If the circuit is wired with 14ga wire, and it probably is, then no, a 20A circuit breaker may not be used, you may only replace a 15A with a 15A.

Thanks normel,
How do I know what guage the wire is? Do I look in the circuit breaker box (with the cover off), and are the wires easily marked? Thanks.

Thanks greg,
I'll have my husband change it soon.
In the meantime, would it be good just to not put much load on it? Thanks.

Since the circuit had a 15A breaker to begin with, I would assume that the circuit is wired with 14ga wire. It can be difficult for an inexperienced eye to tell the difference between 12ga and 14ga just by looking at the wire. However, if this wiring is only a few years old, the sheathing may be color coded. If you have some wiring that has a yellow outer jacket and other that is white or orange, the white is 14ga (12ga is yellow, 10ga is orange.)

Thanks Normel,
The house is 31 years old, so I think we'll just replace it with the 15 amp.
The guy was being very nice to do it, but its disappointing that he said the 20 amp was okay. I just wish I had known better myself, so that I had insisted on the 15 amp. (which I had on-hand too).
Thanks for your help.

I really appreciated your quick responses, Normel and greg.
Otherwise, I would have given the guy extra money, for doing something potentially dangerous.
I decided to handle it this way. When he finished and brought me the bill, I said "This is sort of embarrassing, but I just talked to an electrician friend, and he said that you should never replace a 15 amp with a 20. Could you please change it for me?" He said "no problem" and chanaged it. Hopefully he will remember this and not do it to anyone else.
He "just" services my geo twice a year, but I would think he should know these things for sure.
Thank heavens for places like this. You 2 really helped me out and I appreciate it!

What I want to know is, why did you have replacement breakers floating around the house? Unlike fuses, they're not normally an item that's likely to need replacement.

Many years ago, when breakers were becoming more common than fuses, I read that one of the advantages of breakers over fuses was that homeowners couldn't as easily just arbitrarily upsize them to "fix" frequent trips. I'm sure breakers are indeed less frequently oversized than fuses were/are. But based on the number of posts we get here asking if it's OK to swap out a 15 for a 20, I'm starting to wonder if it's such a good idea for breakers to be so readily available in the hardware and big-box stores.

Hi david,
We live out in the country, and in the past, our breakers have gone out at the worst times. So we've learned to keep a couple spares around.....and it was a good thing.
I'm just glad I found out here that it wasn't a good thing to up the circuit breaker amps. I had this incorrect notion that if the service could deliver 20 amps, wouldn't that be better than just 15? I didn't realize that the 15 amp breaker was put there, based on what the need was of the things it was supplying and that it very well might have had wiring that was unable to handle that load.
The guy offered to change it for me, so I assumed he knew what he was doing. Wrong assumption.
We have needed to replace probably about 8-10 in the past 23 years.

our breakers have gone out at the worst times.

What kind of panel do you have? How many failures have you had? What was the nature of the failures? Were they regular breakers, GFI breakers, and/or AFCI breakers? Have you any idea what caused them?

From what I've seen, actual breaker failure is pretty rare. Personally, I've only ever had one breaker fail. It died after a nearby lightning strike - it simply would not reset. But that's the only one. So I'm very surprised that you would have more than one breaker failure, and wondering about the above. Hope I'm not being too nibby.

Hi David,
I can't remember all the different situations that the failures occurred in. We would just notice that a whole circuit was out. Once we changed the breaker, everything was fine. (They never kept tripping, and we ignored it. They would just go out all of a sudden). The problem yesterday seemed to be the switch was broken on the breaker. You could feel, when you'd toggle the switch back and forth, that it didn't have any snap.
We have the usual kind of breaker box. The only things I can see on it are "EQ load Center", and "ITE". It has 40 breakers.
When I say they go out at the worst times, I mean the most inconvenient times. (But when is it ever inconvenient to lose power?)
We have had a couple lightening strikes that hit our well pump, and our geo thermostat, so maybe that has been involved in the past, but I can't remember for sure.
Maybe they get dust in them and wear out sooner??
Maybe we have inferior breakers in this area of the states?
Maybe my 8-10 guess was a little high.
We do have one "bad buss", which we can't use.

"The problem yesterday seemed to be the switch was broken on the breaker. You could feel, when you'd toggle the switch back and forth, that it didn't have any snap."

When most breakers trip the handle is disconnected from the internal maechanism. This is to prevent a breaker from being held closed by the handle being blocked.
To reset a breaker it must be pushed firmly to the full off position, then moved back to the on position.

Outside of one vender (Federal Pacific) bad breakers are actually very rare.

Hi brickeyee,
This switch was totally limp. I understand what you mean about resetting them, but this one was kaput.

You have a bad bus? You mean that an entire half of the panel is defective?? Yikes! It sounds like you should be thinking about a new panel.

Cutler-Hamer and Square D QO are reliable brands. Some folks like Siemens. I've used GE and they're fine, but they're probably a notch or two below the top two I named above. Of course you'll find plenty of opinions on these matters. ;-)

Hi david,
Well, I say "bad buss", because that's what the electrician called it. What I mean was that there is just one individual connection off the main thing that was bad, so there's one breaker I can't use. I think the ones I've used recently are Siemens.

If I were you I'd get a new panel before it causes a fire. You say your electrician claimed your panel had a "bad bus"... don't take this lightly! If this is true (and it sounds like it by the rate you had to replace breakers) you have a dangerous situation on your hands. A poor connection between the bus and the breaker causes heat to build up. Heat building up causes fire!

I mean no offence when I say this, but you seem to have a somewhat carefree attitude towards electrical wiring and equipment. Equipment not in proper working order, and over fused circuits can and do cause devastating fires!

It is not normal to have to replace breakers at the rate you do! I had an old Square D panel in my house from 1959 and I never had to replace a breaker once in it 'till the day it was retired last year. Please hire a qualified licensed electrician (no handymen) to look at your panel... something isn't right.

Thankyou rtscoach.
PLEASE don't assume I take any of this lightly. I am an excessively cautious person with my family's safety. I have had numerous electricians out here for various reasons, and no one has ever said I have a problem. I will talk to another electrician, but please don't assume I'm taking anything lightly.

P.S. I talked with the REMC guy who's very reliable, and he agreed that we've had too many breakers go out, so he's coming out next week to look at the service panel. Thanks for letting me know that this wasn't an acceptable situation to continue with.
I just figured everything breaks down sooner or later and replacements were a normal thing.
He said he would look at the conditon of the buss, the wires, and run a few tests, etc.
We were hoping to build a new addition before having to do anything major on the old stuff, but this is too important to take any chances by putting things off.
Thanks again for your honest feedback.