Help with temperature controller wiring

[vincemash]

I am working on a temperature controller, it controls a separate heating and cooling circuit...I want to hook it up so a fan also comes on any time the heating or cooling is activated.

The 4 circles are going to be outlets that I can plug into...the whole thing will be mounted into a radio shack project box.

Does the image below look like the best way to achieve this, or are there better options other than a relay:

[PLAIN]http://www.brew-beer.com/wiring%20fermenter.jpg

 

[dlgoff]

Generally in the stability chambers I've worked in (+40°C, 75%HR to -85°C storage) you keep the fan running all the time and depending on the operational point you're trying to achieve determines how to run the heaters and coolers. If say you were wanting to keep the room/camber at room temp (25°C, 40%RH) not only would you keep the fan running but also the cooler/air-conditioner (sized to keep the room much below 25°C without adding heat). Then all you need is one controller to add heat and maintain your set-point. In my case where relative humidity need to be controlled, another controller was required with a RH sensor and an output to heat a steam generator; as the air-conditioner removes humidity. It is fairly easy to maintain ±1°C and ±5%RH. This is because you are "always fighting" the environment inside the chamber. This makes, once you reached your set-point, it very stable; nice straight line on your graph.

Now if the situation was that you wanted to keep it very cold (much below room temperature), you probably don't need a heater. There will be enough loss to the external environment to create the "fight".

Hope this helps.

Edit: I don't think your relay from Radio Shack will have good enough contacts/rating(?) But in any case, you would need to design it to be locked out to service, and in an enclosure that is NEMA certified for the job. IMO