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Our garage has a panel but no main breaker, instead what would be the "main" is a 60 amp breaker in the basement panel. If I want to install a 50 or 60 amp breaker on the garage panel, would there be any issues?

This is my second time installing a breaker, I did one with my dad but it was a standard outlet on the main panel which had hundreds of amps. Im not sure how close a breaker can be to the breaker before it in amps.

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  • If your garage panel is fed by a 60 sure you can install a 50 or 60amp as a main if it is listed for a main breaker, some panels can not be simply updated this way, a back fed breaker is one way to do this, a photo of the panel may provide some additional helpful advice (some small panels less than 12 positions that I have worked with do not allow a back fed main) everything depends on the listing.
    – Ed Beal
    Mar 11 at 20:17
  • Probably the only issues you would have, is if you did not turn off the power for the panel. Size of one breaker next to another one does not matter in most panels. Should add pictures of the panel to your question in case of other issues.
    – crip659
    Mar 11 at 20:20
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    Could you clarify if you are adding a 50/60A circuit or adding a main breaker in the panel. There is not a requirement for a main breaker in a sub panel if it is in the same building. If an added load would be permitted by Code depends on a "load calculation" or ampacity of the circuits served by the panel. There are some peculiarity dealing with specific devices. Best way to start is to post a picture of the panel and panel schedule, and the actual amps/watts of connected heat, motors, and the details of what you will be feeding with the new circuit.. Mar 11 at 22:00
  • Can you post photos of the panel please, including the label on the inside of the door? Mar 12 at 4:26

2 Answers 2

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What you are describing sounds like a subpanel and yes, as long as you have sufficient panel space to install the breaker, you can. To be safe, shut off the 60A feeder breaker in the main panel any time you are working on the subpanel.

For your second question, you need to consider the other loads that are in the panel as well as your intended use for this NEMA 14-50. The sum of the loads that are used together at the same time shouldn't exceed the rated capacity of the main. Most circuits don't get used anywhere near their rated capacity, so don't get hung up on adding up the capacities of each branch circuit.

Since this is a garage, I am guessing you intend to use it for an EV charger? In that case, you will need to consider the EV load as continuous, which I believe means that it cannot exceed 80% of the rated breaker amperage. For a NEMA 14-50R, you can feed it with either a 40A or 50A 2-pole breaker. Max load on it if you fed it with a 40A would be 32A, and max load if you fed it with a 50A would be 40A.

40A on a 60A main doesn't leave a lot of capacity left over, but if the other loads total less than 8A continuous, which is common if the other branch circuits are just lighting and convenience outlets, you should be fine.

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  • Chris read my comment, without the panel listing we can not say if it can be backfed some small panels can not or the other 2 positions in that row are no longer able to be used quite common in older panels, take out 4 positions to provide a local disconnect in many cases it’s better to replace with a newer panel. There are maximum draws on even modern panels with “back to back” loading . EV’s, lighting & motor loads all require 125% of tha load value to be used OR .8 of the breaker as you stated
    – Ed Beal
    Mar 11 at 20:32
  • @EdBeal I don't see him asking anything about backfeeding or adding a main. I see him asking if he can safely add a breaker for his 14-50 outlet. Perhaps the OP should clarify what he is asking, but that's my interpretation.
    – Chris O
    Mar 11 at 20:34
  • Maybe I mis read it because he mentions no main and a 60 amp in the basement but it still depends on the panel size and if a 50 amp load is being added to a 60 amp panel, we would need to know what else is on the panel, just because it fits won’t help if he burns the home down due to overloading. Having a 60a main ??? Feet Away from the main panel you mention it will be fine if loads are lighting. lighting also requires continuous rating and we don’t know what that load is either.
    – Ed Beal
    Mar 11 at 20:44
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You don't have a 60A subpanel.

I know this because the size of a subpanel is decided by the capacity of the feeder wires... and there is no such thing as 60A wire.

Really. Don't believe me, go look at NEC Table 310.15(B)(16). No wire is 60A.

So, what you actually have is one of these:

  • 55A wire - in which a 60A breaker is used due to the "round up" rule in 240.4(B). You can't plan to use more than 55A, though.
  • 65A or larger wire, and they just went with a 60A breaker because they are cheaper than 70A breakers.

So your next step is to find out what size and metal of wire you actually have, as well as which insulation type. Then we can figure out the ampacity of the cable, and that tells you how much room you have for EV charging.

Next, a load calculation on the loads served by the subpanel.

There is a standard format for Load Calculations. Do it for the loads which are now served out of the subpanel. That tells you how many amps you are using now.

Subtract one from the other and...

Electric vehicle charging is a "soft setting" anyway!

Given that your amp need is variable, I gather we're charging an EV and you are installing an EVSE (the thing that goes on the wall with a J1772 cord coming off it).

The ampacity of an EV is adjustable (on the fly actually) - here's a technology briefer on how that works.

When you install or "Commission" an EVSE, you configure how many amps it has at the breaker, by cracking it open and setting DIP switches (or an intentionally difficult means using a special WiFi network).

So for instance if you find your circuit is really 55A and you have 13A of load already provisioned, you have 42A "left" for EV charging. You tell the EVSE that. Internally it will multiply that by 80% giving 33.6A, and tell the EV not to draw more than that when it charges.

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