Dual Stage Temp Controller

[aakour]

I recently built a dual stage temperature controller that works great, if you can deal with your temp being in C.

:mtool: STOP! This project involves working with electricity and electrical components. If you are not comfortable working with electricity, do not peruse the project. I make no warranties, express or implied, for this project. If you like the idea, but are uncomfortable working with electricity, consult an electrician licensed in your jurisdiction. While I may have knowledge and experience workign with electricity and am authorized to do electrical work on federal facilities, I A) am not licensed in any municipal jurisdiction-including yours, and B) assume no liability or responsibility for this project.

Now that the legal mumbo jumbo is taken care of, I'm going to split the BOM here because the controller itself has 10A relays, and my chiller's spec plate says 11A min 15A peak. I have a quite old 1/3HP chiller I got for $100, I think it's an older aqua star-not sure-it has a Copeland compressor and somewhere it says R22, so it's definitely not new, and it has no control circuitry. This project is also intended for US 110v, 60Hz, single phase main supplies.

At this point I assume if you are continuing that you either have common sense, and know at least a little about electricity, or have a death wish-which hey, to each their own.

Before beginning, calculate your amperage load for cooling and heating. For cooling use the peak amps from the spec plate on the chiller, not the compressor. Most chillers have compressor and control circuitry, you need to power both. Then for heating, calculate your amperage divide the total watts of heating by 110v-this will get us close enough for AC current. After calculating your amperage loads, make sure your circuit for your tc equipment is rated to handle a minimum of the higher heating/cooling amps-if using a dedicated circuit, or-more practically common-that many amps+the rest of your tank equipment+any other stuff plugged into that circuit. If you've been using all of this stuff fine on one circuit before this build, you are probably ok since the controller doesn't draw much more current, but don't come after me if you trip a breaker to your tank, or burn your house down.

My max cooling load is 15A and max heating load is ~2A.

Tools Required:
Phillips #1
Small Standard Screwdriver
Wire Stripper
Wire Cutter
Rotary Tool with Cutoff Wheel
OR any substitutions that may work.

The basic part-if both of your peak loads are 10A or less:
1, STC-1000 110v Temperature Controller ~$20
1, Project Box 8x6x3-I recommend the Radio Shack one ~$8
1, 110v Dual Outlet-rated for your max amps ~$2-$8 Depending on Color
1, Outlet Cover Plat ~$0.25-$6 Depending on Color and Style
1, Grounded Extension Cord or Power Supple Cord-rated for your max Amps ~$6-$20 Depending on Color, Type, and Load
5, Terminal Block Connectors-Rated for Higher than your max Amps ~$6 for 24 10A blocks.

So if you only need 10A or less, the cost is as low as about $38 for the equivalent of many $150+ devices.

For higher than 10A for cooling you need to add:
1, Solid State AC to AC Relay with 110v in the range on both sides-rated for your max amps or higher ~$9 for 20A
2, Terminal Block Connectors-Rated for Higher than your max Amps ~$6 for 24 10A blocks.
1, Smidge(~.25g) of Thermal Paste ~$5 for 1.5g if Using External Relays
4, Smide Silcon or 2, Bolts and Drill to Secure Relays ~$0.20 or less of silicon

If you need the extra 10 amps for cooling the cost is about $48, still saving $100+

I am not going to go into higher than 20A for cooling or more than 10A for cooling AND heating, because that requires additional heat sinks, complexity, and cost-potentially including rewiring your house. And lets face it, if you can afford heating and/or cooling that pulls more than 20A why are you looking to save only a few bucks in comparison to your other costs.

 

[aakour]

I apologize in advance for not taking any pictures along the way, I hadn’t fully though about posting this build, and I wanted to make sure it worked wall and I was pleased with it before I did. Also, I actually built the higher amperage model with an additional relay, which I also did not take pictures of.

Now for the build:
For 10A or less:

Start with the project box, mark an area big enough for the controller to fit through but still be covered by its bezel about ½ to ¾ in from the top centered. Next do the same for the outlet about ¾ in from the bottom, but making sure that the mounting screw holes are still on the plastic, not the hole you will be cutting. For the basic 10A model, mark a 1/8 in by ¼ in notch on the top rear centered for the temperature probe. Do the same for the bottom, but big enough for your power supply cord to fit though. Now make those cuts using your rotary tool, or a drill and hacksaw, etc.

Prepare the outlet. With the outlet facing you, you need to work on the right (hot) side. Remove the tab connecting the metal plate to both screws. This will separate the outlet from 2 plugs on one circuit to independent circuits. Leave the left (neutral) side intact.

Prepare the controller. Remove the orange retainer clips and set aside. Unscrew and remove the back cover from the terminals and discard.

Next we will begin working with your wires. Cut your cord to leave no more than 3-5ft with the plug-save the excess. Separate 2 to 3in of hot and neutral, and 1in of ground and strip 1/8 your wires. Put the green into one end of one terminal block and tighten. Do the same with neutral. For hot leave 3 blocks connected and put your hot supply into one side of one block. For hot, cut 2 2in wires from you excess when trimming the cord, and strip 1/8 in from both ends of both. In the same hole as hot supply, put one end of the jumper wire, tighten, on the next connected block, insert the other end of the jumper, and one end of the other jumper on the same side and tighten, then put the other end of the second jumper into the last block on the same side and tighten.

At this point, the supply cord and terminal blocks need to be behind the project box, and the controller and outlet need to be in front of it by the holes you cut for them.

Connections to outlet. Cut a 3in piece of wire for the ground to outlet. Strip 1/8in on one end, insert into the ground terminal block and tighten. Strip ¼ to ½ in from the other end, stick it through the hole in the box for the outlet. Wrap it around the ground screw on the outlet and tighten. Now, cut 2 more pieces of wire about 3in long for neutral. Strip 1/8 in from one end on both and ¼ to ¼ in on the other end of both. Insert the shorter end of on into the neutral terminal block and tighten. Stick the cord through the outlet hole. Wrap the longer end of the same cord wrap it around the lower neutral screw on the left side of the outlet and tighten. Wrap the longer end of the other wire around the top neutral screw on the left and tighten. Cut one 3in and one 5in wire for hot to outlet. Strip 1/8in from one end of both, and ¼ to ½in from the other end of both. Wrap the longer end of the 5in wire around the lower hot side screw on the right side of the outlet. Do the same with the 3in wire for the top hot side screw on the right. At this point, ensure all the wires go through the outlet hole into the box, and you can go ahead and secure the outlet to the box in its hole. You can also go ahead and put the cover plate on if you want to.

Connections to controller. Due to limited space and the angle you need to connect the controller while it’s outside the box. Cut 3, 3 to 5 in wires for hot supply to the controller. Strip 1/8in on both ends of all three. Insert and tighten the hot supply wires into the supply side of the circuits for the controller, heat circuit, and cooling circuit. Refer to the diagram on the controller for reference. Insert the other end of the cooling circuit into the terminal block directly connected to the hot from the supply line and tighten. Insert the other end of the heating circuit in the 2nd hot terminal block 1 jumper away and tighten. Then insert the other end of the controller supply into the third terminal block 2 jumpers form the hot supply and tighten. Connect the temperature probe to the controller referring to the diagram on the controller. Take the 5in wire from the outlet and connect it to the output of the cooling circuit on the controller and tighten. Then connect the 3in wire from the outlet to the output of the heating circuit on the controller and tighten. Last connect the extra wire from the neutral side of the outlet to the neutral side of the controller supply and tighten. Now put the back of the controller through the hole you cut for it, slide the retaining clips you removed earlier back onto the controller. Fully insert the controller and push the clips all the way forward until they are tight.

If you have not already done so, secure the outlet and attach the faceplate. Make sure the temperature probe is running through the top hole and the supply cord runs through the bottom hole you cut. For this design, use the plastic box cover and secure with included screws.

 

[aakour]

Testing: Do not connect your heater or chiller yet. Use a lamp or two, or something like that. Connect one to each outlet. Plug the supply line into the wall. I’m not sure where the controller starts, but I think the heat light come on right away on the controller, if not, put it in a cup of ice water until it does. When the heat light is on, the tope device should have power, and the bottom should not. Now, hold the probe in your hand until the cool light come on, now the bottom should have power and the top should not. There is also an in between area where neither should have power. If this doesn’t happen check your wiring, and make sure you completely broke off the middle connection on the metal tab of the outlet. If this doesn’t fix it, you have a faulty controller.

Operating the controller. First determine your desired tank temp in C. Now with the unit plugged in, hold the S button fro about 3sec, F1 should show on the display. Hold the S button while pressing up or down arrow to adjust the temp. When you reach the desired temp, press the power button to save. Now hold the S button again until F1 displays, release the S button then press the up arrow to F2 on the display, adjust this like F1 to about .6 and then press the power button to save. This sets a 1 degree differential in each direction, meaning a 2 degree total differential. Now we set the short cycle timer. Determine the duty cycle of your chiller, you may have to contact the manufacturer. Hold S until F1 displays, release S, press the arrows until F3 displays. Hold S and the up or down arrow to set the number of minutes for compressor lockout to prevent short cycling. Press power to save. F4 is adjusted the same way as F2 but for most people is not needed on new units. F4 is a temperature compensation setting for temp calibration.

Now put the probe where you want it in your tank and wait about 2min for the temp to stabilize in the unit. Connect your heater to the top outlet, and your chiller to the bottom and you are good to go.

Make sure to follow drip loop rules, and make sureyou don’t put your controller where it will be splashed or dripped into, even by accident.

I will post instructions for the higher amp design when I have a chance. I will also get pictures of my finished unit and possibly a schematic up as soon as I can.