081/3 "2007-08-07T02:12:28Z")

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Typical concentric vent installation instructions:

[http://www.htproducts.com/literature/lp-166.pdf](http://www.htproducts.com/literature/lp-166.pdf)

> **[N2\_4u799.pdf](https://johnsonsupply.com/york2001/PUB/65075/OUT/N2_4u799.pdf)**
>
> 77.63 KB

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**Author:** ![dandersen](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dandersen/32/59398_2.png) [@dandersen](https://forum.nachi.org/u/dandersen)\
**Post date:** [August 7, 2007, 2:16am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081/4 "2007-08-07T02:16:01Z")

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All pipe should flow back to the furnace. This includes rain.

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**Author:** ![mmorgan](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@mmorgan](https://forum.nachi.org/u/mmorgan)\
**Post date:** [August 8, 2007, 2:10am UTC](https://forum.nachi.org/t/please-help-with-high-efficiency-furnace/19081/5 "2007-08-08T02:10:24Z")

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Thanks all. I sure appreciate the info.

Mike