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I see a 100 Amp breaker in the mains, which means my electric panel is 100 Amps. I see may arrays of circuit breakers on it, as many as 18. When I add the total amps on them, it adds upto 375 Amps.

Although, I use 1 dishwasher, 1 microwave, 1 dryer, 1 washer, 3-4 Ac's and lights, 1 sauna, I haven't observed mains or individual breakers going down. I have 40 Amp double pole and a 30 Amp breakers among them and rest are 15 Amp and 20 Amp.

I am trying to install a Tesla charger, which has a recommended breaker of 60 AMP.

Is there any possibility to support a new breaker? I do see empty slots. e.g., if I use 60 AMP charger in the night, I will not use any other appliance, will that work? please guide. of course, last alternative is to upgrade to 200 AMP panel, which is easy response.enter image description here

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    Please add a picture of your current panel. No breakers should trip under normal usage, but that doesn't mean you aren't close to the limit. 100A is not big by today's standards and one concern would be even if you normally the car charger at night, what happens if it is a hot night so the air conditioning (20A or more) is running and you are using the dryer and you zap a midnight snack in the microwave etc. Need more info. – manassehkatz-Moving 2 Codidact Dec 5 '19 at 2:38
  • If you want quality answers, we'll need a photo of your panel's breakers and also the labeling sheet that states which breakers serve which loads. – Harper - Reinstate Monica Dec 5 '19 at 3:10
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    @marcKatz -- can we have an actual photo of the label on the inside front of the panel please? Also, we still need the square footage of your house, and what's that 20 right below "Floodlights" used for? – ThreePhaseEel Dec 5 '19 at 4:42
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    An actual picture, as opposed to a diagram, adds value. Specifically, there are often non-obvious problems due to mismatched breakers, panels known to have serious problems, etc. which are obvious to the pros (and in some cases even to amateurs like me) in a picture. – manassehkatz-Moving 2 Codidact Dec 5 '19 at 4:48
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    I really wish I could see a picture of the breakers proper to see if there's anything we are missing. – Harper - Reinstate Monica Dec 5 '19 at 19:03
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If it wasn't a QO or Murray panel... I would say this is just too close. However, I think we can "cheat it", especially if you are willing to fit a subpanel.

I'll disregard the 120V loads for now; it looks like a gas dryer. Based on what you've mentioned, it appears the large 240V loads are

  • 30A sauna
  • 40A range

If there are others, do the same thing with them.

Add a subpanel for your large loads

So add a small (16 space) "QO" main-lug subpanel right next to this panel, and migrate your large loads there - the sauna, 40A/range, and whatever other large appliances I haven't deduced.

Feed that subpanel from an appropriate 2-pole breaker in the panel.

Interlock the subpanel and 60A EVSE breakers

With this beauty, a $20 QO2DTI generator interlock.

enter image description here

This clips onto a 2-pole breaker and interlocks with a 2-pole breaker below it (or 1-pole breaker). Only one can be on at a time: the loads in the subpanel, or the EVSE.

Note that normally, this is used where the breakers are backfeeding, and so the breakers need to be bolted down, requiring a separate bolt-down kit. However, since these are normal loads, they do not require a bolt-down.

Now you will need to turn off the one that's on, and turn on the one you want.

But it should solve the load factors in your panel. The 120V loads seem like a lot, but #1 they are split among the two poles, so it's only half what it appears; and #2 they are not likely to be all heavily loaded at the same time. Probably your worst loads will be your 120V A/C units, and you should make sure there are evenly loaded on the 2 poles (2 on each pole).

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  • Thanks. That was a great suggestion. just to clarify, I am assuming this solution allows me to shut large appliances down while I charge my EV, thereby reducing the load. It is similar to manually switching off large appliance breakers before EV charging, but protects me from inadvertent mistakes. – marc Katz Dec 6 '19 at 0:06
  • Just to add, instead of subpanel, can I use the interlock on 60 AMP and 30 AMP circuit breaker by arranging them one over the other? is there a way to interlock multiple breakers? or is there a bigger benefit to adding a subpanel? thanks. – marc Katz Dec 6 '19 at 0:08
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    Yes, Code gives no credence whatsoever to "paper procedures as a safety device". It's an interesting idea stacking two of the Square D interlocks, not sure if that would work. The big benefit to having a subpanel is not being out of spaces. That means you have spaces for what you need in the future; e.g. the next need. – Harper - Reinstate Monica Dec 6 '19 at 0:23
  • @Harper, what is the max main breaker size allowed in this panel? I'm concerned that adding the 30+A for a 7.5kW solar install would exceed the bus bar capacity, especially after adding the car charger. – Eric Simpson Dec 8 '19 at 12:49
  • It appears a Q0C24UF or US cover only fits a 24 slot panel with a max 125A main. Please seriously consider replacing your current panel with a 30-40 space 200A panel and upgrading your service to 200A. – Eric Simpson Dec 8 '19 at 13:58
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Overall adding breakers to empty slots is not an issue. What is a major issue is that the combined currents of all appliances that are turned ON must NOT exceed the rating of the main breaker. Ideally you want some safety room as well, at least twenty amps to spare.

The reason for a safety margin is that when large electric motors startup the current can briefly be three times the run current, assuming the motor is not overloaded. You should NEVER encounter a situation where you are consuming most of what your breaker panel can offer.

To run your Tesla charger make sure other high current loads are manually turned OFF. This is the compromise you have to make, or fork out lots of money for a 200 amp panel.

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  • Thanks, I don't want to spend for an upgrade. I am also planning to go solar. Will the solar decision make any difference? I am planning to install 7.5 KW panels. Also, it seems I do not use 2 20 AMP breakers, can I feed those lines to an existing breaker? – marc Katz Dec 5 '19 at 4:23
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    @marcKatz Adding solar to the equation here will not help and may even make things worse. Your panel is out-of-date capacity-wise and as a part of your "investment" in a Tesla and solar you need to upgrade your service as well. Note also that you may not be able to just upgrade a 100A service to 200A by changing panels. The power company may need to upgrade the lines and transformer as well. – jwh20 Dec 5 '19 at 10:41
  • @marc Katz, it appears the two 20A breakers are half-height (aka double-stuffed), taking up one space. The 60A breaker will require two full spaces side-by-side, e.g. spaces 2 & 4. Adding solar will likely require 2 more adjacent spaces. Can your existing breakers be rearranged to allow that? If not, you'll have to replace the panel or add a subpanel to get more spaces. Given your plans, I'll recommend upgrading your panel & service to 200A. – Eric Simpson Dec 8 '19 at 13:26
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This really feels too close. You only have 40A available once the charger is going, and you run the AC at night. Heating/cooling is one of the biggest energy usages in a house, and that doesn't stop at night. I think downgrading to a 30A charger should be safe, (and will still recharge your car overnight.)

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  • I am fine downgrading to 30 AMP charger, do you know what are the demerits in doing so, other than taking longer to charge during nights? – marc Katz Dec 5 '19 at 4:24
  • Another comment - I have a 30 AMP breaker that feeds to my sauna. Is it possible to use the same for the charger? I will not to use both sauna and charging at the same time, or may be replace the 30 AMP with 60 AMP and use it for both purposes? what will I need to do such a change? – marc Katz Dec 5 '19 at 4:32
  • I am unaware of any non-obvious effects of using a 30A charging circuit instead of 60A. Replacing the 30A sauna breaker with a 60A is missing the point. You also can't "share" any of the existing 30A circuits, because as a rule of thumb, 30A+ stuff (including saunas) requires dedicated breakers by code. You need to add a new 30A breaker dedicated to this task. – user3757614 Dec 5 '19 at 5:09
  • Oh, and you might as well use 60A rated wire for this circuit, in case you want to upgrade later. Wire is cheap. – user3757614 Dec 5 '19 at 5:14
  • @user3757614 wire, properly installed the first time is cheap. Installing the proper wire later is usually costly. – FreeMan Dec 5 '19 at 12:40

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