Electrical Plugs and wiring and new to me equipment

[Erik Loza]

Just my take, but I always felt that if I ever did something stupid, I think I'd prefer that the plug came out of the outlet as opposed to the cord tearing and having bare live wire laying there. (sorry, slightly off topic).

I hear you. Funny: I guess my logic is opposite. Seen shops with machines where the plug was "sort of" in the socket. I got turned onto twist-locs back when Minimax was doing the trade show circuit. That's "the" connector any convention center or hall uses, so you must have one them your machines. Just got used to them.

Erik

[John TenEyck]

I have several machines that I plug into the same 220V - 30 amp circuit. There are two different receptacles, side by side, to handle different machines. Of course, I only run one at a time, but some are as low as 2 HP, one is 5 HP. All have their own protection built into their starter. This seemed like a very practical and safe approach to me.

John

[Chris Padilla]

if it was me - I would wire for 30 amps including plug but start out with a 20 amp breaker. as long as you don't start both motors at the same time you are unlikely to trip the 20 amp breaker. the breaker is to not only protect the cord & plug but also your motors - bigger is not better as it takes a larger current surge (and therefore damage) to trip the breaker - the 30 amp cord may be OK but your motor might not

you trip the 20 amp more than rarely then you can go to 30amp with a new breaker

Breakers only protect the wiring in the wall...not the load connected to said wiring in the wall. The motors ought to have their own thermal protection and the extension cord, plug and receptacle used should be appropriately sized to handle the expected current flow.

...and I like twist-locks myself and use them on all my 240V circuits. They just feel more secure to me.

[Garth Almgren]

I'd go with 6-30 and a matching 30 amp breaker with 10/2 wire. Twist lock seems excessive unless it's a ceiling plug.

[Wade Lippman]

Breakers only protect the wiring in the wall...not the load connected to said wiring in the wall.

People say this all the time, but it is just not true. Code is only concerned with protecting the house wiring, but breakers provide just as much protection to the load as they do to the house wiring. Since it is all one circuit, it couldn't be any other way; the breaker doesn't know where the outlet is.

The motors ought to have their own thermal protection and the extension cord, plug and receptacle used should be appropriately sized to handle the expected current flow.

Well, almost true. The plug and receptacle have to be sized to the breaker. Hopefully the breaker and wiring are sized to handle the expected current.

[keith wootton]

receptacles and plugs are designed and rated (in writing molded into fixture) to prevent inserting plug of higher amp drawing plug into lower rated receptacle. so based on question asked, you need a 30 amp plug.

[Chris Padilla]

People say this all the time, but it is just not true. Code is only concerned with protecting the house wiring, but breakers provide just as much protection to the load as they do to the house wiring. Since it is all one circuit, it couldn't be any other way; the breaker doesn't know where the outlet is.

So you said it isn't true and then you immediately state that the Code says it is true. While the breakers CAN protect loads, they aren't specifically designed or expected to do such things. If I design a product that plugs into an outlet, it wouldn't be wise to only rely on the breaker to protect my product...kind of like the thermal protection in a motor. Many products have fuses designed it.

[Tom M King]

I have never regretted buying the twistlock Hubbells. Of course, they're a lot more expensive now. I bought probably more than I would ever need in the mid '70s. I still have a few new ones still in the boxes. Only one has "worn out" over the years, and that one was still plugged into the side of the step van I used to work out of that had a big air compressor in it, and was drug down the road after pulling out of the temporary pole. I think the SO cord survived the torture.

[David Ashley]

Wow this is turning into quite the conversation piece. I know the saw has a four prong input but it looks like its European I haven't looked into it yet but the schematics seem to show only three wires are being used with no neutral. I wonder if Wood working equipmentnormally only uses three wires in a 240 set up normally

So it seems everyone is in agreement that a 30 amp 220 plug be the twist lock or straight plug is ok to use and whatever you use is what everything else in the shop will end up using. I guess I'm just more curious why there's multiple versions of the same kind of plug now. Only thing that comes to mind is twist style taking more room away from the wall vs straight style being more streamlined.

[David Ashley]

I'm not an electrician, but I would put the 30 amp breaker in. I would get a outlet and plug that matches other 220 outlets I have in the shop. I keep one style of outlet in shop. I'm sure someone with more experience will chime in.

That is the thing this is a new shop, so I have to decide on a standard. Sounds like twist lock is kind on industry standard though.

[David Ashley]

I would ask the manufacturer what they recommend. If it is really 21.3a then you must have at least a 30a circuit; possibly a 40a circuit. The same plug as on 20a circuits would be quite improper.
Likewise, I can't imagine why 12/3 for a cord would be recommended over 10/2. I suppose the additional voltage drop in an 8' cord would be small, but why do it? And why /3?

Well the manual I downloaded online states 20 amp, but it also lists smaller size motors, think it is older manual. Waiting for manual from the company.

Don't forget cords /3 = 3 wires and romex /3 = 3 + 1 bare ground.

I did ended up getting /4 but only because it might get repurposed in the future, again setup is in flux.

[Steve Peterson]

I use twist locks for all of my 220V equipment. There are not very many plugs and each one is dedicated to a specific piece of equipment, so the additional cost is minimal.

I also broke the cord on my table saw about 2' from the saw and added a set of extension cord twist locks. This allows me to disconnect power from the tablesaw without having to crawl under the table and reach for the wall plug.

Steve

[Wade Lippman]

So you said it isn't true and then you immediately state that the Code says it is true.

No I don't. I just said "code is only concerned with protecting the house wiring"; I certainly didn't say that code says that breakers don't protect power cords.

While the breakers CAN protect loads, they aren't specifically designed or expected to do such things. If I design a product that plugs into an outlet, it wouldn't be wise to only rely on the breaker to protect my product...kind of like the thermal protection in a motor. Many products have fuses designed it.

Of course; but whether they are specifically designed to protect such things or not, they do. You said they don't.

[Bruce Wrenn]

the breaker is to not only protect the cord & plug but also your motors -

Breaker is strictly to protect building wiring. Overloads on motor are to protect it.

[Jim Becker]

I'll also chime in that 30amp service to the tool is what is required. You always round up from "total" to the needed circuit size with very few exceptions, if any. My slider has essentially similar specifications to yours from a motor perspective and it's running cheerfully on the 30 amp circuit mandated by the manufacturer. My J/P has the same rating. The 3.5hp motor on my BS is happy on a 20 amp circuit.

I use twist-locks on all of my big machine circuits. Yea, they cost a little more, but they don't disconnect if accidentally bumped. I like that "positive" locking feature.