Oil furnace air return vent

[Dottie]

Hi,

My Heritage soap stone stove has been doing much better, it's kind of funny the more I learn the better it gets! Anyway, I have a question. Right outside the living room in the hallway there is a "air return" , I guess it's called, for the oil furnace, it's a big vent returning down to the furnace, not for heat.

Well when I sit in the living room there's sort of a cold draft, even when the stove is really cranking. Just to see if it would help, I stopped up the vent almost completely with 1 inch styrofoam insulation and it seems much less drafty. Is this a safe enough thing to do?

I haven't used the furnace since I tried this. and I've been trying to use the furnace exclusively, but the the furnace may come on if I go away for a long time, or if I just haven't started the fire and we have a cold snap. Will it be ok to leave the insulation in or is it dangerous?

Thanks for any help.

Dottie

 

[brogsie]

Dottie,

A cold air return is to help circulate or spread out the heat from the furnace more evenly. It brings cold air to the furnace to be heated while the warm air supplies push out the heat. Is the cold air return ducted directly to the furnace? If it's just an open grate I don't know that it would hurt anything but some parts of the house may be hotter or colder. If it is connected to the furnace you should remove the insulation when the furnace is running.

 

[Dottie]

Thank you for your reply.

I don't really care about some rooms being colder than others, they already are. I suppose I just want to know if it could be harmful in any way. I intend to use the wood stove as my primary heat, but there may be the odd slip-up or illness etc. I would remove it the insulation if I knew I was going to be using the furnace or an extended period of time.

Dottie

 

[brooktrout]

If there is ductwork going from the return vent in your floor to the furnace, do not run it with it blocked off. If there are any other return vents in the house (there should be) then yes, you can block that one off. As long as you have at least one or two returns, you'll be okay. Of course, the more return air, the more efficiently the furnace will run. I covered up the one that is closest to our stove, but I have two others that stay uncovered, as the furnace will kick on about 1/2 hour before I get home from work before I can reload...

 

[bcnu]

This bring up a question I have. When we remodeled last year we removed the cold air return the upstairs (two wall grates that vented into a small closet with a raised floor). We lowered the closet floor and so the upstairs doesn't have any cold air return. However, the full basement does have the return duct which was also modified in an earlier remodel. So the furnace is drawing all it's cold air from that one basement return. What's your take on that?

 

[begreen]

Complete blockage of the sole return air duct will very likely damage the blower fan motor. Don't do this. Partial blockage can have the same effect. A well designed warm air system is balanced and designed so that a specific load and pressure is maintained. Blocking off grilles, removing ducts, imbalances the system. It usually causes the blower to run much faster and often shortens the blower motor's life.

If you are getting significant cold air pulled through the return duct when the stove is going, that may be because the stove needs combustion air and is pulling it from the room. Consider adding an outside air intake on the stove to alleviate the problem instead of blocking off the return air grille.

 

[brooktrout]

This bring up a question I have. When we remodeled last year we removed the cold air return the upstairs (two wall grates that vented into a small closet with a raised floor). We lowered the closet floor and so the upstairs doesn't have any cold air return. However, the full basement does have the return duct which was also modified in an earlier remodel. So the furnace is drawing all it's cold air from that one basement return. What's your take on that?

With the furnace blower running, open the filter replacement door. If the door is hard to remove due to static resistance, then you need more return air. If you can hear the blower motor drop in rpms, then you REALLY need more return air. The perfect system has the same amount of return as it does supply, but this is rarely the case in real world installs.

 

[Dottie]

Thanks for your replies. I'm afraid that this the only return air, so I guess that if I use the furnace at all the insulation will have to go, or I'll have to make sure that the furnace is switched off and can't kick on. The way the weather is I doubt if it will anyway. I think that this is the winter that wasn't, at least here in Virginia.

I do want to ask something else that "BeGreen" brought up about the outside air supply. I thought that they were generally used when the house is super insulated and sealed up. I must say that this is not the case in my house. It's an old house, with plaster walls, which I'm pretty sure have no insulation. It's not uncomfortable, probably because I'm used to a cooler house than most, but I never noticed a draft until I got the wood stove, there's a noticeable cool draft when the stove is on.

Could someone please explain about the outside air supply thing, how it works, and how it's hooked up? As I said I have a Heritage soap stone, and I don't think it mentions anything about an outside vent, but I may have missed that.

Thank you.

Dottie

 

[begreen]

This bring up a question I have. When we remodeled last year we removed the cold air return the upstairs (two wall grates that vented into a small closet with a raised floor). We lowered the closet floor and so the upstairs doesn't have any cold air return. However, the full basement does have the return duct which was also modified in an earlier remodel. So the furnace is drawing all it's cold air from that one basement return. What's your take on that?

With the furnace blower running, open the filter replacement door. If the door is hard to remove due to static resistance, then you need more return air. If you can hear the blower motor drop in rpms, then you REALLY need more return air. The perfect system has the same amount of return as it does supply, but this is rarely the case in real world installs.

That test is a bit subjective. The system should be designed to operate under a certain static pressure load. Opening the filter door will allow the fan to run unloaded, in "free air", which will change the rpms a bit. The best way to test is static pressure tests with the system running.

Note, however, like woodstove installations, there are many HVAC systems that are installed seat of the pants and never really checked or balanced. A good installer may spend an hour balancing a system, but this step is often forgone in rush installations.

(broken link removed to http://www.contractingbusiness.com/25/Issue/Article/False/43340/)

 

[begreen]

Thanks for your replies. I'm afraid that this the only return air, so I guess that if I use the furnace at all the insulation will have to go, or I'll have to make sure that the furnace is switched off and can't kick on. The way the weather is I doubt if it will anyway. I think that this is the winter that wasn't, at least here in Virginia.

I do want to ask something else that "BeGreen" brought up about the outside air supply. I thought that they were generally used when the house is super insulated and sealed up. I must say that this is not the case in my house. It's an old house, with plaster walls, which I'm pretty sure have no insulation. It's not uncomfortable, probably because I'm used to a cooler house than most, but I never noticed a draft until I got the wood stove, there's a noticeable cool draft when the stove is on.

Could someone please explain about the outside air supply thing, how it works, and how it's hooked up? As I said I have a Heritage soap stone, and I don't think it mentions anything about an outside vent, but I may have missed that.

Thank you.

Dottie

A better solution, that will benefit twice, would be to have the duct system cleaned, sealed and insulated. That will save energy when the furnace is running and will greatly reduce the cooling air coming from the ductwork. Since doing this in our old farmhouse, cold drafts from vents has become an non-issue.

Although outside air can be a necessity for supertight houses, that doesn't mean a leaky old farmhouse won't benefit. The woodstove is consuming interior air for combustion. This creates a negative pressure in the house that pulls in replacement air through cracks and gaps.

There are mixed opinions about it, but I am in the camp with OAKs saving heat.
Here's some reading material for you:

https://www.hearth.com/talk/threads/12297/
(broken link removed to http://www.chimneysweeponline.com/hooa.htm)
(broken link removed to http://www.chimneysweeponline.com/hooa3.htm)

However, before rushing to add an OAK, here's another POV:
(broken link removed to http://www.woodheat.org/outdoorair/outdoorairmyth.htm)

 

[Henz]

I have the same problem. I basically cover every air duct and return in my house while we are home and turn off the thermostat (programmable) so I make sure that the furnace wont be kicking on. It makes a huge difference

 

[woodsie8]

So, if I cover all my heat out vents to all rooms except lets say the one room my stove will not reach and leave the cold air return alone, then will my furnace be fine and also if I use just the summer fan, will it draw the heat from my stove into the return to take it to that cold room that my stove will not reach????