Who leaves furnace fan on?

[AndrewM]

Originally Posted by Ken07AOVette

Over the last 2 weeks of real cold spells I ran 2 days fan on constant, 2 days auto, and when the fan ran non stop the furnace ran at least an hour more each day. I use a NEST thermostat which tracks everything.

Auto only for me from now on.

Wouldn't that be because you are getting better heat distribution throughout your house?

[Ken07AOVette]

I would say it ran longer because it is drawing-35 air from outside

[AndrewM]

Originally Posted by Ken07AOVette

I would say it ran longer because it is drawing-35 air from outside

Does your fan run slower when it is just in circulating mode? I am going to watch my fresh air vent and see if it is drawing in any cold air. I figured since the fan was running much slower that it wouldn't be drawing in much from outside.

[Rastus]

My fan has 3 speeds, 1 for normal, (which is were normally is), 2 for heat, and 3 for air conditioner, and I leave it on normal, except when the heat is on or the air conditioner is on. Never change it, it comes on by itself.

[Ken07AOVette]

Originally Posted by AndrewM

Does your fan run slower when it is just in circulating mode? I am going to watch my fresh air vent and see if it is drawing in any cold air. I figured since the fan was running much slower that it wouldn't be drawing in much from outside.

It does, yes much slower but you can still feel quite a draft. There is definately cold air coming in, that works very well lol.
The furnace is a dual stage multi speed.

[CNP]

For those considering a furnace retrofit from AC powered blowers to DC powered blowers. According to the blog here a retrofit is possible for most furnaces if you do not have a belt driven blower.

In my opinion having an AC blower on 24/7 consumes too much energy and it is too loud. A newer high efficiency furnace with an AC blower would be the best candidate for a DC retrofit in my mind.


Saskatoon based company.

[Dan Foss]

Here's a question for you guys... as some of you seem way more knowledgeable than me....

I have a Air exchanger drawing fresh air from outside, but also have a combustion air intake drawing air in from outside. Basement has always been cold (previous owner developed basement himself, cheaped out on wall insulation and subfloor) but with this more recent cold snap i noticed a draft in the basement coming from furnace room.... My 5in combustion Air vent is just dumping cold air into the basement even when the furnace is not running. Freezing the side of my water tank which i noticed we struggled a bit more with hot water the last two weeks which is what started me wondering what is going on with everything.

So my questions....

1. Do i really need the Combustion air intake if i already have a air exchanger drawing fresh outside air? (would love to seal it if i dont)
2. where would the exchanger draw air from inside the house?
3. The draw from combustion intale while the furnace is not running also makes me think potential negative pressure in the basement? but really wouldn't i only see the negative pressure while the furnace runs and shortly after?


Also, after reading this thread yesterday, i Decided to put my fan to on for a couple days to see what happens, flipped it back to auto before bed because all it did was create a cold draft on main level of the house, even with the thermostat already bumped up a degree.

[Immigrant]

Originally Posted by Dan Foss

Here's a question for you guys... as some of you seem way more knowledgeable than me....

I have a Air exchanger drawing fresh air from outside, but also have a combustion air intake drawing air in from outside. Basement has always been cold......My 5in combustion Air vent is just dumping cold air into the basement even when the furnace is not running......
So my questions....

1. Do i really need the Combustion air intake if i already have a air exchanger drawing fresh outside air? (would love to seal it if i dont)
2. where would the exchanger draw air from inside the house?
3. The draw from combustion intale while the furnace is not running also makes me think potential negative pressure in the basement? but really wouldn't i only see the negative pressure while the furnace runs and shortly after?
.

I am no expert, but here is what I experienced. Recently did a big reno and its been an air balancing act since.
The air exchange sucks in what it blows out. Providing it is balanced and installed properly. It is not combustion air. I had a 5” combustion air intake like you. With the renovations we took it out to replace my old furnace with a new high efficiency. The plumber did the 2 inch air exhaust for the new furnace from the mechanical room to outside, and we were going to use the existing furnace exhaust stack as the air intake for the new furnace. The plumber then mentioned that my existing furnace is still in good shape, so I could probably run it a few more years before installing the new one. I should have just installed the new one and get it over with, but figured why not run the old furnace and “save” the new one for a few more years. Needless to say, the 2” exhaust for the new furnace now acts as my combustion air. Its not enough, because when my furnace kicks in it sucks in air through my pellet stove fresh air intake from across the room because it needs combustion air, as well as air it exhausts through the stack.
My point is you probably need the 5” combustion air intake. There is a damper on the market that will only open when your furnace kicks in, and closes when it stops. The constant cold air coming in through your combustion intake is because hot air is escaping out your furnace exhaust even though it is not running. Also called the stack effect.
I finally got my air exchange working right last week. It seems during the initial install they had to join the 6” insulated flexible duct. They simply crumpled up the one end and stuffed it in to the other and taped it up, thereby restricting the intake flow down to probably 3” causing a constant negative pressure as the exhaust was still 6” and a 10 foot shorter run.
I will finish installing the new furnace soon....

[CaberTosser]

Originally Posted by Dan Foss

1. Do i really need the Combustion air intake if i already have a air exchanger drawing fresh outside air? (would love to seal it if i dont)
2. where would the exchanger draw air from inside the house?
3. The draw from combustion intale while the furnace is not running also makes me think potential negative pressure in the basement? but really wouldn't i only see the negative pressure while the furnace runs and shortly after?

.

1: Yes,,you still need a combustion air. If you get new direct-vent appliances their combustion air supplies can be piped directly to each appliance through independent pipes from outside. This eliminates the cold draft from the combustion air bucket that got superseded.

2: An HRV can draw air from the furnace return air or it can have independent ducts running to rooms such as a kitchen or bathroom that require more airflow.

3: Just because your appliances are not firing doesn’t mean your chimney isn’t drawing heat out of your home. Natural draft appliances such as an older furnace will always have air flowing up the chimney. Idle conventional water heaters will have a greater chimney draft than the furnace because the heat exchange pipe through the tank itself is surrounded by hot water, that hot water heats the air and creates a much stronger draft than a furnace that has cooled off; this effect of course cools the water and will prompt the tank to fire once it has shed enough temperature. This chimney effect is a primary component of what we call ‘standby loss’, though there are other sources such as the small amount of heat lost through the water heaters insulation jacket, etc (though conversely, at least that standby heat loss is shed into the house). Direct vent appliances that have their own dedicated combustion air piped right to them save utility costs by drastically reducing standby losses through the chimney. A pair of intake and exhaust pipes to a direct vent appliance will generally be installed at the same level (or reasonably close) and as a result will have either no or very little natural chimney effect occurring.

[Dan Foss]

Great responses guys, Thanks!

Sounds like a bigger overall problem that I will have to tackle with a bit of a update to my HVAC system down the road... Not necessarily what I wanted to hear, but good to know.

I never really noticed it last year, it was only this cold snap that I started noticing serious draft and impacts to the water heater. normally it is not this bad.

[AndrewM]

What about the bucket or the Hoyme dampener? Do you have either or those?
http://www.outdoorsmenforum.ca/showthread.php?t=312028

[Sideways]

Great read! Thanks for the tips. I never heard this before