Home heat savings?

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If I put a box over the heat vent in the kitchen and over the living room, might not heat those rooms as much. Save a buck on energy?
Anyone tried this?
Gonna be below zero tonight, and windy. My heat bill will be up a bit, or a lot.
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On 02/27/2014 03:44 PM, Stormin Mormon wrote:

Yeah
A few years back I closed the vents totally to two rooms and just kept the doors closed and saved money.
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On 2/27/2014 5:26 PM, philo wrote:

Thank you. I don't have any way to compare open or closed vents, but I'll try it.
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Can you close the ductwork closer to the furnace? That would probably be better than just a box over the vent.
Is there a cold air return in those rooms? I closed the vents to an unused bedroom then realized I was sucking 60° air back down to the furnace through the cold air return. That's not very efficient. I made a cover from a rubber pad and put a heavy box in front of the return to stop it from sucking air.
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On Thu, 27 Feb 2014 23:16:10 +0000 (UTC), DerbyDad03

Yes, years ago and I'm still doing it. Well, I close the vent using the lever that does that. I assume I'm saving money to the extent parts of the house (that I don't use much) are colder than they would be. The basement is definitely colder. In fact maybe I should open the vent since now I have the computer down here and I'm here so much. I have the spare bedroom door closed, a towell under its door, and the vent closed, and it's definitely cooler in that room. Never gets cold I think. Maybe heat goes through the door and the walls. Etc .
I've been told, here probably, that if I close too many, that will cause combustion problems with my oil furnace, but now that I think about it, that makes little or no sense. The air I'm preventing from circulating is not the combustion air. That comes in somewhere (????) and goes out the chimney.
The air I'm stopping is the air on the other side of the heat exchanger. If that circulates less, I suppose it gets hotter while it's in the furnace, but not so hot it's going to heat the fire chamber** and change the combustion characteristics of the oil fire.
**That is, fail to cool the fire chamber as much. It will do that a little, but it's already so hot in the middle of an atomized oil fire, I don't think it will change anything.

I can't.

No. The first two houses I lived in were built right and had that, but I only have two air returns, one close to the celing of the second floor in the stairwell, and one close to the floor of the basement in the same stairwell. The second is only about an 18 inche duct ride to the furnace input.
No doors to close off the stairs, or separate the living room from the dining "area" or the hall from the kitchen. But it makes a small house look and feel bigger when heat and AC are not a consideration.

Not good, for sure, but not so much the part where you reheat 60* air. That just makes it easier to heat. I think the problem that was bad, or worse, was heating the room you intended to be cool

V. Good.
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I'm not sure what you are trying to say here. In reverse order, why do you think something was heating the room I was intending to be cool? The heat ducts were closed at the furnace. No heat was blowing into the room. It was definitely cool in that room, sometimes into the mid-50’s during the coldest days.
As far as the return air, why would I want to mix 55° - 60° air in with the 68° degree from the rest of the house and then reheat it? Why isn't that a bad thing?

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On Fri, 28 Feb 2014 04:03:04 +0000 (UTC), DerbyDad03

Because you were sucking heated air through the room on its way to the retrun duct. It says 60° , which I presume is my computers version of 60 degree. I dind't pay attention to that, but how could it be that cold if it came from the heated part of your house. I get it. The room was 60, but when you sucked out the 60 degree air it was replaced with 67 degree air from the rest of the house, so that's warming the room, and cooling part of the return air. .

I don't know if you want to but isn't that what happens when the cold air duct was sucking air out of the room. That air was replaced with air from the rest of the house, right?
Or from leaks around the windows I guess. if that was most of it, then I'm mostly wrong.
So from which entryway, both of which were intended to be close, is leaking air into the room more.

When I posted, I thought -- and it still may be the case afaik -- that the air was 60 because it cooled off in the unheated room (while heating the room) and it had been 67 say, because it came from the heated rooms. I figure you have to reheat the air no matter where it came from, but the problem was that it was 60, and that happened in the unheated room.
So now I don't know where the return air from that room comes from, the rest of hte house or the outside.
Sorry for the confusion.
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wrote:

If you had a non-primitive heating system, the combustion air would be drawn from outside the building directly into the furnace/boiler, not drawn through the house. (Balanced flue/room sealed)
If you close off your combustion air vents, you risk carbon monoxide poisoning.
http://www.centralheating.org.uk/Central%20Heating/Boiler_Flues.htm
You need to catch up with the rest of the world.
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On Friday, February 28, 2014 6:36:08 AM UTC-5, harry wrote:

He's talking about the return air vents for a forced air furnace, which has nothing to do with combustion air, idiot.
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Just so that there is no misunderstanding, my cold air returns are not my "combustion air vents".
While I do draw combustion air from inside the house, it is drawn in right at the furnace through a dedicated inlet pipe.
Closing a cold air return in an unheated room won't impact the combustion air intake.
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On Fri, 28 Feb 2014 21:13:19 +0000 (UTC), DerbyDad03

temperature will rize too high due to restricted air flow. This causes the high limit switch to shut off the burner untill the blower sucks the heat out of the heat exchanger, when it will relight. This makes the efficiency of the furnace drop SIGNIFICANTLY.
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On 2/28/2014 9:16 PM, snipped-for-privacy@snyder.on.ca wrote:

Heat can go into one of a couple places. Into the house, into the cellar, up the chimney. When efficiency drops SIGNIFIGANTLY, the heat is lost some where.
So the burner shuts off, and the blower still runs. How does this make the furnace less EFFICIENT? I don't picture it. Shutting off the gas lowers the efficiency? Really?
At church we have converted oil furnaces, which now run NG. They have a high limit sensor in the discharge air, when it gets to 110 or 120 it turns off the flame. The three blowers keep running.
So, turning off the gas now and again makes the efficiency of the furnace drop SIGNIFICANTLY? How's that, again?
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On Fri, 28 Feb 2014 22:35:34 -0500, Stormin Mormon

in-efficient zone for more of the time. The heat goes up the stack instead of into the house.

http://www.ehow.com/info_12081271_short-cycling-furnace-problems.html
http://www.ask.com/question/why-does-my-furnace-keep-going-on-and-off http://books.google.ca/books?id=Vdxw6PLk-msC&pg=PA410&lpg=PA410&dq=furnace+short+cycle+efficiency&source=bl&ots=knxrMrG7sF&sig=VtPgT_064A9WGsWHDNgtw53Yy1E&hl=en&sa=X&ei=eGwRU-D9J4qwygHXtIGACg&ved HAQ6AEwBjgK#v=onepage&q=furnace%20short%20cycle%20efficiency&flse
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On 3/1/2014 12:22 AM, snipped-for-privacy@snyder.on.ca wrote:

is going up the stack, you say? I'd think the heat is going into the building.

SM: Says decresed efficiency, but doesn't explain the process, and where the heat goes.

your limit for the day (my limit seems to be zero).
SM: I still don't see it, sorry.
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On Saturday, March 1, 2014 6:45:14 AM UTC-5, Stormin Mormon wrote:

_064A9WGsWHDNgtw53Yy1E&hl=en&sa=X&ei=eGwRU-D9J4qwygHXtIGACg&ved H AQ6AEwBjgK#v=onepage&q=furnace%20short%20cycle%20efficiency&flse

A few things. In any correctly designed and installed forced air furnace, you'd have to close down a lot more than one or two vents to have the furnace shut down due to exceeding the high temp limit. And in any recent vintage furnace, I don't think it's just going to restart. More likely it's going to stay off with a fault code flashing. If you choke off enough air flow, you also run the risk of burning out the blower motor, depending on what kind it is.
As to the loss in efficiency, exactly how much you would lose IDK. But you do lose efficiency if a furnace keeps going on and off instead of running continually. For one thing, modern draft inducer models run the blower to purge the system for like 30 secs before starting. Whatever heat there was, it's blowing cold air through it for that period and the heat is being vented outside with the air. At the very least, you're losing that heat. Also, if it does recycle, while it's sitting there cooling off from the over temp, some of that heat is also flowing out the combustion air path, losing heat. Or being lost to an unheated basement, etc.
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On Sat, 1 Mar 2014 05:48:54 -0800 (PST), " snipped-for-privacy@optonline.net"

Isn't the loss of efficiency in large part because of unburned fuel, because of the wrong temperature for the fire chamber. And it's the unburned fuel, gas or oil, that goes up the chimney.
In the case of oil, with a cracked heat exchanger and apparently even with a good heat exchanger, doesn't the unburned oil get on the walls and ceilings and anything else that attracts it, and make the house dirty. And if that's not true all the time because of a misadjusted furnace, it's stil true during the startup time when the firebox is not hot enough. Isn't that what they're referring to when they say oil is dirtier than gas?

Why does it blow it outside? Why not inside? Were my old furnace to run the blower before ignition, it would just blow the heat into the heating vents and out the other end if it ran long enough.

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On Sunday, March 2, 2014 11:32:14 AM UTC-5, micky wrote:

PgT_064A9WGsWHDNgtw53Yy1E&hl=en&sa=X&ei=eGwRU-D9J4qwygHXtIGACg&ved0CHAQ6AEwBjgK#v=onepage&q=furnace%20short%20cycle%20efficiency&fls e

No, because it has little effect on the fuel burning. Close to 100% of the fuel is burned, no matter what.

Irrelevant.
And if that's not true all the time because of a misadjusted

Because combustion gases go outside, not into the house.
Were my old furnace to

Really? It blew combustion gasses into the house? That explains a lot.
You obviously don't understand the difference between an air handler blower and an inducer blower. And I've never seen a furnace run the air handler blower *before* ignition. Everyone has a delay, so that it doesn't blow cold air.
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wrote:

Majority of furnaces in todays housing stock are oversized, so restricting the airflow can very easily overheat the plenum. And restricting airflow REDUCES the load on the blower motor, so you are unlikely to burn out the blower motor.

You are talking the "combustion chamber". The combustion chamber is purged to make sure there is not an explosive mixture of gas and air in the chamber when the ignitor comes on. . You most certainly do NOT want to purge the combustion chamber to the "conditioned space" - it MUST be purged to the outside.. This is NOT the blower that circulates the heat in your house. You must not have ever seen a gas furnace newer than about 20 years.

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On Sunday, March 2, 2014 5:16:47 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

Over sizing the *system* in a house has nothing to do with the ability to overheat the system. If you install a furnace that is too big for the *sytem*, then yes it could overheat easier if you restrict the air flow. But good grief. Stormin is talking about shutting off a couple of vents. I've never heard of that causing a furnace to go over temp and shut down. And if it does, something more is wrong than closing a couple of vents.
And

You might want to re-think that in view of that fact that a lot of new furnaces have ECM motors that are designed to maintain a given CFM of airflow.
>>

Can't you follow a thread? Nothing I said ever stated or implied that the air handler moves combustion air. Yet you're replying to the part that I wrote.
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On Sat, 01 Mar 2014 06:45:14 -0500, Stormin Mormon

You start the cold furnace, and it has to warm up the stack to get a good draft going (unless it is a high efficiency burner - where you get a forced draft, but it still needs to warm up) When it gets up to operating temp, it is running at top effieniency. It warms up the heat exchanger and plenum, and at a certain plenum temperature the blower comes on to extract the heat from the heat exchanger and move it through the house. The Delta T between the return air and the heat exchanger temperature affects the efficiency of heat transfer - the goal is to keep the delta T (temperature difference) between the return air and the heat exchanger in the "sweet spot" where the maximum heat is extracted from the exchanger and delivered to the house. Now, if the airflow cannot extract enough heat, the heat exchanger/plenum gets too hot, and for safety reasons the furnace shuts down (short cycles). Now the firebox/burner/stack go into cooldown mode along with the heat exchanger. When the heat exchanger drops down to the "reset" temperature, the furnace refires and starts the cycle all over again. Much of this time the delta T between the exchanger and the return air is sub-optimal - dropping the heat exchanger efficiency. - and the furnace starts up in it's lower efficiency range untill it warms up again. Low airflow causes the heat exchanger/plenum temp to go above limits again, and the (short) cycle repeats itself. During this whole cycle, the efficiency is less than optimal. When the airflow is not removing the heat from the exchanger efficiently, heat goes up the stack.
In a properly operating system, when the furnace gets the plenum up to temperature and the blower comes on, the correct amount of air passes the exchanger to transfer enough heat from the exchanger to keep the delta T in the "sweet spot" where maximum heat energy is removed from the heat exchanger, and the minimum required heat escapes up the stack. On variable speed blowers, the system is set up for a specific temperature size across the heat exchanger. On my furnace it is spec'd at between 30-60 degree F temperature rize across the heat exchanger with 28000-40000btu output The bigger model of this furnace is 45-75F at 89-72000 btu output. My blower is set at about 650 CFM
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