How to make a High Temp Shut-off

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After seeing a few farmers lose their crops to malfunctioning AC's I decided to post this simple DIY high temp shut-off that works for light controllers from 1-50 lights. NOTE: Be sure to size the contactor appropriately for the number of running amps. Ex. if it is rate at 30 Amps then you can only run 6 lights on the contactor and remember that ballasts pull an additional 20% at start-up so size appropriately. Here are the directions:

A. 2 wire Electric baseboard thermostat from Home Depot - 20$
B. A length of 16 gauge wire long enough to go from your controller to your room.
C. female disconnects from HD - 3$ this is what they look like:

D. 3 pole definite purpose contactor - here is a link for one but any 3 pole with 120V coil will do:

All you have to do is interrupt the power from the supply to the controller with the contactor. So look at the picture from the link you will see 6 screws.

1. Turn off your power. Attach the wires from your power supply (white(common), black, red) to T1, T2 and T3.
2. Now attach the wires that go to your controller on L1, L2, L3. The order is not important but what IS important is that the wires on both sides match up, i.e., black with black, etc.

Ok see those buttons in the middle? They are what activate the coil. Basically this thing has a little magnet on the inside that when it is energized it makes the connections between t1,t2,t3 and l1,l2,l3. When it is not energized no power can get across. The idea is that you set your thermostat to say, 90F and so long as the temp in your room is less then 90F the thermostat will send a signal to the contactor to energize. This is how you wire the thermostat:

3. You can't see them in the picture, but there will be little metal tabs sticking out (not the ones attached to the screws) lower on the contactor that activate the coil. You need to first run a wire (this is important) from either the black or red wire (a power wire) on the T side, to thermostat.

3a. Attach a female disconnect to a piece of wire that is connected to your thermostat and push in on one of the metal tabs (black or red) THAT IS PART OF THE SCREW on the contactor, not one of the metal tabs that is lower down.

4. Attach the other wire from the thermostat to one of the metal tabs that is NOT part of any of the screws using a female disconnect.

4a. You should now have one wire coming from the contactor going to the thermo and one wire leaving the thermo going to the contactor.

5. Attach a small length of from one side of the tab that powers the coil (the tab you used in part 4) to the WHITE wire tab on T1, again use female disconnects.

You have now completed the whole circuit. So long as the temp in your room is below whatever you set your thermostat to, the thermostat will activate which will complete the circuit from the power that goes into the thermostat to the tab that activates the coil. The small piece of wire from the coil to the white wire power screw completes the entire circuit.

Good luck. If this seems difficult, it is not. If you are not at all familiar with electricity show a buddy who has some electrical knowledge this email and he should get it no problem.


Saw a guy On another thread use a $5 water bed heater. Good thinking! :)


Saw a guy On another thread use a $5 water bed heater. Good thinking! :)

This dude right here! Give him a gold star. This shit is a great Idea...
Mow, I used to have a water bed! Man I loved that thing...Why did I ever give it up? Oh right the heater went out and caught the wood part of my bed on fire. Mow, you listen right Mow! This shit is real talk. When the bag part busted it was apparently started on the bottom. This allowed for the bag that was under pressure (King Size) to rupture at equal rates on all sides to the top and then dropping like the last unicorn tear that was cried in vain, before chuck Norris ate it's brain. You there, what are you doing right meow? Want to know where I was doing during all this? On top of the bed, duh! So I hit my head on the timer that messed up and caught the bed on fire. It cracked my dome and pushed it through the thin wood frame just enough to spark the carpet on fire. Now here I am naked, laying on my back, blood coming from head mixed with less than 1/4 inch water and it spread to the parts of my body that pushed the plastic down with the most weight. I was knocked out naked, legs crossed at ankles, arms out like I was on the cross, blood pooling around head, arms/hands and feet.
My little brother had herd the noise and bust in the room. He quickly turned around and locked the door. He covered me up with a blanket, then let in my parents. Now, my parents did not see my brother go in my room. Brother sees how bad this could look, grabbed my Girlfriends hoodie she had left and stuffed socks in his hoddie and stormed out covering his face and screamed in the best impersonation I have ever heard to date of my GF (now wife) "Call the ambulance, when he wakes up tell him to call me. he then lingered by the back of the ambulance to tell the person working on me what had really happened. My brother and I have just shared a dream. We were in the same room asleep, woke at the same time and had a "dude, where is my car?" feel more than a few times. I know this seems like a lot of typing for a 5 dollar timer..I mean what are the odds That I could almost get killed again by one of these guys....

No, really all jokes ^ aside. This idea will work.

I may have to go lay dowm.
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