Author Topic: Electrically Opened, Manually Resetable, Relay/Breaker/Switch?  (Read 956 times)

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Offline psteichen

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I have a heater with an overheat cutout switch. Unfortunately the manufacturer designed it with a switch that resets itself when it has cooled a bit. Sounds like a good thing, but it's not. When the filter clogs up triggering an overheat cutout, it results in a never-ending cycle of overheating/resetting. This results in the overheat sensor burning out after a week or so if we don't notice.

I'd like to modify the circuit so that if the circuit is broken by the overheat sensor it stays broken until I manually reset it. The circuit is 24VAC.  My thoughts are to create a circuit that will monitor the situation, and if the overheat sensor cuts the circuit while it is live a manually resetable switch will be opened in the overheat sensor circuit thus keeping it open.

I will also make it so that my backup heating source is triggered, and a small buzzer will be activated to remind us to change the filter.

But my problem is I've never used a manually resetable switch that can be electrically opened.  I don't even know what to call such a thing. I considered using a circuit breaker and simply grounding out the circuit to force a trip upon the overheat sensor resetting itself, but this would probably cause the fuse that runs the whole system to blow as well and is certainly not ideal even if it worked.

Any advice would be appreciated.
 

Offline Pillager

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Re: Electrically Opened, Manually Resetable, Relay/Breaker/Switch?
« Reply #1 on: April 27, 2014, 03:03:30 AM »
Why not just build a simple latch circuit with a relay?

Use the cutout switch to reset the circuit and a simple push button to set it.
Then use the relay to switch the heater and whatever else comes to mind.

Of course, you will have to push the button to start the heater, when you had it unplugged, but let's call it a feature  ;D
Greets

Tom
 

Offline Pillager

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Re: Electrically Opened, Manually Resetable, Relay/Breaker/Switch?
« Reply #2 on: April 27, 2014, 03:25:26 AM »
See circuit:

When you press S1, the relay switches and latches via the contact next to S1.
When T1 (your cutout switch) opens, the relay returns to its original state and won't switch again, until you press S1.

Then you can use the other relay contact to switch your heater (make sure the relay can handle the load!). If you need more contacts to switch stuff, just get a relay with 4 or more contacts...
Greets

Tom
 

Offline SeanB

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Re: Electrically Opened, Manually Resetable, Relay/Breaker/Switch?
« Reply #3 on: April 27, 2014, 03:50:33 AM »
Just buy a thermal cutout with a manual reset option. Klixon makes them in assorted temperature values and they are  the same as the existing switch. You just have to make an insulated rod to reach in and press the reset button, or just have it behind a cover that has a disconnect safety switch and needs tools to open for safety.
 


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