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Safety plug for 240V outlet

D.E.

Uncorked
Oct 12, 2016
895
1,206
Ann Arbor, MI
65A3C9BF-A66B-4F1F-A8CD-DB2D8C06C39D.jpeg 3A61804C-0578-4157-B672-11C991E8540A.jpeg

I had a 30A 240V outlet installed to charge the car. We have a grandchild that visits 2-3 times a week. They make household plugs to block 120V outlets in the house but as far as I know there aren't any for large 240V outlets.

I bought a matching plug at Lowes, about $15. With the plug assembled, there is an opening, made for the wire, that needs to be blocked. There are slots in the wire opening designed for wire retention hardware. A coin, US nickel, will block the opening but it rattles in the slot. A disk of plastic was cut from a plastic milk container lid, slightly larger than the nickel. It shims the nickel and prevents movement.

This should childproof the outlet when it isn't being used.
 

outdoors

🌲🛶⛺️🏔♻︎🙂
Supporting Member
Aug 10, 2014
1,899
3,432
Mountain West
Imagine me growing up in a time without safety wall outlets.
These days all plugs in Europe are protected with sliding bits of plastic that most of the time refuse to slide.

Imagine the one time your grandchild sticks anything in it. You wouldn't have a grandchild any longer. Not a risk worth taking. Kudos @D.E. to a workable solution.
 
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brkaus

Well-Known Member
Jul 8, 2014
8,799
7,471
Austin, TX
View attachment 341934 View attachment 341935

I had a 30A 240V outlet installed to charge the car. We have a grandchild that visits 2-3 times a week. They make household plugs to block 120V outlets in the house but as far as I know there aren't any for large 240V outlets.

I bought a matching plug at Lowes, about $15. With the plug assembled, there is an opening, made for the wire, that needs to be blocked. There are slots in the wire opening designed for wire retention hardware. A coin, US nickel, will block the opening but it rattles in the slot. A disk of plastic was cut from a plastic milk container lid, slightly larger than the nickel. It shims the nickel and prevents movement.

This should childproof the outlet when it isn't being used.
Nice idea. I find coins for patching openings to be quite useful. Many times I cover with silicone caulk/adhesive.

The thing that concerns me with plugs is a partially removed plug may present more danger than the holes. That’s how o always remember being zapped as a child with the Christmas lights :)

Be nice to find something like this in plastic. Or yank out the two hot prongs?
 
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Imagine me growing up in a time without safety wall outlets.
These days all plugs in Europe are protected with sliding bits of plastic that most of the time refuse to slide.
My garage was built 7 years ago and has these, believe it is standard on new construction.

A 14-50 is quite stiff a small child should have a hard time pulling one out enough to get zapped, easy to find something to stick in if open though.
 
Nice idea. I find coins for patching openings to be quite useful. Many times I cover with silicone caulk/adhesive.

The thing that concerns me with plugs is a partially removed plug may present more danger than the holes. That’s how o always remember being zapped as a child with the Christmas lights :)

Be nice to find something like this in plastic. Or yank out the two hot prongs?

He won't be strong enough to pull it part way out for a while yet. Also his hands are too small to effectively grasp the plug. Still, he might be able to pry it out with whatever he plans to stick into the outlet. You make a very good point. It could use some sort of retention device and/or nonconductive prongs. I could probably make flat prongs from samples of countertop laminate. Or I can just 3D print an outlet plug.
 

ewoodrick

Well-Known Member
Apr 13, 2018
5,285
4,292
Buford, GA
Great idea. But this suggest that you are plugging and unplugging your UMC on a regular/daily basis. This is going to cause stress on the plug and will eventually cause issues.

Keep the UMC plugged in, instead of the dummy plug. Also, once the grandchild sees you remove it, then they will try to as well, and you probably just made the problem worse.
 

MorrisonHiker

Well-Known Member
Moderator
Mar 8, 2015
10,731
11,007
Colorado
Kind of too late for the outlet pictured but when we had our 14-50 outlets installed, we had them put in nearly 6 feet off the floor. We recently installed the Signature WCs to replace the 14-50 outlets. We left the wiring and relocated the 14-50 outlets to the ceiling...so it would be very difficult for a child to ever access them. Also, since they aren't actively used any longer, the breakers are turned off in the breaker box.
 
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The issues you describe are specifically addressed by the Society of Automotive Engineer's J-1772 standardization committee a decade ago. The wire leading to the J-plug is not energized until after it is plugged into the car and all grounds are confirmed to be true, the car is in park, etc. Even one of the new portable EVSE's that plug into a 14-50 can be permanently mounted, so the little ones will only see parents inserting the J-plug into the socket. And of course all Tesla's come with a J-plug to Tesla socket adapter. I have two adapters, one in the car and one I permanently leave attached to my J-plug.

When my non-Tesla friends need a charge I just pull out the adapter and hand them the J-plug.
 
I don't plan to unplug the car adapter often, I doubt he'll ever see me plug or unplug the adapter from the wall.

The wire to the plug was originally a 30A 120V that was used for an RV plug. It is not practical to run a new wire, if it were, I'd have put in a 4 wire 50 A with a 14-50 outlet. Or a 60A or 100A to a Tesla wall charger. So it is a 3 wire 240V 30A to a Nema 10-30 outlet now. Since Tesla no longer sells a 10-30 adapter, I have a 10-30 male to 14-50 female adapter ordered. I'll plug the Tesla 14-50 into the adapter and limit charging to 30A. That ordered adapter will be here in the next day or so. The outlet blocking plug is just intended for use until the adapter gets here then occasionally in the future only if the Tesla charging adapter is disconnected, say for a trip.

The GFI option, I think that monitors a hot to ground short. I am not sure it will trip with a little hand on a hot and another little hand on the ground but no outright short.

I did not investigate use of a J-plug. Is that an option with just a 3 wire (hot, hot, ground) supplied outlet?

I can have the outlet relocated 6 feet from the floor. I didn't think of it this week when we installed the current outlet in the garage. I do like that idea.

The child does not routinely play in the garage and we do watch him. The plug is meant to be just an additional safety measure.
 
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MorrisonHiker

Well-Known Member
Moderator
Mar 8, 2015
10,731
11,007
Colorado
The wire to the plug was originally a 30A 120V that was used for an RV plug. It is not practical to run a new wire, if it were, I'd have put in a 4 wire 50 A with a 14-50 outlet. Or a 60A or 100A to a Tesla wall charger. So it is a 3 wire 240V 30A to a Nema 10-30 outlet now. Since Tesla no longer sells a 10-30 adapter, I have a 10-30 male to 14-50 female adapter ordered. I'll plug the Tesla 14-50 into the adapter and limit charging to 30A. That ordered adapter will be here in the next day or so. The outlet blocking plug is just intended for use until the adapter gets here then occasionally in the future only if the Tesla charging adapter is disconnected, say for a trip.
You can get a gen 1 10-30 adapter from Tesla here: Model S/X Gen 1 NEMA Adapters or a gen 2 10-30 adapter from Tesla here: Model S/X/3 Gen 2 NEMA Adapters
 
I got my 10-30 to 14-50 adapter today. I hooked it up and set the car's charge current to 30A. After 10 minutes or so the 30A breakers tripped. I reset the breaker, dropped the car's charge current to 25A and am trying again.

Shouldn't the 30A breakers allow continuous 30A? Am I missing something?
 

MorrisonHiker

Well-Known Member
Moderator
Mar 8, 2015
10,731
11,007
Colorado
I got my 10-30 to 14-50 adapter today. I hooked it up and set the car's charge current to 30A. After 10 minutes or so the 30A breakers tripped. I reset the breaker, dropped the car's charge current to 25A and am trying again.

Shouldn't the 30A breakers allow continuous 30A? Am I missing something?
The continuous load is 80% of the rated breaker. The 10-30 outlet should only do 24 amps of continuous load. If you get an official Tesla adapter, it will correctly limit it to 24 amps.

If you are going to set the amps manually, you should set it to 24 amps.
 
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