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I'm pretty new to electronics. I'm building a device that has an aluminum enclosure, is powered by a 120V AC outlet, and requires roughly 520W of total power.

My circuit is:

  1. AC input with a hot, neutral and ground
  2. On/off switch with hot and neutral for the AC input, and hot and neutral for the load
  3. 1 to 4 AC power splitter with hot, neutral, ground
  4. 4 loads (240W, 240W, 25W, 10W) that are all individually certified (presumably grounded)

The switch doesn't have a ground connection, but my loads do. Also, my enclosure is aluminum.

I'm thinking I'll connect the the ground connection of the AC input to the ground of the power splitter, bypassing the switch. Additionally, I'll ground the enclosure with a lug and also connect that to the AC input ground.

For any wire connections I'm gonna use heat shrink tubing / solder / crimp connectors to keep it tidy.

Is this a reasonably safe method of building this circuit? Thank you in advance.

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  • \$\begingroup\$ Sounds good - the only problem is in the details how exactly you will be wiring it, with what kind of lug, washers and screws to chassis, and with what gauge/size of wires. There are electrical codes and regulations how these are required to be made, and you need to know your safety regulations. One possible problem is the aluminum, as it will form an insulating oxide, making it more difficult to make good enough earth connection compared to many other metals like steel. \$\endgroup\$
    – Justme
    Apr 17 at 19:52
  • \$\begingroup\$ @Justme thank you for mentioning. was planning to use 10AWG which I think is on the conservative side for my circuit. as for the lug - I've never done it before and I did hear about the oxide problem that you mentioned. will try to do my best. \$\endgroup\$ Apr 17 at 20:11

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It's correct that the ground (earth) should always be connected without any means of disconnecting it. So it must indeed bypass the switch.

The only thing that seems to be missing from your build is a fuse in the hot coming into the device. Apart from that, there's nothing wrong with what you've described.

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    \$\begingroup\$ It's been too long since I've done this, but for US locations, one doesn't usually switch the neutral line for polarized connections or non-double insulated devices. I don't know if it is code breaking if you do, or if it's just more economical if you don't, but you should look into it. \$\endgroup\$ Apr 17 at 20:30
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Use a good metal chassis that is connected to AC mains ground so if any fault occurs (wires break or something shorts to ground). Use a fuse or a breaker so if there is any over current (a short will cause over current) it will blow the fuse or trip the breaker.

If you have max 520W @ 120V that would be roughly 4.3A of current max, so a 6A fuse or breaker ought to cover the fault condition.

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  • \$\begingroup\$ Thank you very much. Didn't know about the fuse part, will do! \$\endgroup\$ Apr 17 at 19:46
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For this sort of thing I like to use an IEC C14 inlet, with a built in switch and fuse holder. Something like this. That has spade connectors on the inside, and insulated female connectors are easy to crimp on with the same tool you'll be using for a ring connector that goes on your earthing stud.

Best practices I was taught include:

  • Strapping the cables together close to the inlet such that if the whole lot were pulled the earth would disconnect last similarly at the other end if those cables are crimped.
  • Putting the ring terminal for the incoming earth connection on the stud before any others. This is your primary earth point, to which all others connect
  • The nut securing the earth ring should be locked (with a star washer or 2 nuts jammed together, for example)
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