Air circulation

[jlore]

my central air unit has a fan only setting that works great for spreading warm air all through out my house. 2 questions? one are duct fans hard on eletric? and does running only the fan hard on my ac unit?

please relocate if this is in the wrong forum.

thanks for your help!

 

[woodgeek]

1st question: depends...in fan only, does it blow as hard as when the heat/cool is on? Does it run 100% of the time, or cycle on and off? If it is blowing full out at 100% of the time, yes, it will pull some elec (several hundred watts+). Otherwise it will use less. Can you pull a manual.

2nd question: wouldn't expect it to be a strain on the unit, esp if its running less than full speed.

Comment: Are your ducts inside the insulated part of your house, or an unheated attic/crawlspace? If the latter, you might be losing a lot of heat. A lot of folks around here don't recommend you use the central for distribution, but it really comes down to the install and duct insulation details.

 

[jlore]

yes it runs 100% of the time. yes the ducts are well insulated. they run through the attic. it works great; i'll just have to see if it's worth it when i get my elec bill. thanks for your imput.

 

[madison]

I tried the same technique with our A/C (attic blower/ducting), and came to the conclusion that there was way too much heat loss from my insulated duct in the attic, and the rooms farthest (SP?) away from the wood stove only had a 1 degree temp increase.

So I bagged it, and now use multiple ceiling fans, some pushing up, some pushing down, etc etc, and still experimenting, but feel that it works better and uses way less electricity, and is quieter.

The snow/frost melt on attic roof was a real telling. I even tried laying extra R-30 on top/sides of the A/C ducts in the attic, another waste of $$. At least i was able to move the R-30 to the rafters after this failed experiment. I now pull the ceiling A/C registers in the fall and stuff insulation in the outlets and inlets. Which really cuts down on the drafts down out of the registers.

 

[mackconsult]

I am a mechanical engineer with electrical and mechanical experience.

In my house all the ducting for the central air system appears to be insulated for moving air around the house.

I.E. when our our A/C is on or our AUX heat you can get a good amount of cool or warm air coming out at all the vents around our house. This is probably mainly due to the fact that when the A/C or AUX is on the temp differential coming out of the central unit in the attic is quite high.

I am planning on soon installing a Magnum ZC in place of our existing factory fireplace. With this will be some framing work, facade work, and a new 8" chimney. Planning on having a blower in the magnum which will do a great job at keeping our "great room" comfortable during the winter time. Our great room is about half of our 1500 ft^2.

Toying with the idea of putting a DC powered fan at the intake of our central unit. The intake of our central unit is at the very peak of our great room. This makes it the highest point of the heated area of our house, and I am sure when we start using wood to heat that this area will be 3-4 degrees warmer than the rest of the great room (heat rises). If the DC fan idea doesn't work, what might even work better is to have a electrical setup that would run the AC fan in our central air unit run at a much slower speed. In fact our plan is for the wood stove to burn every night during the winter, and so I would like the AC fan of our central air unit to come on every other hour distributing the warm air of the great room around the rest of the house. Logistically I don't know if this will work, but I want to start playing around with it. Will be monitoring power consumption of the house to see any difference.

It's got to be better than that AUX unit we have. I remember one winter having a $400/mn power bill and I know it wasn't the XMAS lights.

 

[DeePee]

Consider replacing the furnace blower with a variable speed DC unit. I run mine 24x7 year round with significantly less noise and financial impact than the 120VAC unit that came with the house.

 

[mackconsult]

Cool. Can you post more information for me?

I.E. how you hook it up in place of the AC unit? What model did you use?

quote author="DeePee" date="1255997747"]Consider replacing the furnace blower with a variable speed DC unit. I run mine 24x7 year round with significantly less noise and financial impact than the 120VAC unit that came with the house.[/quote]

 

[afblue]

I am interested myself in a DC blower unit, hopefully even one that can be inline. I am looking to take the cold air returns in the upstairs of the house, and running a setup to draw the cold air returns down into the dining room adjacent the livingroom where the fireplace is. The disapated air will create a loop that will coax the warm air in the living room up the stairs, and into the bedrooms.

 

[semipro]

Consider replacing the furnace blower with a variable speed DC unit. I run mine 24x7 year round with significantly less noise and financial impact than the 120VAC unit that came with the house.

Most air handler motors are already variable speed. They'll usually have 3 or 4 speeds depending upon which hot wire is connected on the motor. Find the motor model and look it up on the web or check the motor's wiring diagram on the side plate. I'm thinking you maybe could use a separate circuit to power the existing fan on low speed if that's really the way you want to go.

You'll find most of the folks on this board prefer to instead move cold air to the stove, finding that works better than trying to move the hot air around.

 

[DeePee]

quote author="DeePee" date="1255997747"]Consider replacing the furnace blower with a variable speed DC unit. I run mine 24x7 year round with significantly less noise and financial impact than the 120VAC unit that came with the house.

Cool. Can you post more information for me?

I.E. how you hook it up in place of the AC unit? What model did you use?[/quote]

The blower is integrated into the furnace I had installed - Goodman GMVC95. I keep it in circulate mode 24x7. I had this unit installed as part of an eco retrofit program, with the tax credits and rebates from the hydro company it hardly cost anything to install. When it was shiny and new, my old man put his meter on it for me and if my memory is not failing me, it was consuming 45w in circulate mode.