47WDXPW
Well-known member
I just found that my home heater (NG) was installed without a fresh air intake, its high efficiency with a PVC exhaust line should a fresh air line be installed ?
Home heater fresh air intake
- Thread starter 47WDXPW
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Dagny
Well-known member
not necessarily if the room its taking the air from is large enough . first I should ask if you mean for combustion or just fresh air.
The room is the basement with no rooms and 900 sf. Dagny your question is at the root of my confusion, the furnace is shipped as a direct vent with sealed combustion and may be installed as direct vent or as non direct vent so if there is enough air from inside the home to feed combustion is there any good reason (comfort, air quality) to get combustion air from outside ? As Im in the process of tightening the air seal of the home where does fresh air come into play ?
larry4406
Well-known member
Find the make and model number
Obtain manual for said unit.
Read manual for venting requirements.
Most 90+ furnaces can be vented in a multitude of ways including single pipe exhaust and using existing space to provide combustion air. Check carefully on transfer grilles if furnace room is a small space.
I would recommend piping in the combustion air to reduce drafts to the home.
Obtain manual for said unit.
Read manual for venting requirements.
Most 90+ furnaces can be vented in a multitude of ways including single pipe exhaust and using existing space to provide combustion air. Check carefully on transfer grilles if furnace room is a small space.
I would recommend piping in the combustion air to reduce drafts to the home.
forAK
Well-known member
Does it have a intake at the top of the heater? I'd find it odd if installed by a quality installer that it would be left off.
BillK
Well-known member
One of the advantages of a direct vent furnace is that it is not pulling cold air for combustion through leaky windows etc. Mine has the inlet line run right next to the exhaust. Cannot imagine not doing it that way and having fresh combustion air from outside the house.
zmaxmotorsports
Well-known member
It depends on what the efficiency rating of the furnace is,some are,designed to be single piped.
The unit should still be able to condense w/inside air and get the burner efficiency -- outside air is colder.
It's the taking in of conditioned air that inefficient. instead of using outside air -- you are taking air that was heated/cooled. that air is replaced by outside air leaking into the house. same with kitchen/bath exhausts .. vented dryers.
zmaxmotorsports
Well-known member
I'm pretty sure most 92% furnaces are made for a single pipe,you could upgrade it with a combustion air pipe though.
6768rogues
Banned
I have an old house and the basement is stone walls with a concrete floor. Even though I try to keep it clean, it gets dusty. Therefore I only want outside air for combustion to keep all that dust out of my furnace.
Some can be one or two pipe. I am in the market for a new furnace and my regular guy says his can be one or two pipe, but he always puts in two pipes. Find out what is recommended by the manufacturer and make a decision.
Some can be one or two pipe. I am in the market for a new furnace and my regular guy says his can be one or two pipe, but he always puts in two pipes. Find out what is recommended by the manufacturer and make a decision.
I consider direct venting as more of a safety issue. You contain the flue gas by-products. As well, many people simply assume that they have adequate combustion air. The code calls for 50cu ft/1000 btu of input. Frequently when someone buys a house with an open basement the first thing they do is drag a pile of 2x4's down to the basement and build a wall around the water heater, furnace or boiler. The other issue is that people will fill the basement half way to the floor joist and there you go again. Even with what calls as sufficient air doesn't take into consideration the number of ways we push air out of a house. bath fans, dryer vents, range hoods. We have taken the technology of the thermos bottle and applied it to home construction. A lack of combustion air generally doesn't happen all the time, but conditions can occur and you need to remember that every system has a personality. You hope that it is more Jeckyl than Hyde...or is that the other way around. I was a rep in the 6 New England states and sold oil and gas equipment as well as chimney products and power venters. I have seen hundreds of homes with exactly the problems I'm describing here. Why not just two pipe it and be done with the worry.
If you want to maximize the efficiency then use a concentric vent pipe system. That way the cold intake air is being pre-heated by the exhaust gas.
zmaxmotorsports
Well-known member
That can be a problem with any furnace.
scout4bta
Well-known member
We just moved into a house built in 1979, and had to figure out the combustion air. Heres one for NJ, Combustion Air IRC 2006.
Dagny
Well-known member
If you remove air from the basement it will come in somewhere. I don't know if that is good or bad. I like a little fresh air and this is a cheap way to get it. You can make the house air tight then spend a couple grand on heat recovery ventilator so you don't suffocate .
larry4406
Well-known member
OP - what does your manual say/permit ?
Concentric kits are good when the flue is parallel to floor joists, allows a smooth basement ceiling without hacking joists. If perpendicular then 2 pipe often works better, at least for me.
Concentric kits are good when the flue is parallel to floor joists, allows a smooth basement ceiling without hacking joists. If perpendicular then 2 pipe often works better, at least for me.
lakeroadster
Well-known member
Does the basement itself have an outside air intake?
Our last home had (2). They looked like dryer vents, but were actually just 4" o.d. vents open into the basement.
Our last home had (2). They looked like dryer vents, but were actually just 4" o.d. vents open into the basement.
There are no means of make up air installed in the home as I just sealed the attic before installing more insulation I was taken back as to the amount of openings in the attic one being 5" wide and 7' long so with the attic having been addressed it has brought in to focus all of the above issues. The installers guide suggest using 2 horizontal installations and a Bayvent one side by side and one concentric.
LS6 Tommy
Well-known member
Where does your return duct take it's air from? It's against code to have your return air and combustion air use the same air source.
Tommy
Tommy
Tommy, Im not a HVAC guy but I believe the return air comes from vents at the top of rooms on the first and second floors and the combustion air mostly comes from the basement where the furnance is located which is a completely open space. So if there is not a way to get fresh air in place is getting combustion from air leaks considered OK ?
TractorJeff
Well-known member
As stated in two previous posts, getting combustion air from inside the house creates drafts. Across the room to the Cellar door. Where does this air come from? Attic doorway, back drafting bathroom vents, windows, external doors.
eddieK
Well-known member
Fresh air with a 90 percent plus furnace is usually Combustion air, the air used to support combustion. In the scenario you described, if the air in the space is not mixed with the conditioned space it is considered "free" air and an intake for fresh air to the outside is not required.
eddieK
Well-known member
Common misconception by the uneducated. This is not "lazy"...it is in fact up to code and up to the manufacturers requirements. Free air is allowed when a furnace is installed as described here.
LS6 Tommy
Well-known member
bczygan
Well-known member
It is better and more efficient and saves money to get outside combustion air. Install the PVC intake venting.
Bill
Bill
larry4406
Well-known member
What does the manual say for your unit? You never seem to address this.
Sorry about that, the manual states 50 cu. ft. or more per 1000 btu./hr. input all equipment installed for an unconfined space which I believe the installer thought was met with the open layout of the basement and no vents were installed for fresh air. My unit is 100,000 btu. Right below this info is in bold print Out side air is recommended; The use of indoor air for most applications is acceptable, unless there is the presence of corrosive chemicals or contamination. Certain types of installation will require the use of outside for combustion. Below this is a sample of confined spaces and a list of unacceptable chemicals requiring outside air for combustion.