Looking for safety double check for project

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Old 10-17-16, 05:06 PM
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Looking for safety double check for project

Hello All.

Working on my first High Voltage arduino project, I have tried to build the whole thing with safety in mind. Hoping for double check of anything you think I might have not thought of or if I am just wrong.


This is an Aquarium controller for medium sized aquarium.

The whole thing is ran off a dedicated 20 amp breaker wired with 12/2. With a dead face 20 amp GFCI, The GFCI then goes to a 20 amp outlet. That outlet then runs a 12/2 to the enclosure Then I have ground probes plugged into that 20amp outlet running to the aquarium and to the filter.

The enclosure has one 8 position 600v/25amp terminal block for Ground, Neutral, and Hot, as well as one for the Hot Load off the relays. All the wiring from Line to relay's and current sensors are 12/2. The only place that is not 12/2 is runs out to the controlled outlets which are 15amp outlets and they are 14/2 wires.

The whole system if everything was at full current draws 9.87Amps according to my kill-a-watt and my current sensors, however typically 6 Amps. The highest load is my pump which is 3.12 Amps. The relays in the enclosure are only rated at [email protected]

While not perfect system I also have the current sensors monitoring each relay and set to switch it off at >8Amps.

The enclosure is wood, however all sides and backing are screwed and silicone together. the top of the enclosure is only screwed on as I might have to open it. All places where wires come into the sides are also silicone to ensure water can't run down the wires and into the enclosure.

One thing I have decided to add that's not pictured is one of those outdoor covers for my gang box to provide a second safety net. The system is not meant to be submerged just provide protection from splash or spray.


GFCI
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Outlet
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Enclosure Bottom (Line N, Line Ground, Relay Hot) Bottom Right Side (Line Hot)

Enclosure Top Right side (12 V Ground, 12v Positive) Feed From 10 AMP AC/DC conveter.

Enclosure Top Left (Shared Arduino Ground, I2C, and 1 Wire Termainal)
Enclosure Bottom Left (Arduino Positive)

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LV Wiring
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Old 10-17-16, 05:11 PM
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Forgot.

My Understanding of how the GFCI works is it uses a CT on Hot and Neutral, and expects they are equal. So I am expecting that if in the tank/filter if there is a failure the ground probe completes the circuit using Ground which should make an imbalance seen and acted on by the GFCI. Its my hope with how I have this laid out Ground closer to the hots in the enclosure that if something caused a dead short inside the enclosure that it would hopfully short to ground first and tripping gfci.
 
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Old 10-17-16, 07:38 PM
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Moved to the electrical forum.

The only place that is not 12/2 is runs out to the controlled outlets which are 15amp outlets and they are 14/2 wires
Wrong.
You have your project protected with a 20A breaker. That means all mains wiring needs to be #12.

While I'm on the protection train of thought. It's hard for us to comment on your work. It looks overly complicated but it's your project. You brought a 20A circuit in to your unit. GFI protection is mandatory and you have that covered. It looks like everything is connected directly to the 20A circuit. When I build projects like yours I bring in the circuit that's needed to a fuse strip and then every load is protected at it's actual operating current with its own fuse. It also protects your smaller interconnection wiring from handling more current than it should.

This looks scary and should be removed. Picking up the ground from a plug is not correct.
What if the plugs were removed ? No more ground. There is a common ground bar in your project and all grounds should connect there.

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Your understanding of a GFI's operation is correct.
An imbalance between hot and neutral will trip it.

I have this laid out ground closer to the hots in the enclosure that if something caused a dead short inside the enclosure that it would hopefully short to ground first and tripping gfci.
No... that is a misunderstanding. Placing the hot closer to ground does not insure any additional protection. FYI..... A short between hot and neutral will not trip the GFI.
 
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Old 10-17-16, 08:24 PM
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I agree short between hot and neutral won't trip gfci.
I was going to fuse each relay, but was not sure if it really bought any safety. My thinking was if it was not me making this but just plugged right into the Wall it wouldn't be fused. But it's a cheap change it will add fuses also cheap to change the wire to 12/2 for the controlled outlets.


I am confused by you saying I should remove the ground probes?

They are not the common ground they are to ground the water to the ground, there is a common ground all the ac connection share in the enclosure.

Can you help my understand why the ground probes are scary? I have never used them before normally just trusted gfci. However my understanding is if therected is a failure in the water it's isolated from Ground until I stick my hand in. At that time I act as ground and hopefully trigger the gfci. But having a ground probe to my understanding means as soon as there is a fault in the water it's ground by that prob closing the circuit and tripping the gfci.
 
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Old 10-17-16, 09:10 PM
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Sorry to post so much. Can you recommend a good fuse holder? All the ones I see on amazon for 5x20 or 1/4 are only rated at 15amps 125v. I was planning on using the gma-6 amp fuse, and I saw some board that held several fuse but that looked scaryou nothing covering themvery I like to try and keep hot Coverdale as much as possible prevent touching.
 
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Old 10-17-16, 09:20 PM
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It's not the ground probes that I questioned. It was the method of obtaining ground from one wire in a three prong plug.

Your hot terminal strip isn't covered.... so no real need to cover the fuses.

Those types of fuseholders are fine. They are rated at 15A max per fuse.
Aren't all your fuses under 15A ?
 
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Old 10-17-16, 09:33 PM
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Thank you for the advice order placed, the hot is covered with plastic cover, just hard to see though in my photo. I will move the ground probes to the enclosure for sure no one would mistakenly unplug it.

Yes all the fuses will be 6amps I just get iffy on glass fuses. Back in the day I had a glass fuse in my car stereo over current so much it melted the filament across the glass keeping the circuit closed. luckily the fuses at the amp blew. So I try to size every thing to avoid fire.
 
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