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Furnace air intake question.
- Thread starter acer66
- Start date
Jim greengo
Well-known member
As long as theres enough combustion air,lowers efficiency rating of furnace though.
It depends upon how the product is listed. I suspect it is ok to install this way, but direct venting is the better option. Taht way you are not depending upon building air to support the combustion process. It was easier for the installer to do this rather than adding the other penetration.
esmith2039
Well-known member
The system I just had installed just vented the exhaust and left the intake open minus the elbow. They said they preferred not to run it outside if possible since nests are a problem. Mine's in a basement and old one so not worried.
HoosierBuddy
Well-known member
The system I just had installed just vented the exhaust and left the intake open minus the elbow. They said they preferred not to run it outside if possible since nests are a problem. Mine's in a basement and old one so not worried.
Yeah...I suspect they didn't want to run it outside because it can be a huge PIA to get a hole big enough through basement wall and have the intake come out where it is allowed to be (required clearances and height off the ground).
When I was doing my own, I spent the extra time (took me probably an extra 3 hours) to terminate the intake outside the house.
The furnace manufacturer does not say that the furnace will be more efficient by sucking in outside air...because it won't be. Furnaces are rated on the percentage of available heat from the fuel source that makes it into the air stream being blown into the ducts. They don't have to deduct for the loss that will occur when you **** (heated) combustion air out of the house and then have to reheat cold air getting sucked in around windows and doors or through other gaps that will now have to be heated by the furnace.
In an unheated basement it would make less of a difference, especially if the basement isn't that tight to begin with....but to me it made sense to do the extra work to make the system just a bit better.
In the 5 years or so since I did this I haven't had any nests of any kind or any issue with the vent.
Phil
e36jon
Well-known member
Out here in CA the rules say that we can only have an open intake in the space if we have a certain amount of open venting to the exterior. If you want to build a sealed space for the furnace and water heater (To make it safer to work with solvents in the garage, for instance.) then you have to bring in a certain amount of venting based on the BTU capacity of the appliances.
I am about to buy a new high efficiency furnace and the venting / intake can be handled by a concentric unit so there is only a single roof penetration: https://www.homedepot.com/p/Diversitech-3-in-PVC-Concentric-Vent-Kit-CVENT3/204514478
I am about to buy a new high efficiency furnace and the venting / intake can be handled by a concentric unit so there is only a single roof penetration: https://www.homedepot.com/p/Diversitech-3-in-PVC-Concentric-Vent-Kit-CVENT3/204514478