Supplies list.
1 - 120V to 24V transformer
1 - Thermostat like you would use at your house
1 - Relay with 24V coil rated for 120V or more on the load
1 - Heating device, I will use overhead fixture with ceramic
Some electrical wire with 3 wires inside, 12 guage
Some thermostat wire with 2 or more wires inside, usually 18 guage
First, here is a wiring diagram of sorts. Where my devices had or I used white wire, I used blue in the diagram since the background is white.
Next, this is wiring up the plug. Lowe's didn't have indoor wire so this is outdoor wire, but it works the same, just rated for direct sunlight. You want to strip just a bit off the end of each wire. Connect the white to the silver screw, the black to the brass screw, and the green or bare wire should connect to the oddball plug at the bottom.
Next pic is wiring up the transformer. Just match like colors. If you don't have a green wire in your 12 gauge wire you bought you should have a bare. Green and bare are the same in prewired devices. These are labeled 1, 2, and 3 in the diagram. I used some connections I had around the house in all these pics. You can use wire nuts, electrical tape, or whatever.
Now your transformer should be wired up. If you have a multimeter or a testing device, you can test it now if you like.
This next pic is hooking up the wires in the thermostat. Your thermostat will have a very simple wiring diagram in the directions. Actually, it will probably have 4 or 5 diagrams. The one I needed was labeled "heat only". There are a series of screws inside the thermostat, 5 in my case, to hook up various wires. On the "heat only" wiring diagram I need to run a wire from the screw labeled "W" to the heat valve/relay and a wire from the screw "RH" to the 24V source. On the diagram I posted at the top, these are labeled 6 and 4 respectively. The other screws are not used for a heat only control setup. There is also a preinstalled jumper wire from the screw labeled "RH" to the screw labeled "RC". My particular wiring diagram shows to leave this installed. So, I used the thermostat wire I bought. I hooked the white up to the "W" screw and the red to the "RH" screw but really color is arbitrary when using wire you bought but NOT when using lead wires from a preassembled device.
This next image is fairly busy but not that complex really. All the wires coming from the grey wire to the transformer are hookups 1, 2. and 3 in the diagram and should already be hooked up. The red wire going into the front of the transformer is #4 and the opposite end was hooked up to the screw labeled "RH" inside the thermostat in the previous step. Now for wire 5. This is the green wire that hooks between the relay and the transformer. Make sure to hook this to the coil on the relay. Wire 6 is the white wire coming off of the relay opposite the side of the green wire. This is the white wire whose opposite end was hooked into the thermostat screw labeled "W". The white and black wires running horizontally across the relay are wires 7, 8, and 9. Take the cord on your heating device and carefully cut into one of the wires, it doesn't matter. If you end up cutting both wires just splice one of them back together, like I did. Which ever wire you cut remove a piece a few inches long, roughly the length of your relay or just shorter. Now hook these two ends up on the opposite sides of the relay. This is a double pole single throw relay. The double pole means I could hook up another heating element or device. The single throw means my circuit can be on or off. A double throw would switch between two different circuits. If you are just running one device all you need is a single pole single throw relay. However, they can be hard to find if you live in a small town and you might have to get a double pole single throw like I did, or a double pole double throw. The cost difference is minimal and they will all work fine. If you have questions on the difference between them just email me.
As you can see in the next pic, the set temp is 65 but the actual temp is 70. As we would hope, the light (which will be replaced by a heater) is not on.
In this pic you can see the set temp was changed to be higher than the actual temp and as we would hope, the light did come on.
There is a couple things left to do. I will have to unhook the two wires in the thermostat, mount the thermostat inside my tank where I would like for the temperature to be taken, drill a small hole behind the thermostat mounting site, and run my wires back through. This is pretty self explainatory and your thermostat directions should tell you how to access the mounting holes if they don't have access already. I will also put a clear plastic housing over my thermostat so a bored snake doesn't accidently change temps. Make sure you buy a cover designed for a thermostat so air will flow through the cover and the thermostat will read an accurate temp.
I also need to program my thermostat. The whole reason I did this project is so I can play weather man. If you don't buy a programmable thermostat, you might as well by a cheap one off the shelf and save money and time. With a programmable thermostat like mine (which was only 20 something dollars) you can change set points 4 times a day and the weekend can have different set points than the weekdays. You can also buy thermostats to change everyday if you like. If you have access to Grainger, you can get the transformer and relay cheaper than anywhere else. Here is a rough cost for the project if you can order through Grainger. After completing this project you can still use a dimmer switch to control the temperature gradient if you like. Just wire it in anywhere along the line of your heating device.
I am in no way an electrician or HVAC certified or anything like that. If you have ever been shocked by a household outlet, that is the worst shock you should receive doing this project, but if you seriously fry yourself or a piece of your equipment, IT AIN'T MY FAULT!
Transformer - $10
Relay - $10
Thermostat - $30
Thermostat cover - $20
Plug and misc. wire - $10
Please feel free to PM or email me with any questions.
Linear Mode
