Dangerous situation

[gcyeaw]

I thought posting this experience could prevent someone else from having a more serious outcome.

I was programming a motion sensor the other day, and inadvertantly turned on the attic fan. I was in the basement and didn't notice it. Since it is winter, all the windows in the house were closed. A little later my wife came down and commented how warm it was in the basement. After some looking around I descovered that the low preasure created by the exhaust fan was pulling air in through the furnace flue, along with the heat and Carbon Monoxide from the burner!

So the upshot is, I installed a carbon monoxide detector. I still need to determine what to do about the fan. Perhaps a sensor of some kind to determine the furnace status and a script or possably mechanical device to prevent both the furnace burner and exhaust fan from operating at the same time?

[firtha]

Maybe just turning off the circuit breaker for the fan in winter time? (Assuming the fan is the only thing on the breaker)


Or, add a conventional wall switch in the circuit to turn off power to the fan, regardless of what X-10 is doing.

[dale]

We had an attic fan in our old house and I miss having one now. I installed the fan with a timer switch (non-X10) and a manaul overide switch in tandem so that the timer switch could not turn on the fan without the manual switch being turned on. I used this safe-guard since each winter I climbed up into the attic and placed a bat of insulation on top of the louvers to prevent heat loss. I did not want that fan coming on with the insulation in place. Perhaps you could do something similar.

[Skibum]

Isn't this as a result of an improperly set damper?

[gcyeaw]

I am about to start a small addition along with a new kitchen, so I will have an oportunity to do some wiring changes. I am thinking about using single adequate amperage 3-way switch configured to enable the fan OR the furnace. That way in the warmer weather when I normally shut the furnace off, the fan will be enabled. Also with this setup, no one else (kids, guests, Homeseer, me?) will be able to have both on at the same time.

Thanks for your suggestions. Mainly I just wanted to raise peoples awareness of this kind of situation.

[rekadau]

Please, don't just shut off the furnace when the whole house fan is running. The water heater gases will also be drawn into the house. You have to have windows open when you run a whole house fan, even in the summer. The fan sucks air, and a lot of it. If you have everything shut, it will suck the air backwards through your chimneys. No flue damper will prevent this, because if it did the exhaust wouldn't be getting out, and you would have the same problem. So, unless you have your furnace and water heater shut-off and there is no pilot in either of these appliances you will have a problem. But wait, you may be running a dryer and who knows what will happen then. It's better to be safe by only running the whole house fan when enough windows are open to keep the pressure from becoming too negative. The only other solution would be to have all your gas appliances in a room atmospherically isolated from the rest of the house. Is 'atmospherically' a word?

Roger