New High Efficiency Furnace Install Raises Questions

Old 08-27-12, 02:54 PM
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New High Efficiency Furnace Install Raises Questions

I just had a new high efficency furnace installed. It is a Bryant, and I question the PVC ducting they ran to the outside.

There are 2 PVC ducts running outside. 1 is angled down with a 90 degree elbow (this one is proabably ok), the other is angled up with a 90 degree elbow at the top. I am concerened that water will get into this ducting and travel down to the furnace.

Is this normally how they are installed? If necessary, I can attach a photo.

Old 08-27-12, 03:30 PM
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sounds normal. Water can go down the pipe and it will be fine as water collects inside the pipe from flue gases anyway. The pvc vent system is connected to a condensate drain in the furnace and will get rid of the excess water.
Old 08-27-12, 07:58 PM
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hvactech is correct.

Natural gas produces a lot of water vapor when the gas is burned. Lower efficiency furnaces kept the combustion gasses hot enough that the vapor didn't condense in the furnace or vent system --- 400 degrees F or higher.

High efficiency furnaces are designed to condense the water vapor into liquid water. Just as it takes a lot of energy to boil water into a vapor, if you condense vapor into water you recover that latent heat and can use it to heat your house.

Typically that can amount to about a gallon of water produced per hour if the burner were run continuously. The furnace and venting system is designed to drain away that liquid water.

Also, in addition to recovering that latent heat, you can also cool down the combustion gasses to around 100 degree F, recovering additional heat.

So it shouldn't be an issue.
Old 09-24-12, 01:44 PM
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the instruction manual for that equipment shows an additional 90 on the pvc that goes up. Water getting into these pipes goes to the internal drain and is not a problem unless the intake is pointing up
- there is no drain for the intake.
40+ years in HVAC field

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