Similar to another thread, I have recently had a single circuit breaker that has started to trip erratically. My townhouse is 5 years old. Starting Monday, the breaker has tripped 3 times. Heres the kicker: it doesn't trip when you plug something in or something turns on, it will just trip. Last night, I walked into the hosue and was talking to my wife in the living room. We are standing in the middle of the room and the breaker tripped. We have been here for a little over two years and it has just started doing this this week. The breaker apparently controls our second floor living room (lights and outlets) and the lights in the kitchen. It is a 15A breaker. Does it sound like the breaker is just old and needs replacing? This is our most heavily used room.

Also, can I upgrade the breaker to a 20A? I do not know the wiring size for this level of the house,and all the walls are finished so I would have no easy access to view the wiring. I am assuming it would be per code and maybe 12 gauge? I am going to check everything that is connected to this circuit because I eventually want to add recessed lighting to the living room (currently only one switched outlet with a floor lamp provides lighting). That is why if I can upgrade to the 20A I would like to to provide for future electrical load.

Thanks for the help and sorry for the long post!!

-Neil

 

It is quite unlikely that you could 'upgrade' to a 20A breaker. A 20A breaker costs no more than a 15A breaker, but 12ga wire costs more than 14ga wire. If an electrician were to run 12ga wire, then they would have used a 20A breaker. You can only use a 20A breaker if all of the branch circuit conductors are 12ga, and if all of the devices are rated to be connected to a 20A circuit (note: 15A receptacles are rated to connect to a 20A circuit under US code).

It doesn't hurt to check; maybe they only had a 15A breaker on the truck or something silly like that. But I would not count on this being possible.

If the breaker is randomly tripping, this could mean one of several things: a bad breaker that is overheating and tripping because of temperature, a _loose_ connection at the breaker, causing heat that makes it trip, a slightly overloaded circuit that is simply taking a long time to trip, an intermittent short circuit that is periodically causing a fault and tripping the breaker at the fault, or some other gremlin.

You will probably have quite a bit of investigation in order to solve this problem.

I'd suggest using a clamp meter to measure the current in this circuit, to see if it should be close to tripping. I'd also suggest feeling the breaker when it trips to see if it is warm. I'd next try simply replacing the breaker with another 15A breaker, checking that the panel bus is in good shape and that the wires are screwed down tight. The next thing to check is the condition of all of the wires in all of the boxes on this circuit.

-Jon

 

Thanks for the quick reply Jon. Some additional questions/clarifications:

Is there an easy way to tell the wire size by looking at it? And where should I look for the wire? Behind a receptacle? At the panel? Where can I look to find out if it is 12 or 14?

From what I can recall, we have no more appliances or extra load at this time than we did last year. Just lights for the Christmas tree, space heater, and 3 candle lights in the window. Same set up as last year and the year before, but the breaker hasn't tripped until this year.

Where can I get an inexpensive clamp meter and where would I clamp it?

Would it be safe to assume, as a first stab at solving the problem, that the breaker has worn out? If so, I think the easiest solution (and least expensive) would be to replace the breaker. But would this possibly just be masking another underlying problem? If I replace the breaker and it doesn't trip again this year, is it safe to assume that that was the problem, or could a short somewhere in the line still eventually cause the new breaker to eventually go bad (which would be the real problem, being masked by a tripping breaker)? I hope I explained that correctly.

I don't recall the breaker being warm when I reset it. It seems to be truly random, as my wife hadn't changed anything all day (she works from home), and it didn't trip until I walked in the door. Maybe it is something electrifying about me....

Thanks again,
Neil

 

The 'Space Heater' raises a big red flag.

Space heaters use quite a lot of power. My guess is that the circuit is slightly overloaded, and that the breaker was simply on the verge of tripping last year, and this year is doing it.

Breakers have a certain 'tolerance' range. If you have several '15A' breaker, one might trip very quickly at 16A, and another might _never_ trip at 18A. If the circuit is slightly overloaded, then it might take hours to trip, and the trip would appear to be random. The trip characteristics will change with age and ambient conditions (maybe your breaker panel is just a bit warmer this year rather than last year).

Each time the breaker trips, the contacts get a bit worn, and then the next time the breaker runs just a bit hotter.

I don't know where to get a 'cheap' clamp meter. I'd suggest that you add up the wattage of everything plugged into this circuit; anything more than 1500W total means that this circuit is overloaded.

Replacing the breaker might solve the immediate problem yet mask the slight overload...or it might fix the problem if the problem is with the breaker itself.

The best way to figure out the wire size is to look at the printing on the side of the cables. You can also simply look at a piece of known #14 and known #12; the size difference is pretty obvious.

-Jon

 

Thanks again Jon. One quick question: Thinking back to college physics, doesn't watts/volts=amps? Therefore, I could run up to 1800 watts on this circuit (1800/120=15 amps). Or is some head room required? It is still overloaded, but just curious about figuring out the exact amperage load.

 

You are correct, 15 amps at 120 volts is 1800 watts.

 

15A at 120V is 1800W. However for _continuous_ loading you are required to operate at 80% of breaker capacity.

This means that you can load the circuit to 1800W on a non-continuous basis, but if you operate at 1501W for long periods of time (greater than 3 hours at a stretch), then the circuit breaker is overloaded.

-Jon

 

rockford33, I thought Jon was referring to the 80 percent rule, but didn't want to go there.

Now before you do your math again, 80 percent of 1800 is 1440, not 1500. However, if you use 125 volts at 15 amps = 1875 watts, and then you take 80 percent you do indeed get 1500 watts.

The bigger question is, do you as a homeowner need to worry about the 80 percent rule? Generally speaking you don't need to be concerned about it. Most of what we do as homeowners is not for extended periods of time. We may have something turned on all day, for days or months at a time, but t doesn't mean it's consuming lots of energy all the time. Just about everything we run cycles on and off.

Where this should be a concern to us is if you have load that will be on for long periods of time.

 

Thanks Jon. I figured there was some logic to it.

 

Thanks for the info. I agree that I usually do not have a continuous load on circuits.

As a side question, are there any books that you or Jon might recommend for wiring basics (or even more advanced stuff as well)? I have the Home Depot 1-2-3 book, and their specific wiring book. Over the weekend, I looked through the Better Homes and Garden Big Book of Home How-To, which I thought was really good in explaining things, variety of projects for both finished and unfinsihed spaces, wiring diagrams, etc. I also started to look at the Creative Homeowner Wiring book but ran out of time. Any thoughts on some good reading material for a Christmas present?

 

The 1500W number was a cranial gaseous event (brain fart). Usually I know how to multiply.

Generally you won't hit the 80% limit in residential use, because as Racraft says things cycle on and off. However on an overloaded circuit you might be in this range already.

FYI: a breaker is 'in spec' even if it doesn't trip at 120% of rated current for may hours. At the same time, a breaker is considered overloaded if it is at 80% of rated current for an extended period of time. If you are up in this load regime you can expect unreliable operation.

For books, I recommend just about anything on home wiring by Rex Cauldwell.

-Jon

 

Well, I replaced the breaker this weekend and the wife just called me to say the breaker had tripped again. I really don't know why we are having this problem suddenly. We used the same space heater, had the same TV, etc. all plugged in last year with no problems. Granted, a 1500 watt heater is sucking up 12.5 amps on a 15 amp circuit, but how can you get around that? Why would manufacturers make a device that you realistically can't safely use on your circuits? Is it possible there is some wire damage somewhere? Maybe I will get a plug in circuit tester and check the outlet circuit itself. If I recall, we actually had the heater plugged into a different outlet (on the same circuit) last year with no problems. Maybe it is the outlet itself, maybe loose wiring? Any thoughts are appreciated.

Thanks,
Neil

 

You are pulling more than the 15 amps through the circuit that the breaker will allow.

Don't use the space heater. Buy a new space heater. Move it to a different circuit (a 20 amp circuit).

 

The heater is your problem. It is overloading the circuit. A 1500 watt heater should be used on a circuit by itself. There could be several reasons it is tripping now and not last year.
1. You have more stuff on the circuit. Bigger tv. VCR, lamp
2. The power company has increased the voltage slightly. This will cause more current draw.

 

Thanks for the replies guys.

Racraft,
I would love to put the heater on its own circuit, but the entire living room is a single 15A circuit. With all of the walls finished (from garage to top floor), there would be no easy way to run a new circuit. And I would find it hard to justify the cost of a pro to come in and do it, patch the drywall, etc. just to run a space heater for a couple of months a year.

Joed,
I actually don't have anything more on the circuit than last year. Same TV, cable box, etc. That was the first thought I had was more/bigger stuff plugged in to the circuit. I don't know if the power company has increased the voltage at all.

The one thing that has changed is which wall outlet we plugged the heater in to. For an experiment, I had the wife plug the heater back into the outlet we used last year. Unfortunately, she didn't turn the heater on yet because she was upstairs. She will probably use it sometime today, so we will see if it trips on this other outlet. I am also going to check the load ratings for the TV and cable box. Other than one halogen lamp and Christmas lights, there are no other items plugged into this circuit. I am going to add up the loads and see what my total is. We try to minimize using the heater, but even though the house if fairly new (5 years), it was a quickly built townhouse and has some air leaks and the garage below the living room is not heated or completely insulated.

I appreciate all of the help and thoughts. I hope everyone is having a good (and warm) holiday season!

-Neil

 

Neil,

Only you can decide whether it is worth the cost of running a new circuit. It's a trade off decision you will need to make. Run a new circuit and use the space heater, or don't use it and be a little colder, perhaps wearing another layer of clothes.

As for why the breaker trips this year and not last year, there could be several reasons. The heater is older, perhaps drawing a little more current. The receptacle is older (or in this case you say a different receptacle), perhaps the plug doesn't fit as well so more current is pulled. Or perhaps, as joed suggested, the power is a little different this year.

 

You could switch to a lower wattage heater.