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If you think your generator will get you out of a pinch...think again

If you think your generator will get you out of a pinch...think again

As I've commented on other posts here we have a 15kW generator (22kW surge) and after trying many different scenarios our Model 3 won't charge from it. It will run our whole house, but since we have a 5hp well and a 5 ton HVAC system it won't run them both at the same time. Technically, it would run them both, but there isn't enough surge wattage to start one while the other is running since start up draws a lot more amperage.

The error I'm getting on the touchscreen in the car is related insufficient ground even though the generator is connected to an 8' ground rod with a 4 gauge ground cable. I've tried charging directly from the generator plugs (240v - 50amp, 240v - 30amp and 110v - 20amp) and charging from the dryer plug in the house when the generator is powering the house. I've preloaded it with another load and did finally get a few mph charge, but it was on and off. The car really didn't like it, and I got a message stating that if the condition persisted to contact Tesla Service. I don't want to damage the onboard charger.

I thought it was the age of our generator, but when testing a new, out-of-the-box Honda inverter style generator with two 110v - 20amp plugs I got the same results. And no it isn't grounded through a ground rod. There is no place to hook up an external ground provided on that particular generator. It does power other loads just fine.

My point is: Don't lull yourself into complacency, and then find out your generator won't charge your Tesla when you think/hope it will.

https://vimeo.com/357199824

Magic 8 Ball | 2019年9月1日

My understanding is that "small" generators put out "dirty" electricity mostly because of imperceptible changes in RPM. Nice to know the car is sensitive enough to know when it is being fed the good stuff. ; ).

PECo CT | 2019年9月1日

I have no experience with this, but watched a YouTube video about it a while ago. A quick Google search cane up with this. I hope it can help:

https://generatorgrid.com/blog/tesla/

gmr6415 | 2019年9月1日

@Magic 8 Ball, I wouldn't consider our 15kW (22kW surge) generator a small generator (at least not for a residential use generator), and it's obviously putting out dirtier electricity than the car likes.

Supposedly, the newer inverter generators produce a clean sine wave, because it's generated electronically and is not engine rpm dependent.

gmr6415 | 2019年9月1日

@PECo CT, Thank you. That's a very good article.

"Some examples of inverter generators that do have a pure sine wave output are the Champion 9200W/11500W, the Generac iQ2000, and Honda’s EU2200i and EU7000iAT1 models."

"For the Honda generators, this is definitely the case. To remedy this, you’ll need a special adapter plug that bridges the ground and the neutral with a resister."

The one in my video is listed above (EU2200i) but we didn't have the bridging adapter that the article references. Good to know if in fact it is available. Time to do some searching.

kaffine | 2019年9月1日

gmr6415 said The error I'm getting on the touchscreen in the car is related insufficient ground even though the generator is connected to an 8' ground rod with a 4 gauge ground cable.

How is the generator wired in? Is there a Transfer switch is it automatic or manual? What is between the power meter and transfer switch and the breaker panel that supplies power to Tesla connector?

Tesla doesn't have a way to check for actual earth ground it is checking the Equipment Grounding Conductor (EGC). The way it checks the ground is to put a small current on the ground (less than 5mA). In a normal system the ground is tied to the neutral at the main panel and only at the main panel so the current has a complete path. My guess is the transfer switch is located between where the EGC is tied to the neutral and the panel that feeds the Tesla. So when it switches to the generator the EGC is no longer connected to the neutral. Since the neutral and EGC are not tied together when running on the generator there is not a complete path for current to flow and this is what is giving the error message.

It isn't uncommon for a transfer switch to switch both hots and the neutral, however if it is switching all 3 then the generator needs to have a connection between the neutral and the EGC.

Magic 8 Ball | 2019年9月1日

@gmr6415 Sorry, I did not mean to make this a size matters discussion. It looks like the article even shows some portable choices that may be able to be used.

gmr6415 | 2019年9月1日

@kaffine, no transfer switch at all. Years ago when we were going through three hurricanes in 6 weeks in FL I installed a 240v 50 amp breaker in the box and designated it as a generator connection. There is an outside 15-40 outlet wired directly to that breaker with the appropriate ground and neutral going to their respective posts in the breaker box.

When we use the generator we flip a 250 amp disconnect that's between the meter and the breaker box (installed by the power company because of our solar arrays), plug the generator into that outlet, start the generator and then flip on the 50amp breaker in the box. This was approved and rubber stamped by our power company during the process of going through our interconnect agreement for our solar installation.

When we purchased the Tesla I started using that same plug to connect the mobile charger, and the breaker that was once designated as the generator breaker is left on for charging the Tesla.

When I attempted to charge the Tesla with the generator connected to the house the generator was connected as noted above and I connected the mobile Tesla cable to the dryer plug when is a few feet away. (obviously at that point the 250 amp disconnect between the meter and the box has been tripped)

I do have an 8' ground rod in the ground where we place the generator and the frame of the generator is grounded with a 4 gauge ground cable to that ground rod.

Passion2Fly | 2019年9月1日

My neighbor uses regularly a gas generator to charge his Model X. It’s a small/portable generator. It works for him.

gmr6415 | 2019年9月1日

Correction 14-50 in all places I stated 15-40. I knew that didn't look right.

gmr6415 | 2019年9月1日

So I tried the neutral to ground jumper. First I used a resistor and the highest rate of charge I could get was 3mph...not really worth it. Then I used a 12 gauge wire as a jumper and was able to obtain 11mph maximum, but I still had to use a 1500 watt space heater as a secondary load in order to stabilize the generator enough.

All in all that would be worth it if I was also powering the house during an outage. I wouldn't need the space heater then.

Thank you @PECo CT, that article you linked to was insightful and helped me get over an issue I've been working on every now and then for quite some time.

Would I rather charge at a full 32 amps? Yes, but 11mph isn't bad.

https://ibb.co/album/frimaa

PECo CT | 2019年9月1日

@gmr6415

Thanks for following up with an update. I don’t foresee a time when I’ll ever need to charge my Model 3 with a portable generator, but I’m glad to hear that it can be done.

kaffine | 2019年9月1日

@kaffine, no transfer switch at all. Years ago when we were going through three hurricanes in 6 weeks in FL I installed a 240v 50 amp breaker in the box and designated it as a generator connection. There is an outside 15-40 outlet wired directly to that breaker with the appropriate ground and neutral going to their respective posts in the breaker box.

When we use the generator we flip a 250 amp disconnect that's between the meter and the breaker box (installed by the power company because of our solar arrays), plug the generator into that outlet, start the generator and then flip on the 50amp breaker in the box. This was approved and rubber stamped by our power company during the process of going through our interconnect agreement for our solar installation.

When we purchased the Tesla I started using that same plug to connect the mobile charger, and the breaker that was once designated as the generator breaker is left on for charging the Tesla.

When I attempted to charge the Tesla with the generator connected to the house the generator was connected as noted above and I connected the mobile Tesla cable to the dryer plug when is a few feet away. (obviously at that point the 250 amp disconnect between the meter and the box has been tripped)

I do have an 8' ground rod in the ground where we place the generator and the frame of the generator is grounded with a 4 gauge ground cable to that ground rod.

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WOW. I am surprised at how some things get approved and past inspectors.

Your neutral ground bond should be in the disconnect and the neutral is likely being disconnected so it isn't bonded anymore when the generator is running.

The generator should not be plugging into a receptacle the mobile connector can plug into. The generator cord where it connects to the house should have the female receptacle on it and the house side should be the male plug just the opposite of the mobile connector. There should also be a lockout of some kind to make sure it can't be powered from the house side. This is done with either a transfer switch or a lockout breaker arrangement in the panel. A disconnect switch that doesn't lockout the generator circuit does not meet the requirement. The physical lockout is required for a few reasons. Fist as the generator connection on the house is the male plug if the circuit isn't turned off when using grid power then the exposed terminal are energized and a major shock hazard. Second is you have to make sure the generator can not back-feed to the grid if the grid is down and linemen are working on it the generator could back-feed into the grid energizing the grid the linemen think is dead. Third since the generator is not synced to the grid if it was still running when the power is restored bad things can happen.

My guess is if you check you will find the generator neutral is not bonded to the ground. This is a problem as if a hot gets shorted to ground it won't trip a breaker and will energize everything that is connected to the ground. If you were to bond the neutral to ground in the generator it will likely allow the Tesla to charge. The bond jumper will need to be a good size wire I would go with the same size as the hots to make sure there is a good path in case of a hot wire is shorted to ground it will be able to trip a breaker.

Passion2Fly | 2019年9月2日

+1
I agree, a backup generator without an approved ATS (automatic transfer switch) and a backup loads panel will never pass inspection. at least in CA...

jonathangreene | 2019年9月2日

Glad I found this .... we have a 20Kw Generator, a Model 3P and an X coming at the end of the month. Was just realizing it will be good to have the wall connector linked on our generator for those just in case scenarios. We can run most of the house, but currently don’t have any open panel switches on the generator panel so it might require some give and take.

gmr6415 | 2019年9月2日

@kaffine and @Passion2Fly, As I stated above, not only did it pass inspection in FL, the disconnect box was installed by the power company. The state requires it with every solar installation.

The 250 amp manual disconnect disconnects the house completely from the grid...no risk of someone up line getting zapped by the generator or the solar array. That said, the required disconnect on a solar array is redundant. If the Sunny Boy inverter doesn't see the sine wave from the grid it shuts down.

https://ibb.co/FDy6ywQ

gmr6415 | 2019年9月2日

@Passion2Fly, Are you saying that even when powering the entire house with a backup generator that the state of CA requires a separate backup loads panel?

That seems pretty ridiculous.

rxlawdude | 2019年9月2日

@gmr, I think he means an AUTOMATIC TRANSFER SWITCH.

Installed to code, perfectly acceptable in CA.

hcdavis3 | 2019年9月2日

My 20Kw generac charges my model 3 with no issues. I just don’t use any other high load appliances, oven or dryer while charging. My usual charging routine only lasts about an hour. After that I simply unplug the cable.

hcdavis3 | 2019年9月2日

My generac has a 100 amp breaker built in. It uses an automatic transfer switch. I will rarely if ever need to use the generac to charge my 3. But it’s there if I need it.

jebinc | 2019年9月2日

While house General here as well. No issues.

Cactusone | 2019年9月2日

Here is a video of the Neutral to Ground trick for your generator

https://youtu.be/4MR-uKp6u8M

SteveWin1 | 2019年9月2日

My 6000 watt powerstroke generator will charge my model 3 with the 110 plugs out of the box. The 30amp 240V outlet doesn't work though, unfortunately. Luckily the 110 plug is enough to get around town to run errands and I can still power other things as the same time. I make sure my car is charged before hurricanes so I probably wouldn't need a charge before the power was back on anyway, but it's nice to know it's an option.

kaffine | 2019年9月2日

gmr6415 | September 2, 2019
@kaffine and @Passion2Fly, As I stated above, not only did it pass inspection in FL, the disconnect box was installed by the power company. The state requires it with every solar installation.

The 250 amp manual disconnect disconnects the house completely from the grid...no risk of someone up line getting zapped by the generator or the solar array. That said, the required disconnect on a solar array is redundant. If the Sunny Boy inverter doesn't see the sine wave from the grid it shuts down.

https://ibb.co/FDy6ywQ

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The issue is there is no mechanical interlock for the disconnect switch to be in the off position before the generator is started. And unless I misunderstood you plug your generator into a 14-50 outlet. If you were to disconnect the plug while the generator is running the exposed metal on the plug is energized and a major shock hazard. Just because it passed inspection doesn't mean it was done to code inspectors miss things all the time. Of course I am just reading some of how it is wired not actually inspecting it, I could be misunderstanding how it is setup and it really is code compliant.

gmr6415 | 2019年9月3日

@kaffine "The issue is there is no mechanical interlock for the disconnect switch to be in the off position before the generator is started."

I manually disconnect the house from the grid before starting the generator. End of story. As part of my interconnect agreement with the power company I had to sigh off authority allowing the power company to come onto the property and make sure the switch has been flipped if they so desire. If not they have the authority to flip it themselves. Neither has happened in 15 years. If something does happen down line, and it falls on me, I have agreed in writing (in the interconnect agreement) that the liability is on me.

@kaffine, "And unless I misunderstood you plug your generator into a 14-50 outlet. If you were to disconnect the plug while the generator is running the exposed metal on the plug is energized and a major shock hazard."

Getting caught in a metal row boat in a lightning storm is a major shock hazard too. Using a stick welder with an exposed electrode is a major shock hazard under certain conditions, but millions of people use them every day. Playing golf in Florida with the risk of pop-up thunder storms is a major shock hazard. People get struck weekly here during the rainy season. It's not a code violation to play golf here. It's a shock hazard to be on the beach in Florida, but 10s of millions of people do it, and it's not a code violation.

Have you looked at the warning labels on a ladder? Millions of them are used every day. How about a chain saw or a circular saw. Both are dangerous to use, yet they aren't illegal or some sort of code violation.

@kaffine, "Just because it passed inspection doesn't mean it was done to code inspectors miss things all the time."

The 14-50 generator outlet was installed by a state certified and licensed installer at the time of my solar installation in 2004. A permit application with the wiring diagram including the 14-50 receptacle noted as to be used for a portable generator connect was submitted to and approved by the county and the power company (as required by FL law for any solar installation and any ancillary equipment to be installed at the time) prior to installation and inspected by both the county inspector and the power company supplying power to our house as required by Florida law at the time.

I don't know what state and county you are in, but what I have was approved and permitted prior to installation based on wiring diagrams supplied to the county and the power company prior to installation.

We have an 1880s farm house on 90 acres in Northwest AR. It was retrofitted with copper wire insulated with cloth sometime in the early 1900s. That wire still powers the house using the old screw in type fuses. Is it illegal? No. Is it a risk? By today's standards yes, but nothing has happened in almost 100 years of it being that way, and to this day there is no building code at all in that town or that county. I know that because we own the town of Sandiff, AR. https://www.google.com/maps/place/Sandiff,+Poff+Township,+AR+72153/@35.6478531,-92.2407188,14z/data=!3m1!4b1!4m5!3m4!1s0x87d216b3362cbca9:0xa67022f5347e697e!8m2!3d35.6478549!4d-92.2232092

Atoms | 2019年9月3日

The ground rod has no relevance because your car is on insulating tires. What matters is the voltage and resistance between neutral and ground or current returning on your ground. The Tesla is checking to see if your generator is safe and determined it is not.

gmr6415 | 2019年9月3日

@Atoms, Maybe someone needs to tell Generac, Honda and a whole slew of other companies building generators that Teslas won't charge from, that they aren't building and selling safe generators.

jdcollins5 | 2019年9月3日

This thread is very timely for me. I sold a 2010 Prius when I bought my 3. I had a 2000W inverter that I could connect to HV battery for power outages during hurricanes.

With Dorian approaching, I bought a Cat 6500W generator. After reading this thread, I tried charging my car. Same result as others, it would start and slowly ramp up to about 3-4 amps and then drop back to 0. The engine could not hold speed tight enough. I did not get any error messages.

I am going to miss the Prius. I am hoping that Tesla will help us in the future with Vehicle-to-Grid capability so we can power our houses during power outages.

rxlawdude | 2019年9月3日

@gmr, it's good to own the town. What's the population besides your homestead?

kaffine | 2019年9月3日

gmr6415 :

From the description here your generator was not installed to code and has several major safety issues. You are the one complaining that it doesn't work to charge your car. Maybe these things are related? I don't have a copy of NEC code book that old to check but I doubt it was code compliant back then to install a generator in the manner you have described. It doesn't matter to me who did it or what license they held it was done wrong. Of course all I have to go on is your descriptions so I could be misunderstanding you in how it is setup.

gmr6415 | 2019年9月17日

@kaffine, you are trying to make this a one size fits all issue. Codes vary depending on where you live. It doesn't matter what "recommendations" the NEC code book makes. It doesn't mean any one given municipality or county adheres to them.

Since hurricane Andrew hit in 1995 Miami came up with hurricane code that was much more strict when it came to shingles used (shingles specifically manufactured to meet Miami wind rating standards), how the shingles are installed, number of nails per square foot of sheathing, Number of nails per shingle, gluing the shingled down on the drip edge, metal tie downs for rafters, wind speed ratings for windows, etc, etc, etc.

It was years before most other counties in the state of Florida adopted similar code. Just because that was done in Florida does that mean that someone living in Ohio, rated the least likely state to be hit by a hurricane or tornado, is required to adopt the same code standards?

Secondly I wasn't complaining. I was bring up the point that many generators/portable generators may not charge a Tesla, so don't wait until the last minute to try it before you end up dependent on it, and it won't do it.

kaffine | 2019年9月17日

NEC is the National Electric Code. It is what most places base theirs on. Some places add on making things more restrictive I'm not aware of places that make things less stringent. Some places might be a few code cycles behind.