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Hooking up my high temp kill switch....?

S

Spanishwilly

Member
HI,
I just stole this little quote from a great article I'm reading on sealed grows...

"Note that if your A/C fails, your room can be subject to very high and very dangerous temperatures. Clever growers wire a 240V heating thermostat in line to the power supply of their lighting controls. The thermostat thinks that the lights are a heater and will keep the circuit open (supplying power to the lamps and ballasts) until a pre-set temperature is exceeded (i.e 92.5°F), then the power supplying the lamps will be shut-off saving you and your crop from disaster in the event of a failure in the A/C system."

This is great, but here's my question. Do I wire it before my timer so that it would cut off power to the timer? Would that work?
Or should I wire it between the timer and the contactor?
Will it carry enough load to go straight to my lamps (4x600)?
Or what?
I'm in Europe.
 
G

guest456mpy

Since you already have a contactor I would use a low voltage thermostat and wire it in series with the contactor's start relay.

That way the logic would be:
If Time = "day" and temp = "safe" then light = on
else lights = off

Doing all the logic in low voltage is safer. The logic circuit is more reliable and easier to troubleshoot as well.
 
B

Bud Bug

If you have a contactor already on the board you can use the Sentinel Master Timer http://grow-gps.com/?page_id=21 which has a built in kill switch with a manual restart- you have to press a button to reset the kill switch, this is the proper way to do it.

Or here's a 4 light timer board I have laying around with a kill switch but with out the reset feature.

picture.php


The timer is plugged into a 120 power supple and the main power supply is brought into the contractor (R/B/W wires). The timer turn on/off the contactor but the Can Arm thermostat interrupts one of the wires from the timer to the contactor and shuts off the contactor when it gets too hot.
 
Stay Puft

Stay Puft

Member
I would put a latching relay between the timer and the coil of your contactor, and put the over-temp switch to the "Reset" input of a latching relay...Then i would put a push-button switch to the "Set" input. see below:
Bud Bug makes a great point that you really should design your system so the lights will remain off until a human hits a reset button. (after they find out why it got too hot in the first place) You can do this with a "latching relay", but if a timer has this feature built in and it doesn't cost a fortune... i would go that route.

Here is good site to learn about "latching" relays:
http://www.magnecraft.com/latching-tool.php#
 
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Stay Puft

Stay Puft

Member
I should mention that I went through the same thing with relays... and in the end I would have been better off getting a PLC to start with. See this thread: https://www.icmag.com/ic/showthread.php?t=99252
There is nothing wrong with doing this with relays... It just doesn't seem cost effective anymore. (MPUs have taken over) They still use "ladder logic" which was implemented with relays long before micro controllers.
I.E. >-Next week you will want your controller to trigger a auto-dialer. (do you want to spend more $ on relays?)
Regards,
Puft
 
Lazyman

Lazyman

Overkill is under-rated.
Veteran
Man I tried using one of CAP's HLC-3E boxes (high temp shutdown and retart delay) both before and after my digital timer to my lighting relays, and they don't work for shit. It kicks off fine, then when it cools down it keeps opening and closing the circuit every few seconds, "click, off, click, off, click, off" not exactly good for relays and ballasts alike.
 
S

Spanishwilly

Member
Listen you guys,
Thank you for your responses, but none of those controller devices are available to me in Europe (as far as I know), so I have to make something work, like a heater thermostat switch or something.
Additionally, I'm trying to get something really simple to hook up for a non-electrician. That's why a heater switch appealed to me. Before you jump down my throat, I can get an electrician if I have to.
The guy at my grow shop in London has never heard of a high temp kill switch.
 
B

Bud Bug

Well this would be the easiest way but I'm not an electrician.

This is the inside of a CAP MLC-4 (4 light board). Its a pretty simple relay box to build. You'll notice the box has a trigger cord that plugs into a power source/timer which witches on the replays to send power to the receptacles to turn on the ballasts.

picture.php


The trigger cord can be powered by a timer like this.

picture.php


But to get a heat kill you could use a line voltage thermostat like this one (example) which has a piggy back cord on it.

What you would do is plug in the timer then plug in the thermostat piggy back into the timer then the relay box trigger cord would plug into the piggy back.

picture.php


The Cruise Temp or other thermostats like it have both a cooling or heating setting. So what you do is open is up and wire up the red (heat) wire to where the blue (cooling) wire is. Then set the temp to say 95 and when the temps in the room hit that the Cruise Temp would shut off the powet supply to the trigger cord on the relay box while the timer is still counting time.
 
G

guest456mpy

Well this would be the easiest way but I'm not an electrician.

This is the inside of a CAP MLC-4 (4 light board). Its a pretty simple relay box to build. You'll notice the box has a trigger cord that plugs into a power source/timer which witches on the replays to send power to the receptacles to turn on the ballasts.



The trigger cord can be powered by a timer like this.



But to get a heat kill you could use a line voltage thermostat like this one (example) which has a piggy back cord on it.

What you would do is plug in the timer then plug in the thermostat piggy back into the timer then the relay box trigger cord would plug into the piggy back.



The Cruise Temp or other thermostats like it have both a cooling or heating setting. So what you do is open is up and wire up the red (heat) wire to where the blue (cooling) wire is. Then set the temp to say 95 and when the temps in the room hit that the Cruise Temp would shut off the powet supply to the trigger cord on the relay box while the timer is still counting time.
Click to expand...
Does exactly what I said to do in post #2...

Since you already have a contactor I would use a low voltage thermostat and wire it in series with the contactor's start relay.

That way the logic would be:
If Time = "day" and temp = "safe" then light = on
else lights = off

Doing all the logic in low voltage is safer. The logic circuit is more reliable and easier to troubleshoot as well.
 
Dorje113

Dorje113

Member
Spanishwilly said:
Listen you guys,
Thank you for your responses, but none of those controller devices are available to me in Europe (as far as I know), so I have to make something work, like a heater thermostat switch or something.
Additionally, I'm trying to get something really simple to hook up for a non-electrician. That's why a heater switch appealed to me. Before you jump down my throat, I can get an electrician if I have to.
The guy at my grow shop in London has never heard of a high temp kill switch.
Click to expand...

You got your answer in the 1st response.

Use a thermostat to control the electromagnetic switch inside a contactor, could be the same contactor you use to switch on and off the lights if you are clever.
 
S

Spanishwilly

Member
Dorje113 said:
You got your answer in the 1st response.

Use a thermostat to control the electromagnetic switch inside a contactor, could be the same contactor you use to switch on and off the lights if you are clever.
Click to expand...
Well you know, I thought that first response was probably it. It was all that logic talk that got me nervous.
I don't unerstand electronics, and that sounds like writing a computer program to me.
Clearly I'm not clever enough for this detail. I have to buy another contactor?
 
Dorje113

Dorje113

Member
Spanishwilly said:
Well you know, I thought that first response was probably it. It was all that logic talk that got me nervous.
I don't unerstand electronics, and that sounds like writing a computer program to me.
Clearly I'm not clever enough for this detail. I have to buy another contactor?
Click to expand...

Relays act like logic statements in computer programming. Google types of relays and how to write logic diagrams, you will get it otherwise someone can suggest a plan.... but you should try to understand it, it is a very useful skill in growing and many other things.
 
Dorje113

Dorje113

Member
Hempyguy said:
No extra relay, just the thermostat and a bit of wire.
First, a bit of reading...
Series and parallel wiring

So the thermostat should be wired in series with the timer.
Click to expand...

yes, and to avoid confusion you'd need a line voltage heating thermostat, probably with a remote probe. So if you think of your lights as a heater, it will keep them on until the temp you set on the thermostat, then turn them back on when the temp goes back down.... if you can, get one with a large or adjustable hysterisis band so the lights cycle on/off less rapidly. Ideally... if the thermostat turns off I'd want the whole thing to remain off and give me a call on my cell phone because something major has malfunctioned for this to happen and it needs immediate attention.
 
rives

rives

Inveterate Tinkerer
Mentor
ICMag Donor
Veteran
Can't draw out what I want with the format changing when it posts!
 
Last edited:
rives

rives

Inveterate Tinkerer
Mentor
ICMag Donor
Veteran
If you add a relay and a normally open pushbutton, you can set it up so that it will have to be manually restarted. The following circuit is a simple start/stop circuit using the thermostat (set in the heating mode - the contacts will open on temperature rise) as the stop button.
 

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G

guest456mpy

If you add a relay and a normally open pushbutton, you can set it up so that it will have to be manually restarted. The following circuit is a simple start/stop circuit using the thermostat (set in the heating mode - the contacts will open on temperature rise) as the stop button.
Click to expand...
Exactly...
Why pay for a prepackaged solution when you can build one for a fraction of what they would charge.
 
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