L6-30 240 volt

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Srv52761

Srv52761

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Location
lowa
Occupation
Energy Manager
Christmas break project for our school district
I am under the impression:
- all new 240 volt receptacle circuits are to be 4-wire
- 3-wire receptacles previously installed are grandfathered in when attaching new equipment via 250.140 (exception) with several qualifiers:
1. the neutral is insulated or SE that lands at service main panel
2. the exception is limited to dryers, ranges, or ovens

Situation A) A new 240 volt circuit for a 3 hp table saw attached via cord and plug in a detached building with a 100 amp sub panel under NEC 2017.
Am I correct that the circuit must be 4-wire? Our maintenance personnel will be running the circuit. He wants to use a L6-30R to match the other outlets.
I contend he must use a 4-wire circuit.

Situation B). Same location. We also have a new 240 volt planer. He wants to adapt the cord to use a previously installed 3-wire L6-30R.
I contend the exception specifically states dryer, range oven; that a new 4-wire circuit must be run.

D05E5A56-C9B3-4634-A650-8D1C56A2D569.jpeg

His argument is the 4-wire requirement is for residential dwellings, not shops; that receptacles for 240 volt equipment are routinely run on 3-wire or even 2-wire devices.
His plan is to run two 10awg thhn with the conduit as the ground.
Is this code compliant?
Is 4-wire for dwellings only?
How far off am I?
 
Starting with the 1996 NEC a separate EGC is required for ranges and dryers. Previously the neutral could be used for the neutral and EGC. There is no requirement that a receptacle have a neutral if the equipment being plugged doesn't require one. A straight 240V load requires 2 hots and 1 EGC (or metal raceway).
 
You do not need a neutral conductor if the load being served does not utilize a neutral.

You never was able to use same conductor for neutral and equipment grounding at the branch circuit level other than for ranges and dryers with some conditions.

If the power tools in question here are straight 240 volt and do not utilize a neutral conductor then that L6-30 configuration is fine. If you did run a neutral there would be nothing to connect it to in the tool/appliance.

Add: if you do need a neutral then you need to use L14-30 configuration.
 
NEMA L6 receptacles are for straight 240V loads, Hot, Hot, _Ground_. This can be a 3 wire install.

NEMA L14 receptacles are for 120V/240V loads, Hot, Hot, Neutral, Ground.

NEMA L10 receptacles were previously used for 120/240V loads, where the neutral was serving double duty as the safety ground. This is no longer permitted for new installations, was never permitted from a 'subpanel', and should not be used.

So as others have said: if you have a straight 240V load an 3 wire install using the appropriate receptacle configuration is just fine, but if you have a 120/240V load you need a 4 wire install.

-Jon
 
Thank you. I bought our maintenance staff donuts and promised not to question their judgement for at least a week.
 
They could have a spec where they want a neutral in every circuit to allow easy reconfiguration. To me, that means you just run all 4 wires to the box, but connect only what you need to the receptacle. An L6-30 doesn't use the neutral, so cap it and push it to be back of the box.
 
Not sure what you mean when you say "he wants to adapt the cord"?

Cutting the plug off a listed appliance and putting a different plug on it wouldn't be allowed.

If you mean he wants to adapt an existing drop cord or receptacle, that might be ok.
 
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