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This is an extension on a previous question about a 240V outlet in my garage.

At that time, I took the advice that I should:

  • replace the 40A breaker in the garage with a 30A version (from the proper manufacturer)
  • replace the NEMA 6-15P outlet (240V 15A) with a NEMA 6-30P (240V 30A)
  • make sure the electrical cable is at least AWG 10

However, I stopped the project and never actually ran the intended electrical heater because of what I found at the other side (i.e. the panel in my main house)...

The breaker that leads to the garage appears to have been altered. In particular, it looks to me that the rating number has been etched in by hand and reads 15A. Is it common practice to etch in a current rating? Could this really be a 15A breaker (this is what worried me, and why I never plugged in the 20A heater)? Can I replace this with a 30A breaker to power intended setup shown below?

breaker AWG10

. original

. desired

10
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    Remove it and check the official rating. – Solar Mike Nov 25 '20 at 4:23
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    It is probably a 15A because the end receptacle was a 15A. Don't bother to replace the 40A with a 30A, it will already be protected by the 30 you need to put in the Main panel. – NoSparksPlease Nov 25 '20 at 4:46
  • Are you sure it's etched/scratched in, and not raised numerals instead? – ThreePhaseEel Nov 25 '20 at 5:09
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    Looks lasered to me. But as Solar Mike suggests/alludes, pull the breaker and check for more markings. There is likely to be a part number, if nothing else, and that'll reveal or confirm the rating. Also, put in a filler blank or an unused circuit breaker to fill that gap! – Greg Hill Nov 25 '20 at 6:45
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    You've got an empty hole in the panel waiting to burn off a curious finger. Get any ordinary Square D QO breaker (preferably a size you might use) and stick it in that hole. I'm not a fan of the "blanking plates" they also sell; they cost near as much of a breaker, and are hard to find and quite flimsy. – Harper - Reinstate Monica Nov 25 '20 at 17:32
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I have a variety of old and new Square D breakers in my panel. It seems that the older ones have this type of rating on the handle, while it is printed on the newer ones. I'm not sure what the cut-off would be in terms of age / production year, but it's not important.

It looks to me like that breaker is rated at 15A, and the etching is factory-applied, not done by someone after the fact as you suspect. You could check the side of the breaker if you can turn the power off and remove it to be sure the ratings there match the handle rating. I just checked a spare breaker and there is no other place the amperage rating is expressed anywhere on it. The only place I could find is the handle.

Here is a picture of my panel showing the variety of ways the rating is printed on the handles: enter image description here

Upon reading harper's comment, I checked a spare 30 amp breaker I have to see what the other info on it reveals in more details. Stuff stamped on the side is all related to terminal ratings. There are also a couple of stickers, but those do not reveal the trip rating either. The part number is very well hidden, on the bottom of the breaker, in a slot between the line terminals. In my case, it says 235-07. Square D lists this breaker as part number QO235. The product page lists all the details you need, and is easy to find with an internet search for the number and brand of the breaker. enter image description here

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  • However side info may state a model number of the breaker, and the model number would reveal the trip (possibly embedded in the number). – Harper - Reinstate Monica Nov 25 '20 at 17:20
  • Well I pulled out the breaker and replaced with Square D 30A. The breaker I pulled out looks just like yours, including the molded 235-07 product number. I was not able to find the official manufacturer page showing 235-07 is rated to 15A. But I did find some examples online similar to yours, showing this is in fact a 15A breaker. Anyways, enough to conclude this was a factory "15" marking and so I had to replace for my project. – Roberto Nov 28 '20 at 13:48

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