Does code require all the pins on a receptacle to be used?

hbiss said:
Yes. For the same reason we can't install it as a 3-wire dryer receptacle.

-Hal
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OK, let's say the receptacle and circuit are existing. Can you install a 10-30P on the equipment and supply it with 30 amps 240 volts?
 
CoolWill said:
Here's a scenario to ponder: Let's say you needed 240 volts, 30 amps. Normally you would use a 6-30R receptacle with a matching plug. But maybe you only have a 10-30R on hand. Assume the main panel is where you get your circuit, ground and neutral bar are one in the same. Would it be a violation to use the 10-30 in this manner?
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Just to be clear: you are not asking about supplying a 120/240V load using a 3 pin receptacle. You are asking about using a 10-30R to supply a straight 240V load, with the third pin used as the EGC.

For background to anyone not familiar: the 10-30 pattern the NEMA configuration for an ungrounded connection supplying hot, hot, neutral to a 120/240V load. Dryers used this configuration, and then used the circuit neutral conductor to bond the frame under a code exception.

IMHO if this is used to supply a straight 240V load, I don't believe this is a direct code violation as long as this is the only way the 10-30 pattern is used in a location. However it is probably a violation of the receptacle/plug listing and manufacturer's instruction, since there are probably specific requirements for the ground pin making contact first and instructions to connect the white wire to the neutral pin.
 
CoolWill said:
OK, let's say the receptacle and circuit are existing. Can you install a 10-30P on the equipment and supply it with 30 amps 240 volts?
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The 10-30R would have 2 hots and a ground. If the equipment has not need for a neutral at the equipment that is strictly 240 it would work. If the equipment is 3 phase as originally reported you need a 11-30R and not the 10-30
 
winnie said:
Just to be clear: you are not asking about supplying a 120/240V load using a 3 pin receptacle. You are asking about using a 10-30R to supply a straight 240V load, with the third pin used as the EGC.

For background to anyone not familiar: the 10-30 pattern the NEMA configuration for an ungrounded connection supplying hot, hot, neutral to a 120/240V load. Dryers used this configuration, and then used the circuit neutral conductor to bond the frame under a code exception.

IMHO if this is used to supply a straight 240V load, I don't believe this is a direct code violation as long as this is the only way the 10-30 pattern is used in a location. However it is probably a violation of the receptacle/plug listing and manufacturer's instruction, since there are probably specific requirements for the ground pin making contact first and instructions to connect the white wire to the neutral pin.
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Fred B said:
The 10-30R would have 2 hots and a ground. If the equipment has not need for a neutral at the equipment that is strictly 240 it would work. If the equipment is 3 phase as originally reported you need a 11-30R and not the 10-30
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The scenario I imagine is one where the wire connected to the neutral terminal of the receptacle goes back to the service equipment and is landed on the same bar as any EGC or neutral. If someone were to put a dryer in the location, it would be legal. But instead of a dryer, you put, say, a welder. In either scenario the machine is grounded to the third pin, just in one case it also carries neutral current. In one case the wire is a neutral and a ground, in the other case it is just a ground. I don't see a real problem using it for a straight 240 load.
 
CoolWill said:
The scenario I imagine is one where the wire connected to the neutral terminal of the receptacle goes back to the service equipment and is landed on the same bar as any EGC or neutral. If someone were to put a dryer in the location, it would be legal. But instead of a dryer, you put, say, a welder. In either scenario the machine is grounded to the third pin, just in one case it also carries neutral current. In one case the wire is a neutral and a ground, in the other case it is just a ground. I don't see a real problem using it for a straight 240 load.
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In this example, there isn't a catastrophic failure mode if someone plugs in an appliance commonly designed for a 10-30 receptacle.

But back to the OP's case: what happens if you have a straight 240V load, so you install a 14-30 receptacle (4 pins, hot, hot, neutral, ground) but simply don't connect the neutral. Your straight 240V load will work perfectly. A normal dryer probably wouldn't work. What code have you violated?

Separate situation: you run a test facility. You have single phase 120V AC on L5 receptacles, 240V AC on L6, 277V on L7, 480V on L8 and 600V on L9. You have no three phase loads. Your boss comes in and says you need to install receptacles for 380V 50Hz single phase. I contend that you could use L16 pattern receptacles (normally for 3 phase 480V) and leave one of the poles unused, and be totally kosher.
 
Late to this thread but I'm gonna say that the violation is 110.3(A)(1) and (7). Or, that's what I'd write up if I were AHJ.

110.3(A)(1) is a kind of catch-all fallback for the case of "what you're doing is really really stupid and therefore needs to be against the rules even if there isn't a specific rule against it". Wiring up a 4 prong receptacle with an open neutral falls under that, for example. Simply, the receptacle is not suitable for that application. I don't care if it's used consistently as such on a premise if it's used consistently in a different way on most other premises. (I agree with Hal that particular language is outdated. Code doesn't need to call out NEMA in actual requirements, but should get close to that.)
 
I suppose if someone somehow had, say, a 50A, 120V load, wiring up one ungrounded terminal of a 14-50 receptacle might be ok. Suitability can be a judgement call based on 'this won't lead someone to make an assumption that will cause a dangerous situation' and 'there isn't a commonly available and used alternative'.
 
brycenesbitt said:
Absolutely not.
But you could try to petition NEMA to create a NEMA 14-50A with a blank spot for the neutral,
and a NEMA 14-50PA with the neutral pin missing.

Or petition NFPA to allow locking connectors to be used for EVSE, in which case you have more choice.
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I'm pretty sure a lot of ECs are installing 14-50s without neutrals for EVSEs.

The real question here is why do the EVSE manufacturers insist on 14-50 plugs when 6-50R exists. Some offer 6-50 options as an upsell, but the 14-50 is standard issue universally.
 
NoahsArc said:
I'm pretty sure a lot of ECs are installing 14-50s without neutrals for EVSEs.

The real question here is why do the EVSE manufacturers insist on 14-50 plugs when 6-50R exists. Some offer 6-50 options as an upsell, but the 14-50 is standard issue universally.
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The reason I’ve heard is to facilitate charging at RV parks.
 
Who puts an oven in their garage?
It's not an RVing community, but that is a good point if it was.
retirede said:
The reason I’ve heard is to facilitate charging at RV parks.
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I feel like most Tesla owners only ever drive past RV parks on the way to their lake houses, but I guess it would serve in a pinch.
 
retirede said:
The reason I’ve heard is to facilitate charging at RV parks.
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Yep, that. From back in the day when Nissan Leaf drivers would scrounge electrons anywhere they could.

It's like an entrenched meander in geology:
https://en.wikipedia.org/wiki/Entrenched_river
Something that exists in its present form, because of a past reason that no longer applies.

And it's a consequence of the motor and clock in electric ranges needing a neutral, even for an appliance that could be designed, without any particular problem, to operate on hot/hot/ground.
The way out here is to encourage AHAM and others to start making no-neutral 240V appliances common, then match those up with new construction with 6-50R plugs, outlets or receptacles. This will also greatly reduce the monkey problem when untrained big box employees are unable to count from 3 to 4 when hooking up appliance cords.

While hating on NEMA 14-50, let's mention how hard it is to unplug, without touching the pins with a grasping hand?
 
brycenesbitt said:
Yep, that. From back in the day when Nissan Leaf drivers would scrounge electrons anywhere they could.

It's like an entrenched meander in geology:
https://en.wikipedia.org/wiki/Entrenched_river
Something that exists in its present form, because of a past reason that no longer applies.

And it's a consequence of the motor and clock in electric ranges needing a neutral, even for an appliance that could be designed, without any particular problem, to operate on hot/hot/ground.
The way out here is to encourage AHAM and others to start making no-neutral 240V appliances common, then match those up with new construction with 6-50R plugs, outlets or receptacles. This will also greatly reduce the monkey problem when untrained big box employees are unable to count from 3 to 4 when hooking up appliance cords.

While hating on NEMA 14-50, let's mention how hard it is to unplug, without touching the pins with a grasping hand?
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Just a little aside, but for years I used to like our Edison system, thought it was cool and handy to be able to get two different voltages. I've come to really hate it actually. This stupid neutral conductor conductor just run everywhere 😡. I wonder how many pounds of unnecessary copper I've pulled in my life running stupid neutrals just things that could very simply be redesigned to not need them.
 
electrofelon said:
Just a little aside, but for years I used to like our Edison system, thought it was cool and handy to be able to get two different voltages. I've come to really hate it actually. This stupid neutral conductor conductor just run everywhere 😡. I wonder how many pounds of unnecessary copper I've pulled in my life running stupid neutrals just things that could very simply be redesigned to not need them.
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I hear in Europe they use 400Y/230. It's simple I'm told.
 
NoahsArc said:
Who puts an oven in their garage?
It's not an RVing community, but that is a good point if it was.

I feel like most Tesla owners only ever drive past RV parks on the way to their lake houses, but I guess it would serve in a pinch.
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Most RVs big enough to have a 14-50P won’t fit into a residential garage.

15 years ago when public charging was scarce, an RV park may been a lot of driver’s only option.
 
NoahsArc said:
I'm pretty sure a lot of ECs are installing 14-50s without neutrals for EVSEs.

The real question here is why do the EVSE manufacturers insist on 14-50 plugs when 6-50R exists. Some offer 6-50 options as an upsell, but the 14-50 is standard issue universally.
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Yeah I have been doing more 'service work' to stay busy and am expected to quick fix stuff, 'just go replace the problem outlet simple job right?' I run into this combo of 6/2 NM and a 14-50 more often than not.
One lady said she had the dealerships A+ certified EV installer install it, seems like other EC's do it also, pull in 6/2 on rough-in install a 6-50 or just leave a blank cover and the EV owner replaces it with a 14-50.
Thank you all for your feedback, I think I am going to insist on 6-50's and let the EV owner order the correct 6-50p cord.

nema-14-50-outlet.png
 
pipe_bender said:
Thank you all for your feedback, I think I am going to insist on 6-50's and let the EV owner order the correct 6-50p cord.

View attachment 2576798
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Connecting the undersized ground to the neutral terminal is IMHO a flat out violation on several fronts.

IMHO far better to leave the neutral terminal not connected.

Best (as you say) is to use the proper 6-50 configuration.
 
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