Is Nema 10-50 illegal?

[400bird]

This is questionably far off topic for a PV forum, but I know we have some members with great knowledge of the NEC code.

I could use some help finding the NEC code evidence to prove weather or not NEMA 10 series receptacles (10-20r, 10-30r, or 10-50r) are not suitable for new work.
At least that is what "the google" says.

I believe the issues is that nema 10 receptacles don't have a ground connection, just hot (*2) and neutral.

The closest thing I can find is 406.4(A)

Except as provided in 406.4(D), receptacles installed on 15- and 20-ampere branch circuits shall be of the grounding type. Grounding-type receptacles shall be installed only on circuits of the voltage class and current for which they are rated, except as provided in Table 210.21(B)(2) and Table 210.21(B)(3).

But that only applies to 15-20 amp circuits, not the 50 amp 10-50r that I am specifically interested in.

Thanks for your assistance and time.

 

[Quattrohead]

Illegal to use, no.
Not allowed for new installations or rework where an inspection will be required, yes. Since 1996.

 

[BentleyJ]

Ungrounded electrical circuits should be avoided, they are simply not safe. If you substitute a ground wire for the neutral on the NEMA 10 then that would make it safe BUT you have lost the neutral and basically turned the NEMA10 into a NEMA 6 but the wiring would not correspond to the standard for the NEMA 10. If there is some extraordinary reason you must use the NEMA 10 as intended, you should provide a means of grounding the device or appliance. Either with a separate conductor or the NEC does allow the use of Metalic Conduit as ground under certain circumstances but I am not an expert in that regard. Mike Holt's Forum is very good with these types of code questions.

 

[400bird]

I'm looking for documentation in NEC (or other official documents) showing this. I've read about the 1996 date, I'm just looking for backup to talk someone out of stalling a 10-50p on a piece of equipment.

I realize it's not safe, but I don't think he does.
I believe the problem is understanding the difference between neutral and ground.

 

[Quattrohead]

It's not exactly unsafe, it's just NEC thought there was a better way to do it to keep up with the times.
Depends exactly what they are trying to do.

 

[Ampster]

I'm just looking for backup to talk someone out of stalling a 10-50p on a piece of equipment.

Backup? My typical relationship with people I hire is that I pay them to perform tasks in the manner I request. Fire him and hire someone that you do not have to argue with.

 

[400bird]

Backup? My typical relationship with people I hire is that I pay them to perform tasks in the manner I request. Fire him and hire someone that you do not have to argue with.

Lol, I wish I could. It's my boss

 

[400bird]

It's not exactly unsafe, it's just NEC thought there was a better way to do it to keep up with the times.
Depends exactly what they are trying to do.

It is unsafe when your piece of equipment is connected to the two lines and the metal case of the equipment is connect to the 3rd pin.

 

[time2roll]

For split phase use a 14-50. For a 240 load use a 6-50.

If you have an old 10-50 just use it but don't install it.

If you want to get into the code I suggest Mike Holt forum.

https://forums.mikeholt.com/

 

[400bird]

Yeah, that's probably my best option. I'm just not a member there. I'm off to sign up.

 

[Tecnodave]

NEMA 10-50 is old code and not allowed anymore on new installations...

HERE IS THE REASON WHY........

OK say we are dealing with a kitchen stove, many have a 120 volt outlet to power a toaster, some have 120 volt controls, oven timer etc. When the main burners are used they have no neutral, they are balanced 240 volt , all is good, BUT when you plug in that 1500 watt toaster into the 120 volt outlet where is the neutral? You do not have a neutral...you are flowing 12.5 amps down the ground wire!!! Can you see anything wrong with that? Even if the Range does not have a 120 volt outlet (most do) how about the oven light? 40 watt oven lamp .3333 amps....quite enough to kill....And the dryer as well, most electric dryers have 120 volt controls and lights as well....same deal

That is exactly why NEMA 14-50 is required for stoves is now the code.....motorhomes 120/240 service...14-50 as well......dryers and dishwashers 14-30 ...same reason.

New code is written on bad accidents and burndowns....Its from real life experiences

Please note.....The NEC is NOT written by some government agency, Its written by the NFPA...National Fire Protection Association......IN THE INTEREST OF PUBLIC SAFETY....directly as a result of all the national databases of system failures and hazards that result in burndown and injuries and deaths.

 

[400bird]

Thanks for responding.

NEMA 10-50 is old code and not allowed anymore on new installations...

Understood, do you by chance have the code reference?

HERE IS THE REASON WHY........

OK say we are dealing with a kitchen stove, many have a 120 volt outlet

What! That's nice, I've never seen that. But my range is probably 40 years old.

to power a toaster, some have 120 volt controls, oven timer etc. When the main burners are used they have no neutral, they are balanced 240 volt , all is good, BUT when you plug in that 1500 watt toaster into the 120 volt outlet where is the neutral? You do not have a neutral...you are flowing 12.5 amps down the ground wire!!!

Nema 10-50 is Line, Line, Neutral. No ground.

Can you see anything wrong with that? Even if the Range does not have a 120 volt outlet (most do) how about the oven light? 40 watt oven lamp .3333 amps....quite enough to kill....And the dryer as well, most electric dryers have 120 volt controls and lights as well....same deal

That is exactly why NEMA 14-50 is required for stoves is now the code.....motorhomes 120/240 service...14-50 as well......dryers and dishwashers 14-30 ...same reason.

New code is written on bad accidents and burndowns....Its from real life experiences

Please note.....The NEC is NOT written by some government agency, Its written by the NFPA...National Fire Protection Association......IN THE INTEREST OF PUBLIC SAFETY....directly as a result of all the national databases of system failures and hazards that result in burndown and injuries and deaths.

Good point, I had forgotten that.

 

[Tecnodave]

Nema 10-50 is Line, Line, Neutral. No ground.

It is supposed to be.....but my old 1950’s Lincoln Arc Welder is 240 volts only and it is line, line, ground
NEMA 14-30 fixes that

In any case NEMA 10-30 and 10-50 is obsolete, it still can be used but cannot be installed, BUT....here in California NOT if you rent or sell that house....You must change it to 4 wire standard

 

[400bird]

Ah, then we're on the same page. That's what he is proposing and he doesn't see that issue.

 

[Tecnodave]

Do not let people sway you on this issue, there is liability if you know something is wrong and you do it anyway to save a few bucks....for what?

 

[400bird]

I've said my piece to the boss. But, this is his personal side project. It's not work related.

 

[Tecnodave]

Depending on the total load on the system neutral can be offset from ground by up to 10 volts or more, depending on voltage drop and large 120 volt loads, Ive seen that several times in old installations

 

[Tecnodave]

One truth ? The boss is always right....well maybe?

 

[400bird]

He's listening, but hasn't yet understood the reasoning or importance of not connecting his ground to the neutral line on the building side.

Any input on the NEC code? Or even the section? I have access to the full 2019 code, but ran out of ideas on where to look.

 

[Tecnodave]

Not readily available at this time.