3 phase outlet or not?

Plant machinist · May 8, 2017

When I bought my South Bend 16 ( 3 hp 3 phase) the previous owner had it running from an outlet . should I continue to use an outlet or should I hardwire ?

jim rozen · May 8, 2017

Plant machinist said:
When I bought my South Bend 16 ( 3 hp 3 phase) the previous owner had it running from an outlet . should I continue to use an outlet or should I hardwire ?

One advantage of having a plug and receptacle is you can positively disconnect when you doing service. If hard-wired it's a nice idea to have a lockable disconnect there. Not just a breaker in
a sub-panel, which is typically out of sight.

The downside on portable cordage to a cord cap is that the S cord does not stand up terribly well in a rough environment. But I do use heavy SO cord and a cord cap in my installations at home.

tfoley · May 8, 2017

I would agree with jim rozen about having a quick way to positively disconnect the machine for maintenance or repair. I am using SO cord and receptacles on several of my machines and plug and unplug as needed. I will say that after a number of plugging and unplugging the receptacles loosen up as in the screws holding the receptacles loosen up and it seems I can constantly tightening them. However you mileage may vary. Maybe I just have a lower quality receptacle even though they are Hubbell brand.

gadget73 · May 8, 2017

I like plugs, but if you want to hard wire I might suggest a disconnect box placed near the lathe if the breaker is going to be running other things, or if the breaker panel isn't easy to get to.

Plant machinist · May 8, 2017

I thought about a disconnect and hard wire but since some of the small stuff like small cutoff saw and a few grinders are on outlets here at work I may just go that route. They even run some welders on outlets here. I think I'll compare cost and go from there.

SteveBausch · May 8, 2017

If I was concerned about wear and tear on the cord, perhap slipping it into a section of liquid tight would help.

Or garden hose?

Plant machinist · May 8, 2017

No concern about the cord wear. It will only be about 4’
long with no traffic near it.

SteveBausch · May 8, 2017

. screws holding the receptacles loosen up and it seems I can constantly tightening them. However you mileage may vary.

There's four holes on the strap, two are 6-32 tapped. Not adequate for me when an exposed work square box cover (Raco 801c) is involved. Drill cover to accept 8-32 trusshead screws, nut from behind, crush threads with ViseGrip.

Perhaps LocTite on the 6-32s would be adequate.

No rule says you have to lock them in...

k3vyl · May 8, 2017

Assuming the cord and plug are still with the lathe,and not some obsolete type that you can't get easily,the cheapest way will be to get a receptacle and reuse the cord and plug. You then have a code legal disconnect on your machine at minimum cost.

Plant machinist · May 8, 2017

k3vyl said:
Assuming the cord and plug are still with the lathe,and not some obsolete type that you can't get easily,the cheapest way will be to get a receptacle and reuse the cord and plug. You then have a code legal disconnect on your machine at minimum cost.

That is what I have decided to do.

cyanidekid · May 8, 2017

have to add, "lock out-tag out" is't just a nice thing to have, it is most certainly required in any plant setting, at least.

disconnect means, with provision for lock out tag out. It is OSHA that has authority in the workplace, so it is not always NEC that has the last word here. seems it could get confusing, but if you provide a disconnect with the little hasp for a padlock, (within sight of the machine?), for each hardwired machine, you are probably good. for a plug, the little plastic basket with a padlock, believe it or not, is all you need.

it could actually be cheaper to use the proper NEMA plug and receptacle, and you can switch machines too.

(oh, and do make sure the correct plug is on it now)

k3vyl · May 8, 2017

Long before the plastic baskets were available DuPont plants used plug lockout devices made from copper tubing that fit over the plug and had a cap drilled for the cord. The open end was cross drilled for a long shank padlock. They were made in the machine shop with a pipe fitter doing the soldering and an electrician doing the final installation. Those plastic clamshells are a real money saver..

LKeithR · May 8, 2017

When setting up a previous shop--many years ago--we thought we had a perfect layout for all the machines and accessories.
Hard wired everything in place with conduit runs to a junction box and a short piece of teck cable. Took only a couple weeks
to figure out that our layout was wrong.....sigh. After moving the machines around we left the conduits as they were, put plugs
in the junction boxes and ran heavy cabtire cords to each machine. Worked fine and the cords lasted for years. That was 30+
years ago and I don't think we've hard wired a machine since...

Plant machinist · May 9, 2017

LKeithR said:
When setting up a previous shop--many years ago--we thought we had a perfect layout for all the machines and accessories.
Hard wired everything in place with conduit runs to a junction box and a short piece of teck cable. Took only a couple weeks
to figure out that our layout was wrong.....sigh. After moving the machines around we left the conduits as they were, put plugs
in the junction boxes and ran heavy cabtire cords to each machine. Worked fine and the cords lasted for years. That was 30+
years ago and I don't think we've hard wired a machine since...

Good advice

danil · May 9, 2017

My rule of thumb is that if it is 10 hp or more-- hardwire it; as the twist and lock plugs that I use get spendy once the amperage gets up there.

I like using the twist n lock plugs for smaller items-- especially since I have multiple occasional use machines that don't require their own dedicated drop.

Vladymere gr · May 9, 2017

I believe every machine should have a dedicated magnetic motor starter with included overload protection.

Being a one man shop I used a cut out switch assembly between the single phase AC panel and the RPC. RPC feeds to a three phase breaker box with a breaker for each machine circuit. Each machine circuit is hardwired to a dedicated motor starter and then the machine wired into the motor starter.

My experience with outlets is that overtime the plug and socket connection loosen up.

Vlad

k3vyl · May 9, 2017

The amp rating is definitely the money factor. Once you get into the pin and sleeve devises 100 amp and up,the prices are really up there. They are used on welding machines commonly. Many times we would do temporary hardwire on a welding machine because of the price of those devices. Money in my pocket instead of Hubbell's

gadget73 · May 10, 2017

I've seen a lot of people use stove or drier outlets for higher current. I believe stove circuits are 50 amp. More modern ones have enough pins for 3 phase work too. Not twist-lock though.

mcruff · May 10, 2017

Put a twist lock plug from a ceiling mounted box with a strain relief. That way you can remove if need be. Easy to sweep around also since it's not draped across crap. Every shop I have ever worked in but my current one had these for all machines that were 3 phase.

3 phase outlet or not?

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