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Hot topics: Wire size for a 60 Amp circuit



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Original Post: Cable size for a 60 amp circuit

BuzzHazzard – Visiting guest

I connect a subpanel for a workshop. I will have a 2HP Dust Collection system on a dedicated circuit, lighting on a dedicated circuit and two 20 amp connectors currently. I might want to expand to a 240V circuit for a 3HP table saw sometime as well, and maybe add an air compressor.

Anyway, a 50 Amp circuit will suffice and I know I should use 6-3 w / G to feed the subpanel and isolate the neutral bus bar from the ground bus bar in the subpanel.

But if I choose to go with a 60 Amp subpanel supply instead, what size cable do I use? I know that 6 AWG is good for 55 amps. Still, I have an oven with two spare element heaters on 60 Amp circuit breakers. Everyone looks like the electrician used a 6-2 cable for the circuit, although I can not find any writing on the mantle that I can safely say. And I̵

7;ve never seen a 4-3 NM-B cable.

I have a number of very good books on the subject, but no one addresses this issue other than that I would use SER cable to feed sub-panels at or above 100A and NM-B 6-3 for a 50 Amp.

Thanks in advance.

Oh, BTW, in Lowes today I bought a subpanel with 125 amp rating. The guy in that department said I would “use” cable that met that rating even though I plan to feed the panel with a 50 (or 60) amplifier circuit. It did not sound at all. Am I confused or was he?

John NelsonMember

6/3 supports either a 50-amp or a 60-amp subpanel (with the next larger standard size rule in 240.4 (B)).

The information you received from Lowes is certainly not the dumbest thing I have ever heard from a home improvement store, and at least it’s not dangerous, but the advice you received was both stupid and wrong anyway. He’s confused. You are not.

BuzzHazzard – Thread starter

Thanks. As an “advanced amateur” I know the 240.4B rule as it was mentioned in one of my books, but I wanted to make sure I did not use it incorrectly in my case.

noxx – Visiting guest

You can continue with cable # 6 for the load you are planning right now. Personally, I would run number 2 to enable an expansion of your store in the future up to a 100A flow. Wire is quite cheap, saves running it over a few years on the road if your projects take off.

brickeyee – Visiting guest

A dust collector and a 3 HP table saw may have trouble starting with just a 60 A wire. Even if you start one and wait for it to come in a hurry, the other may trip over the head in the sub-panel. 100 amp is more useful in a full wood shop.

sberry27Member

I have a 3 hp and a 5 hp compressors on a 60A sub with a total of 42 drive amplifiers, it stars them just fine and 5 is secondary. Never have problems, but of course bigger is always better.

brickeyee – Visiting guest

I have a 3 HP unisaw installed on a 60 amp panel for a while. It needs 45 amps to start repeatedly, and even after it was up to speed, the dust collector would trip the switch about 25% of the time. Much depends on the quality of the engine. Better quality engines have a higher kVA-locked rotor code and take more power to start. The Unisaw engine would be> 60 hp with the “maximum developed” method. It will also cut through 3 inches of hard maple or even hardwood without slowing it down.

BuzzHazzard – Visiting guest

Thanks corner. I got 6-3 cheap and will go with it for now. In my old house I had a 40 amp subpanel and never had a problem with the same equipment that I plan to use now.

But I will always have access to the drive between Service Entrance (two 200 Amp panels) and my workshop’s subpanel, so if needed I can replace the subpanel supply and buy a new switch. As I said before, my subpanel is rated at 125A.

PATTBAAMember

Art. 430.63 allows the classification of the feeder CB to exceed the classification of the supply conductors where the feeder delivers a “combination load” consisting of motors, luminaires and appliances. It is possible to have a 100 amp CB protective feed conductor marked to 60 amps if the feeder delivers motors.

The 40 amp “difference” would be the full load current of the largest motor multiplied by a factor of 250% (Table 430.52).

The FLC for a 240 volt, 3-HP single phase motor is about 20 amps. If this motor was supplied by a feeder with a 30 amp liting / device load, CB’s rating would be (250% X 20) + 30 = 80 amps. The capacity of the feeder would be (125% X 20) + 30 = 55 amperes.

bubinga1- Visiting guest

I think when I got about 10 feet at Lowes, it was about $ 1.00 per foot. 4




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