thermostat with timer for fan?

I have a two-story house that is currently being blasted by the heat dome in the NE. What I have been doing the past few days is switching the fan on my thermostat from AUTO to ON in the evening so the upstairs won't be so hot then turning it back to AUTO before I go to bed. I only have one thermostat downstairs so it is always cooler downstairs. The attic fan that blows out the gable vent is running almost constantly.
I have already blocked all the return vents downstairs and closed all of the downstairs registers and it has dramatically improved the temp upstairs but it still needs work. I would like to avoid redoing the ductwork and making the 2nd floor a separate zone.
I was hoping I could find a thermostat that would kick on the fan say 20 minutes out of every hour regardless of the call for the compressor.
Any ideas?
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You might want to consider an Insteon thermostat. You can control it from a computer, or other Insteon accessories and tell it to do pretty much anything. I suppose the minimum to get this going would be a timer device and the thermostat.
http://www.smarthome.com/2491T1/Venstar-Thermostat-INSTEON-Remote-Control-Thermostat-1-Day-Programmable/p.aspx ($160) http://www.smarthome.com/2456S3T/TimerLinc-INSTEON-Plug-In-Timer/p.aspx ($50)
But you should check with the Insteon techies to make sure it can actually be configured to do what you want (whether the timer device can control only the fan). There's a free chat page on their website. You should also browse through their other thermostat products as I wouldn't be surprised if they have some functionality on their other thermostats that might suit your needs better.
John
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The Honeywell VisionPro thermostats do that. At least the newer ones, not sure about older ones. The fan has 3 settings, on, auto, and circulate. The first two are the modes all thermostats have. The circulate mode turns the blower on about 30% of the time, randomly, during periods when the heat or cooling is not being called for. You can find them on Ebay for a reasonable price.
On the other hand, from some experimenting with it, I can't say that having the blower on 30% or even constantly makes a noticeable, worhtwhile difference at my house. I'd also caution about closing off too many ducts in your house. I close off two ducts downstairs that are on the duct that also feeds upstairs. I also added an inline blower to that duct and those efforts produced significant improvement. Closing off all the ducts downstairs sounds extreme and you may not be getting sufficient air flow through the coils.
It's sad because these problems could be avoided entirely if anyone had reasonable skills and gave a damn during construction. Afterwards, it can be difficult to impossible. If you have means to add more return duct capacity upstairs that would probably be a big improvement.
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wrote:

Limp, forgot to mention. Since you mentioned a timer in your post, the VisionPro circulate feature that I described can also be programmed into any of the 4 periods for each day of the week. So, if you want the fan randomly circulating the air 30% of the time when the AC isn't cooling, you can have that for just during the day period. The other 3 periods could then be automatic fan, meaning it only runs when the AC is cooling. Or any of the periods could be fan on as well.
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wrote:

Thanks. Sounds like VisionPro is the thermostat for me. Now all I have to do is figure out which one I need to buy. Odd that they don't mention the fan feature but it is in the manual. I can't be the only person who lives in a slapped together tract house with an unbalanced forced air system.
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The only difference among the current ones that I'm aware of is whether they support 1 stage, 2 stage, or 3 stage sytems. You just need one that supports what you have as minimum, ie you can use a 2 stage on a 1 stage system.
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