Forums

NEMA 14-50 receptacle with stranded wire?

NEMA 14-50 receptacle with stranded wire?

Hi,

I plan to replace a cheap NEMA 14-50 outlet that overheats in one of the pins with the recommended Hubbell HBL9450A receptacle.

When I pulled the old receptacle out I noticed the electrician used 6 AWG stranded wire. The individual wires looked deformed from the stress of the screws. I'm a bit concerned about the connector security if I just screw down the stranded wires to the new receptacle. The last thing I want is a fire caused by a loose connection. Shall I put wire ferrules on the wire before screwing the wires down or it is not a concern at all? I am just a homeowner, not an electrician.

Thanks,

Ken

CharleyBC | August 7, 2018

I'm also not an electrician. But if you think the wire is compromised, I'd be concerned, as you already are. That would include any strands that have broken off, or any that are sort of scored such that their cross section--ability to carry power--is reduced.

Is there a bit of slack? That is, can you cut the deformed part off, strip back a tad, and use fresh wire?

rxlawdude | August 7, 2018

I'm not an electrician, either, but there are lots of electricians' sites out there that discuss. Some claim NEC 310 prohibits stranded below 8AWG, but I don't see that in 310, and the majority of electricians discussing this topic thank their lucky stars for stranded, as pushing thick solid conductors through conduit is a bear.

In other words, stranded shouldn't be a problem. MAKE SURE YOUR RECEPTACLE IS RATED FOR STRANDED CONDUCTORS!

TeslaTap.com | August 7, 2018

Just published a today guide specifically for home wiring that should help (and stranded #6 wire is normal and expected): https://teslatap.com/articles/home-charging-wiring-guide/

I agree with Charley's suggestion too.

Not sure I've heard of any NEMA 14-50 that are not rated/designed for stranded conductors. More of an issue at 15 and 20 amp outlets where most are designed for solid wire only.

Frank99 | August 7, 2018

"prohibits stranded below 8AWG"
I'm pretty sure they're arguing about AWG 10, 12, 14, and not about AWG 6 or 4.

Mechanical damage to individual strands is pretty normal, and not a cause for concern. Copper is pretty soft, and so under clamping forces some of it will get deformed. However, if you see things that reduce the cross-section of multiple strands (cuts, etc), then cut off the damaged section, strip off a bit more insulation, and you're good to go.

As far as I can tell, the HBL9450A is suitable for both solid and stranded conductors up to 6 AWG.

KenSmith | August 7, 2018

The deformation I observed on the wire is from normal clamping force from the terminal block of the previous receptacle. There was no cut observed. The HBL9450A's spec sheet says "Terminals identified in accordance with UL 498 and CSA" (http://ecatalog.hubbell-wiring.com/productinformation/specsheets/3A/Live...). I assume it supports stranded wires.

However, is there any downside of installing wire ferrule in this application? I may still want to add ferrules just for a peace of mind.

Yodrak. | August 7, 2018

Current density is highest on the surface of a wire, and decreases towards the center of the wire. Stranded wire has a lot more surface area than solid wire. (Note that the word 'wire' is used in two different ways in the preceding sentences.) A flattened cross section does not create a problem and, as another poster has written, is to be expected if it has been tightly clamped, as it should be. A solid (single strand) wire will also be deformed (cross section changed from round to oval) when properly clamped.

Frank99 | August 7, 2018

There's no need for ferrules, and the extra joint (wire->ferrule, ferrule->outlet) is simply a source of additional resistance and heat. Unless you're an electrician with the proper tools, you're unlikely to install one correctly. So, IMHO, don't install one.

Rocky_H | August 8, 2018

Stranded wire is the standard that is used everywhere for large gauge. That’s certainly not a concern.

@Frank99 +1 Quote: “Copper is pretty soft, and so under clamping forces some of it will get deformed.”

Yeah, that’s normal that there will always be flattened and crimped marks on it if it has been attached in something before—it’s not a problem.

(And that's why to copy text before submitting--stupid forum just logged me out as I submitted the comment.)

TeslaTap.com | August 8, 2018

Rocky - the trick I use to recover text after being forced to login - after logging in, use the back history to jump directly back to the page you were working on (not multiple back presses). This is done by holding down the black button - it then shows a short history list.

You'll get a message to refresh, which I do. Then select back once more and voila - the text reappears in the edit box. It's saved me many times. I use Chrome, so other browsers may work differently.

Rocky_H | August 8, 2018

@TT, I think it is you who have told me about that "trick" multiple times, and I have replied multiple times that I have tried it, and it doesn't work. I use a PC with a mouse, so the back history is when right clicking on the back button. Maybe it is a browser difference. I use Firefox. But it's fine. More than 98% of the time, I remember to copy the text or just compose it in a different window before posting it. I didn't lose anything here either. I just added that parenthetical comment to help people since I had to paste my comment back in again here.

milesbb | August 8, 2018

"NEC 310.106 (C)
Stranded Conductors. Where installed in raceways, conductors 8 AWG and larger, not specifically permitted or required elsewhere in this Code to be solid,
shall be stranded."

With some exceptions # 6 AWG wire is required to be stranded. From the Hubble Receptacle cut sheet " Terminal Accommodation: #12 AWG through #4 AWG copper wire only" Use of a ferrule would not be acceptable.

Rutrow 3 | August 9, 2018

Use a torque screwdriver to get the proper bite on the wire. Too little, and you can cause overheating and arcing, too much and you'll strip the threads, causing overheating and arcing. Both possibilities are dangerous. Many hardware and auto parts stores lend tools for free (deposit required?)

TeslaTap.com | August 9, 2018

@Rocky - Sorry for the repeats - Thought it might help others who run into the same situation. Always aggravating when it happens :(

Rocky_H | August 9, 2018

I know--you're trying to help. I just gave it a try again today just to check, and it doesn't work in Firefox. I had copied stuff though, because I know it logs me out about that time every morning.

TeslaTap.com | August 10, 2018

more eliezer. spam - please flag.

KenSmith | August 10, 2018

Thank you all for your replies. I have an update:

I received and installed the Hubbell HBL9450A receptacle today. I was surprised to find that the screw terminal on the Hubbell is of a different design from the one on the cheap receptacle it replaced. The terminal contact is made of copper (the cheap one isn't) and it has a V shape plate at the bottom that, upon tightening, will clamp the stranded wires to a top flat plate. This way all the stranded wires will be clamped together to form a good connection. No ferrule is needed.

Also you need an allen wrench to install the wires. This is much better than the flat head screw on the cheap one which stripped easily when applying great force. The instruction says it needs 75lb-in of force. I just hand tightened as much as I could.

No wonder Tesla recommends the Hubbell. It is a high quality, well designed product.

Frank99 | August 10, 2018

The main problem with the HBL9450A is finding a cover with a hole large enough to go around it. The HBL9450A is a bit less than 2.5" in diameter (2-31/64", to be precise), much larger than the common Leviton 2.15" outlet. There are a couple at Amazon:
https://www.amazon.com/Plate-Wall-2-Gang-Silver/dp/B0078QU1SK
https://www.amazon.com/Pass-Seymour-Standard-Stainless-Receptacle/dp/B00...

But, yes, it's built like a tank compared with the Leviton versions...

Frank99 | August 10, 2018

A cheaper cover plate that appears to be the right size (and is PRIME):
https://www.amazon.com/Leviton-S701-GY-Receptacle-Wallplate-Steel-Alumin...

KenSmith | August 11, 2018

The size of the Hubbell was another surprise when I tried to install it. I was replacing the receptacle inside an outdoor rainproof enclosure, which was already secured to the house and sealed with caulking. I had no choice but to spend a grueling hour to enlarge the hole in the faceplace using a hand file :-(

rxlawdude | August 11, 2018

@Frank, is that "tank" worth literally 10x more? The Leviton (a respectable brand) is $9 and the Hubbell was $80+.

I'm just not sure it's that good justify that cost difference in a residential application.

Frank99 | August 12, 2018

Dang good question, rxlawdude. I looked at those two devices for a long time before deciding to spring for the Hubbell. Unfortunately, the spec sheets for the various outlets don't provide any useful information that would be helpful in comparing them.
I'm not an electrician, but I end up doing a lot of electrical work around the house. I've installed the cheapest outlets from Home Depot, and occasionally the most expensive ones. In my experience, all of them work fine - the cheapies are made of thinner metal, have sharp edges, and have wire clamps that can be questionable, but if you're willing to spend an extra minute or two during installation they're safe and usable. Also, the cheapies don't tend to grip a plug as well as the good ones - I'm always surprised when I plug the vacuum cleaner into one of the good outlets in the house and notice how secure the cord is compared with the cheap ones. I expect that these differences would be similar to what you'd see if comparing the $10 Leviton outlet with the $80 Hubbell outlet.
The Hubbell is designed for rugged use - RV parks in the sand on the Florida coast with Joe SixPack plugging and/or unplugging 100 times a year using a plug that he's run over once or twice. Small concert venues with bands where the musicians are their own roadies plugging and unplugging 365 times a year. Large concert venues where solid reliability is the difference between success and bankruptcy. In these kinds of usages, I'd expect the Leviton to require frequent attention - and even if the Hubbell only lasts twice as long, the cost of the additional electrician visits is more than the cost difference between the outlets.

Is the Hubbell worth 10 times the Leviton? Probably not - though I'd happily pay 2-3 times. The Hubbell, however, probably sells 1% as many units as the Leviton, and only sells to relatively cost-insensitive customers who want to install it once and never have to worry about it again. Frankly, I plugged my UMC in three months ago, and haven't touched the outlet side since, so it's not clear to me that I'm getting much advantage from the additional cost. But, the engineer in me appreciates that I don't have to worry about that outlet.

rxlawdude | August 12, 2018

@Frank, good points. But the vast majority of residential users will not be plugging and unplugging hundreds of times in harsh environments (unless their garages are harsh).

You're right from the standpoint that one electrician visit would cost more than the difference between the Leviton and Hubbell, but the question is how often would the Leviton fail, requiring replacement.

Frank99 | August 12, 2018

>>> how often would the Leviton fail, requiring replacement.
In my garage, if installed correctly, probably never.

vlinev | September 21, 2019

2 years ago, after hurricane, i did install outside GE 240V/50Amp receptacle for a new 10 000 W generator. From Home Depot-4x6 AWG solid copper wires, 1" conduit, 50 Amp braker for a braker box and so on. This June I was in need to install NEMA 14-50 outlet next to a braker box for Tesla charging.I did visit as minimum 10 electro stores and I was unable to find 6 AWG SOLID wires. In one of supply stores guy told me, looking at me like at idiot:"We do not use 6 AWG solid copper wires in America (he heard my Russian accent). Something changed for last 2 years in electrical wires world?
So, I had to use stranded wires and they are much harder to secure under screws. About Leviton-yes, when you install it, you need check tightness of "JAWS" for a good contact. I have 2 adapters so, I do not take one out. But, anyway, it needs to be regularly checked for a good contact. Just my 2 cents...

Frank99 | September 21, 2019

vlinev -
milesbb quoted the National Electrical Code (NEC) earlier in this thread. Basically, paragraph 310.106 (C) requires that 6 AWG wire be stranded. I agree that it's harder to terminate at the outlet than a solid conductor, but it's vastly easier to pull through conduit (which it's required to be installed in).

grins.va | September 22, 2019

That is why Tesla requires ferrules for the wire connections.