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:
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.
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.
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.
