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Adding 50 amp breaker to 100 amp sub panel

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Hello. I’m new to EV vehicles and getting ready to receive my model 3 in a few days. I currently running a 200 amp main breaker with a 100amp break running to the sub panel. The sub panel is at a detached garage, so really doesn’t get used much. I see that o have 3 30 amp breakers but really I think I only use 1 to power a A/C unit. I’m wondering if a 50 amp breaker will be fine to install on the sub panel.
 

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Really need to know more about the other circuits. Its >possible< that a new 50 amps circuit will work. You should also check the make/model(or nameplate) of the AC you use, because they are frequently given considerably larger breakers than their actual expected power usage due to startup-currents. You can ignore the startup-current issue for load calculations.
 
If you have space on the panel, I don't see why not, as long as you know not to overload the panel (don't run more than 100A at a time).

The best way to do it is to do a load calculation. Follow each breaker to all the loads it powers. Look up how many amps (or watts/VA) is used for operation of that load (this should be lower than the breaker number, in many times significantly lower). Put everything in a spreadsheet. You can sum up them all up and see how much spare capacity you have. Note that the 20A single slot breakers only use one leg, so account for that difference (or you may have an easier time just converting everything into watts or VA).

If there are timed loads (like pool pumps), you can separate the loads out by time. Then you know what times to avoid charging your car (if you are very tight on capacity). Note there are some loads like AC compressors that have a high surge current on start (there are ways to address this like adding a soft start if this is an issue, but typically it doesn't have much of an effect given it doesn't last very long).
 
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Agree with StopCrazyPP's advice. I'm curious why those 30amp breakers aren't labeled on the panel door. But hopefully those other loads are not scheduled when you want to charge your car. Mine is programmed for after midnight. But I know there are no other large loads being imposed overnight in my garage panel.
 
Sure, should be fine. You're way ahead of most of us with a 100A subpanel already right there!

But you should figure out what's going on with all those breakers. It's nice that's it's so ample. but it's an unusual setup. Seven 20A breakers is pretty wild for a garage. And what are the 2 "extra" 30A breakers for? Dryer? Power tools?

Anyway if you can be reasonably careful to not have all that stuff running when the A/C kicks on while the car is charging than it'll be fine. And if not, you know where the breaker is. And if breaker trips are a problem that you can't manage with your own diligence, just reconfigure the charger to a lower rate. Easy. I'd even suggest going up to 60A instead of 50A.
 
I have 200A service in my house, 3-AC units and the usual electric home appliances, except for a gas cooktop instead of an electric one. I installed a 60A breaker with no issues. But checking as suggested above is still a good idea.

You can probably go with a 60 amp breaker if you want too as this will allow you to charge at 48 amps if you use the wall connector. Just be sure to use the correct wire size and type.
 
To be safe you can install a NEMA 6-20 outlet on a 20amp breaker:

 
To be safe you can install a NEMA 6-20 outlet on a 20amp breaker:

That would provide a significantly lower charge rate.
 
To be safe you can install a NEMA 6-20 outlet on a 20amp breaker:


This is actually bad option and should be avoided. Note this can be used on a 5-20 outlet and will draw 16A, which is a violation of code. In OPs case, with a 100A subpanel, a 50A or 60A circuit will be desirable.
 
???

16A on a 5-20 or 6-20 is within specs (80% of breaker capacity).

The OP has concerns about overloading the panel.
Sorry I mis-typed. That device has plugs for a 6-20 or a 5-15 (not the 5-20 I said). On a 15A circuit current is limited to 12A and 16A even exceeds the breaker rating!

I think his concerns about overloading a 100A service panel are overblown, but he would be better offer with the Tesla Mobile connector than the one on Amazon.
 
Sorry I mis-typed. That device has plugs for a 6-20 or a 5-15 (not the 5-20 I said). On a 15A circuit current is limited to 12A and 16A even exceeds the breaker rating!

I think his concerns about overloading a 100A service panel are overblown, but he would be better offer with the Tesla Mobile connector than the one on Amazon.
That's a NEMA 5-20 outlet on a 20A breaker. The NEMA 5-15 to 6-20 adapter is only a concern if using a NEMA 5-15 outlet on a 15A breaker.

On any outlet including a NEMA 6-20 outlet, the above EVSC limits the amperage to 16, and in that respect is actually preferable to the TMC which can allow higher amperages to pass through the outlet depending on the adapters used. In any event my TMC stays in the car at all times for emergency use when on the road.
 
That's a NEMA 5-20 outlet on a 20A breaker. The NEMA 5-15 to 6-20 adapter is only a concern if using a NEMA 5-15 outlet on a 15A breaker.

On any outlet including a NEMA 6-20 outlet, the above EVSC limits the amperage to 16, and in that respect is actually preferable to the TMC which can allow higher amperages to pass through the outlet depending on the adapters used. In any event my TMC stays in the car at all times for emergency use when on the road.
I think he is talking about the fact the one you bought still draws 15A when plugged into a 5-15, which is a code violation (for continuous loads only 12A is allowed on a NEMA 5-15 due to the 80% rule).

The TMC automatically limits the current to the appropriate 80% max depending on which adapter is plugged in (plus it also has temp sensors to sense when the plug is getting hot). For example when using the 5-15 adapter, current is limited to 12A.
 
This is incorrect. So long as you plug the correct Tesla adapter into the correct outlet it will not exceed the circuit rating.
Right. But in the early days there were lots of random plug to 14-50 outlet adapters to which you just plugged in the 14-50 mobile connector. Thankfully we are mostly past that now.

But this is all pretty off topic to the OPs question. OP needs to find out what those other breakers are used for. I’m guessing electric heat.
 
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Right. But in the early days there were lots of random plug to 14-50 outlet adapters to which you just plugged in the 14-50 mobile connector. Thankfully we are mostly past that now.

But this is all pretty off topic to the OPs question. OP needs to find out what those other breakers are used for. I’m guessing electric heat.
Actually in the bottom left corner in OP's picture there are descriptions of the loads written on the cover. It's just either the sticker was put on upside down or the door was put on upside down.