Grounding 12v DC and 240V AC on the same chassis

[snowtires]

Hi all,
My question is regarding an arduino based controller (ardbir) and 12v pump relay which will be powered by a 110v - 12v DC power supply.

I want to connect all these items to the same chassis as a 240v 30amp ssr, contactor, plugs etc.

1) will the 12v DC interfere with the GFCI protection?
2) should i get a plastic box instead to isolate the DC and AC power?
3) should i keep these systems completely separate?

 

[BrunDog]

You can tie the grounds of all your power supplies together. The GFI is tripped when current is mismatched through neutral.

-BD

 

[snowtires]

That is what I suspected. I just wanted to be sure. Thanks brundog. Always better to be safe then electricocksuckered.

 

[snowtires]

Also. Does anyone know if its okay to attach my GFI breaker box and my arduino box together into 1 unit? My breaker box is a small spa panel type, I want to just use the breaker as my main on/off switch for the brew panel

 

[BrunDog]

????

 

[snowtires]

What I mean is, the 12v arduino, ssr, plugs mounted in the box on the right and have the arduino powered by a wall wort in a separate garage plug. Set my brew parameters and everything on the arduino, and use the GFI as the switch to turn on the element. Basically skipping the contactors and switches. Simple

View attachment 1450407224360.jpg

 

[snowtires]

So basically the wiring would be ultra basic, no fuses, no anything, just one hot to the ssr then the element and one right to the element. That's it. I guess the only thing would be, what do I do with the neutral? Just cap the wire off? And if the GFI uses the neutral, then how does it detect ground faults if your not using the neutral?

 

[snowtires]

I just googled about the GFI. The neutral is only needed for 120v if your not using the neutral it will detect the difference between the 2 hot wires, which makes perfect sense. even if you do not have a 4 wire circuit you can still use a GFI just if you don't use a neutral at the breaker then the test button won't work, but you are still protected from ground faults.

 

[BrunDog]

You should not use a breaker as a switch.

 

[snowtires]

I know there are some breakers that are used to switch lights.
I brew about once a month, your supposed to test GFI breakers once a month. So really I would be just testing the breaker by turning on and off my heating element. Thoughts? It really is a switch after all

 

[FuzzeWuzze]

While your *probably* ok, i wouldnt want my failure point to be anywhere near my GFCI breaker.


I consider my GFCI in my breaker panel on the other side of my garage the "oh **** somethings horribly wrong, i need to cut power asap" button.

 

[snowtires]

I think my oh **** somethings horribly wrong would be unplugging from the wall. This is something that would be completely unplugged each time I'm finished brewing. Essentially using the GFI as a switch that's not used excessively to operate my element. According to the NEC, breakers should be constructed in such as way that they should be able to endure switching without excessive wear. Do you guys think that the GFI safety would diminish if the switch were to wear out? Is there any codes that even say you can't use a breaker as a switch?

 

[crane]

I think my oh **** somethings horribly wrong would be unplugging from the wall. This is something that would be completely unplugged each time I'm finished brewing. Essentially using the GFI as a switch that's not used excessively to operate my element. According to the NEC, breakers should be constructed in such as way that they should be able to endure switching without excessive wear. Do you guys think that the GFI safety would diminish if the switch were to wear out? Is there any codes that even say you can't use a breaker as a switch?

If something catastrophic is going on where you need to kill power the last thing I would want to be doing is disconnecting the power source to the GFCI. There is no ground fault protection up stream from the GFCI breaker. If something bad were to happen you have nothing to protect you until 30/50 amps of current runs through your body and the breaker in your main panel trips.

 

[snowtires]

I don't get it. So you mean to say if something bad happens upstream from the GFI? Like lets say a wire leading to the GFI box somehow electrocuted me because its near my brew panel and not GFI protected? Basically the cord leading to my brew panel? Or if the GFI itself explodes or gets splashed with beer then I lose all my means of disconnecting power other then unplugging it?

 

[user 163849]

This is not advise.

I have worked at more than one warehouse type location where all the lights, compressors and such were switched on and off at the breaker. Usually one on and one off operation per day, 5 or more days a week, all year long. Seems to have worked just fine as in most cases if a breaker were to fail I would have been the one called on to replace it, and I do not recall any such events. The failed breakers that I do recall all tripped for legitimate reasons, then refused to close. Maybe they should have been labeled as fuses instead. The fact that the breakers were not designed for that purpose did not seem to interfere with their ability to serve the purpose quite well. They worked that way before I was there and continued to work that way after I left for greener pastures.

This is not advise.

 

[snowtires]

Here it is so far. I haven't decided if I am adding an element switch and contactor or not yet.

View attachment 1450563971474.jpg

 

[BrunDog]

Ya 30A is not going to run through anyone's body unless the voltage is much, much, much higher. Anyway you certainly don't need that to kill you.

Nonetheless I think the breaker is fine to use. A close proximity switch is better, but if the breaker is right there, go for it. You won't cycle it enough to wear it out quickly.

 

[snowtires]

I guess I just really like having the simplicity of the wiring this way. No contactor, no fuses, no terminals, no switches, just a ssr and a plug for wiring. Not much to go haywire really

 

[FuzzeWuzze]

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