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Old 06-05-2010, 09:17 AM   #1
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Whole house fan


True/false?

-If the windows are closed the fan will suck combustion air through the fan and pull CO into the house. The CO diffuses throughout the house.
-If the windows are open the fan may suck combustion air through the fan. In this case you are only in danger of CO if you are in the air path of the fan. Sitting by the windows is OK.

And:
. . .Are there any whole house fans that sense when they are pulling too much of a vacuum and so they are probably stealing combustion air and so they shut down?
. . .In general, what is the tradeoff between the CFM of any house fan, normal house infiltration and combustion air being stolen?

Thanks for your input.

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Old 06-05-2010, 09:57 AM   #2
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Whole house fan


Yoyozit, when you say "combustion air", do you mean combustion byproducts? Combustion air is actually fresh air used by a heater to allow combustion of fuel.

Speaking for myself, the only time I use my whole house fan is during the time of year when the furnace (boiler in my case) is not in use. I don't know why anyone would use a whole house fan during heating season as it's sole purpose is to eliminate warm air from the structure.

I suppose there is the possibility of drawing combustion byproducts (CO) from a gas fueled water heater or stove, but the possibility of poisoning from such a scenario is pretty low because the fan is not meant to run continuously. In my case that is not a factor either because I have a power vented on-demand gas water heater. I've never had an issue with CO from the stove, as usually the vent fan is on when cooking during warm weather anyway.

The whole house fan only needs to be run for a few minutes in the evening, when the outside air has cooled, to expel warm air from the structure and pull cool air into the house through lower level windows.

I have a CO meter and it has never alarmed. I recommend one for any home that uses fuel burning appliances whether the home has a whole house fan or not.

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Old 06-05-2010, 11:11 AM   #3
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Whole house fan


Quote:
Originally Posted by fabrk8r View Post
Yoyozit, when you say "combustion air", do you mean combustion byproducts? Combustion air is actually fresh air used by a heater to allow combustion of fuel.

Speaking for myself, the only time I use my whole house fan is during the time of year when the furnace (boiler in my case) is not in use. I don't know why anyone would use a whole house fan during heating season as it's sole purpose is to eliminate warm air from the structure.

I suppose there is the possibility of drawing combustion byproducts (CO) from a gas fueled water heater or stove, but the possibility of poisoning from such a scenario is pretty low because the fan is not meant to run continuously. In my case that is not a factor either because I have a power vented on-demand gas water heater. I've never had an issue with CO from the stove, as usually the vent fan is on when cooking during warm weather anyway.

The whole house fan only needs to be run for a few minutes in the evening, when the outside air has cooled, to expel warm air from the structure and pull cool air into the house through lower level windows.

I have a CO meter and it has never alarmed. I recommend one for any home that uses fuel burning appliances whether the home has a whole house fan or not.
I meant upsetting the normal draft that fuel burning appliances need, like a water heater.

My CO alarms have never gone off and I use a 16" box fan with a baffle mounted in an upstairs window for ventilation, but the post on a whole house fan got me to thinking about this.
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Old 06-05-2010, 12:59 PM   #4
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Whole house fan


With the windows open. It depends how many windows are open, and how far open they are. Along with how much air the fan is really moving.

And then the location of the water heater in relationship to the fan, and its air paths.

I wouldn't say your safe if sitting at an open window if its pulling combustion byproducts. Since you would eventually have to get up to shut the fan off.

There are controls that can turn it off it the house is under a negative pressure. But seldom used.
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