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Is there a UMC extension cord available anywhere?

I'm looking for an extension cord that will fit between the UMC and the charging adapter. I have a NEMA 14-30p dryer outlet and the Tesla 14-30 adapter, but the dryer outlet is pretty far away from the garage. I actually already have http://www.amazon.com/Camco-55195-E...49278627&sr=8-1&keywords=14-50+extension+cord, but I don't think this will work with my 14-30 adapter. I know I could buy a 14-30 to 14-50 adapter here (http://www.amazon.com/Conntek-14-30...F8&qid=1449278695&sr=8-2&keywords=14-30+14-50) - but I was hoping to use my Tesla supplied adapter and not deal with dialing down the amperage. Any leads?

Thanks!
 

msnow

Active Member
Jul 14, 2015
4,951
2,394
SoCal
I'm looking for an extension cord that will fit between the UMC and the charging adapter. I have a NEMA 14-30p dryer outlet and the Tesla 14-30 adapter, but the dryer outlet is pretty far away from the garage. I actually already have http://www.amazon.com/Camco-55195-E...49278627&sr=8-1&keywords=14-50+extension+cord, but I don't think this will work with my 14-30 adapter. I know I could buy a 14-30 to 14-50 adapter here (http://www.amazon.com/Conntek-14-30...F8&qid=1449278695&sr=8-2&keywords=14-30+14-50) - but I was hoping to use my Tesla supplied adapter and not deal with dialing down the amperage. Any leads?

Thanks!

I researched this once but these may be what you've already seen.

Tesla UMC Extension Cord via Camco 50 AMP 30 PowerGrip - TESLARATI.com

Also see this thread.

NEMA 14-50 Extension cords | Forums | Tesla Motors
 

GSP

Member
Supporting Member
Dec 28, 2007
2,587
836
Making a 14-30 extension cord, or buying one, would be the best option. It would be much lighter and less expensive than a 50 A 14-50 extension cord. Also, the UMC will signal the correct ampacity to the car, preventing any issues that could cause the car to reset to 40 A charging.

GSP
 

tga

Active Member
Supporting Member
Apr 8, 2014
4,126
3,203
New Hampshire
Camco 55195 cable works great, and gives you the flexability of being able to plug into 50amp or 30amp by cutting off the ground pin. Good price too!
Neutral pin, actually.

You could remove the neutral pin from the extension cord's plug, and the 14-30 adapter, but there's probably a ton of reasons why it's a bad idea and I wouldn't recommend it (trashing your no-longer-available 14-30 adapter, enabling someone to plug a >30A load into a 14-30 using your butchered extension cord, blowing up an RV's 120V appliances that connect to the extension cord, etc)
 

linkster

Active Member
Apr 22, 2013
1,128
277
USAX2
Ouch! How much would it weigh to extend the UMC cable for the same length? Wouldn't that solve all the issues better?

6.4 lbs. for the added 30' extension and yes, issues resolved

- - - Updated - - -

No hacked off neutral pins, no remembering to dial down the amps, no adapters, and it has to be easier to handle and have less weight?

+ 1
 
Last edited:

Rocky_H

Well-Known Member
Feb 19, 2015
7,835
9,857
Boise, ID
For practicality’s sake, I wouldn’t like getting the UMC lengthened, because then you have to deal with that extra cord being in the way all of the time, versus the fewer times when you need an extension.

You can adapt what you have for this situation I think, so that the car does manage it with the official Tesla 14-30 adapter and your Camco extension. Since the Tesla charging does not use the neutral, you could cut that pin off of your plug on the Camco extension cord, so it can plug directly into the 14-30 dryer outlet.

On your Tesla 14-30 adapter, you can cut the angled part off of your neutral pin, so it can plug into either a 14-30 or 14-50 outlet (of the Camco cord). EVSE Adapters sells an adapter cable that is made like that, so it can plug into 14-30, 14-50, or 14-60. So then you could have the whole chain properly on 30A—Tesla 14-30 adapter through Camco extension to 14-30 outlet.

@tga had some complaints about the idea of cutting pins, but I think it’s a pretty good solution. No, it would not “blow up” 120V appliances in an RV if the neutral pin were removed. It would obviously be an open circuit, so they would just not get any power. But if you’re going to do this, that cable is for charging your Tesla and just isn’t useful as an RV cord anymore. If I could get a Tesla 14-30 adapter, I would do this, so I didn’t have to dial things down. I have used something sort of like this on a trip. Tesla 14-50 to the Camco extension to a 10-30 adapter cable dryer outlet, and I turned down the current to about 21A.
 

tga

Active Member
Supporting Member
Apr 8, 2014
4,126
3,203
New Hampshire
No, it would not “blow up” 120V appliances in an RV if the neutral pin were removed. It would obviously be an open circuit, so they would just not get any power.
Wrong. A split phase 120/240 system needs a connected neutral to carry the imbalance between the two hots. If the neutral is open, and the loads aren't perfectly in balance, loads on one side will see >120V, while loads on the other side see <120V. If the two sides are too far out of balance, you could see very large swings in voltage.

With an open neutral, turning on a heavy 120V load (like a microwave oven) can cause the voltage on the other leg to swing to 160-180V or higher. Really bad things happen to devices on that other leg.

Don't take my word for it, see what our resident expert says: FAQ: Home Tesla charging infrastructure QA Search for "I HAVE ACCESS TO A NEMA 6-50 WELDER OUTLET. CAN I BUILD AN ADAPTOR CORD TO THE TESLA UMC’S STANDARD 14-50 PLUG?"

Floating Neutral

Here's a good video (using different wattage bulbs to force an imbalance):
 
Last edited by a moderator:

AWDtsla

Active Member
Mar 3, 2013
4,284
4,256
NE
The CAMCO works like a charm. It's a beast of a cable. Must weigh 25#.

Build your own. Waiting for the 25' cable to arrive, UPS weight is only 13lbs, 25% of which is probably the packaging. Two ends weigh nearly nothing. too.

- - - Updated - - -

Ouch! How much would it weigh to extend the UMC cable for the same length? Wouldn't that solve all the issues better?

No hacked off neutral pins, no remembering to dial down the amps, no adapters, and it has to be easier to handle and have less weight?

Build your own, and it's simpler to just not install the neutral pin...

Oh and don't plug RV's into it. Controversy solved.

- - - Updated - - -

Wrong. A split phase 120/240 system needs a connected neutral to carry the imbalance between the two hots. If the neutral is open, and the loads aren't perfectly in balance, loads on one side will see >120V, while loads on the other side see <120V. If the two sides are too far out of balance, you could see very large swings in voltage.

With an open neutral, turning on a heavy 120V load (like a microwave oven) can cause the voltage on the other leg to swing to 160-180V or higher. Really bad things happen to devices on that other leg.

Bonus. Serves the guy right for stealing my Tesla extension....
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
@tga had some complaints about the idea of cutting pins, but I think it’s a pretty good solution. No, it would not “blow up” 120V appliances in an RV if the neutral pin were removed. It would obviously be an open circuit, so they would just not get any power.

Incorrect.

Remember that a split-phase 240V panel in the RV has two legs connected together like this:

L1---120V---N---120V---L2

When "N" is floating (due to an unconnected neutral) but 240V is provided between L1 and L2, the voltages found between L1-N and N-L2 will vary based upon their resistance, and will create an imbalance in the voltages.

It's not an open circuit because current will flow from L1, through powered appliances on the L1-N leg, then through powered appliances on the N-L2 leg, to return to the transformer.

I've seen an open neutral destroy appliances in all sorts of locations - homes, outdoor venues, RV's, etc. Usually, motors are the first things to blow up, since many/most electronics use wide-range switching power supplies, but occasionally you have voltages so far out of balance that it pops a few components.

EDIT: The video does a great job - I had suggested doing your own. But hey, YouTube is great.

- - - Updated - - -

Oh and don't plug RV's into it. Controversy solved.

Be sure it's labeled six ways to Sunday. It's not necessarily the issue if someone steals it, but it's the issue if someone sees it and uses it (e.g., after you sell the Tesla it gets thrown in a box and years later, your son or daughter grabs it when his cousin brings the RV over). There's a reason we have all the different series of NEMA plugs, so that they're not subject to special knowledge of the implementation. Anyone who sees a NEMA 14 receptacle should be able to assume presence of a neutral.
 

Canuck

Well-Known Member
Nov 30, 2013
6,125
5,779
South Surrey, BC
I'm looking for an extension cord that will fit between the UMC and the charging adapter. I have a NEMA 14-30p dryer outlet and the Tesla 14-30 adapter, but the dryer outlet is pretty far away from the garage.

I had to charge using my dryer outlet at my cabin for about a year before I installed a HPWC there. It's pretty easy to make a lightweight extension cord using these parts:

6 3 SOOW So Cord 30 ft HD USA Portable Outdoor Indoor 600 V Flexible Wire Cable | eBay

Camco 55353 50 Amp Female Replacement Receptacle New Free Shipping | eBay

Camco Power Cord Plug 50 Amp Electric Male Connector RV camper Travel Trailer | eBay

But mark it "Tesla Only" since it should never be used for RV's or damage will result!

More here:

How to build a lightweight 50A extension cord
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,835
9,857
Boise, ID
Apparently I am about to learn something, since @tga and @FlasherZ are both correcting me about this open neutral thing, but I still do not understand it. I did watch that video, but it does not make sense. Maybe it’s because my understanding of how they are wired is different.

For one of those light bulbs, the two wires of an AC circuit would be the hot on the one side, and the neutral wire on the other. When he breaks the neutral connection, my thought is that neutral is disconnected from both of them, so why is either bulb still lit at all? I thought both lose their neutral, so each has an open circuit and both should be off. When he says there is 240V across the two bulbs together, that didn’t make any sense, but I guess he is saying that the neutral of both of those circuits are tied together, so it forms a path from one bulb directly to the other bulb? (If that’s the case, that’s not clear at all in his example video.) I’m guess this is the point you are both going to say is true and is why I wasn’t getting this. I thought every 120V circuit gets its own neutral line and are not tied to each other, but thinking backward through the wiring, I guess all of the neutrals go back to a common bus bar, so they are effectively tied, even when you cut off the farther upstream supply to that bus bar.
 
When he disconnects the neutral, the bulbs are no longer connected to the neutral, but they are still connected to each other. The original circuit is hot -> bulb -> neutral <- bulb <- hot. When he disconnects the neutral, it becomes hot -> bulb -> disconnected neutral <- bulb <- hot. The disconnected neutral wire no longer connects to the outside world, but it still does a fine job of connecting the two bulbs together.
 

tga

Active Member
Supporting Member
Apr 8, 2014
4,126
3,203
New Hampshire
Apparently I am about to learn something, since @tga and @FlasherZ are both correcting me about this open neutral thing, but I still do not understand it. I did watch that video, but it does not make sense. Maybe it’s because my understanding of how they are wired is different.
This might help - Split-phase electric power - Wikipedia, the free encyclopedia

Figure 1 shows how the center tapped secondary of the transformer is grounded to provide a neutral, with 2 120V legs on either side and 240 from hot to hot. Since the hots are 180 degrees out of phase, you see 120 from either to neutral, and 240 from hot to hot.

It's easy to draw a diagram showing what's going on when the neutral opens, but it's a picture that's worth 1000 words. I can sketch out an explanation tonight, scan, and upload.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,835
9,857
Boise, ID
When he disconnects the neutral, the bulbs are no longer connected to the neutral, but they are still connected to each other. The original circuit is hot -> bulb -> neutral <- bulb <- hot. When he disconnects the neutral, it becomes hot -> bulb -> disconnected neutral <- bulb <- hot. The disconnected neutral wire no longer connects to the outside world, but it still does a fine job of connecting the two bulbs together.

That is the part that is confusing that I missed. He pointed back to the transformer, but then he makes a disconnection in the wire that goes out to the bulb, so it looks like making a disconnection out in the branch circuit. That looks like the case where you snip one of the two wires of the power cord of a lamp. The lamp will not stay lit. That tiny little one inch loop of wire that you see on that block that the bulbs are screwed into is apparently the same area that would be the main circuit panel of a house or the RV with its power buses.

- - - Updated - - -

This might help - Split-phase electric power - Wikipedia, the free encyclopedia

Figure 1 shows how the center tapped secondary of the transformer is grounded to provide a neutral, with 2 120V legs on either side and 240 from hot to hot. Since the hots are 180 degrees out of phase, you see 120 from either to neutral, and 240 from hot to hot.

It's easy to draw a diagram showing what's going on when the neutral opens, but it's a picture that's worth 1000 words. I can sketch out an explanation tonight, scan, and upload.

I don’t need it that basic. I do know generally how split phase works. It was just not knowing the detail of how the wiring was laid out and where the cut was being made. I was thinking of a cut neutral in a cord that goes to a 120V appliance. The RV thing is the unusual case, because there is the house panel, and then it would seem it’s downstream from that, but it’s feeding another panel in the RV, which I didn’t think about how it would re-connect things. So I do appreciate the explanations, but I do see what I missed.
 

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