Low Mileage User - Can I save $$ and skip the 240v Charger?

[Ingineer]

BTW if it is a 20a breaker it must be #12 wire. I think code says 3% voltage drop max and you are exceeding that amount.
To lose that voltage in #12 wire the circuit would be over 175' so any shorter tells me the drop is in the connections.

You don't know that! How do you know the drop isn't coming before the panel? He didn't measure voltage drop on that circuit, only the TOTAL voltage sag of the whole system! The only valid way to measure voltage drop is to connect one meter lead to the bus bar in the panel, and then the other at the outlet hot terminal, then repeat for neutral. If this had a total 6.5v drop, I'd be very alarmed!

Unless you are very experienced with electricity and qualified to work on exposed live connections, I don't advise removing the cover of the panel for this test. You could also conduct a more accurate and safer voltage drop test by finding an outlet on the same leg, but on a different breaker, and measuring from hot to hot, then neutral to neutral and summing the two. That would be a much more accurate drop reading, and without needing to be exposed to the dangerous live panel.

It's not uncommon to see the incoming connections at the panel sag a handful of volts under a heavy load such as 12A. This is caused by the meter, a potentially long run of service entrance (many are aluminum), and the transformer itself.

-Phil

 

[Nubo]

BTW if it is a 20a breaker it must be #12 wire. I think code says 3% voltage drop max and you are exceeding that amount.
To lose that voltage in #12 wire the circuit would be over 175' so any shorter tells me the drop is in the connections.

You don't know that! How do you know the drop isn't coming before the panel? He didn't measure voltage drop on that circuit, only the TOTAL voltage sag of the whole system! The only valid way to measure voltage drop is to connect one meter lead to the bus bar in the panel, and then the other at the outlet hot terminal, then repeat for neutral. If this had a total 6.5v drop, I'd be very alarmed!

Unless you are very experienced with electricity and qualified to work on exposed live connections, I don't advise removing the cover of the panel for this test. You could also conduct a more accurate and safer voltage drop test by finding an outlet on the same leg, but on a different breaker, and measuring from hot to hot, then neutral to neutral and summing the two. That would be a much more accurate drop reading, and without needing to be exposed to the dangerous live panel.

It's not uncommon to see the incoming connections at the panel sag a handful of volts under a heavy load such as 12A. This is caused by the meter, a potentially long run of service entrance (many are aluminum), and the transformer itself.

-Phil

Thanks Phil. Sorry to keep picking your brain, but am I understanding correctly -- these measurements (e.g.: hot-hot) are between 2 separate outlets, both on same (A or B) leg? Considerably further apart than the leads on my simple multi-meter. Is there a proper way to span that distance without introducing even more error, or does it just cancel out?

Thanks for all of the suggestions and I'll definitely be going over this circuit carefully when I return from an upcoming trip.

 

[garygid]

Any normal extension cord can be used to "extend" a socket for measuring purposes.

 

[Ingineer]

Thanks Phil. Sorry to keep picking your brain, but am I understanding correctly -- these measurements (e.g.: hot-hot) are between 2 separate outlets, both on same (A or B) leg? Considerably further apart than the leads on my simple multi-meter. Is there a proper way to span that distance without introducing even more error, or does it just cancel out?

Thanks for all of the suggestions and I'll definitely be going over this circuit carefully when I return from an upcoming trip.

You would measure hot to hot then neutral to neutral from the charger outlet to another oultet served by a different breaker, but on the same leg. (or as incorrectly often stated "phase".)

You can do this by getting two cheapo non-polarized cord ends, and hooking a wire to one blade on each. (Or by Gary's method above) Run those wires to the input of your meter. Plug them into the two outlets you have verified are served by different breakers, such that the meter wire is connected to hot. (small slot) If you read 240ish volts, you know they are on opposite legs, so find another outlet. Once you read only a few volts or no volts, you can begin the test. Do a reading before on both hot/neutral, record the voltages, then start charging and repeat. You then sum the hot/neutral readings and subtract the initial readings to get your total voltage drop on that circuit. I'd be concerned if it's over a few volts.

-Phil

 

[LTLFTcomposite]

I'll toss this out there, and would welcome phil's comments, but IMO two common problems that can be easily corrected are crappy worn out devices (receptacles) and receptacles that are "stabbed" with the wire into those holes that rely on pressure of a spring contact against the conductor. There is also some debate whether it's a good idea to use the second set of screw terminals on the device as a connection point to wire through the circuit to the next outlet (I'm not talking about the case of GFI receptacles where it is important that you DO to provide GFI protection to the other outlets on the circuit).

Regardless of whether it's a 15 or 20 amp circuit, it only costs a few dollars to replace old worn out devices. Also take the time to wire to the side screw terminals. For a little more you can get a "spec grade" device for the outlet you will be plugging the EVSE into. For other outlets on the circuit in the "daisy chain" use a short piece of wire as a pigtail and make the wire-through connections with wire nuts instead of making the connection through the device.

Again, JMO, and don't undertake this project if you aren't comfortable with this sort of thing.

 

[planet4ever]

There is also some debate whether it's a good idea to use the second set of screw terminals on the device as a connection point to wire through the circuit to the next outlet

When I did some wiring for an addition at our home a number of years back the city inpector insisted that I "pigtail" the outlets, i.e. use wire nuts in the box and a short piece of wire from there to the outlet, rather than have two wires connected together on the outlet. If you do that, and then stab the outlet, you can get some voltage drop (and heat) within that outlet, but you won't get progressive drops down the chain from multiple stab connections. Aren't wire nut connections on solid wire very efficient?

Ray

 

[Nubo]

Did a bit of work Friday afternoon before departing for a week. No-load voltage this time was just over 122v. It was a rainy day, fwiw.

The total drop this time was 5v. Measurement between outlets gave a sum of 3.8v.

Put in a new plug w/side terminals. restripped the wires and cleaned the copper. Likewise cleaned the conductors and put on new wire nuts (there were pigtails). Redid the wire nuts in the switch box that was closer to the panel.

Afterwards the cross-outlet sum was 3.6 volts under the charger load.

 

[smkettner]

Well if they are all pigtailed it will not be a collective issue to worry about each connection.
Still I will never install a stab outlet.

 

[DaveEV]

Afterwards the cross-outlet sum was 3.6 volts under the charger load.

That indicates that you're losing about 40+W (3.6V * 12A) somewhere between where you plug your EVSE in and main panel. If it's along the entire wire run, mostly likely fine, but could be an issue if it's concentrated in a small spot somewhere along the run. You can use a voltage drop calculator like this one to figure out how much of an issue you might have.

For example, assuming 12A, 120V, 14ga wire and 50ft run, you get a 3.6V drop, in which case you're doing just fine!