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I just a bought a house and discovered that a double 30 amp breaker is hooked up to three rooms with approximately 12-15 receptacles. Is this dangerous or am I good?

Update:

I have been informed that there is a sub panel with four fuses/breakers to offset the power. I was first informed about the 30amp breaker from a guy installing a receptacle that did not know about the subpanel.

Box and subpanel:

enter image description here

enter image description here

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    Where are you on the planet? What size wire is connected to the breaker? A pic inside the breaker box would help as well.
    – RMDman
    Commented May 28 at 19:34
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    Assuming you're located in the US, and these are standard receptacles with standard wiring (not 10ga or thicker), yes this is against code and dangerous. Can you add pictures of your breaker panel? Commented May 28 at 19:34
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    Idle question: did you have a home inspection? This is a huge and easy to find red flag that should have been on the report. Commented May 28 at 21:35
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    Was the guy that came out a licensed electrician? If so, I would trust his opinion over strangers on the Internet who haven't seen your wiring.
    – spuck
    Commented May 28 at 23:09
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    Those fuses on the subpanel are antiques. One danger is that the previous resident put pennies behind them to keep them from blowing. IMHO, and I am not an electrician, that subpanel should be replaced with a modern one, which will afford an opportunity to examine the wiring, as some have suggested.
    – Wastrel
    Commented May 29 at 13:17

3 Answers 3

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Since this is feeding a subpanel, then this is most likely fine

The other answers are correct that regular North American receptacles are not rated for 30A. However, since there's a subpanel breaking that 30A feeder into multiple smaller (15A or 20A) circuits, you are fine as long as the wires connecting that 30A breaker to the subpanel are 10AWG.

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    @Mazura -- not without running afoul of the small conductor ampacity limits Commented May 29 at 3:56
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    diy.stackexchange.com/a/169298/23295 "In copper, 14AWG is limited to 15A, 12AWG to 20A, and 10AWG to 30A not by the ampacity tables or even necessarily termination ratings, but by the small conductor rules set forth in NEC 240.4(D)"
    – Mazura
    Commented May 29 at 4:24
  • I need to check again but I believe there are two 20A, one 25A, and possibly one 30A fuses Commented May 29 at 17:18
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    @JoelPierce -- yeah, that's probably something that should be investigated then Commented May 30 at 3:05
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Note: This answer pertains to an earlier version of the question when the small fuse panel was undiscovered and OP thought the rooms were all directly on a 30A breaker. While that does not turn out to be the the case, the answer may be useful to anyone who does find that situation, or as a reminder to anyone who wrongly thinks they do as happened here.

It is bad, and you are not good. Just how dangerous it is depends on what wiring was used for the rooms. In the extremely unlikely event that 30-amp #10 wiring was used throughout, there are some dangers and you should address it. Assuming #12 and #14 wire was used, it's actually very dangerous. You should not plug any high-powered things into any outlet (heaters, window A/Cs, appliances, hair dryers etc) and you should immediately change the breaker to a pair of 15A ones until you know more about what other incorrect things were done. There's more ... you need to look at how neutrals were treated and what size cabling was used. Get someone knowledgeable to look at this ASAP. Who knows what other short cuts were taken.

A little background: The breaker's main job is to protect the wires inside your walls from overheating and starting a fire. Typical wiring for outlets is rated for either 15A or 20A. If a wire rated for 15A is protected by a 30A breaker, you are one big step closer to a fire. It's not automatic instant death, but there are now all kinds of innocent little problems that rarely happen, but if one does, you are not protected.

Seriously -- if you have kids with hair dryers, take them away. If you have window A/Cs, unplug them and tell everyone not to use them. Do this now, before you go to bed tonight. It's that serious.

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    Ya if the 30A breaker is correctly wired to feed a small subpanel that might be fine. If you add that info to the question I'll delete this answer.
    – jay613
    Commented May 29 at 0:19
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    @jay613 I don't think you should delete the answer. Next person with the same problem might not have a subpanel.
    – DonQuiKong
    Commented May 29 at 5:42
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    I'm trying to decide if to delete this or not, and watching the votes on the previous two comments is a nail-biter. My thoughts; The problem OP originally thought he had, is not a common one, and my answer is not helpful as an abstract one to non-specific future questions. Everyone knows it's dangerous. The actual problem "didn't know about sub" has come up from time to time, and OP's is an interesting variation with an upstairs fuse subpanel, I've never seen that before. Better to leave that the focus?
    – jay613
    Commented May 29 at 16:40
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    @jay613, I don't think you should delete it, but you should definitely put in something about how it applies (or rather, doesn't apply) to the modified question.
    – Martha
    Commented May 29 at 19:58
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    I guess the fuse panel was the main panel once, there was an upgrade with a breaker panel and new wiring for downstairs especially the kitchen, but the upstairs was left alone and the original panel turned into a sub with its downstairs connections removed. Makes sense. May not be so unique. I haven't seen a 4-fuse main before, that's small, but apparently it was common.
    – jay613
    Commented May 30 at 12:14
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It is bad. For 30 amps the wires must be at least 10 gauge, which I highly doubt.

If it is a double breaker, it is most likely a MWBC, two circuits sharing a neutral. A double breaker of the right size is good on a MWBC.

Check the wire gauge. The gauge will be marked on the wire/cable covering. Outlets/receptacles and light switches(common) are rated for 15 to 20 amps max. So three sources for a fire, the wires in the walls, the outlets, and whatever is plugged into them if something goes wrong.

A light(desk) on a proper circuit can only take max 1800 watts when stuff happens. On a 30 amp circuit that goes up to 3600 watts. That is an extra 1800w, which is much more than most space heaters inside of your walls.

If 14 gauge, then you need a 15 amp double breaker. For 12 gauge you can use a 20 amp breaker, but all the wires on that circuit must be 12 gauge. If not sure all are or know some are 14 gauge, you need to stay with a 15 amp breaker.

When finding a too large breaker, a common reason is the people were tripping the breaker often, usually trying to make tea and toast at the same time, or two space heaters, two hair dryers.

Larger breaker stopped the tripping, but it can/does lead to house fires.

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  • As an update I had a guy come and look at it and upstairs is a smaller breaker with 4 round breaker/fuses (I'm an idiot sorry) and these should help offset the power. Is this correct? Commented May 28 at 22:34
  • @JoelPierce With the 30 amp breaker powering a sub panel is good. Still check that the wire/cable is 10 gauge on the 30 amp breaker, and those fuses are 15 or 20 amp.
    – crip659
    Commented May 29 at 10:18
  • The fuses I believe are 20 and 25. Commented May 29 at 12:29
  • @JoelPierce The 25 amp fuse is probably too big, unless it powers something specific and the wires/cables are 10 gauge. Fuses/breakers protect wires from burning(quite bad inside a wall).
    – crip659
    Commented May 29 at 14:27
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    @JoelPierce It would be reasonable to replace all 4 fuses with 15-Amp rating until you identify a specific allowance for 20. Commented May 30 at 19:24

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