main panel has 30 amp to garage panel, what are the options

[hybrid>EV]

If a main electrical panel in the house has 30 amp breaker labeled GARAGE, does that mean garage will get max of 30 amp - and I assume if any garage light is turned on during charging, breaker will trip?

Wanting to install wall connector in the detached garage soon. The sub panel in garage only has 2 breakers >> 1x 15 amp GFI and 1x 15 amp lights breaker. Would the solution be replacing the 30 amp breaker in the main panel to a bigger one? How many amps?

 

[father_of_6]

Full disclosure: I'm not an electrician.

If the breaker to the garage is 30 amps, it's very likely that the wiring to the garage is not rated for more than 30 amps.

Some things that would be helpful to know:

• What's the service coming into the home? 100 amps? 200?
• Have you had a load calculation done to determine how much amperage you can spare?
• Is the circuit from the main to the garage easily accessible if you wanted to replace it?

Ideally, you'll want to get a 50 amp circuit for 40 amp charging (max 80% for continuous loads like an EV). To do that, you're going to need to answer those questions or get an electrician to do this for you.

Your existing options are limited without electrical work. You don't want to be charging at 12 amps, which is the best you can get from one of those garage circuits (80% of 15 amps).

 

[BroncoAZ]

Also not an electrician and don’t know what code may be where you live. I would engage an electrician to assess the situation, check the existing install, complete the upgrades if needed.

Assuming the 30 amp breaker for the garage is 30 amps at 220v (two hot legs) they you should be able to add a 30 amp 220v breaker in the garage panel and charge at 24 amps (80% of 30 amps) without major issue. You shouldn’t run anything else in the garage while the car is charging. Exceeding an additional 6 amps of load would trip the breaker, but any part of that 6 amps is safety factor and shouldn’t be used. The size of the wire and length of run to the detached garage really need to be looked at. If you have a 100’ run of 12/2 then it won’t support 20 amps. I would prefer to run a larger wire and breaker to a larger capacity sub panel in the garage if it were feasible, but I also own two welders.

 

[hybrid>EV]

The main panel is labeled 200 amp. This is the from main panel, which is at least 50 ft from garage sub panel & circuit is not easily accessible. Here is a pic from the main house panel. Does this mean I have 2x 30 amp and a total of 60 amp to garage?

I also see this for the dryer on the main panel, and I know the dryer plugs into a NEMA 14-30 outlet in laundry. However, for both the dryer and garage breakers, there looks like 2 breakers tied together. In both cases, one of the two has a label. Does that mean there is untapped capacity on these circuits?

 

[ucmndd]

Here is a pic from the main house panel. Does this mean I have 2x 30 amp and a total of 60 amp to garage?

No. It means you have 30 amp service at 240 volts to the garage.

If you’re the slightest bit adventurous, you can remove the cover from the main panel so you can see the wire going in to that breaker to determine what size it is. That’s the main thing you need to know to determine your options for adding additional capacity to the garage.

However, for both the dryer and garage breakers, there looks like 2 breakers tied together. In both cases, one of the two has a label. Does that mean there is untapped capacity on these circuits?

240v breakers use two slots because of the way split-phase power works. It does not mean you have extra capacity beyond the stamped rating on the breaker (in this case 30 amps).

 

[flai54]

To be on the safe side you should always have an electrician create a dedicated circuit breaker for the EV charger and not try to cannibalize an existing circuit breaker slot. Most circuit breakers that are dedicated for the "Garage" are already tied to the 15A circuits in the garage or for the garage door opener.

In addition you need to really check the wiring used that is needed for an EV charger. You definitely want 6 AWG wire for an EV charger anyways which most existing AWG wire to a garage is not sufficient since it is not carrying 40A to a single circuit.

 

[ucmndd]

In addition you need to really check the wiring used that is needed for an EV charger. You definitely want 6 AWG wire for an EV charger anyways which most existing AWG wire to a garage is not sufficient since it is not carrying 40A to a single circuit.

This is all “rule of thumb” stuff but not strictly true for every situation.

OP has 30 amps available to his garage via a dedicated sub panel. They said above there are two 120v 15 amp circuits on it, no doubt powering the garage opener and a basic lights and plugs circuit. Under normal circumstances these draw almost negligible power, with plenty left over for a 240v circuit.

OP could very easily add a 240v 20 amp circuit with a NEMA 6-20 receptacle to the existing sub panel (or a wall connector or other EVSE configured for 20 amps) and charge at ~4kw. That’s more than enough for most people.

A NEMA 14-30 drawing 24 continuous amps would probably also work fine in practice presuming there are no other heavy loads in the garage but is cutting it close and runs the risk of nuisance trips. It’s probably also not to code.

I’d probably go for the 6-20 and call it a day.

 

[Sophias_dad]

There's basically zero chance of nuisance trips with a few (LED) lights, a battery charger or two and a garage door opener in the garage in addition to an EVSE set to a 30 amp breaker(drawing 24 amps continuously). The GDO is an extremely small load that runs for 20 seconds, while the LEDs and other stuff are an even smaller load. There is LOTS of short term (small) overload tolerance in circuit breakers, and 24 amps isn't even quite in overload)

The nuisance trips will come when OP starts using the shop vac or table saw in the garage while charging.

Its not likely to pass inspection with a 30A EV charger or 14-30 or 10-30 outlet. It >might< pass inspection with an outlet, if it isn't obvious that outlet is intended for EV charging use.

 

[kpanda17]

If a main electrical panel in the house has 30 amp breaker labeled GARAGE, does that mean garage will get max of 30 amp - and I assume if any garage light is turned on during charging, breaker will trip?

Wanting to install wall connector in the detached garage soon. The sub panel in garage only has 2 breakers >> 1x 15 amp GFI and 1x 15 amp lights breaker. Would the solution be replacing the 30 amp breaker in the main panel to a bigger one? How many amps?

Here are the current step sizes for the WC:

If there is space in this sub panel for a 30amp breaker, for the physical breaker and max current draw on the 30 amp feed, you can add this load. The problem is you could easily pop the breaker feeding this panel if any other load is used at the same time. You will have to make sure nothing gets turned on, no lights or outlets. In a home’s main panel with a 200 amp main breaker, all of the line breakers after the main in the panel add up to a draw above the size of the main, ok based on all of those loads never draw at the same time to the max. But in your case the 30amp sub panel main breaker and the WC load are equal leaving no room for competing loads to run at the same time.
Ideally run new wire to the garbage and redo the sizing for a larger main and increase the WC breaker to as close to 60 amps you can get.
Otherwise, run the 30amp WC via scheduled late at night to make sure it does not compete with any other electrical use by the other loads.

Note, an empty Model 3 LR or Y LR or Perf, will take approx 10-11 hours to charge at 30/24amps.
Half that for 60/48 amps.

Good luck.

 

[tga]

If you’re the slightest bit adventurous, you can remove the cover from the main panel so you can see the wire going in to that breaker to determine what size it is. That’s the main thing you need to know to determine your options for adding additional capacity to the garage.

At the risk of sounding like a bit of a jerk, I would never suggest that someone who doesn't know the difference between a single and double pole breaker take the cover off their panel. OP should have a little more electrical knowledge before considering that, IMHO.

@hybrid>EV, I am in a similar situation with a 30A garage breaker in my main panel. The garage sub panel had 2-3 circuits for lights and outlets. I added a 30A breaker in the garage subpanel to feed a 14-30 outlet and charge with my mobile connector. I dial the charge current in the car down to 20A from the default of 24A to leave a little headroom for the exterior motion sensor floodlights that come on randomly. I have been doing this for several years without issue. 20A/240V charging adds ~5%/hour to my MYLR.

I have a gen 2 WC that I am installing this spring and will set for a 25A circuit (20A charging) to enforce my "reserve 5A for lighting" rule. Unfortunately, the current gen 3 WC's don't have a setting for a (somewhat uncommon) 25A circuit, but it's "only software" so they could add it someday with a firmware update.

 

[Cosmacelf]

Sure, you can install a Wall Connector in the garage. If all you have is some lights and a garage door opener, then you could use a 30A breaker in the garage panel. If you have a freezer or refrigerator, or use a heavy duty table saw occasionally, I’d just use a 20A breaker.

Connect it to the garage subpanel with a 30A or 20A dual pole breaker (like the one you have coming from the main panel).

 

[hybrid>EV]

Yes I will hire an electrician to do this. Sounds like the solution is to replace the 30 amp breaker in the main panel with something bigger like 50 or 60 amp one, replace the under ground circuit, install a new 30 amp or 50 amp breaker in the garage sub panel that feeds the charger. The distance is actually 75 ft, and I read just to replace the circuit is going to be > $2500. Thanks Everyone.

 

[Cosmacelf]

Yes I will hire an electrician to do this. Sounds like the solution is to replace the 30 amp breaker in the main panel with something bigger like 50 or 60 amp one, replace the under ground circuit, install a new 30 amp or 50 amp breaker in the garage sub panel that feeds the charger. The distance is actually 75 ft, and I read just to replace the circuit is going to be > $2500. Thanks Everyone.

Well that all depends if you need or want to charge at 48A. If charging at 20A/240V works for you, then you can do it a lot cheaper. Depends on how much you drive.

 

[kpanda17]

Yes I will hire an electrician to do this. Sounds like the solution is to replace the 30 amp breaker in the main panel with something bigger like 50 or 60 amp one, replace the under ground circuit, install a new 30 amp or 50 amp breaker in the garage sub panel that feeds the charger. The distance is actually 75 ft, and I read just to replace the circuit is going to be > $2500. Thanks Everyone.

4 AWG copper wire at a minimum, no aluminum, make sure the electrician does this, no GFI breaker necessary as the WC has it built in
read the WC install guide and make sure the electrician follows it to the note, such as torquing the screws down to the req lbs

 

[Cosmacelf]

4 AWG copper wire at a minimum, no aluminum, make sure the electrician does this, no GFI breaker necessary as the WC has it built in
read the WC install guide and make sure the electrician follows it to the note, such as torquing the screws down to the req lbs

Why 4 AWG? 6 AWG THHN in conduit or MC cable will work just fine.

 

[kpanda17]

Why 4 AWG? 6 AWG THHN in conduit or MC cable will work just fine.

75 feet, best using a bigger gauge copper, THHN in conduit or MC is fine, exterior in the garage I like in conduit
bx has to be used with caution in locations by the shore, salty air
but use copper every time, aluminum has had so many issues over the years

 

[father_of_6]

If charging at 20A/240V works for you, then you can do it a lot cheaper. Depends on how much you drive.

Faster charging is nice when it's needed @hybrid>EV, but really it would be trivial to go the 20 amp route. Much less expensive and probably still sufficient for your driving needs. In cold climates, slower charging can't always cut it.

You could go the 20 amp route for very little cost and see how it works out for you, then upgrade to 40 or 48 amps later if you feel the need.

 

[posity]

20A @ 240v is going to give you 15 MPH charge rate on a MY. That's 150 miles of charge during a 10 hour overnight charge. Unless your daily commute is way over 100 miles each day, that's a very good charge rate.

Since it will presumably be quite inexpensive to add a 2 pole 20A breaker in your garage, I would just try that to start with. Probably a complete waste of money to go to all the added extra expense to upgrade your wiring out to the garage. I did this at our house for over a year and it was way more than I actually needed.

Keep in mind that the ability to add 150 miles every night ratchets you up to the 250 mile 8O% charge easily in 2 nights. So even if you go over 150 miles on a particular day, you are back up to an 80% full tank in 2 nights. I believe there is almost no chance you have a use case where you need more than that 15 MPH charge rate.

Ultimately it comes down to
1) How many miles is your daily commute?
2) How many hours is your car at home (charging) each day?

And don't forget, weekends can get you fully recharged ...

 

[ucmndd]

I agree… spending thousands to pull new conductors as a first option is overkill unless there are other circumstances at play. Putting in a 6-20 could be done for less than $100.

 

[ucmndd]

75 feet, best using a bigger gauge copper

75 feet isn’t really that long.

#4 conductors at 240v/48a will result in ~0.86% voltage loss.

#6 conductors? ~1.3%.

Negligible.