New Load to Circuit Trips Breaker After a Period of Time

It's probably tripping on heat...You have a loose connection or a partial short...Do you have an Amprobe, continuity tester or any diagnostic equipment? Could also be a weak breaker...to check this, switch load to another 20a breaker and see if the same thing happens..

You might want to make sure your homeowner insurance policy is current, too.

I just shoved a penny up in thare. Seems to work great now!

"I have just installed two ceiling fans and rerouted some lighting on my new covered patio."

That means that it is an outside (wet) installation. It should be wired to a ground fault breaker if that is the case. If it is, then you might be tripping on excessive ground current, rather than overcurrent. This seems more likely since: "with the switches off to the new equipment" you shouldn't be drawing any current, unless there is a short somewhere.

Ground fault for ceiling fans and lighting................or just outlets?

From what I can tell, only kitchen, bathroom and outdoor "receptacles" (outlets) are on GFCI circuits but just realized this house has AFCI and BRAF combo on all non appliance circuits, including this one. The existing outdoor lighting (flood and porch light) were on this non GFCI circuit. Any possibility the AFCI is the culprit. Remember, this has always tripped after what I consider a lengthy delay of many many minutes. Thanks for your input

It could come from a few different things. Don't make the same mistake that I always make, and assume that the new fans you bought are automatically good.

If you don't feel like getting into testing right away, you can turn one fan on and leave the other off, and vice versa................same with the lights. If it stops happening with one particular item turned off, you have a starting place for where to start looking............................maybe.

AFCI would only be the culprit if the breaker is bad. If anything was arcing it would pop immediately, plus you would probably notice.

Good question, and one that I posed to the electricians around here. The answer I got was "it depends". For a receptacle yes, for an outlet (switch, junction box tie in...) no.

To me it seems that grabbing a metal fan that is "hot", is a lot more likely than sticking my finger in the hot side of a receptacle. And what about those 99 cent sockets that you screw into a porch light to run the Christmas lights? No NEC code that I know of says it is now a receptacle and has to have a GFCI.

Better safe than dead.

True, but some things create problems on a GFI circuit................which I found out the hard way when I went ahead and wired my bathroom light and vent fan into the same GFI circuit that I had the receptacles on. It didn't like it and kept on tripping.

No NEC code that I know of says it is now a receptacle and has to have a GFCI.

Also true, but I would hope that even a novice would know to turn off power at the switch before hooking anything up, whereas a receptical is always hot.

You can check the total circuit impedance to see if the breaker is tripping on heat due to high contact resistance.

Assuming the impedance at the panel looking back into PoCo is 0 ohms, load the circuit with 10A and watch the voltage drop at the load. Knowing the distance back to the panel and the wire gauge and material (I assume copper) you can figure what drop you should be seeing. A half volt more than the predicted drop probably means a bad connection.

For 50' [100' loop distance] of #14 copper you should be seeing 26 milliohms x 10 A = 0.26v change in the nominal outlet voltage.

Thank ya'll (you guys) for your inputs. I think I have found the problem and the fans (and the rest of the circuit) are "spinning" continuously. It is pouring rain and my house isn't on fire yet. GA to Kramarat for his present posts/previous questions which helped me put my own knoggin to good use. No thanks for Cam beating the Texans. My conclusion is that the AFCI sensed I had applied a wire nut and also stuffed a junction box carelessly. Something I always worry about. Idiot proof is hard to attain, but a good thing for me in this instance. Still do not understand the reason for the delayed trip. Anyone?

My $0.02.....

The AFCI didn't detect the application of the wire nut it sensed an undesirable arc signature most probably from that joint.

When you tidied up and probably retightened any mechanical joints in that Jbox. you eliminated an arcing point that probably developed with heating (all joints heat), like it didn't start to arc until it warmed up. Hence the observed delay.

Now apparently AFCI are prone to nuisance tripping so there may not have been anything wrong with your work.....

You sorted it and that's the main thing.

I have never encountered an AFCI. Are they commonly deployed in the US?

Good news sadibo!

I've never seen or heard of an entire house being on AFCI breakers.

Interesting:

http://en.wikipedia.org/wiki/Arc-fault_circuit_interrupter

From wiki:

An AFCI should, but may not always, distinguish between a working arc that may occur in the brushes of a vacuum cleaner, on operation of a light switch, the insertion or removal of a plug into an electrical receptacle, or during the operation of other household devices and a non-working arc that can occur.

If you're sure that everything is good to go and you continue to have problems in the future, I'd replace the AFCI breaker with a regular 20 amp one.

{Edit}

If you find that you have to do that, you would still need GFCI outlets, which you could do by installing one at the beginning of the run.

GA, Kramarat.. The 2012 changes in the NEC states that any NEW installations must be on AFCIs or GFCIs. Mo money, Mo Money..

They just never know when to say stop with the stupid rules do they?

They always go past the point of what is good and enter the land of negative returns.

My house only has to be up to 1986 codes, although I will check, and follow, later codes if it is prudent, which is rare.

Just a little side note:

When I'm running a new circuit, or tying into an old one, via a junction box, on my perpetual fixer upper, when joining wires I will physically twist the wires together first, (rather than relying on the wire nut alone to hold them together), followed by a wire nut, and finally, I fill the wire nut with 2 part epoxy cement and allow it to cure before jamming the wires in the junction box.......................leaving just enough slack, in case I ever have to cut it out.

Needless to say, arcing is not a problem.

"They always go past the point of what is good and enter the land of negative returns."

Actually they go to point of endless profits for NEMA while taking advantage of the public's Zero Risk Bias. I don't see anyone on the code panels that represents the public and understands diminishing returns. And with 1700 people dying each year in the US from electrical causes, this is way down in the noise as far as what kills people.

With a $10 circuit breaker you get $10 worth of safety. With an AFCI you get nuisance tripping and replacing appliances with life still in them.

Also, the NEC has made it a rule to have GFCIs in car washes even though there has never been an incident and even the people who make a fortune interpreting these rules for the every day electrician are surprised at this.

The NEC has found a cash cow and they are going to ride it like a rented mule.

Which is why I've taken it upon myself to learn how to do my own electrical, plumbing, car work, carpentry...................................

People that don't know how to work on anything amaze me. You would think that curiosity alone would draw them in, but it doesn't. One thing is for sure................they need to be making a lot of money doing something, to be able to afford to hire others to fix the simplest of things on a regular basis.

AFCI's (Arc Fault Circuit Interruptors) are a good idea. They don't prevent electrocutions, they prevent fires from low current arcing. An excellent example is our older share cooperative, which has only two outlets per room, on 14 gauge wire, no ground. Old ladies run cheap extension cords around the bedroom for their lights and heating pads and extra TV and alarm clock and radio, typically around the feet of their bed frame, and tightly. All you need for a nice fire in the bedroom carpet is to lift up the bed leg a little and have the extension cord slide under the bed leg. Your extra weight on the bed, and the softening of the cord from the heater you just turned on lets the wire inside the cord just barely arc, not enough to trip the breaker. Did I mention there are two 20 amp breakers for the whole apartment? People die a LOT in bedroom fires. I'm pretty sure new construction and remodel in California require ARC fault in bedrooms, and GFCI in rooms with plumbing, and outdoors everything.

I REALLY dislike this attitude about big government is making electricity too expensive. Work in a burn ward or ICU for a while. Gives you a whole different attitude about the costs of electrical regulation. I really like ARC fault interruptors, because they fill a very important need -- FIRE PREVENTION!

From Wiki:

Each year in the United States, over 40,000 fires are attributed to home electrical wiring. These fires result in over 350 deaths and over 1,400 injuries each year.

It's wonderful that a country of over 300 million people, that is over $15 trillion in debt can take these measures, (and many others), to save a relative few. I can't help but wonder how long we can continue to tighten the weave on the public safety net until it eventually suffocates us. Do we continue until all possible causes of accidental death are eliminated?

Ran out of edit time.

Here are some real numbers. Electrical isn't even a blip.

You have identified one instance in which AFCI's are a good idea. I agree..............they should be used there. But not in every new home across the US.

Like I said before AFCI are new to me too.

I think that they are a good idea but this nuisance tripping makes them undesirable. From what I have read so far they can also fail to detect undesirable arcing.

They could do with some improvement.

I was thinking how one would commission an AFCI to be sure it wasn't 'blind" beyond just pressing the test button. Would you have a set of calibrated arc signatures that you could introduce into the reticulation to see whether they were detected or ignored correctly and reliably....?

If they worked reliably they could even be an aid (tool) to detecting poor connectivity in new and existing installations.

I think I will have a sniff around my local electrical importer/wholesaler depots to see if these are lobbing in already.