Temperatur switching/control of fans

[mithko]

I am looking for a system that can be used to cool and ventilate a workshop as follows:
1. At temperatures below 28 deg C,only a few of the fans are on.
Say 10 of the 20 fans.
2. At temparetures above 28 deg C, the rest of the fans switch
on.
3. The fans that are normally on (the 10 that are on when
temperature is below 28 Deg C)should alternate every week.

Any ideas as to what I can use.

Regards

 

[MintJulep]

Two temperature switches, a timer and a relay.

 

[flash3780]

^What he said.
Something like this:

http://www.newark.com/microtherm/03en15t044-30-20/thermal-switch-nc-30-c/dp/07WX4443

 

[btrueblood]

Today I might do it with one temperature sensor and a smart (programmable) relay. Would need to know the amp draw of the fans to size the relay(s).

digikey.com is another source for suitable equipment, as is McMaster or Grainger...