Electrical Circuit Question

Electrical Circuit Question

I wish to install a 240v circuit with 14-50 outlet in my condo's garage. I checked the SCE breaker for my unit which is in a common closet with seven other unit's meters. My unit's breaker is only 40 amp. Is this sufficient? What will electrician/SCE need to do to provide the necessary circuit?

BTW, the electrical closet is 75 feet and four garages away from my garage and there is a unit (1st flr) between my garage (ground flr) and my unit's (2nd flr) sub panel.

Anybody have experience to answer this?

jbunn | May 5, 2013

Your unit is set up for 40 amp service, meaning the total electrical load for everything - lights, dryer, stove, ect all running at once cannot exceed 40 amps without tripping your breaker.

This leaves very little power left over for the car. With everything in your apartment OFF, you can get 40 amps to your car, which is all you can take with a single charger. Your best option would be to set the car to charge at a lower rate - say 20 amps to avoid popping the breaker. I had to dial mine back at home if the wife was doing laundry, else the breaker would pop. You can still get a good charge overnight at that rate.

Next option would be to have the electrician add a separate meter with a 50 amp service. The electrical closet would than have 8 meters, two being yours. One for your unit, and one for the car.

jbunn | May 5, 2013

Hmm... Actually a third option occurred to me. Possible that the electrician may be able to upgrade your service by replacing the wire between the main service panel and your meter, and replacing your breaker with a larger one.

Wild guess though because I don't know what you really have. Assuming the condo association is cool with it, you should have an electrician look at it. Only way you'll get a definitive answer.

Docrob | May 5, 2013

It's also possible that the existing wire and circuit is capable of handling more then 40A and the size of the breaker was chosen because it was considered adequate for the needs of a condominium the size of yours. In which case it may be a very simple matter of upgrading the breaker. The bottom line is call an electrician and have them come have a look. Even better if you know any have them take a look because it is possible an electrician might try to upsell you a total redo of the main bus rewiring even if it's not necessary. | May 6, 2013

Also you can only safely continuously take 80% of the breaker's rating. For a 40A breaker, than means a maximum of 32 amps for everything (house and car).

For the mobile charger cord, it is recommended you have a 50 amp breaker/circuit for it alone, where you can safely contentiously draw 40 amps.

I'm sort of amazed you can get by without tripping the breaker in the condo by itself.

bt77057 | May 6, 2013

There are quite a few hypotheticals here:

1) electrical contractors don't typically provide larger wire than necessary. Larger = more copper; more copper = more $$$

2) it is unlikely a a license electrician will stake their license, and install a 40 amp or even a 30 amp branch circuit, when the main is a 40 amp.

The Model S allows to reduce the current actually drawn, when it senses the adapter used on the UMC.

So I see you probably have two options

Cheaper option: install the largest breaker allowable, and manually reduce the current draw from the charging menu (the Model S will remember this setting based on GPS location)

More expensive option: upgrades like ones mentioned above, new meter or upgrading existing infrastructure. In either case they will require HOA releases, since you are in a condo with multiple units.

Good luck, hope you can this one resolved to your satisfaction.

rick524 | May 6, 2013

Thank you all for the useful information. Electrician is on the way.

shop | May 6, 2013

Remember that you don't need to install a full 50 amp breaker. Youcould install a 30amp dryer plug, for instance, and that would charge your Tesla just fine as well.