Generating 220V from 110V on the go or in a host garage overnight

[FlasherZ]

Have you read this: http://www.quick220.com/-A220-20D.html, which claims in part:

Yes. I realize they've built some protection into it. They appear to have done their best to ensure that it is safe. It is still dangerous if that protection fails in some fashion.

Nonetheless, it's still a violation of the NEC. That creates significant liability and insurance implications should you suffer a loss.

Do it right, keep yourself or your property safe. I'd hate to see someone lose $100k or more as the result of using one of these devices.

 

[Puyallup Bill]

Well, FlasherZ and Puyallup Bill, I had to see for myself. So built a quick and dirty 2x120V adapter with no protection. I found two 120V non-GFCI circuits on different legs. Checked to make sure there was 240V across the hots of my adapter. Plugged in the UMC. Green lights, it was happy. Dialed down the car charging screen to 12A. Plugged in the UMC into the car. Car starts charging and I'm getting between 6 and 7 miles per hour charge, 12A at 234V. Unplugged one of the 120V plugs at the wall. A double beep comes from the car, the UMC lights go out, charging stops. I test to see if there is now voltage across the ground and hot of the plug I just unplugged. Gulp, it reads 120V. Well, maybe it won't be much current? So I touch them. Ouch. Definitely enough current to not do that test again

So yes, I've confirmed that with the Tesla UMC you DEFINITELY need protection to protect against a shock hazard should one of the two 120V plugs be unplugged. 120V relays here I come!

Thank you for doing that test. But, please, DO NOT DO THAT 'TOUCH' TEST AGAIN.

I was about to disable the relays in my box to once again check that the danger does indeed exist, but now there is no need for me to do that. A well grounded person touching that second hot prong is very vulnerable.

 

[Cosmacelf]

Yeah, yeah. But really, what's the big deal about getting zapped with 120V? I've been zapped with 120V many times doing one stupid thing or another, and it is annoying but hardly life threatening.

When I build my adapter, I'll use three relays, two SPST to unhook the 120V plugs when they get unplugged, and one 240V DPST to make sure the output only ever sees 240V across the hots when both 120V plugs are plugged in (and only if both 120V connections are wired correctly). Here's what I"m thinking of doing:

 

[Puyallup Bill]

Yeah, yeah. But really, what's the big deal about getting zapped with 120V? I've been zapped with 120V many times doing one stupid thing or another, and it is annoying but hardly life threatening.

When I build my adapter, I'll use three relays, two SPST to unhook the 120V plugs when they get unplugged, and one 240V DPST to make sure the output only ever sees 240V across the hots when both 120V plugs are plugged in (and only if both 120V connections are wired correctly). Here's what I"m thinking of doing:

View attachment 23432

Two questions:
1) What is the purpose of the final 240 volt coil relay?
2) Why small amp contacts on the 120 volt coil relays, and 30 Amp contacts on the final relay? Doesn't the same current flow through all the relay contacts?

Instead of a 240 volt output relay, I just wired in a 240 volt neon indicator light.

 

[mknox]

Yeah, yeah. But really, what's the big deal about getting zapped with 120V? I've been zapped with 120V many times doing one stupid thing or another, and it is annoying but hardly life threatening.

120 volts is most definitely life threatening. If the current crosses between your left and right hand, or from hand to foot it will likely cause cardiac arrest and death. Trust me.. I have over 30 years in the electric utility industry, don't fool around with this stuff.

 

[Cosmacelf]

Two questions:
1) What is the purpose of the final 240 volt coil relay?
2) Why small amp contacts on the 120 volt coil relays, and 30 Amp contacts on the final relay? Doesn't the same current flow through all the relay contacts?

Instead of a 240 volt output relay, I just wired in a 240 volt neon indicator light.

The 240V relay is there so if you plug into two 120V plugs that are wired to the same leg, you won't have two in-phase 120V hots presenting on the output hots. It's a minor thing, but I just want the output to be a clean as possible.

In actual fact, I'll be using 30A contacts for the 120V relays as well since they only cost $5, but you COULD use smaller amperage contacts since the only current running through them will be powering the 240V coil which won't draw much power at all.

I'll be using a 240V indicator light as well connected to the two output hots.

The main reason why I'm building one rather than buying the Quick220 or similar product is that I'm going to put TT-30 plugs on the inputs along with 30A rated cable. That way I can potentially draw 24A at 240V if I run into a 30A only campground. And then I can just use a simple TT-30 to NEMA 5-15 modular adapter to also plug into 120V wall circuits.

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120 volts is most definitely life threatening. If the current crosses between your left and right hand, or from hand to foot it will likely cause cardiac arrest and death. Trust me.. I have over 30 years in the electric utility industry, don't fool around with this stuff.

I had no idea. AFAIK all my shocks have been very momentary, but thinking about it, they tend to start small then build in a fraction of a second, maybe as the path to ground gets better. I guess I shouldn't have tested my horse hot wire fence that time by grabbing it with one hand (which had little effect) and then sticking my other hand into the ground (which had a big effect!).

 

[FlasherZ]

Yeah, yeah. But really, what's the big deal about getting zapped with 120V? I've been zapped with 120V many times doing one stupid thing or another, and it is annoying but hardly life threatening.

As mentioned by mknox, it's not the voltage that kills, it's the current. Hand-to-hand currents (e.g., those used in "Down Periscope" ) are the most dangerous because the currents can easily pass through the heart, but any current is dangerous.

From "Carr, Joseph J.; Safety for Electronic Hobbyists; Popular Electronics; October 1997":
"In general, for limb-contact electrical shocks, accepted rules of thumb are: 1-5 mA is the level of perception; 10 mA is the level where pain is sensed; at 100 mA severe muscular contraction occurs, and at 100-300 mA electrocution occurs."

Higher voltages are more dangerous for current flow through the body because of the Ohm's Law relationship: I=V/R.

When I build my adapter, I'll use three relays, two SPST to unhook the 120V plugs when they get unplugged, and one 240V DPST to make sure the output only ever sees 240V across the hots when both 120V plugs are plugged in (and only if both 120V connections are wired correctly). Here's what I"m thinking of doing:

Ensure that your 240V coil's activation voltage is well-above 180V or so, so that it won't activate if one of the receptacles is mis-wired. It wouldn't cause a problem (except perhaps a red light on the UMC if the wrong leg gets 0V to ground), but it would only leave you with 120V, which would defeat the purpose.

 

[Dave EV]

When I build my adapter, I'll use three relays, two SPST to unhook the 120V plugs when they get unplugged, and one 240V DPST to make sure the output only ever sees 240V across the hots when both 120V plugs are plugged in (and only if both 120V connections are wired correctly). Here's what I"m thinking of doing:

Why reinvent the wheel?

...build your own easy 240.

From that thread, this post specifically:

Here's a quick schematic of a basic safe unit: (Update: There is a more complex version with the audible indicator here.)

The area in the shaded box is optional if you'd like to hook up an LED. You can also use any pilot lamp rated for 240v operation.

I recommend heavy-duty relays such as this:



-Phil

You can replace the LED circuit with a 240V neon light as Bill above suggests and obviously replace the L6-20 with something more appropriate for a Tesla if desired. Make sure you dial down the current in the car first!

 

[FlasherZ]

You can replace the LED circuit with a 240V neon light as Bill above suggests and obviously replace the L6-20 with something more appropriate for a Tesla if desired. Make sure you dial down the current in the car first!

This one may still light the LED if one of the outlets is reversed and you have only 120V presented. A 240V pilot lamp is probably a safer change there.

Also, care should be taken with the grounds in a circuit like this, as you can create a current through this device via the multiple grounds, and in some cases present a shock hazard.

 

[Cosmacelf]

Why reinvent the wheel?

My circuit is similar to that one, but it has an added benefit of not having two in-phase 120V hots on the output if you plug into the same leg. I didn't reinvent it, I changed it/improved it.

- - - Updated - - -

Also, care should be taken with the grounds in a circuit like this, as you can create a current through this device via the multiple grounds, and in some cases present a shock hazard.

Yes I was wondering about that. You are essentially creating a "ground loop". If both plugs are from the same breaker panel, it probably won't be an issue.

I guess you could also connect just one of the plug's ground to the output ground, rather than both. That way you wouldn't create a ground loop. You'd want to have my 240V relay to make sure the output was unconnected unless both 120V plugs were plugged in.

 

[FlasherZ]

Yes I was wondering about that. You are essentially creating a "ground loop". If both plugs are from the same breaker panel, it probably won't be an issue.

In most cases it's unlikely to be an issue during normal operation as the length of the cords will provide enough resistance to ward off ground loop issues... however, all bets are off if there is some type of failure, especially on older infrastructure.

I do recall a case a number of years ago where there was a 3-wire feed to a detached shop/garage and the neutral in the feeder had failed, so 120V return was going through the grounding electrode system. If this device was used in that particular failure scenario, with one plug connected to the house, and one connected to the detached shed, the return current for the detached building's portion of the "quick/easy 220/240" (and for everything else in that detached building) would be carried through the ground conductor to the easy/quick 220/240 and then through the ground of the home's supply circuit!

The same thing could happen if there were a neutral failure in older RV parks that used 2- or 3-wire feeders with bonded ground electrodes at each pedestal, just the type of place you'd use one of these devices.

 

[Cosmacelf]

If one of the neutrals failed, that would cause the relay to not energize, and thus everything would stay isolated.

 

[FlasherZ]

If one of the neutrals failed, that would cause the relay to not energize, and thus everything would stay isolated.

That is only true if the direct neutral on that cord failed, but not for infrastructure neutral failures in certain infrastructures - you would still have a path back to the transformer, although it would be ugly. Assuming the grounds of both circuits were both connected at such a device (as the schematic shows), your normal path of current return for the second plug would be:

Plug 2 neutral - receptacle 2 neutral - pedestal 2 neutral bus - feeder 2 neutral - service panel neutral bus - transformer neutral

Now, if the feeder 2 neutral suffers a failure, you get this:

Plug 2 neutral - receptacle 2 neutral - (pedestal 2 neutral bus - neutral/ground bonding screw - pedestal 2 ground bus) - Plug 2 ground - easy220 chassis/ground - Plug 1 ground - (pedestal 1 ground bus - neutral/ground bonding screw - pedestal 1 neutral bus) - feeder 1 neutral - service panel neutral bus - transformer neutral

That is the lowest impedance path. There's also another path here:

Plug 2 neutral - receptacle 2 neutral - (pedestal 2 neutral bus - neutral/ground bonding screw - pedestal 2 ground bus) - pedestal 2 grounding electrode - earth - service panel grounding electrode - (service panel ground bus - neutral/ground bonding screw - service panel neutral bus) - transformer neutral

In both these cases, these paths will allow for reasonable current draw, so your relays will activate and the device will technically *work*, but you may have some odd effects. In the first path you may be overloading pedestal 1's neutral. The second path can create shocks if a human creates a third path to ground through his body -- remember that electricity never takes just one path, it will divide current among multiple paths inversely proportional to the resistance of paths.

(There are other paths as well, through other pedestals, but I think we've established there's enough ways to get return current delivered at this point. )

A couple of notes:

1. Anywhere you see a (neutral - bonding - ground) or vice-versa in the diagrams above, it's likely that a shortcut was taken and neutrals/grounds were on the same bus, but I spell it out anyway.

2. Any other loads in pedestal 2 (for example, another RV using another receptacle) will happily also use this return path to neutral for 120V loads, meaning you can end up with a heckuva lot more current through the device's ground than you might think.

3. The good news: NEC 2008 changed the requirement for subpanels to use 4-wire feeders to avoid specifically this condition (except detached structures / pedestals with no other metallic paths interconnecting them), and NEC 2011 eliminated that exclusion. So anything built starting with NEC 2011 is immune to this (in a neutral feeder failure, it would just stop working). The bad news: anything built before 2012ish is still susceptible, as standard practice was to use 3-wire feeders because of the cost involved with pulling a fourth wire for ground; and some jurisdictions haven't even adopted NEC 2011 yet.

Now, one solution is to leave one ground floating so that a circuit isn't completed but that is even more dangerous. Let's say that you decided to use plug 2's ground and leave plug 1's unconnected to avoid this problem. If feeder 2's neutral has failed, you've now left the chassis of the device at high potential. This is because the hot is now connected to the chassis:

plug 2 hot - plug 2 relay coil - plug 2 neutral - pedestal 2 neutral/ground bonding - plug 2 ground - device chassis/ground

In this case, the relay will not close because you likely won't get enough current through it, unless it sits in a puddle. However, anyone who touches the device chassis or one of its screws and has a ground connection (feet on concrete, touching another grounded device, etc.) will conduct the plug 2 relay coil current to ground, completing the circuit. This might be enough current to kill a human.

I tried to explain it as simply as I could, sorry for the complexity here. This is the difference between something working, and something working safely (especially under failure conditions). How often does a feeder neutral fail? More often then you think, especially in campgrounds.

 

[FlasherZ]

A footnote - from time-to-time when someone meets me they invariably ask why I'm so against rigging things on the spot or using adapters, even temporarily while making sure the current has been "dialed down", etc. The truth is that it's the "even temporarily" part that makes it so dangerous.

First, my house in the SF bay area nearly burned down about 15 years ago due to a bad wiring splice connector in the wall, and a Federal-Pacific Electric breaker panel that did not trip once the wiring insulation had melted & created a dead short in the circuit. I was about 15-20 minutes away from losing everything. In that case, things were installed correctly, but it turned out that FPE had hidden bad test results from the UL. So already, I have a lot of respect for electricity and a heightened sense of safety.

But more importantly -- all it takes is one bad move and someone dies. A few years ago, there was a lineman killed when the line he was working to reconnect downed lines; a homeowner connected a generator to the circuit, causing a backfeed into the line he was working on. As it was reported following the investigation, the homeowner had fully documented the process for doing this backfeeding "safely" -- to include ensuring the two-male-connector "suicide cord" was attached before breakers were opened, ensuring the main was turned off before the dryer receptacle breaker was turned on, etc. However, that night the documenting homeowner was away and the boss (the other homeowner) was following his instructions as documented... except she missed/skipped one accidentally: turning off the main breaker to the home. At the time, everything appeared to work ok, but she didn't know that her mistake was sending electricity down the lines. Now, this wasn't because the wife was following her husband's instructions, it was because unsafe instructions were used in the first place; he could have easily forgotten to throw the main breaker as well. It's because something unsafe was done in the first place.

Now I put "safely" in quotes above because short of using the proper mechanical interlock or break-then-make transfer switches prescribed by the NEC, there is no safe way to guarantee that everything's been disconnected safely. Most power companies & their contractors will now take extra precautions because of the availability of generators to avoid such mishaps and the stupidity of the people who do this. Most power companies are fined if they don't do this and something happens, but that's after someone dies or is severely injured.

What we are talking about here is akin to this - it's also like installing a gas pump at your home to fill your ICE, and because the hose isn't long enough you rig up a garden hose, a funnel, and some duct tape to make it work, neglecting issues such as static build-up, possible leakage, etc. It may work 99 times out of 100, but the 1 time it doesn't work you lose your property or even your life.

 

[mknox]

A few years ago, there was a lineman killed when the line he was working to reconnect downed lines; a homeowner connected a generator to the circuit, causing a backfeed into the line he was working on.

This is a big concern for us utility guys. With the prevalence of renewable generation like solar and wind, the problem becomes even more widespread. Properly installed grid-tie solar/wind will have an automatic disconnect to isolate the system in the event of a disruption to grid power. Without it, FlasherZ's back-feed scenario would be happening all over the place. My utility requires a separate disconnect switch for the generation located near the meter, because these automatic systems can fail (or are removed by the homeowner so they can continue to have power during a utility interruption). We record all locations, and linemen will open and tag these switches before working on powerlines. I bring this up as another example of a seemingly "innocent" situation turning deadly.

 

[Cosmacelf]

Well, I finally finished it. My own 120V to 240V adapter. I used the schematic I posted in post #23 of this thread, with the addition of a 240V green indicator light across the two output hots. I also wanted to make it useful for TT-30 receptacles as well as 120V household receptacles, so I bought a 50' 10 gauge extension cord from Home Depot, cut off the ends and made two 25' 10 gauge cords, which I then terminated in male TT-30 plugs. I then bought two of these adapters so I can use this box with either TT-30 receptacles or household receptacles. As a bonus this will allow me to draw 24A, finally, from a TT-30 receptacle rather than being limited to 20A.

I wanted to make it "small" so I used a 4x4x4 Carlon electrical box from Home Depot. I decided to use a NEMA 6-50 receptacle as the output receptacle (bought off the shelf at Home Depot) since they are a lot smaller than the NEMA 14-50 receptacle and I had a Tesla 6-50 adapter anyways. I used two 120V 30A relays, and one 240V 30A relay.

Some hole drilling, misc. hardware, crimped connectors, and voila:

Here's the box with everything in and wired together.

I ended up only connecting one ground wire, as you can see. Since the output receptacle is completely isolated and unconnected unless BOTH 120V plugs are plugged (and plugged into different 120V legs), I figured just having one ground connection was better than cross connecting grounds together.

I may never use this, but it was fun building it

 

[Neech]

Cosmacelf -- did you at least try it out to see if it works?

 

[Cosmacelf]

Well yes, I did try it out on two 120V household circuits. When connected to the same leg, or just one plug plugged in, no light and no voltage across the other plug. I got about 7 miles/hour charging when plugged into the Tesla and connected to two different legs.

 

[FlasherZ]

I ended up only connecting one ground wire, as you can see. Since the output receptacle is completely isolated and unconnected unless BOTH 120V plugs are plugged (and plugged into different 120V legs), I figured just having one ground connection was better than cross connecting grounds together.

Except this ("completely isolated") is not true for older RV supply pedestals (pre-NEC 2008). If there is a neutral failure on the feeder supplying the panel that supplies the upper plug in your device (the one you use ground from), those 4 screws on top of the device will go hot in reference to ground and touching them will give you a shock. It is NOT TRUE that your relays protect you, because it's the relay coil (not contacts) that causes those screws to go hot in the first place. (hot->relay coil->neutral->bonding->ground)

 

[mrrjm]

So I'm using the schematic in #28 with some changes. I ordered the wrong relay's be accident. I ordered the Magnecraft 9As1a52-240 instead of -120. So I changed the circuit by dropping the neutrals and only using the hots and grounds. The hots from 2 separate phases power the coils. This works better IMO because neither relay turns on unless you are plugged into separate phases. Then each relay will switch a hot to a NEMA 6 50 receptacle. Then I'll connect both grounds to the ground on the NEMA 6 50. I have a 240 volt pilot lamp on the outputs. I wired all this up on a piece of wood (bread board style) without the NEMA 6 50 and it seems to work fine. No load yet expect the pilot lamp. So the question is is this safe? Here is how I plan to use it. First I should say I understand that the current on the car has to be dialed down to 12 amps if I'm on a 15 amp circuits or 16 amps if I'm on 20 amp circuits. I'll use this in my shop if I want to charge indoors. My HPWC is outside. And if I go to a hotel that will let me plug in outside. We were in the Wisconsin Dells and the hotel had 120 volt outlets set up for EV charging. It was subzero at night and 120V 12 amps doesn't do it. At least with this converter charging will be somewhat useful. Thanks in advance for the help. -Ray