How To Automate Circulating Fan?

[gpop]

I have a 2 story 2300 sq ft home that is on a single system (no zones). The temperature gradient between the two levels is insane unless I run the fan quite a bit. My question is , is there any device on the market to help me automate the fan so that it cycles at set times for set periods of time? I would like to run the fan for 15 minutes every hour except for the times that the house is vacant. I hope to find something like a programmable thermostat that will allow me to program my fan cycle too.

GPOP

[fms2k]

Maybe you could look at using a Grasslin Digi-42 series electronic time clock to do what you're looking to do. It provides 24-hour or 7-day time based switching with up to 21 on and 21 off programs. Contacts rated @ 16A up to 277 vac. Runs from 24 or 120 vac power supply. Has battery backup and holiday programming features. Not really expensive. Kele stocks them. Go to http://www.kele.com to check it out. Hope this was helpful.

[BaldLoonie]

Totaline's P374-1100 has that feature, the Vision Pro stats will randomly run the blower part of each hour.

[gatorguy]

I like the Robertshaw 9720i (heat pump) thermostat. See it here:

http://www.icca.invensys.com/SellShe.../150-1656E.pdf

You can make the fan come on for a certain number of minutes every so many minutes. Just what you are asking for, but it does not differentiate between occupied and unoccupied. You'd have to switch it back to "auto" when you returned home.

Also, you can set the fan to "auto" or "on" during each program interval.

This may or may not be what you are looking for.

[pstu]

All the previous answers have merit, here is one more that is used in the Building America program:
http://www.aircycler.com/

They offer several models. The higher ones are oriented toward controlling outside fresh air in addition to just cycling the fan. As I understand it the most basic model would do what you ask, and work with your present thermostat.

The Honeywell Visionpro looks very nice aesthetically. Customers seem to like them. Their concept of cycling is fixed at a flat 35% duty cycle, and runs at random times. The Aircycler and I believe the Robertshaw, will refrain from running in the few minutes just following and AC shutdown. This can be important to good humidity control if that is important in your climate. In my hot-humid climate I would refuse to buy the Visionpro until they fix this flaw.

Best of luck -- P.Student

[beenthere]

Check out the honeywell vision pro, i believe you'll find the 3201 has a fan cycling set up, that would be what you want.

[aerlpam]

I just recently installed a device that does what you want, it's called an AirCycler. you can find details on the company website at http://www.AirCycler.com.

Pretty simple to install and works great. The nice feature is it resets itself whenever your furnace/ac shuts off so if you want it to turn your fan on every hour or so it will start counting AFTER your furnace shuts off. Time delay and fan run time are easily set.

Hope this helps.

[Edited by BC1 on 03-09-2005 at 01:05 PM]