Wiring an STC-1000 heat and cool thermostat... step by step

[fragmatic]

This is my build if you make one you are doing so at your own risk. I am showing you how I do it. If you copy my example you are claiming to have the skills and safety knowledge to do so.

This will be done as a visual aid to how an STC-1000 is wired using two external relays to handle our heavy heater loads. This step by step is to be considered as a visual wiring diagram. If I was to do this as a working assembly I may need to make my wires longer, etc. I am doing it in such a way that makes it easy to see and follow. This is a valid method but I do not have to do it exactly like the demo pictures as long as I make the same connections.

I am going to show how I would build the circuit if I was not going to put it into an enclosure to make it easy to see.

This is the relay I will be using: Search results for "70132401" - Allied Electronics

Here is one of many links to the STC-1000 that I could of used: All-purpose Temperature Controller STC-1000 Auto switch between refrigerating and heating - Amazon.com

About the STC-1000
The STC-1000 is a thermo control unit that is used by the thousands in the food, brewing, and manufacturing industries. It is very reliable and accurate. It reads in C and will hold a reef tank to within about .6° C if you have enough heater and cooling capacity (this is "about" barely over 1°f). You can get this device delivered to your door for $35 or less because of the quantity they are manufactured and sold in. Since I live in the US I was careful to find one shipped from inside the states. I was also careful to buy one that is designed to work at 110VAC (wall socket) because they come in several voltage configurations. The STC-1000 comes with the 6' temp probe included in the box and a set of instructions that take some background in this type device to understand easily (if you get my drift).

I will need some 14 gauge wire. I will use two colors. (I only need a few feet)
I will need some 25 gauge ( I will call this wire the light gauge wire) or similar sized wire in three colors. (I only need a few feet)
I will be using a terminal strip but it is not required, I use it because it makes it easier for me to demonstrate how I wired it with more clarity.
I will be using some forked terminal ends and two sizes of female spade quick disconnect ends.
I will be using two cheap, 6 foot, three prong, multi-socket extension cords rated for at least 10 amps.

Not shown are the light gauge wire, wire nuts, .... and the female spade connectors only represent the three kinds I will actually be using from my kit.

Here are most of the parts I used laid out.

 

[dwilliams87]

Sweet. Following along. Love DIYs

Sent Via the R2R Forum APP

 

[fragmatic]

Now let me post this link too. This a KILLER way to mount the STC-1000. However, I know I should use the external relays as I am about to show I do. I could stick the external relays on the back or side of this 2X box and have a killer housing for my controller. or.. use a 3 gang box and have room inside, then I could wire one set of plugs for "HEAT" & the other set of plugs for "COOL".

Another idea is to buy a deep single box and the single cover to use as a housing for the STC-1000 and the relays then I could hang the cords, as shown in this DIY, out the bottom.

Thanx to Kheebl for finding this link.

EBay fish tank controller build using Wal-mart parts - Home Brew Forums

 

[fragmatic]

I purchased two cheap multi socket three prong extension cords. I spent about $6.50 each at Home Depot. The ones I purchased are rated at 13 amps. Since the whole point is to make sure the heaters and fans do not come on at the same time I have decided in my case these cords are heavy enough.

I cut them to the lengths I needed to reach my heater's and fan's plugs, ... and my power outlet.

 

[fragmatic]

Next I simply use my wire cutters to separate the wires.

x

 

[fragmatic]

Then I split them back a couple of inches and strip about 1/4" as shown.

 

[fragmatic]

I did not have to use a terminal strip but by me using one I be able to demonstrate how I ran my wires much easier. The key advantage for using the strip here is to make it easy to connect several wires together. This also keeps it clear to me as to which side of the power cord I am connecting my wires.

So I now can clearly see black going up and white going down. To be correct I want the black wires to be connected to the wire on the "pig tale" (cord) which is connected to the thinner of the two flat prongs.

 

[fragmatic]

Now in the next few pictures I am going to wire the STC-1000 with the lighter gauge wires. These wires only feed the STC-1000 and the relay coils so they aren't going to carry hardly any current.

I cut three light gauge black wires. The lengths aren't critical but are about 7" and 2". In a real layout I would need to be sure they are long enough to fit the component layout inside my enclosure. Extra wire length is not going to hurt a thing here.

 

[fragmatic]

This is a hard step...LOL..
I twisted them together as shown.

 

[fragmatic]

Now I put the end and new formed twisted ends into the STC-1000 terminal strip as shown. I will be using connection ports 1, 5, & 7.

In this picture, looking at the diagram on the top of the STC-1000 helps me clearly understand which ports are which.

Now I crimp on a fork connector as shown.

So, I have now provided the hot 110VAC wires to the STC-1000 and also to one side of the two built in 10 amp relay normally open contacts.... well hot ...IF I was to plug it in,.... I will not be plugging it in!!!)

 

[fragmatic]

Sorry for the fuzzy picture, I found out too late to redo it.

Now I make a light gauge white wire and run it from the white side of the terminal strip and to the #2 terminal port of the STC-1000.

 

[fragmatic]

Next I label my relays as "A" & "B" and make two white light gauge wires and crimp on 3/16" female spade lugs, one on one end of each and push them onto the spades as shown then connect them to the white side of the power strip. This is only to power the coils of the relays and will not carry much current.

The second picture is just for clarity.

 

[fragmatic]

Now I cut two light gauge red wires and add 3/16" female spade lugs to one end of each and push them onto the relay spades as shown.

Then I connect the one from relay "A" to the STC-1000 at terminal port # 6. Next I connect the one from relay "B" to the STC-1000 at terminal port # 8.

IF .. I were to power up the STC-1000 at this time it would operate... except it would only be turning the relays on and off and not my fans and heaters. "A" is for the heaters and "B" for the fans.

Now if I want to run a chiller off this device I leave out relay "A" and "B" and connect the chiller thermostat wires straight into the STC-1000's terminal ports 7 and 8. Then I can program it to have a delayed start so it prevents my chiller's compressor from short cycling. I need to BE SURE I understand I do not power the chiller off the STC-1000, I use it as the thermostat.

 

[fragmatic]

Now I wire in the temp probe. I simply connect it to the STC-1000's terminal ports 3 & 4. Polarity doesn't matter.

 

[fragmatic]

It is time for me to grab my extension cord ends from the pile, I am going to wire them in.

 

[fragmatic]

I then label one "HEAT" and one "COOL" and put a 1/4" female spade lug on the wire that connects to the thinner slot of the sockets of each cord. I find the small ridges on the skin of one wire on each and know that is the one that goes to the thinner slot. If it was a different kind of cord with round covering I would know it is the wire with black insulation.

I push the lug of the one that says HEAT onto the "NO" (normally open) spade of relay "A". Yes, that spade actually has a "NO" label near it on the relay.

Then I do the same for the "COOL" cord except on the "B" relay.

IN THE PICTURE: I have wired them to the wrong relay.. if you caught this you get a point for being on your toes. Do what I say not what I did in the picture. I could say I did it to test you.. but no I guess it was because of all the camera work.. LOL... all I needed to do was alcohol off the "heat" and "cool" and re-label but I wasn't smart enough to catch it until now, days later.

 

[fragmatic]

Now I make two black 14 gauge wires the the length that work for my layout. Then put 1/4" female spade lugs onto one end of each. These wires will handle the actual current of my heaters and fans.

 

[fragmatic]

I then crimp a fork lug on the other end of each of these black wires and connect them to the black side of the terminal strip, and push the spades onto the remaining lugs on the left in the relays as shown. The lug on right as shown it this view of the relays will not be used.

 

[fragmatic]

Next I make two 6" long pieces of 14 gauge white wire and crimp a fork lug to one end of each. I take a wire nut and twist the other end to the remaining white wires from the cords. This completes my power to the heaters and fans through the relay normally open contacts so that the STC-1000 can have control of them. I will turn my heaters up to 85°f so their thermostats will not interfere with the newly gained accuracy and reliability.

 

[fragmatic]

At last, I cut a 6" long piece of 14 gauge green wire and use wire nuts to connect the ground leads of all my cords for safety.

This guys and gals is how I wire my STC-1000 when I am not doing it inside a housing or enclosure.

I hope you find it useful... I would rather DIY when there is a way because it builds a mental tool box of skills. AND, often it is far less expensive. Another reason I DIY is to keep things in a KISS mode. (Keep It Simple Stupid). Then there is one more reason.. ... . this is a hobby.. DIY projects just add to the depth of it as a hobby!