CNC Lathe Build - Circuit Breaker Protection and Conductor size questions

[tq60]

Huge code violation!

First thing is put a 30 amp breaker on that wire YESTERDAY!

If something happens and that is found, heap of trouble.

Next, measure the conduit size and try to remember how many bends and where they are.

Call your local building department and ask them the largest size wire that can fit inside that conduit for the required amount of conductors.

Required amount...?

Normal would be 4, L1, L2 Neutral and safety ground.

But due to distance and other factors you may be able to use a smaller safety ground and or use a ground rod at the shop.

Larger wire is very little more money now so largest you can pull.

Code limits conduit fill by diameter, bends and sweeps may reduce it further, your electrician may advise there.

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[JimDawson]

Conduit fill table

https://www.stateelectric.com/resources/conduit-fill-table

 

[Reddinr]

For the house to shop run, the other conduit factor is the type of conduit and wire type. EMT conduit has slightly more room in it than some of the plastic stuff for example If it is PVC schedule 40, and you used 4 x #4 or #6 AWG THHN, for example, you would need at least 1" conduit (without factoring in the number of bends etc.). If you want to reuse the wire, pull in a stout rope when you pull out the old wire. Then use the rope to pull the new wire. That way you don't stress the old wire any more than necessary. Then again, wire is not the driving cost of your CNC setup really. Be sure to use pulling lube when you pull the new wire. Makes it easier and it is less stress on the wires.

I noticed that the current rating of the drives seemed to be for the lowest input voltage the drive is rated for, 115V I think. Since you are powering with 240, that current will likely get cut in about half. The instruction manuals for the drive probably have tables for the input currents.

Gotta run again. Will check back in later.

 

[vtcnc]

#6 AWG aluminum wire ok to use for replacement?

 

[ttabbal]

#6 AWG aluminum wire ok to use for replacement?

https://www.usawire-cable.com/pdfs/NEC%20AMPACITIES.pdf

My guess is no. Aluminum has lower ampacity than copper. I also tend to upsize my conductors, so perhaps I'm a bit conservative. It looks like it's at 60A if THHN (the most common I see around here) and at 90C, which is hotter than I like it. And it says that the main table does not take voltage drop into account. You would be running 3 current carrying conductors, 2 hot, 1 neutral. Ground doesn't count against you on that, but it might get tough to pull depending on the sizes. The length also makes me want to de-rate a size. If you do a separate ground rod, in most areas it needs to be bonded to the service entrance ground rod with at least #6 copper.

Any idea what the conduit size and type is? If it's my setup, I'd run #6 copper or #4 aluminum for a 60A run of that length. I didn't even think about the size of the main feed, I don't have the ampacity memorized that big.

 

[vtcnc]

Ok. Forgive me everyone. The photos tell the tale...

My first photo this morning yielded this:

I jumped to the conclusion that this four conductor cable is 10 AWG.

After our discussion today, first thing I did was pop open the sub panel and got a photo of this:

Upon

Further review, it appears I have 6AWG copper on the hots and neutral and 10AWG on the ground.

My apologies for dragging you all through this. I should have checked the sub panel and paid more attention to the writing on the feeder cable. However, I have learned quite bit that I didn’t know before and I have all of you to thank for that!


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[JimDawson]

Yeah, I think you're good there.

 

[vtcnc]

I'm so embarassed...this is a good example of what panic can do to a person. I need to calm the heck down...

 

[ttabbal]

So glad to see you have a good install. That would have been a bit crazy for an electrician to do that. Now you can focus on the fun part!

 

[Reddinr]

Great news. Glad it is #6 after-all.