Steam at vent

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#1

Originally Posted By: pdacey
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7 year old gas fired induced draft furnace. Noticed steam coming from vent on roof while doing the exterior inspection. The steam is present for the first 5 minutes or so when the heat kicks on and then it goes away. This happens every time the heat kicks on. Is it an issue? Never seen this before. It has been unseasonably cold here since yesterday, in the mid 30s.


[ Image: http://www.nachi.org/bbsystem/usrimages/I/IMG_0828.JPG ]

#2

Originally Posted By: aleleika
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icon_biggrin.gif


Patrick, sorry for smiling at this but I was a little amused being from the Midwest and how cold it has been lately. Go down any street here in the dead on winter and this is what you see coming out of all the flue stacks.


Have you seen your breath the last few days also. If its below freezing then you can....or like in the city when you see the steam rising out of the sewer covers in the middle of a cold winter night. The hot air coming out of the flue hitting the cold air causes this.

--
A. Dan Leleika
www.a-teamhomeinspections.com

#3

Originally Posted By: mboyett
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of condensation and others nearby and even on other homes will not. I saw this a few months ago on a gas water heater but none others in the area were doing it. It kind of made me wonder if there was some type of excessive moisture being injected into the vent stream somewhere. I didn’t write it up at the time but I still wonder about it.

#4

Originally Posted By: pbolliger
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The products of combustion of natural Gas are Carbon Dioxide and (moisture / water )… Burning Natural gas 10:1 Air / gas ratio will give you water (moisture) and heat. Moisture is release when the gas is burned. The condensing units or High efficiency FAU Cat 4 units, positive pressure that have PVC for a “flue” have condensation issues so hence the need for proper piping / goose neck trap and some have pumps to deal with that.


The evidence of rust on a draft hood Cat 1 natural draft unit , negative pressure or Alydehides (stinky sock) ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif) smell and some whitish particles should tell you something is not right. Like lack of enough combustion air. Improper combustion and potential CO generation will happen.

Stay safe guys..

Steam is ok... rusty , stinky smell... No way! (poor rime, sorry)

#5

Originally Posted By: rcooke
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A small bit of information what you see is condensation .


You can not see steam .


Look at you kettle next time it is boiling and at the spout there should be a small area where you can see nothing out for about 1/4 inch or more then you can see where it has condensed.


Roy sr

#6

Originally Posted By: pdacey
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Thanks Dan, Patrick, Mike & Roy.


mboyett wrote:
.... one vent will be showing excessive signs of condensation and others nearby and even on other homes will not.


That's why I asked. I didn't write anything in the report about it because I knew it had to be just from the hot combustion gases hitting the cold air, but, it's usually not this cold here and you never see this type of thing.