Install 50amp breaker in 100 amp subpanel with 60amp breaker in main

[hg46038]

I have been charging with 110V outlet for a month now. It's ok for range since I drive 40 miles daily. but it took about 10 hours to charge back to 80% each day. I'm trying to install 14-50 220v outlet myself. My subpanel is 100 amp, but the breaker for it in the main is 60 amp. My question is, can I install the 50 amp breaker in the subpanel? The subpanel currently has a 30amp breaker for AC and a couple of 20 and 15A ones.
Thanks!

 

[iluvmacs]

Unlikely. You need to perform a load calculation based on the circuits already present, with a 60A limit. My gut is telling me that a 20-30A circuit is the most you can do, but that's just a guess based on if the A/C is running and the other small circuits are in medium load use. An electrician could calculate the real answer for you.

 

[ivan801]

I can almost guarantee that the answer is no. But you may be able to do a 20A 240V outlet, and that should be a nice upgrade from where you are. Just order a matching plug from Tesla, they are like $35.

 

[hg46038]

That's a good idea. It at least doubles my current charge rate.

 

[Manitoba Keith]

Yep, just because the sub-panel is 100 amps, the breaker in the main panel (and probably the wire feeding it) limits you to 60 amps. If you are NOT running the other loads, then you could put a 40 amp breaker in and charge @ 32 Amps.
Probably a LOT easier to just use a 2-Pole 30 amp breaker and corresponding receptacle. Heck just converting to 240 V @ 12 amps will cut the time in half.

 

[KenC]

Take a pic of your panel so we can see your other loads. Why did the electrician install a 60amp fuse in your 100amp sub panel?

 

[hg46038]

The wire feeding it looks like 6 gauge. The panel is full now.

 

[Sophias_dad]

You should probably get a real electrician to take a look at increasing that main breaker, if possible.

The panel being full may or may not be an issue. There are tandem breakers available for some panels that can feed two independent circuits with a single breaker slot. Additionally, there are some duplex tandem breakers(for some panels) that can feed two independent 240v circuits from two breaker slots.

Sounds like you are pretty close to the edge on that 60 amp breaker right now. You definitely can't expect anything like 40A from the remains of that capacity.

It might be worth looking at the specs of your AC's compressor to see if it really ever draws 30 amps continuous. If its more like 10 when running, you have a bit more headroom.

 

[nayr14]

Are you sure you have 100amp service? That box looks a bit small... I'd recommend a electrician.

I ended up doing the same thing. I have a 100amp panel but all major appliances are natural gas (water heater, furnace, oven, dryer). The only real consumer in the home is the AC which pulls 16 amps. If we added in an electric dryer that would start pushing it, but even with the car charging at 48a that leaves plunty over overhead, and the EV charger is used mostly at night. I'm sure a proper load calculation wouldn't take into account the time that the appliances are used, but for my purposes it works fine.

I did not use an electrician but my setup was fairly simple. I had enough fill available in the raceway that ran out into the garage for the AC wires, then I ran another conduit to the back of the garage.

 

[hg46038]

The panel is 100 amp, but is limited to 60 amp by main panel breaker. AC pulls about 15-16 amps. I'll probably just do 240v 20 A to be safe and it's 3 times fast as my current 110v charging. My setup is simple. Just 2 feet drop from the panel. The electrician that replaced the panels for me (I think he's good) quoted me $400 for installing 14-50. I plan to try myself. with 6-20, it should be easier.

 

[PrGrPa]

60A. Reminds me of my only charging problem so far. First though, I'm in the UK. My supply is nominally 230VAC but where I am it is commonly 240VAC.

I have 2 consumer units connected to my main supply. This is due to a combination of numerous circuits and some house history - it was converted into apartments sometime in the 1960s or 1970s I believe.

When McNally's installed my 7kW charger in 2017 they popped it into a spare 32A breaker. Ideal. The current draw should not be much above 30A under normal use.

All was AOK until one stormy night later that winter...

We had the family at home, lights on, TVs & computers on, washing machine, dishwasher, and tumble drier probably on too. And then I arrived home and plugged the car in. Fine.

Except, later that night something changed and everything went dark. Well, everything in our house. A quick look out int the street showed only we had no electricity.

Seems that trying to pull 30A + whatever else was on + whatever changed proved too much for our ancient 60A supply fuse.

In the UK that fuse is on the electricity supplier's side of things and can't be dealt with by the consumer. NW Electricity were really helpful and fast and within a couple of hours we had a neat, new 100A supply fuse and some even fatter 'tails' connecting the supply to the consumer units.

Is there a message here? Plan conservatively, get the right supply for your needs, know the number to call if it all goes awry.

 

[kkillebrew]

I would try a 40 amp breaker with a 10-30 or 14-30 dryer receptacle (you may already have one). The Tesla 10-30 or 14-30 NEMA adapters are $35, usually delivered in a few days, and will automatically adjust current to something below 30 amps and giving you around 17 or 18 miles per hour. I had a similar issue at a friends house with only a dryer connection, I purchased the 14-30 adapter and it was all automatic and worked great!

 

[davewill]

I would try a 40 amp breaker with a 10-30 or 14-30 dryer receptacle (you may already have one). The Tesla 10-30 or 14-30 NEMA adapters are $35, usually delivered in a few days, and will automatically adjust current to something below 30 amps and giving you around 17 or 18 miles per hour. I had a similar issue at a friends house with only a dryer connection, I purchased the 14-30 adapter and it was all automatic and worked great!

It would be incorrect to go over a 30a breaker with those receptacles. You also are not allowed to install 10-30 receptacles except as replacements on circuits that already have them.

 

[mike123abc]

That's a good idea. It at least doubles my current charge rate.

It will actually more than double it. Most likely you are using 15A 120, but even if you are using 20A 120, 240 more than doubles since you only pay for the "charging overhead" once.

 

[Sophias_dad]

The panel is 100 amp, but is limited to 60 amp by main panel breaker. AC pulls about 15-16 amps. I'll probably just do 240v 20 A to be safe and it's 3 times fast as my current 110v charging. My setup is simple. Just 2 feet drop from the panel. The electrician that replaced the panels for me (I think he's good) quoted me $400 for installing 14-50. I plan to try myself. with 6-20, it should be easier.

Is the main breaker far away? The only breaker on the outside of the house(near the meter)? I think your plan is fine, but you'll still be really near the limit.

 

[kkillebrew]

It would be incorrect to go over a 30a breaker with those receptacles. You also are not allowed to install 10-30 receptacles except as replacements on circuits that already have them.

Yes it does exceed the rating of the receptacle so use a 30amp to be code-worthy. The circuit will not draw more than about 22 amps so a dedicated run with #8 romex and a 30 amp breaker, but with a 14R-30 if the 10-30 is obsolete, will be just fine. In fact I have tested this exact scenario from my home dryer receptacle with a 14R-30 & 30 amp breaker. I was worried that a continuous 22-23 amp pull would pop the breaker but it did not, and no voltage drop what-so-ever.

 

[hg46038]

Is the main breaker far away? The only breaker on the outside of the house(near the meter)? I think your plan is fine, but you'll still be really near the limit.

Yeah, it's in the basement at the other side of house, over 100 feet away. I think as long as I don't run AC at the same time as charging very often, it should be ok.

 

[user212_nr]

100 feet is not that far, assuming that it is all indoors. Also, $400 is a good deal, assuming that he's going to run a new cable and upgrade your breaker. He might be running a new cable only for the outlet and putting a 50A breaker in the main, as your sub-panel is out of spaces. No reason to buy a 100A cable.

So he's got 300$ in parts and 100$ labor. Your DIY cost will be $100 for parts and 3-5 hours labor.

Its a great deal, especially if it is YOUR house

 

[hg46038]

I finally decided to get an electrician instead of DIY. He said I can't install 14-50 since the cable going in the subpanel can only handle 80A. He installed 30A. But he put in 10-30 outlet. I forgot that it's obsolete and paid. He did use a metal box and ground it. Will 10-30 outlet work? I saw some people had issues. Is it safe or legal to install 10-30? Should I ask him to replace with 14-30? Thanks!

 

[Rocky_H]

I finally decided to get an electrician instead of DIY. He said I can't install 14-50 since the cable going in the subpanel can only handle 80A. He installed 30A. But he put in 10-30 outlet. I forgot that it's obsolete and paid. He did use a metal box and ground it. Will 10-30 outlet work? I saw some people had issues. Is it safe or legal to install 10-30? Should I ask him to replace with 14-30? Thanks!

There wouldn't be any real problems with using a 10-30 outlet. You can buy an adapter plug for that and it will work just fine. The only concerning part is "What the hell is this electrician thinking?" NEC was updated many years ago, which has not allowed the installation of any new 10-XX series outlets since 1996.

I would change it to something else. Depending on how many wires are available in the cable, I would switch it to either a 6-30 (240V only) or the 14-30 (dual voltage 120V/240V).