Tesla Wall Charger installation heads-up

Tesla Wall Charger installation heads-up

I'm (im)patiently awaiting delivery of my Model S having suffered two delays. In preparation, I had a Tesla Wall Charger installed yesterday and thought I should pass on the installer's warning. I'm sure this will be known and understood, but better safe...

I'm in the UK, but the same principle will likely apply elsewhere. I'm on a single-phase rural electricity supply which has the earth derived from neutral. There's no separate earth. The installer put in an RCCD so that power to the charger will trip if a leakage to earth is detected. However, he was concerned that, in certain fault situations, the power will attempt to make an earth connection through the car and/or anyone touching it. He decided that it would probably be necessary to fit an earth rod, but checked with the UK electrical standards body to be sure. They agreed with his assessment. He suggested that I make others aware of the need for this earth connection when the incoming supply is live and neutral only.

I'm sure there are many of you are far more expert than me on the subject - that wouldn't be difficult - and I hope you'll correct me if I'm not entirely accurate with my explanation. But the installer didn't want any harm coming to me or the car. I'm not sure what his order of importance was.

So now I have a shiny new wall charger with a nice green light on it, but the space beside it is curiously still empty. I'm counting the minutes.

mdmgso | 2018年1月19日


Your concerns are groundless.

Sorry. You probably won't get the pun, but I couldn't resist.

Alan75DUK | 2018年1月19日

When my charging point was installed, the electrician included an earth rod saying that the existing earth was not sufficient to support the charging point - probably the same reasoning as the original post. I have a dedicated 3-phase supply since my house layout does not support the charging point being added to the existing house single phase supply. I chose 3-phase to provide some future proofing for larger batteries and a second EV. As far as the earth rod is concerned, I am not an electrician so cannot argue the point, but since I have an outside installation exposed to the weather, anything intended to keep things safe is okay with me.

Unfortunately for me, I do get the pun - groan.

Don Schmidt | 2018年1月19日

I got a charge out of your pun.

Our home, in Vancouver, WA USA was built in 1981 and in 2011 had the breaker box changed out due to some failures. At that time the electrician added a second ground rod to ensure safety and be in compliant with the electrical code which was upgraded since 1981.


sr.smr | 2018年1月19日

The primary circuit breaker panel should have a dedicated conductor from the ground buss bar to the incoming water pipe, which is considered the ground source according to code in my jurisdiction in the US. I'm not a licensed electrician, but I remember that a ground rod alone was not an acceptable ground.

MuirWoods | 2018年1月19日

Mdmgso - I've no feelings either way about your pun. Generally neutral.

Sr.smr - A problem I have is that the incoming water pipe and gas pipe are plastic.

It seems from the reports that it's a well-understood issue that's been dealt with properly by the professionals. Just hope they didn't *charge* too much :-)

tes-s | 2018年1月19日

I'm not sure I understand. Is the wall charger somehow different than other devices that it requires special wiring?

Mine is simply connected to the ground at my panel. It happens to be a subpanel, so the ground is not bonded to the neutral - that happens at the main panel, where the ground and neutral are bonded, and is also attached to grounding rods.

murphyS90D | 2018年1月19日

In the USA.
The HPWC has three wire connections. Two wires to provide 240 volts and an earth ground. All three go back to the supply panel and get connected to the appropriate points. No special wiring is required. Neutral is not involved in the wiring of a true 240 volt appliance.

I don't know anything about wiring in other countries.

p.c.mcavoy | 2018年1月20日

If I understood @MuirWoods original post, he indicated that his panel has the ground (earth) derived from neutral without a separate ground. That is why I understand his electrician recommended installing a dedicated grounding wire to the panel. I'm not an electrician, but this seems like a reasonable approach given the power levels involved with a HPWC. Even if it's was overkill, nothing wrong with being cautious.

I would agree that the approach recommended was well grounded.

barrykmd | 2018年1月20日

mdmgso - Nice one! I got a charge out of it.

Tropopause | 2018年1月20日

I think everyone here is tripping.

rxlawdude | 2018年1月20日

There's a spark of humour (UK spelling for OP) here on the forum.

Haggy | 2018年1月21日

"Your concerns are groundless."

I believe that in the UK, you need to say "your concerns are earthless."

leemorzak | 2019年10月6日

Hi sr.smr, just FYI, in the UK the use of gas and water pipes as your earthing does not meet the wiring regulations, suitable earthing needs to be established.

Hi MuirWoods, not only is an earth rod desired on an EV install, but it is a requirement to the regulations - there are other possible ways of preventing the PME issues such as an isolating transformer etc., but the earth rod solution is the simplest and usually the cheapest.

HETZ | 2019年10月6日

After reading this I would be concerned (which is why I clicked on it), but fortunately my electrician went out of his way to point out to me that he double checked the grounding and that the solar installers had put a ground rod in addition to the water line into the house.

Thank you MuirWoods for posting this heads up.