After building a Son of a Fermentation Chiller and using it for a while.

I found the following problems:
· It would only hold one carboy
· The analog thermostat sucked
· It is a PIA to deal with the ice in deep narrow ice chambers

So I redesigned the controller first to use a digital remote sensing thermostat for under $25.

The Controller

The RiteTemp Model 8029B digital thermostat can usually be found for less than $25 at your local home improvement warehouse.

It is run by two AA batteries and has a thermistor on the circuit board. It is easy to modify the thermistor to remote sensing. It will go as low as 35°F (1.6C).

Disassembly

The first thing you do is to remove the battery compartment.

Then remove the SIX screws that hold the upper circuit board on.

Do Not Remove the two screws on the left of the circuit board.

It will not blow up you just don’t need to remove them.

Remove the upper circuit board.

Remove the screws holding the lower circuit board on.

Carefully remove the lower circuit board.

Do Not tip the front case over lots of stuff will fall out!

If you tip it over all the little goodies will fall out. This is how they looked before you dumped them out.

Locate the thermistor on the upper corner of the lower circuit board.

Carefully heat the solder and pull out the thermistor wires one at a time.

If you have a solder sucker you can clean out the holes but it’s not necessary.

Solder two wires in place of the thermistor.
You can heat the solder up and push the wire through.

I used solid core 24awg wire I had from another project.

I got the wire from Radio Shack it was 4 conductor and I just stripped two off.

Make sure you have a good solder joint.

I use a low wattage soldering iron with a pencil point.

No Solder Guns Please.

Clip off the extra wire with a wire cutter or nail clipper.

Reinstall the lower board.

Reinstall the upper board.

Route wires as shown or your favorite way.

Reinstall the battery compartment.

Route the wires as shown or your favorite way.

Solder the thermistor to the ends of the wire.

Put heat shrink tubing on the wires before you solder.

Tin the ends of the wire and solder each one on.

Slide the heat shrink over the joint and shrink.

Complete the project by putting a larger heat shrink tube over the entire thermistor and the solder joints.

After installing on your fermentation chiller tape the thermistor to the side of the carboy.

Put a couple of paper towels folded up as shown or a square of bubble wrap over the thermistor for insulation from the ambient air.

Connections

If you need to switch over 24 volts use a relay.

The capacitor across the switched legs can’t take 120vac. How do I know, well I tried so you don’t have to smell the smoke when it comes out.

This is a general diagram on the hookup for the controller using a 12 – 24 volt fan and power supply.

This is the general hook up if you use a relay to control a 120 volt AC device like a fan or a pump.

Make sure the relay contacts are rated for at least 120 volts AC and are rated to handle the load amps.

This is a wiring diagram if you're using a DC fan and pump for the glycol chilling system. (Thanks Joe)

Installed

Here it is installed on the front of my fermentation chiller.

If you need any more information just let me know.

John