How much voltage difference between 2 legs is acceptable?

[smokey0066]

I finally finished the installation of my sub panel and my tesla EVSE. I setup the EVSE and noticed there is a 1-2v difference between L1 and L2. I think it was like 119/117 bouncing around a bit. Is this voltage difference acceptable? Everything was torqued, jiggled, and retorqued. I don't have a car here to test it with a load but do you guys think I need to go back in and retorque all my connections one more time?

 

[rlitman]

A couple of volts is normal, so long as your neutral does not have over a few volts to ground you're fine.
Are you testing this under load. If there's no load, you could have zero torque on the connections and get good readings. Voltage drop across loose connections only happens when current is flowing!

 

[smokey0066]

A couple of volts is normal, so long as your neutral does not have over a few volts to ground you're fine.
Are you testing this under load. If there's no load, you could have zero torque on the connections and get good readings. Voltage drop across loose connections only happens when current is flowing!

I gotta wait until the wife gets home with the car to load it. I will recheck the readings in the Tesla app while its charging. I did religiously torque all the connections because I was constantly seeing that being brought up on various posts and videos.

I forgot to check what kind of voltage I was seeing at the main panel when I connect the sub panel this morning. I'm a little bit lazy to take that main panel cover off again.

 

[RPH]

Within the parameters of the meter. Most general purpose meters are not that accurate, +/- 2 least significant bit of resolution on the display.

 

[American Locomotive]

Perfectly normal and well within tolerance. Tolerance on any leg is generally 120v +/- 5%. So 114-126v is considered acceptable.

Really this is sort of a case of "too much information can be unhelpful". The EVSE should just tell you if the incoming power is acceptable or not.

 

[smokey0066]

Perfectly normal and well within tolerance. Tolerance on any leg is generally 120v +/- 5%. So 114-126v is considered acceptable.

Really this is sort of a case of "too much information can be unhelpful". The EVSE should just tell you if the incoming power is acceptable or not.

I’d like to see exactly what you mentioned, a nominal with tolerance next to the readout. Or the could put a bar underneath to give you an idea of what they’re looking for.

Anyways thank you. I’ll quit worrying about it and check again when it’s under load.

 

[mike93lx]

I gotta wait until the wife gets home with the car to load it. I will recheck the readings in the Tesla app while its charging. I did religiously torque all the connections because I was constantly seeing that being brought up on various posts and videos.

I forgot to check what kind of voltage I was seeing at the main panel when I connect the sub panel this morning. I'm a little bit lazy to take that main panel cover off again.

It's not just the load on that circuit, it's other loads in the house

 

[rlitman]

It's not just the load on that circuit, it's other loads in the house

Exactly. Loads in your house (and even neighbors on the same transformer) will affect the voltage balance, and test the connection resistance upstream. That's what is causing this (minimal) fluctuation, since the vehicle isn't providing any load. And this much is perfectly normal.

I'm not suggesting probing live circuits, but I will say this much. Voltages tell you about upstream resistance, so measuring the voltage at the EVSE breaker doesn't tell you anything about how well your torqued the connections in the wall receptacle, but measuring the voltage INSIDE the EVSE does, at least while a vehicle is charging.

 

[larry_g]

Your fine. As said above all within normal range. What is your voltage L1 to L2? That is what is important..

lg
no neat sig line

 

[smokey0066]

Your fine. As said above all within normal range. What is your voltage L1 to L2? That is what is important..

lg
no neat sig line

It was showing around 240, forgot the exact number but it looked normal to me. Wife just got home and it’s pulling 40a at 232v. I’ll keep an eye on it for the next few days.