DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (http://www.diychatroom.com/)
-   Building & Construction (http://www.diychatroom.com/f19/)
-   -   Furnance question. (http://www.diychatroom.com/f19/furnance-question-57549/)

diy4life 11-19-2009 11:24 AM

Furnance question.
 
That i completed I have Furnance question Okay, I have completed my basement project as much as possible and it definitely made a big difference in the comfort level. But now I have a question about my furnance.

Now, that I have completely blocked all the gaps and cracks in my basement walls and at the rim joists, there is hardly any fresh or outside air coming into my basement. Then, doesn't my 80% furnance need outside air to burn gas more efficiently? There is no fresh air intake for my furnance. What I have been doing is opening one of my tiny rectangluar glass window just slightly enough to let some air into the basement for my furnance. But people I talk to tell me that I don't need to do that and that I already have air in the house to heat and circulate. I may look dumb (LOL), but I learned in my science class that fire needs fuel, oxygen and heat to burn at its best. If my furnance burns off most or all oxygen in my basement, how is it going to burn natural gas. Also, that if you seal all your cracks and gaps, there won't be air in the basement for the furnance byproduct, carbon monoxide (CO), to run out the chimney. Instead, the negative pressure will pull outside air through the chimney and flood CO into your house.

I am baffled. What is the real soultion? Please, help. This is my first time owning a home. So, I am learning as I go.

Bob Mariani 11-19-2009 11:40 AM

I provide a two 6" ducts to the outside to supply fresh air to a furnace, especially since I normally have it in a small room. One vents at the base of the wall and one at the ceiling. This creates a natural air flow without any fans. You can feel the cool air flowing into the furnace.

ccarlisle 11-19-2009 12:11 PM

Don't worry about that...there are 1001 ways air can get into your furnace room that you (or anyone) really doesn't even know about. The laws of thermodynamics take care of air concentration gradients.

diy4life 11-19-2009 01:58 PM

1001 places?
 
Quote:

Originally Posted by ccarlisle (Post 355236)
Don't worry about that...there are 1001 ways air can get into your furnace room that you (or anyone) really doesn't even know about. The laws of thermodynamics take care of air concentration gradients.

Carilse,

You are out of your mind. I know negative pressure will pull outside air from 1001 places, but do you really want outside air to leak into your house from 1001 places. For that, you would rather open all your windows and doors in your house during winter season. When I bought the house, I had plenty of outside air coming into the house like 10000001 cracks and gaps. We were wearing coats and winter gloves the first winter inside the house. We were horrified that no matter what we set the thermostat to, it was cold and the furnance kept running and running but not enough heat.

Furnance defintely needs fresh outside air for combustion, but you have to have control over the fresh air intake or cold outside air will cool all parts of your house. I am sure you don't want that. I bought the house as-is and the basement was unfinished. When I inspected the basement, outside air was gushing into my basement through basement cinder block walls all the way around hitting my rim joists and cooling my first floor. Thus, cooling my living room and kitchen no matter how much we set the thermostat at. After spending nearly $1000.00 on insulation and plastic sheets, I made an effort to seal all these gaps and holes and cracks in the basement. Now, our comfort level has gone up and my furnance doesn't run and run all the time. The only problem I am running into is fresh air intake for my furnace. Now, that I completely seal all my basement, there hardly any fresh air entering my basement for my furnance. So, I leave one of my basement window very slightly open just enough for my furnance and that it won't cool my whole basement. However, this is only temporary. I want to put something in place permenantly. So, I don't have to worry about it.

jogr 11-19-2009 02:02 PM

Please do worry about it. If you've made your house a lot tighter you could be causing incomplete combustion and inadequate draft through your furnace. Hopefully you already have CO detectors in the house (any house with gas should have them). It would be worthwhile to have an HVAC tech come in and check your furnace combustion (they have fancy combustion monitors) to determine whether you nedd an outside air supply.

ccarlisle 11-19-2009 02:15 PM

Whatever, diy4...I guess you live in the only house so airtight it qualifies as a research project, and all based on the huge sum of $1000! The "Theoretical House" you should call it.:laughing:

Oh well, you'll learn one of these years.

:wink:

diy4life 11-19-2009 03:11 PM

I am well aware of the danger, Carsile
 
Quote:

Originally Posted by ccarlisle (Post 355289)
Whatever, diy4...I guess you live in the only house so airtight it qualifies as a research project, and all based on the huge sum of $1000! The "Theoretical House" you should call it.:laughing:

Oh well, you'll learn one of these years.

:wink:

Carsile

After what I've done to my basement, the house is atleast livable. Before there was no difference in the outside or the inside tempature. I do understand that the furnance needs fresh air for combustion. That's why I leave one of my basement window open slightly all the time. So, even if the furnance is not running fresh air is always filling the basement. Whenever my furnance starts running, it will have plenty of fresh air to run on.

I am well aware of the danger. I am just looking for ideas on DiyChatroom.


:laughing::laughing::laughing:

stuart45 11-19-2009 03:46 PM

The position of the air vents for an open flued appliance is important. A vent on the windward side can bring in excessive amounts of cold air, while one on the lee side may actually suck air out. One in a neutral position would be the best place.

It is usually best to vent from another room like a hallway if possible, and then vent this room, or run the vents through ducting in the floors to prevent cold draughts.

concretemasonry 11-19-2009 04:37 PM

I have a fairly tight townhouse. Older efficient windows but little air leakage. Even if they are high efficiency, they are still just a hole in the wall when it comes to radiant heat loss at night when a curtains or drapes do more good that all of the films and gases in between the panes.

My units was built in 1980, but the code required a fresh air intake for combustion (gas furnace, hot water heater, dryer). I have a 6" flex vent from above the roof or between the insulation and the roof. I could feel the cool air coming in continually due to the natural stratification. I put the vent pipe into a 5 gallon pail and close the door to the laundry furnace room. When the furnace or heater run, I can feel the cool air coming in through the vent, but there is little when they are not running. The siphon effect coupled with the draw of units when they need combustion air works!!

Dick

SULTINI 11-19-2009 05:02 PM

Example
 
Maybe you can install something like a dryer vent with a flap damper in it from outside the house into the furnace room to the front of the burner.

When the burner starts it draws air from the pipe.

Or if you check around you can get electric dampers that will open when the thermostat calls for heat and closes when satisfied.

Depends how complicated and expensive you get.

diy4life 11-20-2009 04:21 AM

Air always sucked Pulled in
 
Quote:

Originally Posted by stuart45 (Post 355349)
The position of the air vents for an open flued appliance is important. A vent on the windward side can bring in excessive amounts of cold air, while one on the lee side may actually suck air out. One in a neutral position would be the best place.

It is usually best to vent from another room like a hallway if possible, and then vent this room, or run the vents through ducting in the floors to prevent cold draughts.

Staurt

Living space of house is only 30ft x 20ft two story house with basement. So, whenever my furnace runs it pretty much pulls most of the air from its immediate surrounds creating negative pressure. So, air is always being pulled from outside never sucked out.

I do have a 6" vent hole near the floor for my dryer. I am not sure if I can use it also for furnace fresh air intake with some sort of flap damper.

Tommyt3782 11-20-2009 09:42 AM

Guys,

Fresh air is not required for combustion. I don't care if the air is fresh stale or stinky.

There are 3 things required for combustion. Fuel, Oxygen, and an ingnition source. Oxygen is present in all our air otherwise we would all die from suffication.

Oxygen is present in our atmosphere (about 19-22% concentration)

Its what we breath, and its what your furnace breathes.

It is fine to have a fresh air vent but absolutely not required. Oxygen is present in the atmosphere around us. If a house was truely air tight, eventually the carbon dioxide we exhale and the bi-products of combustion (carbon dioxide, carbon monoxide, water, etc.) would eventually use up all the oxygen in the house's atmosphere. But! No house is air tight. All furnaces are vented for exhaust. My hot water heater and furnace are in a finished basement room, all closed up in the winter, with no vent and we have no problems at all. Oxygen is all around us and gets in every time we open the door, threw every microscopic crack in your house and every window / door frame. Hell it even slowly permiates the walls of your house.

You furnace is fine and I gaurentee unless you pump pure oxygen into your boiler room (Not recommended) you wont notice a difference in efficiency in your furnace with a fresh air vent. In fact you'll probably loose efficiency because of the cold air entering your 6" vent that now has to be heated.

Scuba_Dave 11-20-2009 11:39 AM

If you are that worried about it have an air infiltration test run
They put a blower on the sealed front door & provide an analysis on whole house infiltration

I really doubt what you have done has had a major effect on the average air change for the house:

Quote:

The US national average of air change rates, for existing homes, is between one and two per hour
You were probably MUCH worse then this & have now brought your house closer to the average. I replaced all the basement window, sealed & insulated the rim joist & replaced all the windows in the house
I'm not in the least bit worried about incomplete combustion

diy4life 11-20-2009 11:52 AM

basement furnance combustion air
 
Hello Tommy & Scuba,

Thank you for your reply. I am sorry I keep using Fresh Air Intake. Fresh Air Intake deals with cold air return in your furnace. What I meant to say was outside air for efficient combustion. You are absolutely right that Oxygen is good percent of our atmosphere and that it does seep through cracks and gaps and walls in your house. However, in an enclosed space with a furnace that needs plenty of Oxygen to burn at its best, you need some ways to replenish the depleting Oxygen in the immediate surroundings. Outside Air doesn't just only help your furnace burn efficiently but also you won't have back draft forcing CO and CO2 to fill up your house.

Why do you think High Efficient Furnaces (90% or 95%) have ducts that directly pulls air from outside and runs it through the furnace? That's part of being highly efficient. In other ward, flame heating the heating element in the furnace gets to burn at its best when it gets plenty of outside Oxygenated air. Thus, the furnace heats the circulated air much faster and hotter.

I used to close all the windows and doors tightly as possible thinking that it will prevent heat loss, but as I kept reading about how furnace works and how some of them are highly efficient I learned that the major difference between low efficient and high efficient furnace is the insulated duct work that pulls outside air for combustion. At least that's what I have been told by many contractors and people.

From my personal experience, I can definitely agree with that. Whenever I had all my windows in the basement closed shut, my 80% furnace hardly put out any hot air and sometime less than warm air. Plus, my furnace would run and run for 15 to 30 minutes every 15minutes. After my basement projects and leaving one of my basement window slightly open for outside air, my furnace blows hot air every time and it doesn't keep running for 30minutes to reach the set temperature. It takes only 6 to 8minutes for it do that. The living space is much more comfortable.

Try running your car after stuffing your air intake with cloth LOL.....
You will eventually come to a stop completely. :laughing::lol:

Scuba_Dave 11-20-2009 12:02 PM

If you aren't getting hot air out of your furnace then you have a problem with your furnace
Every door & window is tightly shut in my house
I caulked & sealed every air leak I could find
My system runs at 86% efficeint & I'm not worried
I also burn wood during the winter to help heat house
That takes a heck of a lot more air then a funace as its going constantly


All times are GMT -5. The time now is 01:53 AM.


Copyright 2003-2014 Escalate Media LP. All Rights Reserved