usefulness of a switch to control the NEMA 14-50 outlet?

usefulness of a switch to control the NEMA 14-50 outlet?

What does anyone think about having a switch to control a NEMA 14-50 outlet? On the one hand, it would be good to shut power off when the Tesla is gone, and is an alternative to unplugging the connector. On the other hand, I am hearing and reading that the power draw of a non-Tesla-attached-but-plugged-in connector is negligible. Maybe having a switch is more trouble and expense than it's worth?

jordanrichard | February 24, 2019

Ummmm, no.

There is no power draw if nothing is plugged in. However if you are that worried, there is already a switch to kill power to the outlet, it’s called a circuit breaker.

jerrykham | February 24, 2019

@jordan is correct. With 240v systems like this you normally have just a circuit breaker. Sometimes a "switch" is added, but it is typically the "emergency disconnect" kind and not what you are probably thinking of and is used more often with outdoor setups particularly around hot tubs and air conditioners.

stevenmaifert | February 24, 2019

No need for a switch unless you are mounting the NEMA 14-50 in a location that would be accessible by others. In that case you could still trip the circuit breaker if it located in a lockable breaker box to keep folks from "stealing" electricity.

Yodrak. | February 24, 2019

Most electrical outlets are not controlled by a switch, and many of those outlets have devices plugged that have negligible draw when the device is not in use. (Although many negligible draws can cumulatively add up to be significant.) I don't see anything special about an outlet used to charge an EV that would call for the outlet to be switched, if there were electrical codes would probably require a switch.

kcheng | February 24, 2019

Many exterior power boxes are lockable, so you can prevent access if that's your goal.

Earl and Nagin ... | February 24, 2019

A switch sounds quite useful to me. One should disconnect the 14-50 outlet before plugging in or unplugging. It could avoid overly stressing the switch on the breaker if you plug and unplug regularly. It could also be convenient if the breaker is inaccessible.
I don't have a switch on any of ours but it would be useful.

rxlawdude | February 24, 2019

You'll need a rather substantial double throw switch (like the kind you see to cutoff an A/C compressor.

That said, no problem with installing it, and better the switch than eventually wearing out the NEMA 14-50 if you unplug your UMC routinely.

csun | February 24, 2019

Thanks everyone. My only objective in having a switch would be to save money by conserving power in the situation where I have a mobile connector connected to a live 14-50 outlet but without the Tesla attached (i.e. a dangling connector connected to a live outlet).

However, from what I have seen and ready, the power drain in this situation is negligible? If so, then I am thinking that the cost of installing a switch is not worth the small amount of money I save?

rxlawdude | February 24, 2019

If it's just to save vampire drain of the UMC, you're right. Not worth it. But if you plug and unplug your UMC routinely, it may be a good idea but certainly not critical. | February 25, 2019

@csun - I've measured the MC when not charging, and it takes less than 1ma (the limit of my meter). It might take 50 years of turning off the power to the MC to save the cost of the switch - it the switch lasts that long. Really, there is no need for a switch.

@Earl and Nagin - There should never be any stress on the connector if you disconnect from the car first. If there is no power flowing, there is zero stress on the outlet. | February 25, 2019

I'll also add to save that 10 cents a year of electricity using this switch, there is a high likelihood that someday you'll forget to turn it on and you car will not have charged - leaving you without enough range to get where you want. Better to leave it powered all the time.

Yodrak. | February 25, 2019

"There should never be any stress on the connector if you disconnect from the car first. If there is no power flowing, there is zero stress on the outlet."

No electrical stress, but perhaps a bit of mechanical stress that may weaken the connection between plug and receptacle, especially if it's a cheapo receptacle, over time? | February 26, 2019

@Yodrak - True on mechanical stress. I strongly recommend only using industrial outlets: They are more expensive, but are designed for repeated insertions/removals. Outlets rated as "Residential" are intended for fixed appliances where they might be inserted and removed only a few times in the life of the house.